THE EFFECTS OF DEMOGRAPHIC CHARACTERISTICS ON PREOPERATNE TEACHING OUTCOMES: A META-ANALYSIS

Sepali Guruge

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Graduate Department of Nursing Science University of Toronto

O Copyright by Sepali Guruge 1999

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THE EFFECTS OF DEMOGRAPHIC CHARACT ERlSTlCS

ON PREOPERATIVE TEACHING OUTCOMES: A META-ANALYSIS

Master of Science, 1999

Sepali Guruge

Graduate Department of Nursing Science

University of Toronto

ABSTRACT

A meta-analysis was conducted to identify the demographic

characteristics of patients who participated in preoperative

teaching effectiveness studies and to assess the variation in

anxiety, pain, and LOS outcomes of preoperative teaching in

relation to age, gender, education, and ethnicity.

Moderate-sized effects of preoperative teaching on pain

and LOS outcomes were found. However, effects on anxiety were

not examined due to inconsistencies in primary studies.

Effects of demographic characteristics on these outcomes could

not be discerned since the participants of preoperative

teaching studies were primarily white females of 41-60 years

of age with above secondary level education.

Findings are not generalizable to al1 patients undergoing

surgery, and preoperative teaching may need to be tailored to

each patient's background. Further, research and theories

addressing the influence of demographic characteristics,

particularly education and ethnicity, on the outcomes of

preoperative teaching are needed.

ACKNOWLEDGEMENTS

1 would l i k e t o dedica te t h i s t h e s i s t o Prof- Gai1

Donner- 1 will always be g r a t e f u l t o you f o r encouraging m e t o

apply f o r MSc and f o r being t h e r e f o r m e during the p a s t few

years of d i f f i c u l t times. I t has been an honour knowing you.

Spec ia l thanks t o m y t h e s i s superv isor , Prof , Souraya

S idani , f o r her invaluable guidance, continuous support , and

immense pat ience. Many thanks are a l s o extended t o Profs.

Diane I r v i n e and Barbara Johnson.

My love and h e a r t f e l t thanks t o my p a r e n t s f o r giving m e

s t r e n g t h t o f ace each day. Thanks a l s o t o a l 1 my f r i e n d s f o r

support ing m e through it a l l ,

F ina l ly , 1 would l i k e t o Say thank you t o my Vasthu!

F i r s t of a l l , f o r your pa t ience i n he lp ing m e with s t a t i s t i c s ,

secondly, f o r your support and encouragement, e s p e c i a l l y when

I f e l t l i k e q u i t t i n g , and most of a l l , f o r making sure 1 a t e

well and s tayed healthy.

iii

TABLE OF CONTENTS

. . . . . . . . . . . . . . . . 1 . BACKGROUND TO THE STUDY 1

. . . . . . . . . . . . . . . . . . . . . Introduction 1

. . . . . . . . . . . . . . . . . . Problem Statement 3

. . . . . . . . . . . . . . . . . Purpose of the Study 4

Review of Related Literature . . . . . . . . . . . . . 5

. . . . . . . . . . . . . . Preoperative Teaching 5

Content of Preoperative Teaching . . . . . . 5

. . . . . Structure of Preoperative Teaching 8

Methods of Information Delivery . . . . . 9

Presentation of Preoperative Teaching . . 10

Timing of Preoperative Teaching . . . . . 11

Postoperative Outcomes . . . . . . . . . . . . Relevant Meta-analyses . . . . . . . . . .

Demogxaphic Characteristics of Patients . . . . Age . . . . . . . . . . . . . . . . . . . Gender . . . . . . . . . . . . . . . . . . Level of Education . . . . . . . . . . . . Culture and Ethnicity . . . . . - . . . . Relevant Meta-analyses . . . . . . . . . .

The Conceptual Framework . . . . . . . . . . . . . 26

. . . . . . . . . . . . . . . . . Research Questions

Summary . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . 2 . OVERVIEW O F THE STUDY DESIGN

. . . . . . . . . . . . . . . . . . Sample Selection

. . . . . . . . . . . . Procedures for Data Analysis

. . . . . . . . . . . . . Descriptive Analysis

. . . . . . . . . . . . . . . Frequency Counts

Statistical Techniques . . . . . . . . . . . .

3.RESULTS . . . . . . . . . . . . . . . . . . . . . . . . . . . Results of the Descriptive Analysis of Data

Description of the Sample . . . . . . . . . . . . . . . . . . . Characteristics of the Studies

Characteristics of the Patients . . . . . . - . Methodological Characteristics . . . . . . . . Characteristics of Preoperative Teaching .... Characteristics of the Outcome Variables . . .

Results of t h e Quantitative Analysis of Data . . . . Results of the Frequency Counts . . . . . . . . Results of the S t a t i s t i c a l Analysis . . . . . .

S m a r y . . . . . . . . . . . . . . . . . . . . . .

4 . DISCUSSION . . . . . . . . . . . . . . . . . . . . . . 77

Characteristics of the Studies . . . . . . . . . . . 77

. . . . . . . . . . . . . . . First Research Question 83

Second Research Question . . . . . . . . O - . . . . 88 . . . . . . . . . . . . . . . . . . . . Limitations 101

. . . . . . . . . . . . . . . . . . . . . . Summary 104

. . . . . . . . 5 . SUMMARY. IMPLICATIONS. AND CONCLUSIONS 106

. . . . . . . . . . . . . . . . . . . . . . Summary 106

. . . . . . . . . . . . . . . . . . . . Implications 108

. . . . . . . . . . . . . . . . . . . . . Conclusion 114

RE FERENCES

LIST OF TABLES

. . . . . . . . Instrumentation for Data Extraction

. . . . . . . . . . . . . . . Review of the studies

Study Characteristics . . . . . . . . . . . . . . . Patients1 Characteristics . . . . . . . . O . . . .

. . . . . . . . . . . . Methodology Characteristics

. . . . . . . . . . Review of the Quality of Studies

. . . . . . . . . . . . . . . . Age and LOS Outcome

. . . . . . . . . . . . . . . Gender and LOS Outcome

. . . . . . . . . . . . . Education and LOS Outcome

. . . . . . . . . . . . . Ethnicity and LOS Outcome

Age and Pain Outcome . . . . . . . . . . . . O . . . . . . . . . . . . . . . . . Gender and Pain Outcome

. . . . . . . . . . . . . Education and Pain Outcome

. . . . . . . . . . . . . Ethnicity and Pain Outcome

LIST OF APPENDICES

Statistical Theories and Formulas . . . . . . . . . Review of the studies . , . . . . . . . . . . . . . Study Characteristics . . . . . . . . . O . . . . . Patients' Characteristics . . . . . . . . . . . . . Methodology Characteristics . . . . . . . . . . . . Review of the Quality of Studies . . . . . . . . . .

v i i

LIST OF FIGURES

1 Conceptual Framework . . . . - . - . . 31

v i i i

CHAPTER 1: BACKGROUND TO THE STUDY

Introduction

Providing patient education constitutes an integral part

of nursing practice (Allen, Knight, Falk, & Strang, 1992;

Cupples, 1991; Devine & Cook, 1983) . Although this topic has been addressed extensively in the nursing literature, research

specifically on preoperative teaching commenced only in the

1960s (Cartwright, 1964; Egbert, Battit, Welch, d Bartlett,

1964; Dumas 6 Leonard, 1963; Healy, 1968) . Many research studies have been conducted since then to assess the

effectiveness of preoperative teaching in patients undergoing

surgery.

Preoperative teaching generally involves providing

patients with information about the preoperative preparations

(such as skin preparations, or type, time, and route of

preoperative medication administration), the events,

procedures, or sensations they are likely to experience, and

information about why, how, and when to use certain equipment.

Preoperative teaching also includes information about self-

care actions to be performed such as discontinuing smoking,

adhering to dietary restrictions, requesting analgesics,

performing coughing and breathing exercises, and ambulating

early to reduce discornfort and complications (Devine, 1992;

Devine & Cook, 1986; Hathaway, 1986; Johnson, 1984; Nelmes,

1989; Shimko, 1981). Details about waiting facilities for the

patient's family members and when and where they may see the

patient also are considered part of preoperative information

(Nelmes, 1989).

The effectiveness of preoperative teaching is measured in

terms of improvement in postoperative outcornes. Some of these

outcomes include postoperative vomiting, pain, length of

hospital stay, fear, anxiety, and uncertainty associated with

surgery, earfy ambulation, and early resumption of normal

activities. Improvement in these outcomes ultirnately leads to

an increased patient satisfaction with hospital care. (Devine,

1992; Devine d Cook, 1986; Dumas & Leonard, 1963; Egbert et

al., 1964; Nelmes, 1989; Orr, 1990; Wong & Wong, 1990) . Although many research studies have demonstrated varying

degrees of improvement in these outcomes, little attention

appears to have been given in such studies to the

representativeness of their samples and to the

generalizability of their results to al1 patients undergoing

surgery. These patients Vary in their age, gender, educational

and cultural backgrounds. These demographic characteristics

influence patientsf responses to treatment or to nursing

interventions such as preoperative teaching (Burns & Groove,

1992; Sidani & Braden, 1998) . As such, the results of the preoperative teaching

effectiveness studies based on people of particular

dernographic characteristics may not be applicable,

appropriate, or generalizable to al1 people undergoing

surgery. Therefore, specific dernographic characteristics of

patients participating in preoperative teaching studies should

be examined to identify the patient population to which the

results can be generalized. This study provides a beginning

point in addxessing this gap in the empirical literature on

preoperative teaching.

Problem Statement

Canada is characterized by its diverse age, gender,

educational, ethnic and cultural composition. In particular,

the ethnic and cultural composition of North America has

increased dramatically over the past few decades (Immigration

and Citizenship Canada, 1997; U.S. Bureau of Census, 1995) - As such, this composition should be reflected in the samples of

research studies. Lack of attention to the diversity and the

trends in diversity of the population in research hinders

provision of quality care to patients of al1 backgrounds.

Therefore, research examining the impact and importance of

selected demographic characteristics on various outcomes of

interventions is warranted.

Research studies conducted since the 1960s have

demonstrated the effectiveness of preoperative teaching-

However, these studies appear to be limited in the demographic

representativeness of their samples. Thus, it is important to

identify the sample demographic characteristics in

4

preoperative teaching studies in order to determine the target

population to which the results of these studies can be

generalized. Also of importance is the assessrnent of variation

in outcomes of preoperative teaching in relation to these

dernographic characteristics.

Purpose of the Study

The primary purposes of this meta-analytic study are to

identify the demographic characteristics of patients who

participated in preoperative teaching effectiveness studies

and to assess the variation in outcomes of preoperative

teaching in relation to these demographic characteristics. The

significance of this study relates to its ability to provide

knowledge pertinent to the demographic characteristics of

these patients. This knowledge will assist in determining the

target population to which the results of these studies can be

generalized, and thereby, guide nursing practice related to

preoperative teaching for patients with different demographic

characteristics.

Additionally, this knowledge will contribute to the

development of knowledge in transcultural nursing by

indicating gaps in existing research and providing direction

for further research aimed at determining the effectiveness of

preoperative teaching in patients of various ethnic and

cultural groups.

Review of Related Literature

This section presents a review of the literature

pertinent to the central concepts of the study: preoperative

teaching, postoperative outcomes, and the general importance

of sample demographic characteristics in research-

PreQperati T - c U

The components of preoperative teaching that have been

addressed in the literature are the content, structure,

methods, presentation, and timing of teaching. A brief

overview of each component is given below.

Content of P r e s a t i ve T e a & i n g

Three types of preoperative teaching content were

addressed in the literature: procedural, sensory, and

behavioural. Procedural information relates to the sequence of

surgical, medical, or laboratory procedures (Suls & Wan,

1989). Sensory information includes information about

sensations that the patient will likely experience (Hathaway,

1986; S u l s & Wan, 1989) , whereas, behavioural information

includes strategies patients could adopt to improve

postoperative recovery (Allen et al., 1992; Felton, Huss,

Payne, & Srsic, 1976). Psychosocially supportive interventions

have rarely been considered as part of the preoperative

teaching. Psychosocially supportive interventions included a

combination of the following: (a) identifying and attempting

to alleviate concerns of individual patients; (b) providing

the patients with appropriate reassurance; (c) teaching

patients relaxation techniques; and (d) having a health care

provider available on more than one occasion to discuss

ongoing concerns and issues (Devine, 1992; Hathaway, 1986) . However, most of the primary studies and related meta-analyses

have not considered psychosocially supportive interventions as

part of preoperatîve teaching. Accordingly, similar

interventions were not included as part of preoperative

teaching in this meta-analysis.

Traditionally, the content of preoperative teaching

included only the procedural information (Allen et al., 1992) - Sensory and behavioural information as part of preoperative

teaching content began to be explored in research in the

mid-1970s (Johnson & Rice, 1974; Felton, et al., 1976;

Leventhal, 1982; Suls & Wan, 1989; Thornpson 1981). However,

there have been no conclusions in the literature as to the

best type of preoperative teaching content.

For example, Felton et al. (1976) found that behavioural

information increased patient satisfaction with preoperative

teaching. However, in patients who use denial as a coping

strategy, behavioural information has been shown to increase

heart rate (Shipley, Butt, Horwitz, & Farbry, 1978), use of

analgesics (Andrew, 1970), and frequency of complaints

(Delong, 1970) . In a comparison study, Zeirner (1983) concluded that neither behavioural nor sensory information was more

e f f e c t i v e t h a n t h e o t h e r ; b u t t h e i n c l u s i o n o f b o t h

behav iou ra l and s e n s o r y i n fo rma t ion had a more p o s i t i v e effect

on p o s t o p e r a t i v e r ecove ry t han p r o c e d u r a l i n fo rma t ion a lone .

Leventhal (1982) and Johnson ( 1 9 8 4 ) s t a t e d t h a t s e n s o r y

i n fo rma t ion i s more e f f e c t i v e t h a n p rocedu ra l i n fo rma t ion

a l though Thompson (1981) sugges ted t h a t b e n e f i t s of bo th k inds

of i n fo rma t ion are equa l . M i l l s and Krantz (1979) have

sugges ted t h a t p r o v i d i n g both s e n s o r y and p rocedu ra l

i n fo rma t ion can be overwhelming t o t h e p a t i e ~ t , whereas S u l s

and Wan (1992) i n t h e i r me ta -ana lys i s , concluded t h a t a

combinat ion o f such i n fo rma t ion i s more e f f e c t i v e t h a n e i t h e r

alone.

Based on t h e f i n d i n g s of h e r me ta -ana lys i s , Hathaway

(1986) sugges t ed t h a t t h e p r e o p e r a t i v e t e a c h i n g c o n t e n t shou ld

be adap ted a c c o r d i n g t o t h e p a t i e n t ' s l e v e l o f f e a r and

a n x i e t y . For example, s h e proposed t h a t p rocedu ra l i n fo rma t ion

i s b e n e f i c i a l f o r p a t i e n t s d i s p l a y i n g low f e a r and a n x i e t y

whereas p s y c h o l o g i c a l p r e p a r a t i o n i s b e n e f i c i a l f o r t h o s e w i th

h igh levels o f f e o r and a n x i e t y . I n f a c t , it has a l s o been

found t h a t p a t i e n t s have d i f f e r i n g p r e f e r e n c e s as t o t h e

e x t e n t and t y p e o f i n fo rma t ion t h e y want t o r e c e i v e (Krantz ,

Baum, & Widernan, 1 9 8 0 ) - C a l d w e l l (1991a; 1991b) proposed t h a t

t o o much o r t o o l i t t l e i n fo rma t ion canno t be e f f e c t i v e for

certain p a t i e n t s .

StrtlGtl~r@ of P r e o D e r a t i _ v g G ,

Preoperative teaching can be provided in a structured or

an unstructured manner. Structured preoperative teaching

involves a single teaching plan with previously established

content, method and/or visual aids. Unstructured preoperative

teaching, on the contrary, is teaching according to what, how,

and when the nurse decides. Lack of a formal or uniform plan

in unstructured teaching creates inconsistency and vagueness

in the content provided (Hathaway, 1986; Lindeman & Van

Aernam, 1971) . Research indicates that in comparison to unstructured

teaching, structured preoperative teaching results in better

patient outcomes. Some of these outcomes are improved ability

to deep breathe and cough postoperatively (Lindeman & Van

Aernam, 1971; King & Tarsitano, 1982) ; decreased use of

analgesics (Lindeman & Van Aernam, 1971); improved patient

comfort (Fortin & Kerouac, 1976); and decreased length of

hospital stay (Lindeman & Van Aernam, 1971) . However, a significant reduction in the mean length of hospital stay was

not found in the King and Tarsitano (1982) study. Further,

Hathaway (1986), in her meta-analysis, noted that the "effect

sizes in the structured category represented primarily

procedural content and effect sizes in the unstructured

category represented primarily psychological content" (p.271).

She stated that no conclusions regarding the structure and

9

organization of preoperative teaching could be made since the

level of structure and the content of preoperative teaching

are often confounded.

Information booklets, videos, films, and slides, either

general in content or specific to a particular type of

surgery, are currently used for teaching preoperative

information (Allen et al., 1992; Miner, 1990; Rice & Johnson,

1984).

Preoperative telephone calls entai1 a nurse calling the

patient one to four nights prior to the surgery to assess the

patient's knowledge of the procedure and to provide

preoperative teaching accordingly. Miner (1990), who conducted

a survey involving 15 hospitals across the United States,

stated that telephone calls are the most common preoperative

teaching method in the United States, However, no related

research studies were found.

Another method of delivering preoperative teaching is by

home visits by a nurse (Lindeman & Stetzer, 1973; Miner, 1990;

Shelter, 1972; Wallis, 1971). A literature review demonstrated

contradictory results. For instance, home visit was found to

be an excellent educational method that also promotes

continuity of case throughout the perioperative period in the

King and Tarsitano (1982) study. However, Lindeman and

Stetzer's (1973) study that involved preoperative home visits

10

to 176 patients by operating-room nurses showed that there was

no significant difference made by the visits as measured by

indices such as length of hospital stay, amount of analgesics

used, or level of anxiety.

Only a few researchers have examined the effectiveness of

mailed information versus preoperative teaching provided on

the unit (Mikulaninec, 1987; Rice 6 Johnson, 1984) . Mikulaninec's (1987) study found that patients who received

mail information had higher mean scores on the surgical

checklist than those patients who received preoperative

teaching only a f t e r admission, Additionally, mailed

information promoted independent learning, reduced nursing

time required in teaching surgical exercises, and often

involved family members in learning (Mikulaninec, 1987; Rice &

Johnson, 1984). However, further studies are necessary to

assess the effectiveness of this method in cornparison to the

other educational methods that have been used more frequently.

n of Prp

Group preoperative teaching, in contrast to individual

teaching, has been examined by several authors (Crabtree,

1978; Lindeman, 1972; Meyzanotte, 1970). Group teaching

involves tours and classes offered for a group of patients to

provide preoperative teaching (Miner, 1990) . Although group teaching lacks individualization and depends on patients'

motivation to participate, it is found to be more efficient

and as effective as individual teaching (Crabtree, 1978;

Lindeman, 1973; Miner, 1990) . In contrast, Hathaway (1986) , in her meta-analysis noted that "over half the individual

instruction effect sizes were greater than even the largest

group instruction effect size" (p.271). However, this

conclusion was based on the results of only a few studies

which examined the effect of group teaching unlike the larger

percentage of studies that have been conducted on individual

teaching. Meyzanotte (1950) found that a combined approach,

i f individual and group, was more beneficial for some

patients.

The effects of timing of preoperative teaching have been

examined by several researchers (Christopherson h Pfeiffer,

1980; Fortin & Kerouac, 1976; Rice & Johnson, 1984) . In recent years, the length of preoperative hospital stay has been

reduced due to fiscal restralnts (Allen et al., 1992; Cupples,

1991; Mikulaninec, 1987) . Patients are, in most cases, now being admitted to hospitals the day before or on the same day

of surgery. Thus, a very limited amount of time is available

for post-admission preoperative teaching.

In addition to the decreased time available for teaching,

the fear and anxiety due to various tests, procedures and

preparations, as well as the stress of hospitalization itself

may impede patientfs learning just prior to surgery (Cochran,

1984; Jader & Lekander, 1987; Levesque, Grenier, Kerouac, &

Reidy, 1984; Pieppex, 1985; Volicer, 1974) . Other researchers have suggested that learning is minimal when a situation is

too stressful or anxiety-provoking for the person (Redrnan,

1980; Sarason, 1975; Schrankel, 1978) . As a result of these concerns, some of the teaching is generally conducted in out-

patient (pre-admission) clinics.

In cornparison to the large number of studies that

examined post-admission teaching, only a few studies examined

the effectiveness of pre-admission teaching (Butler, Hurley,

Buchanan et al., 1996; Christopherson & Pfeiffer, 1980;

Johnson, 1984; Lamarche, Taddeo, & Pepler, 1998; Rice &

Johnson, 1984; Wallace, 1984). Most of the published

literature on pre-admission teaching thus far has been

descriptive or experiential (Connaway & Blackledge, 1986;

LeNoble, 1991; Rost, 1991). However, the available research

studies have demonstrated that preoperative teaching improves

postoperative outcomes regardless of the time of teaching. For

example, pre-admission teaching was found to improve mood

(Rice, Mullin, & Jarosz, 1992), exercise performance (Rice &

Johnson, 1984), decrease anxiety (Kempe & Gelazis, 1985) and

length of hospital stay (Persaud & Dawe, 1992). Further,

Levesque et al. (1984) found no statistically significant

difference between the groups who had pre-admission teaching

and post-admission teaching. Somewhat similarly,

Christopherson & Pfeiffer (1980) found that preoperative

teaching carried out one to two days prior to surgery was as

effective as the teaching carried out one to three weeks prior

to surgery.

Pos+QQexa+ive O ' l t c m

A review of related literature demonstrates that

preoperative teaching improves postoperative outcomes in

patients undergoing surgery. Some of these outcomes include

decrease in postoperative vomiting (Dumas & Leonard, 1963);

decrease in postoperative pain (Egbert et al,, 1964); decrease

in length of hospital stay (Lindeman & Van Aernam, 1971; Wong

& Wong, 1990); decrease in fear, anxiety, and uncertainty

associated with surgery (Shipley et al., 1978); decrease in

incidence of medical complications; early ambulation and early

resumption of normal activities (Healy, 1968) . Outcomes can be divided into four broad categories:

1) recovery (physical outcomes); 2) psychological outcomes;

3) psycho-physiological outcomes; and 4) knowledge and s k i l l s

performance. Included in the recovery category are length of

hospital stay, acute postoperative hypertension, acute

pulmonary complications, adulation and resumption of normal

activities. Psychological outcomes include anxiety, fear,

stress, depression, and distress. Outcomes included in the

psycho-physiological category are pain, anxiety about gagging,

anxiety about nausea, and self-rating of cornfort. Finally, the

knowledge and skills performance outcome category included

patient's ability to demonstrate proper deep breathing and

coughing techniques, ability to accurately use patient

controlled analgesia (PCA), or ability to perform leg

exercises (Devine, 1992; Devine & Cook, 1983, 1986; Hathaway,

1986).

In addition to the above mentioned primary studies, these

outcomes have further been examined in seven previously

published meta-analyses. A brief review of these is provided

below .

Seven related meta-analyses have been conducted since

1980: Mumford, Schlesinger, & Glass in 1982; Smith & Naftel in

1984; Devine & Cook in 1983 and 1986; Hathaway in 1986; Suls &

Wan in 1989; and the latest by Devine in 1992. A l 1 of these

meta-analyses except Suls and Wan (1989) examined the

effectiveness of psychoeducational interventions, that is,

psychosocially supportive interventions in addition to the

teaching interventions.

The results of these meta-analyses demonstrate the

following postoperative outcomes: decreased fear and anxiety

(Hathaway, 1986); increased patient satisfaction with care

(Devine & Cook, 1986; Hathaway, 1986); irnprovement in

physiological variables such as vital capacity and pulmonary

f unction (Hathaway, 198 6) ; decreased postoperative

15

complications, and decreased pain and amount of analgesics

used (Devine & Cook, 1986). In the meta-analysis by Mumford et

a1.(1982), psychoeducational interventions were found to

decrease length of hospital stay. However, conflicting results

were found in the meta-analyses by Devine and Cook (1983,

1986). That is, a significant decrease in length of hospital

stay was found in the primary studies reported prior to 1975,

but not in the primary studies reported from 1975 to 1985.

Mumford et al. (1982) concluded that a combined

psychoeducational approach is more effective (effect size (ES)

= 0.65) than one single approach (ES for psychosocial = 0.41,

and for educational = 0.30). Smith and Naftel (1984) conducted

a secondary analysis of the Mumfoxd et al. (1982) data with a

resulting mean ES of 0.49 for the 210 outcome indicators, and

a mean ES of 0.55 for nurse-prcvided interventions and 0.37

for non-nurse-provided interventions.

Devine and Cook's ( 1983) meta-analysis showed that

psychoeducational interventions brought about an estimated

1 1/4 days reduction in postoperative hospital stay.

Hathaway's (1986) meta-analysis demonstrated that patients who

received preoperative teaching had overall 20% more favourable

physiological, psychological, psycho-physiological

postoperative outcomes. The large variance associated with

mean effect sizes indicated that the findings were not

consistent across the studies selected for the meta-analysis.

16

The fifth related meta-analysis which was conducted by

Devine and Cook (1986), showed statistically reliable and

positive effects for each of the four classes of outcome

measures: recovery, pain, psychological well-being, and

satisfaction with hospital care.

Suls and Wan (1989) examined the effects of sensory and

procedural information on coping with stressful medical and

surgical procedures and pain, This study showed that

preoperative teaching was most effective on coping outcornes

when both procedural and sensory information were included in

preoperative teaching.

The most recent meta-analysis conducted by Devine (1992)

reconfirmed the overall effectiveness of psychoeducational

interventions with a larger sample of studies (n=191). She

claimed that despite the recent changes in health care

delivery, small to moderate (beneficial) effect sizes continue

even in the most recent studies.

c-s of Patient?

Patients seen in everyday practice are unique individuals

who may not necessarily share the same demographic

characteristics. Demographic characteristics such as age,

gender, ethnicity, level of education, learning style,

preference for information, socioeconomic status, and support

systems can influence health related interventions (Burns &

Grove, 1993, Sidani & Braden, 1998). As such, patients may or

17

may not respond to the same intervention equally. Therefore,

individual differences must be acknowledged and examined in

research in order to guide practice.

Of importance in this meta-analytic study are the

demographic characteristics age, gender, level of education,

and ethnicity of patients. The importance of each

characteristic relative to care, treatment, and intervention

outcomes is addressed below.

Aae

Age has been proposed to affect intervention outcomes

directly or indirectly (Sidani & Braden, 1998). The indirect

effect of age on learning (for instance, effect of age on

anxiety and effect of anxiety in turn, on learning) has been

demonstrated in studies (Lundeman, Asplund, & Norberg, 1990;

Payne, 1992; Griesbach, 1985).

Preoperative teaching was found to be ineffective for

children under the age of eight in the Melamed, Dearborn, and

Hermecz (1983) study. Further, Brown (1992) found a

statistically significant inverse relationship between the age

and knowledge outcomes of patients with diabetes receiving

psychoeducational interventions. However, no primary studies

have been conducted to examine the direct effect of age on the

effectiveness of preoperative teaching outcornes in adults.

Therefore, studies examining the effectiveness of preoperative

teaching on different age groups are needed.

Historically, women were not included in research,

assuming that the results of studies of men are equally

applicable to women (Bell, 1997; Jensen, 1997 ; Smeltzer,

1992). Men and women may react differently to the same

situation, cope differently with the same illness, and respond

differently to the same medications or the same interventions.

Therefore, health care interventions and treatments based on

studies that included men exclusively may not be effective for

women in general, women of different age groups, or women from

different ethnic and cultural backgrounds, For example,

Richardson, Evans, and Warner (1994) conducted a study on the

f ect written information the perception pain

electromyography. Their study showed that providing

information about the test "significantly decreased pain

perception for women the nerve conduction studies, but

not dur ing the needle examination" (p. 671) , However, a similar

effect was not observed in men. Other results from the same

study indicated that women perceived the test as more painful

than did men. As such, it is imperative to examine the effects

of gender differences in educational intervention studies.

Jtevel of E d u c a + f ~

People vary in their learning needs, learning patterns,

and level of education. Stephens (1992) pointed out that a

discrepancy exists between the reading level of the average

19

adult which is between the 5th and 8th grade level, and the

reading level of the printed health-related materials which is

between the 8th and 12th grade reading levels. In fact,

studies show that most educational material is at the upper

range of grade 8 to 12 reading level (Davis, Crouch, Wills,

Miller, Abdehou, 1990; Meade & Byrd, 1989; Miller & Bodie,

1994; Stephens, 1992; Streiff, 1986). No Canadian studies that

examined the readability of patient education were found in

the literature.

People also Vary in their English language knowledge and

comprehension and therefore, preoperative information

delivered in English may not be as effective for every one.

Beiser (1988) pointed out that, in Canada, about 90% of female

refugees and an almost equal percentage of male refugees speak

neither English nor French. On the other hand, people who have

had a university education, even in countries where English is

not the everyday language, can be exposed to English as the

language of academia. Their reading and comprehension level,

and understanding of complex or technical language may be

equal to or even better than those who have less than grade

eight education in Canada. In addition, those who have had a

university education in Canada, but in a non-scientific

discipline, such as History, for example, may experience

difficulty in understanding the medical and nursing jargon

commonly used in hospitals. Dixon and Park (1990) commented

that much of the patient education material is "highly

technical".

Owing to the reduced length of hospital stay as w e l l as

reduced nursing time spent per patient, nurses rely on printed

materials to reinforce or even to supplement formal patient

teaching. As a result, nurses rely increasingiy on patients '

ability to read and understand preoperative teaching

materials, and their willingness to actively participate in

their care. Consequently, research assessing the impact and

the importance of patients' level of education, English

language knowledge as well as the readability level of

preoperative teaching materials is needed.

During the last two decades, the influx of over a

hundred thousand immigrants and refugees every year has

increased the concentration and diversity of the ethnic

composition of both Canada and the United States. In the 1991

census , 27% of the Canadian population reported ethnic origins

other than British, French, or Aboriginal. Only 29% of the

population reported British; 24% reported French; and 4%

reported aboriginal backgrounds. It wos predicted that by the

year 2000, one in every three people in the United States

(Grossman, 1994) and one in every five people in Canada

(Shareski, 1992) will be non-white. This indicates the

21

importance of understanding the impact of cultural diversity

in the health care system and the need to adopt culturally

congruent care in nursing.

Culture and ethnicity shape people's view of health and

illness, their health-seeking behaviours, their use of health

care services, their selection and adherence to a treatment

modality, and their expectations of that treatment (Ahmann,

1994; Grossman, 1994; Leininger, 1991). Moreover, certain

religious beliefs may restrict or prohibit available treatmenc

choices or procedures; for example, Jehovah's Witnesses do not

accept blood transfusions (Grossman, 1994). In such

situations, information about possible postoperative

complications, the consequences of these complications if not

treated, and available treatments need to be addressed in

preoperative teaching.

Further, in some cultures, men in particular are expected

to tolerate pain without outward expression of it. Zola

(1966), and Zborowski (1969) found major differences in pain

expression, tolerance, and perception among cultures. These

differences need to be addressed and acknowledged in

preoperative teaching effectiveness studies. For example, a

woman whose cultural or religious beliefs include pain and

suffering to be a result of "bad karman may not request

analgesics. The importance and impact of such beliefs on the

validity of the amount of analgesics used by patients in

preoperative teaching studies need to be examined.

Similarly, the patient-care giver roles and relationships

and the importance given to active patient participation in

care rnay Vary between cultures (Kleinman, 1980; Leininger,

1991). For example, in Canada, patients are expected to voice

their concerns and actively participate in their care.

However, in some other cultures, older patients rnay depend on

their children (O'Hara & Zhan, 1994; Turkoski, 1985) or

husbands rnay depend on their wives to care for them during

their hospitalization, and rnay be reluctant to participate

actively in their own care and in their preoperative learning.

In such cases, an emphasis on teaching the patient, instead of

the family rnay not be effective, Additionally, recent

immigrants and refugees rnay feel that their active

participation in an unfamiliar health care system may

jeopardize their care. (Guruge & Donner, 1996) . Further, variations within ethnic and cultural groups rnay

occur due to factors such as age, gender, educational level,

birth place, and religious affiliation (Lea, 1994; Masi,

Mensah, & McLeod, 1993). For example, South Asian immigrants

(across countries such as India, Sri-Lanka, Bangladesh, and

Pakistan) from urban settings are likely to be more fluent and

literate in English than those from the rural settings

(Rajwani, 1996). These dernographic characteristics are in many

ways intertwined and cannot easily be separated into simple

23

and isolated groups. Therefore, it is important to consider

the impact and the importance of each demographic

characteristic as well as compounding effects of several

demographic characteristics.

The following is a brief presentation of the meta-

analyses that examined the impact or the importance of

individual differences and demographic characteristics in

preoperative teaching.

Three of the seven meta-analyses commented on the

possible effect of individual differences on the outcornes of

psychoeducational interventions. These three meta-analyses

were conducted by Mumford et al. (1982), Hathaway (1986) and

Suls and Wan (1989) , Mumford et al. (1982) pointed out that

patients cope with emotional acd physical stress differently

and that they may benefit most from interventions that

complement their particular coping styles. They further added

that this may be the reason for the increased effectiveness of

the psychoeducational approach (which combines both teaching

interventions and psychosocially supportive interventions) in

comparison to teaching alone. Suls and Wan (1989) concluded

that the confidence intervals for some comparisons included

negative effect s i z e s . Therefore, pre-operative teaching

should not be considered as universally helpful, despite the

average positive effect size. Hathaway (1986) commented that

"the multitude of situational variables surrounding the

preoperative experiences undoubtedly are major contributors"

to the large variances associated with effect s i ze s (p.274).

Two other meta-analyses (Devine, 1992; Devine & Cook,

1986) examined the effect of some of the selected dernographic

characteristics. In her meta-analysis, Devine (1992) described u

the participants of the preoperative teaching studies in terms

of their age and gender characteristics. Most of the studies

(68%) examined included both males and fernales, Their average

age ranged between 29-76 years, and in fact, the average age

ranged between 41-50 years for half (48%) of the patients.

However, the effects of the age and gender of the patients who

participated in the studies on the outcomes of preoperative

teaching were not examined in this meta-analysis.

Devine and Cook (1986) examined the generalizability of

the cost-related effects of preoperative teaching as indicated

by the length of hospital stay and the incidence of medical

complications in 50 studies. They divided the patients in

their sample of studies into three categories of age groups:

1) 18-40; 2) 41-50; 3) 51-80. The 18-40 year old group had an

Effect size (ES) of +0.61 with a standard deviation of 0.34,

and the 51-80 year old group had an ES of +0.63 but with a

standard deviation (SD) of 0.67, whereas the 41-50 year old

group had an ES of +0.43 with a SD of 0.34. These results

demonstrated that the magnitude of the effectiveness of

2 5

preoperative psychoeducational interventions varied depending

on the age of the patients. In addition, Devine and Cook

(1986) grouped the studies into those with samples of al1

male, 1-49% of female, 50-998 female, and al1 female. The al1

male group had an ES of 0.33 with a SD of 0.30, and in

cornparison, the al1 female group had an ES of 0.60 with a SD

of 0.40. Although they found cost-related effects in both male

and female groups, the effectiveness of preoperative

psychoeducational interventions clearly varied between groups.

In conclusion, although only two meta-analyses described

the age and gender of the patients who participated in the

primary studies included in their samples, only one meta-

analysis (Devine & Cook, 1986) examined the effects of these

on the outcomes of preoperative psychoeducational

interventions. The results of the latter study demonstrated

that age and gender influenced the cost-related outcornes of

preoperative psychoeducational interventions. However, none of

the meta-analyses examined the importance or the impact of

education or the ethnicity on the outcomes of preoperative

teaching .

The Conceptual Framework

The conceptual framework that guided this study is

illustrated in Figure 1 on page 31. The three concepts that

axe of interest in this meta-analysis are presented below to

explain the theoretical and operational systems in the

research design.

P r - ~ p r a + ive Teach iaQ

The first concept is preoperative teaching which is

defined as providing information about the perioperative

experience, Preoperative teaching varies in the content

presented to patients, in the method of teaching, in the

presentation of the information, and in the time of teaching.

The content of preoperative teaching can be either

procedural, sensory, behavioural, or a combination of these.

Procedural information includes the sequence of procedures

that occur (Suls & Wan, 1992); sensory information includes

the sensations that the patient will likely experience

(Hathaway, 1986) during the perioperative period. Behavioural

information is about the skills and strategies patients can

adopt to improve their recovery (Felton et al., 1976).

The method of teaching could be any of the following:

providing written materials; showing a videotape, film, or

slides; mailing preoperative information to the patient;

making home visits or telephoning the patient at home to

provide necessary information prior to surgery ilen en et al.,

27

1992; Miner, 1990; Rice h Johnson, 1984; Mikulaninec, 1987;

Shelter, 1972; Wallis, 1971).

The presentation of preoperative information is described

in terms of first of all, being done in a structured or

unstructured format, and secondly, being conducted in an

individual or group session. Structured preoperative teaching

involves a single teaching plan that has been previously

established for its content and method; unstructured

preoperative teaching is providing information without such a

plan (Hathaway, 1986; Lindeman 6L Van Aernam, 1971) . Further, the presentation of preoperative information can be done by

having face-to-face contact where a nurse presents and

discusses related information with each patient individually

or with a group of patients (Crabtree, 1978). The last

component of preoperative teaching is the timing of teaching

which can either be pre-admission or post-admission (Fortin &

Kerouac, 1976; Rice & Johnson, 1984) . The above mentioned information regarding the components

of preoperative teaching was systematically extracted £rom

each study as summarized in Table 1 provided in Chapter 2 on

page 38- The details of this process are also provided in

Chapter 2.

t n ~ ~ r a t i v e O u t c m

The second concept of interest in this meta-analysis is

postoperative outcomes. Postoperative outcomes are defined as

28

the changes in the patient's condition occurring in the period

following surgery while the patient is still hospitalized. The

postoperative outcomes relate to the recovery, psycho-

physiological well-being, psychological well-being, and

knowledge and skills performance of patients (Devine, 1992;

Hathaway, 1986) . Of these, only the most prevalent outcomes categories, nameiy: recovery, psycho-physiological well-being,

and psychological well-being were chosen for the purposes of

this meta-analysis. Under each category, the postoperative

outcomes that have been most frequently measured in the

literature -- length of hospital stay, pain, and anxiety -- were chosen to represent the effectiveness of preoperative

teaching . The goal of preoperative teaching is to assist patients

in their postoperative recovery by instructing them in ways to

manage their pain and anxiety, and subsequently to improve

recovery that would reduce the length of hospital stay. Pain

is defined as 'an unpleasant sensory and emotional experience

associated with actual or potential tissue damage, or

described in terrns of such damage" (Merskey & Bogduk, 1994,

p. 210). Anxiety considered here is state anxiety which is

defined as "subjective feelings of tension and apprehension

... that are experienced in situations perceived as threatening" (Spielberger, Gorsuch, & Lushene, 1970, p. 52) . Length of hospital stay is defined as the "number of days the

patient remained in hospital, starting the day following

surgery and up to and including the day of discharge"

(Spalding, 1995, p.528).

The third concept of interest in this meta-analysis is

the patients' personal attributes or dernographic

characteristics that may influence the delivery as well as the

effectiveness of preoperative teaching in achieving the

desired outcomes. Some of the demographic characteristics

which influence health related intervention outcomes are age,

gender, ethnicity, level of education, socioeconomic status,

learning style, and preference for information (Burns & Grove,

1993, Sidani & Braden, 1998) . Of these, the age, gender, educational level, and ethnicity of patients are of interest

in this meta-analysis. These four characteristics were chosen

not only because of the importance of these characteristics in

nursing practice, but also because the effect of these four

characteristics have received very little attention in many

intervention studies. The specific details of the extraction

process as well as a summary of the data extracted from each

study are presented in Table 1 provided in

Chapter 2.

The direct effect of preoperative teaching on each of the

post-operative outcomes, LOS, anxiety, and pain and variation

in these outcomes in relation to each of the dernographic

character is t ics of p a t i e n t s w e r e examined in this meta-

analysis .

Figure 1

An illustraition of the conceptual framework

i I preop teaching postop outcornes

I

demographic characteristics

components of preoperative

teaching

patient outcomes: LOS, pain,

l anxiety

age, gender, ethnicity, education '\/-'+

Research Questions

This meta-analytic study was designed to address the

following research questions:

1) What are the selected demographic characteristics of

patients participating in studies that examined the

effectiveness of preoperative teaching on postoperative

outcomes?

* What is the proportion of patients in different age

categories?

* What is the proportion of male and female patients?

.~r What is the proportion of patients with different

educational levels?

* What is the proportion of patients from different ethnic

and cultural backgrounds?

2) What are the effects of the selected demographic

characteristics on the outcomes of preoperative teaching

intervention?

* What are the magnitudes of the treatment effect of

preoperative teaching on LOS, anxiety, and pain outcomes

in adults undergoing surgery?

* What are the effects of age, gender, level of education,

and ethnicity of patients on LOS, pain, and anxiety

outcomes?

- Research studies examining the effectiveness of

preoperative teaching on various postoperative outcornes have

been conducted since the 1960s. However, a review of related

literature indicated that these studies are limited in the

demographic representativeness of their sarnples and the

generalizability of the results of the studies to al1 patients

undergoing surgery. Also, only two of the seven previously

published meta-analyses have examined the variation of the

effects of preoperative teaching in relation to age and

gender. None of the related meta-analyses examined the effects

of education and ethnicity on the outcornes of preoperative

teaching.

Therefore, this meta-analysis was conducted to examine:

(a} the demographic characteristics of the participants in

preoperative teaching effectiveness studies, and (b) the

influence of age, gender, education, and ethnicity on LOS,

anxiety, and pain outcornes. The next chapter gives an overview

of the study design that was used in answering these two

research questions.

CHAPTER 2:

OVERVIEW OF THE STUOY DESIGN

Valid and xeliable conclusions derived from research

studies, as well as generalizations made from the findings to

a diverse patient population are important in providing

quality nursing care. In order to apply study results to

patients seen in everyday practice, it is important to examine

sample representativeness of the studies, A small sample size

and sample selection criteria in individual studies may limit

its representativeness of patients witn different demographic

characteristics. Therefore, a synthesis of related literature

was conducted in order to examine the demographic

characteristics of patients who participated in studies that

evaluated preoperative teaching.

This chapter outlines the methodology and criteria for

sample selection, and the procedures for the synthesis of data

obtained £rom the studies included in this meta-analysis.

Sample Selection

The sample for this meta-analysis consisted of studies

that evaluated the effects of pre-operative teaching. The

studies were classified into two categories. The first

category included al1 relevant and accessible studies

conducted from 1956 to 1989 that were examined in the seven

meta-analyses discussed in Chapter 1. The second category

included al1 relevant and accessible studies published from

1989 to 1997 which were not examined in any known meta-

analyses. Recent studies in the second category, in comparison

to those included in the first category, were expected to have

included more patients from various ethnic and cultural

backgrounds since the importance of culture and ethnicity in

research has been stressed recently by many health care

professionals (Guruge & Donner, 1996; Sidani & Braden, 1998;

Leininger, 1991) and funding agencies for example, National

Institute for Health.

The sample included al1 retrievable studies that met the

following inclusion criteria: (a) the effect of preoperative

teaching on postoperative outcomes was examined ( L e .

preoperative teaching as an independent variable and the

postoperative outcomes (LOS, anxiety, and pain) as dependent

variables); (b) the sample consisted of adult patients

undergoing surgical procedures or invasive diagnostic

procedures such as cardiac catheterization; (c) an

experimental design that included both experimental and

control groups; (d) the same setting was used for both

experimental and control groups; and (e) patients in the

control group received either usual care that is, routine

preparation, or placebo.

In addition, the studies sampling same-day surgeries were

excluded from this study for the following reasons: first of

all, same-day surgeries involve teaching that is conducted

during patients' visits to clinics; secondly, same-day

surgeries are frequently conducted under local anesthesia, and

are associated with lower risk of severe complications; and

thixdly, the postoperative outcome of LOS is not applicable in

the case of same-day surgeries.

Also, this study included only the studies that were

published in journals or books, and were written in English. A

preliminary search using Dissertation Abstracts International

indicated that over 95% of the unpublished theses and

dissertations that were completed irom 1980 to 1990 would not

meet the inclusion criteria for this meta-analysis. For

instance, they may not have included a control group, may have

chosen children, or may have included psychosocially

supportive interventions under the category of preoperative

teaching. Further, most of the unpublished studies conducted

from 1990 to 1997 were concerned with same-day surgeries.

However, the inclusion of published studies only is not

expected to result in large systemic bias, A review of meta-

analyses conducted by Lipsey and Wilson (1993) indicated that

using only the published studies "does indeed upwardly bias

treatment effect estimates . - . The amount of that bias, however, does not appear to be large enough to account for the

generally positive findings" (p.1195). Similar comments were

made by Preiss and Allen (1995) in an article titled

37

"Understanding and Using Meta-analysisff. In fact, several of

the previously published related meta-analyses demonstrated

that the differences of the effect sizes of the postoperative

outcornes between the published and the unpublished studies

were not considerably large (Devine & Cook, 1983; Devine &

Cook, 1986; Mumford et al., 1982) . dol- foy Sypple Sehction

Reference lists of the seven meta-analyses were explored

for individual studies that could be included in this study

under the first category. The studies published from 1989 to

1997, that is, those that belong to the second category, were

identified by computerized searches using CINAHL, MEDLINE, and

HEALTH STAR. The terms preoperative, education, and teaching

were used in this search.

Procedures for Data Analysis

Data analysis for this study included both descriptive

and quantitative syntheses. The descriptive synthesis of data

across the studies that met the inclusion criteria of this

meta-analysis was used in answering the first research

question defined in Chapter 1. An outline of this procedure is

provided next followed by a detailed description of the

procedure for the quantitative synthesis. The quantitative

synihesis of data £rom the studies was used in answering the

second research question.

for D a + a -tim

Table 1, presented below, depicts the method that was

used to extract and categorize information pertinent to each

variable of interest £rom the individual studies.

Table 1

1 Information extracted

Author

1 year of publication 1 study design

1 sample description:

education

ethnic/cultural (or racial)

timing of teaching

method of teaching f I outcomes measured

Categories

name of the first author

actual year

experimental/ quasi-experimental

number ( # ) of patients consented # of patients withdrew final sample size

range, msasures of central tendency (mean, median, or mode) 6 SD

# of males 6 fernales

years/level of education # of patients in each category

# of patients in each category

type of teaching as reported: structured/ non-structured

timing of teaching as reported: pre-admission/ post-admission

method of teaching as reported: mailed information/ on unit home visits/ telephone calls individual/ group teaching

. .

actual outcomes as reported in each studv

M e t h Q C b b P y fo r D a t a C ; W s j s

Data analysis consisted of descriptive statistics.

Specifically, the data obtained from individual studies were

categorized into percentages or frequencies. With regard to

the independent variables, for example, the frequencies and

percentages of studies that included each component of the

preoperative teashing were calculated.

With regard to the demographic characteristics, measuxes

of central tendency (mean, median, or mode) repcrted in each

study were used to represent continuous variables reflecting

its sample demographic characteristics, For variables that

were measured with either a continuous or a categorical scale,

such as education (number of years or highest level of

education attained), either type of information was extracted

and the continuous scale was c~nverted to a categorical one.

For categorical variables, the modal category with the largest

percentage was used. For example, categories of the ethnicity

of the study participants were defined as 1-25% white, 26-50%

white, 51-75% white, 76-99% white, al1 white, and al1 non-

white'.

With regard to the outcome variables, information that is

needed to calculate effect size, such as sample size, mean and

Most primary studies have reported race of their study p a r t i c i p a n t s instead of t h e e t h n i c i t y or cultural background. Therefore, the c a t e g o r i e s described here are racial.

4 0

standard deviation of the experimental and the control groups

was extracted. When standard deviations of the groups were not

readily available in individual studies, effect sizes were

calculated from other statistics such as t or F values using

the techniques described in detail in Part If of Appendix A.

When none of the required information could be derived from

the individual studies to calculate effect size values, then

the direction of effect sizes as reported in the individual

studies was considered. For instance, if the results of a

study indicated that preoperative teaching had a significant

effect, a positive sign was assigned; if the results indicated

lack of a significant effect, a value of O was assigned.

t i t a t i v i r Svgthes-

Quantitative synthesis used in this meta-analysis

consisted of two approaches, namely, frequency count and

statistical approach. The frequency count approach was used

first as a preliminary step in identifying patterns occurring

as a result of the effects of the demographic characteristics

on the outcomes of preoperative teaching. The frequency count

approach permitted the inclusion of al1 the studies reviewed

including those that did not provide the information needed to

calculate an effect size, In cornparison, the statistical

approach was then used to calculate the magnitude of the

effects of preoperative teaching in LOS, anxiety, and pain

outcomes, and the variation of these outcomes in relation to

the selected demographic characteristics. Explanations of

these two methods are provided in the following sections,

The procedure for the frequency count approach included a

tabulation of the categories of each demographic variable

against the categories of the statistical significance of each

outcome variable, that is, statistically significant

(beneficial effect) in the hypothesized direction (+) versus

statistically non-significant (0). This classification of the

intended outcornes permitted inclusion of al1 20 studies,

including those that did not report the statistical data

required for computing the effect size, in the frequency

count ,

The frequency count within the cells cornprishg the table

was examined. Comparisons of the frequency count across the

cells in the table formed the basis of a preliminary strategy

in identifying relationships between demographic

characteristics and the outcornes of preoperative teaching. The

results obtained £rom the frequency count approach were

verified using the statistical methods described below.

The principal reason for pooling quantitative information

across studies is that in fields such as nursing where the

effect of a treatment is of a moderate size, the sample sizes

of individual studies might not be large enough in most cases

4 2

to produce any statistically significant results. For example,

Table 1.7 in Hedges and Oiein (1985) shows that even when

there is a positive effect of magnitude of 0.5 in the

population, that is, the "true effect size" is 0.5, the

probability a study from that population with a sample size of

20 producing a statistically significant result is only 0.463-

In other words, almost half of such studies may not produce

any significant result, However, the quantitative information

from such studies can be pooled to arrive at a significant

result using meta-analytic techniques.

Statistical rnethods to combine quantitative information

across studies have been in existence since at least as early

as the 1930s (Hedges & Olein 1985; Cooper & Hedges 1994). The

term Meta-Analysis was coined in the 1970s to separate these

methods £rom the statistical techniques usually used at the

level of individual studies. Almost from the beginning, these

methods hâve taken two different directions. One approach

depends on testing for statistical significance of combined

results across studies, and the other relies on estimating

treatment effects across studies. The latter one is more

attractive because it not only provides evidence for a

treatment effect, but gives a rneasure of how much of an effect

a treatment has; this is generally called an effect magnitude.

Two indices of effect magnitude are commonly in use. One

is the product-moment correlation coefficient and is used in a

meta-analysis of correlational studies. The second one is the

effect size and is used when the individual studies to be

combined are experimental.

The rneta-analytic techniques that use effect magnitude

branch into two separate paths depending on the structural

model under which the individual studies are examined. One is

called the Fixed Effect Model and the other the Random Effect

Model. The Random Effect Model is more complex, and allows for

one more level of random variation than what is assumed in the

Fixed Effect Model. However, as in any analysis, use of a

complex, time consuming model is necessary only when the

results obtained using a simpler model are unsatisfactory. For

example, in this particular case, if the effect magnitudes

obtained from a group of studies using the Fixed Effect Model

are not hornogenous, then a better insight into the problem

might possibly be obtained by the use of the Random Effect

Model. As a result, the simpler, Fixed Effect Model is used in

this meta-analysis.

A meta-analytic technique based on the Fixed Effect Model

that obtains a least variant estimate of the effect size

parameter is used in this study. Effect size estimates

calculated £rom individual studies were combined in a linear

fashion to obtain an estimate of the population effect size. A

detailed description of a rigorous developrnent of the

4 4

statistical models, definitions and concepts, together with

the underlying assumptions, resulting formulas and the

precision of the estimates, is given in Appendix A, Only a

brie£ outline of these procedures (which does not include the

mathematical details and formulas) is given below.

First, an effect magnitude of the preoperative teaching

intervention on the outcome variable is obtained by taking the

difference of the means of the outcome variable of the

experimental and control groups. This difference is divided by

the pooled standard deviation of the control and experimental

groups. Since the means and the standard deviation have the

same units, the resulting statistic, called effect size, iç

scale free and facilitates combining quantitative evidence

from a number of studies that may have used different scales

of measurements.

The effect size obtained this way is modified by

multiplying it by a number which is slightly less than unity,

that depends on the sample size of that study in order to

correct for a possible bias resulting from a small sample

size, The modified effect sizes obtained from individual

studies are linearly combined to produce a single estimate of

the population effect size parameter, Crucial in this

combination are the weights given to individual studies. As

explained in Appendix A, these weights are chosen so as to

minimize the variance of the resulting single effect size

4 5

estimate. A confidence interval for the effect size parameter

is obtained using the above estimate together with its

variance.

Finally, a hornogeneity test is performed to determine if

the assumption that al1 studies share a common population

effect size parameter is valid. This is accomplished by

calculating the Q-statistic which is the weighted mean square

deviations of the individual effect sizes from the population

effect size estimate. The value of the Q-statistic obtained is

then compared to the probability values of the chi-square

distribution to determine if the differences in the individual

effect sizes can be explained by chance alone- A more detailed

and precise description of the statistical procedures is given

in Appendix A. - This chapter provided an overview of the study design,

which included an outline of the procedures for sample

selection and data analysis. Al1 relevant and accessible

studies that sampled adults undergoing surgery or invasive

diagnostic procedures and that were written in English and

published £rom 1956 to 1997 were examined in this study.

Important inclusion criteria in the studies that evaluated the

effects of preoperative teaching on LOS, anxiety, and pain,

were the inclusion of an experimental design, a control group

that received routine or placebo preparation, and the same

setting for both experimental and control groups-

The data analysis consisted of descriptive and

quantitative analysis. A descriptive synthesis of data was

used to examine the demographic characteristics of the

patients who participated in the studies. A frequency count

approach was used to assess the influence of the selected

dernographic characteristics on postoperative outcomes. A meta-

analytic technique was used to calculate the overall effects

of preoperative teaching on postoperative outcomes. The

results are presented in the next chapter.

CHAPTER 3:

RESULTS

Part 1 of this chapter provides the results of the

descriptive analysis of data across the 20 studies. Part II

presents the results of the quantitative analysis of data,

including the results of the frequency count followed by the

statistical synthesis of data across the studies.

PART 1

Results of the Descriptive Data Analysis

This section includes a description of the

characteristics of the sample, studies, setting, methodology,

preoperative teaching, and postoperative outcornes. Most

importantly, the description of the demographic

characteristics of the patients who participated in the

preoperative teaching studies included in this study provides

the answer to the first research question of this meta-

analysis .

A total of 103 studies, published either in journals

(n=96, 93.2%) or in books (n=7, 6.8%), in the period prior to

1989, were identified for this meta-analytic study. A total of

38 journal articles, published in the period extending from

1989 to 1997, were found through the computer search. Of these

141 studies, only 20 studies met the inclusion criteria and

were sampled for this meta-analysis.

Loss of studies occurred mostly as a result of: a) lack

of control group in the studies; b) control group receiving an

intervention other than usual care or placebo; c) exclusion of

same day surgeries; and d) incomplete presentation of the data

that are essential to this study such as mean, standard

deviation of control and experimental groups or t- or F-

values. Principal investigators were not contacted to retrieve

missing data not only because of the financi31 and time

constraints, but also because very little new ififormation may

be obtained by doing so, especially for the studies that were

conducted prior to 1985.

Of the final sample, 16 (80%) studies belonged to the

f irst category (published prior to 1989) and four (20%) studies

to the second category (published after 1989). A review of the

20 studies is presented in Table 2 in Appendix B.

Studies were grouped according to the following

characteristics: publication form, publication date, first

author, and the study setting. A summary of these study

characteristics is presented in Table 3 in Appendix B.

Al1 20 (100%) studies were published in journals and none

in books. The publication dates for the final sample of 20

studies ranged from 1970 to 1996. The studies were categorized

into four time periods according to their publication dates:

49

1961-1970, 1371-1980, 1981-1990, and >1991. Only 1 (5%) study

was published in the 1961-1970 period; 7 (35%) studies in the

1971-1980 period; 9 (45%) studies in the 1981-1990 period; and

3 (15%) studies were published after 1991.

F j - t A U t h O f

The first author for half of the studies (n=IO, 50%) were

nurses. The professional affiliation of the first authors of

the remaining studies included occupational therapy (n=l, 5%),

psychology (n=2, IO%), medicine (n=2, IO%), and pharmacology

(n=l, 5%). The backgrounds of the first authors could not be

determined in four (20%) studies.

SetTina

The settings mentioned in the 20 studies included

hospitals from the United States, Canada, and the United

Kingdom- The majority of the studies (n=15, 75%) were

conducted in hospitals in major cities in the United States; 3

(15%) studies were carried out in the United Kingdom; and 2

(10%) studies were conducted in Canada.

A summary of the characteristics of the participants in

the 20 studies is given in Table 4 in Appendix B.

Patients who participated in the 20 studies were

hospitalized for various types of surgery. Most studies (n=15,

75%) included samples of patients undergoing the same type of

50

surgery: abdominal (n=3, 15%). thoracic (n=2, IO%), orthopedic

(n=l, 5%) , gynecological/ genitourinary (n=3, 15%) , and

cataract surgeries (n=2, 10%) . Four (20%) studies included patients ündergoing diagnostic tests or procedures such as

cardiac catheterization. In five (25%) studies, the patients

comprising the sample underwent different types of surgery;

for instance, in one study, 37% were scheduled for orthopedic

surgery, 37.5% for gynecological surgeries, and the remaining

25.5% for general surgery.

. . of the St- P-t-5

Bpe, Sixteen studies reported the mean age (n=14, 70%)

or the mode age (n=2, 10%) of their study participants. The

remaining four (20%) studies did not provide the mean, median,

or the mode age of the participating patients. The 16 studies

reporting the average sample age were categorized into five

groups according to the mean, median, or the mode age of the

participants of their samples: 18-40, 41-50, 51-60, >60; and

the last group consisted of studies that did not provide

relevant information.

The age range of the patients across the majority of

studies (n=13, 65%) was £rom 40 to 60. The average age of the

patients who participated in 7 (35%) studies was in the 41-50

age range; 6 (30%) in the 51-60 range; and 3 (15%) in the >60

range. None of the studies included patients whose average age

fell in the 18-40 age group.

51

Gender, The majority of studies (n=18, 95%) reported the

gender distribution of patients, and most studies (n=12, 60%)

included both genders, Studies were categorized into 7 groups

according to the gender distribution of the participants of

their samples: al1 males (0% female), 1-25% females, 26-50%,

51-75%, 76-99%, al1 (100%) females, and unknown/not given.

Three (15%) studies included only males; 2 (10%) studies

included 1-25% females; 1 (5%) study 26-50%; 5 (25%) studies

51-75%; and 3 (15%) studies included 76-99% fernales in their

study samples, Four (20%) studies had al1 females in their

study samples. The gender distribution w a s not given in 3

(10%) studies.

It should be noted that the gender distribution in the

primary studies was associated with the type of surgery the

patients underwent. However, regardless of the type of

surgery, more studies included more women than men in their

samples.

J,evel of e m a t i m Only 6 (30%) studies provided the

levels of education or the years of education of their study

participants. Studies were categorized into groups according

to the number of years of education or the level of education

of the participants of their studies: elementary, secondary,

and college/university. The average level of education of the

study participants for most of the studies (n=5, 25%) was

secondary, that is, the central tendency of the most studies

were 12, 12, 11.6, 12.43, 8-13 years of education.

. . Ethnicitv, Only 6 (30%) studies provided the ethnic

background of the participants of the studies. These studies

included "whitew patients in the following percentages: 66,

81 -8, 86, 8 4 . 9 , 91 -2, 100. However, only one study (Fortin,

19761, the one conducted in Montreal, described the "white"

patient sample as "Quebec Francophonew.

In addition to the above mentioned patient demographic

characteristics, £ive (25%) additional studies reported

excluding patients if they were not proficient in English,

could not understand the consent fonn, or could not read or

write. This indicates the possible exclusion of patients if

English is not their first language, or if they have not had

at least grade 5 to 8 level of education.

Studies were grouped according to the following

methodology characteristics: research design, manner of

assignment to groups, the type and the number of control and

experimental groups. A summary of these characteristics is

presented in Table 5 in Appendix B.

Al1 20 (100%) studies used either an experimental or

quasi-experimental research design incorporating one or more

control groups in addition to one or more experimental groups.

Random assignment to treatment condition was used in 13 (65%)

53

studies and seven (35%) studies used non-random assignment.

. . te, A t t - r m n Rate and -Syppl@ S l z e

Most studies (n=15, 75%) did not provide the response

rate of the study sample participants. In the 5 studies(25%)

that provided relevant information, the response rate was over

79% for four studies, and only one study had a response rate

of 28%. That specific study provided the reader with a

detailed explanation for this rate.

In 14 (70%) studies, information that would permit

calculation of attrition rate was not provided, The attrition

rate varied among the remaining six studies: in three (15%)

studies the attrition rate was <IO% (1.63, 2.38, 6.25) ; in two

(10%) studies it was >IO% but <15% (10.3, 13.8) ; and in one

(5%) study, the attrition rate was 21.1%. The sample size

included in the 20 studies ranged from 21 to 129 and

represented a total of 1,260 adult patients who agreed to

paxticipate in studies evaluating the effects of preoperative

teaching.

In 3 (15%) of the studies, sample size was more t h a n 100;

in 11 (55%) studies, the sample size ranged between 60-100;

and in 6 (30%) studies, the sample size was less than 60.

nes - of F- andmtrol Gr-

Studies differed in the number of experimental groups

examined. Eleven (55%) studies included only one experimental

group receiving the preoperative teaching. S i x (30%) other

studies included multiple preoperative teaching experimental

groups. The differences among these experimental groups were

due to different teaching methods (n=l), different timing of

teaching (n=l), or different educational content (n=4) . The remaining three (15%) studies employed other intervention

groups in addition to having a preoperative teaching

experimental group. Examples of these other interventions were

psychological support, communication, modeling, and

relaxation, However, these other intervention gzaups were not

applicable to this meta-analysis and were, therefore,

excluded.

Studies also differed in the number or the type of

control groups ernployed in each study. Most studies (n=l6,

80%) employed "usualN or "routineN preoperative preparation

for the control group, and three (20%) studies employed only a

placebo-type control group. One (5%) study employed both a

placebo group as well as a comparison with usual-care control

As mentioned above, studies varied in the number of

control groups and in the number of experimental groups

included. In order to calculate an effect size for the study,

information from only one control group and one experimental

group per study was chosen using the steps given below.

Studies with only one control group were chosen to be

included in the calculation of effect size regardless of

whether it was a usual care or placebo type control group. In

studies with two control groups, comparison with the usual-

care control groups were used to calculate effect size. The

reason for this was that patients undergoing surgery usually

receive some form of preoperative information. Therefore, this

needs to be compared to the experimental condition to examine

whether the experimental condition (formal preoperative

teaching) would bring about further improvements in

postoperative outcomes-

In studies with multiple preoperative teaching

experimental groups, where each group received a different

type of preoperative teaching, only one group was chosen. The

experimental group that would xaximize the total number of

studies in any particular category of preoperative teaching

was selected. The purpose of this selection was to facilitate

the examination of the combined effect sizes of subcategories

of preoperative teaching if it became necessary.

In the case of studies with one preoperative teaching

group in addition to several other intervention groups where

each of these was contrasted with the same control group, only

the preoperative teaching experimental group (in contrast to,

for example, relaxation group or psychological support group)

was selected to be included in the meta-analysis since the

56

focus of this study is on preoperative teaching intervention.

As mentioned in Chapter 2, the formula for the variance

of the modified sample effect size, which is crucial in the

calculation of the least variant estimator of the population

effect size, can be used only when the sample size of each

group is greater than or equal to ten. For this reason,

studies with sample sizes smaller than 10 were not included in

the effect size calculation-

Quality characteristics of the studies that were included

in this meta-analysis were coded and summarized in Table 6 in

Appendix B. The items that were used in examining the quality

of a study were study design, sampling method, presence of a

control group, method of assignment to groups, response rate,

attrition rate, and presence of threats to internal validity-

In terms of the threats to internal validity, the studies were

assessed for the presence of any of the following: history,

maturation, testing, instrumentation, statistical regression,

selection, mortality, interactions with selection, and

diffusion of the treatments (Burns & Grove, 1993) . In a few instances, lack of information provided in the

individual studies made it difficult to determine accurately

whether threats to internal validity were present and to

assess the quality of the studies. In particulax, information

that would permit calculation of the attrition rate was not

57

provided in 14 (70%) studies, The specific characteristics of

those participating versus those declining to participate were

rarely reported. These factors related to the study design can

affect the interna1 validity of the study if the patients who

withdrew from the study are significantly different from those

who completed the study.

The most prevalent threats to the quality of the studies

were related to the instruments and the measurements, These

threats are addressed in detail in later sections.

The characteristics of preoperative teaching of interest

in this meta-analysis are timing, method and presentation,

content, and structure of teaching.

The time of teaching has been categorized as pre-

admission teaching and post-admission teaching. The majority

( 7 5 % , n=15) of the studies offered preoperative teaching after

patients were admitted to the hospital for surgery. Only 25%

(n=5) of the studies offered preoperative teaching to patients

prior to their admission to hospital,

Pre-admission teaching was used in 19% of the studies

that were published pxior to 1989. In cornparison, pre-

admission teaching was offered to patients in 50% of the

studies that were published after 1989,

The majority of the studies used either audio visual

materials (n=6, 30%) or booklets (25%, n=5) as their method of

teaching. Two (10%) studies used a combination of teaching

methods such as a booklet and a tape. Each of the four (20%)

studies with multiple experimental groups employed a different

teaching method for each experimental group. For example, one

study used an audiovisual method for the sensory information

group, but individual teaching for the behavioural group,

With regard to the presentation, four studies (20%)

included group teaching while only two studies (10%) included

individual teaching, The remaining studies (n=14, 70%) did not

provide explicit information about the presentation of

information (teaching) . ucture of Te-

Of the 16 (80%) studies that consisted of only one

experimental group, eight (40%) studies included a combination

of two types of information: sensory and procedural (258,

n=5); procedural and behavioural (IO%, n=2); and sensory and

behavioural (5%, n=l) ) . Six (30%) studies included al1 three types of information (sensory, procedural, and behavioral).

One study (5%) involved only procedural information and

another study ( 5 % ) only behavioral information.

Most studies appeared to have included structured

teaching as indicated by the use of the audiovisual or the

written materials such as booklets and pamphlets. Although

such materials tend to provide information that was formally

approved, in a consistent manner, no definite information with

regard to the structure of teaching was given in rnost (n=18,

90%) studies.

The studies that were included in this meta-analysis also

differed in the types of outcomes measured, namely, recovery,

psycho-physiological outcomes, and psychological outcomes.

Other outcomes that were examined in these studies were

knowledge and skills performance, but were not relevant for

this meta-analysis.

Some of the recovery outcomes that were measured in the

20 studies w e r e length of hospital stay, postoperative

complications such as acute postoperative hypertension and

pulmonary complications, early adulation, time in intensive

care unit, and days spent before first venture £rom home after

discharge. Length.of hospital stay was the most prevalent

postoperative measure that was used to assess recovery outcome

in the 20 studies.

t h gf HosDital Stav, Length of hospital stay (LOS)

was examined as one of the postoperative indicators of

recovery outcome in 11 (55%) studies. LOS was defined in seven

(63.64%) studies and definitions w e r e not provided in four

60

(36.36%) studies. LOS was measured in different ways: in two

(18.18%) studies, LOS w a s measured starting the day of

surgery, and in two (18.18%) other studies, LOS was measured

starting the day following surgery, In three (27.27%) studies,

the LOS was measured with the first day being the day of

admission to the hospital. All the studies considered the last

day as the day of discharge £rom the hospital. Most of the

studies did not report the reliability and validity of the LOS

measurement .

Some of the psycho-physiological outcornes that were

measured in these studies were pain, anxiety about nausea,

anxiety about gagging, self-rating of comfort or self-rating

of recovery. Pain was the most prevalent postoperative measure

that was used to assess the psycho-physiological outcome in

the 20 studies.

Pain, Pain was examined as one of the postoperative

indicators of psycho-physiological outcome in 11 (55%)

studies. In these studies, pain was measured in different

ways: amount of oral, injectable or intravenous analgesics

used; scores on pain analogue scale; and various investigator-

developed pain scales. The most common (n=10, 90.91%) measure

of pain was the dose of analgesics given to patients. Of these

ten studies, one study used only injectable analgesics,

another study used intravenous analgesics (PCA), two studies

61

used a combination of oral and injectable, and in four studies

the route of analgesic administration (oral, IM, or IV) could

not be determined, The remaining t w o (18.18%) studies used

other measures of pain in addition to the doses of analgesics.

The study that reported only the scores of a pain management

questionnaire also used PCA for pain management, however, it

did not report the results of the doses.

The time period (the starting and end points) during

which the use of analgesics were measured were reported only

in four (36.36%) studies. In these 4 studies, the amount of

analgesics used by the patients was measured: 1) during the

first 24 hours (n=2) ; 2)from midnight on the day of surgery to

midnight on the third postoperative day (n=l); and 3) from

surgery to discharge (n=l) , Seven (63.64%) studies did not

provide definitions of the tirne periods.

Further, the reliability and validity of pain

measurements from previous literature were not provided in

most (n=9, 81.82%) studies. Only two (18.18%) studies made

reference to previous literature with regard to the

reliability and validity of their measurements or measurement

techniques.

Some of the psychological outcornes that were measured in

these 20 studies were anxiety, mood, demandingness,

apprehension, distress, depression, and in some cases,

62

psychological well-being. Anxiety was the most prevalent

rneasure that was used to assess the psychological outcorne in

the 20 studies,

Postoperative W + v - Anxiety was examined as one of

the postoperative indicators of psychological outcome in 12

(60%) studies. In these studies, anxiety was assessed using

different measures: State-Trait Anxiety Inventory (STAI),

Palmer Sweat Index (PSI), Profile of Mood States (POMS),

Multiple Affect Adjective List (MAACL), Postopexative Affect

Scale (PAS) , Adjective Check List (ACL) , Persona1 Orientation

Inventory (POI), and scores on various investigator-developed

subjective or objective rating scales. Other measures that

were used were heart rates and doses of sedatives or

anxiolytics used,

In seven (63.64%) studies, only a single measure of

anxiety, mood, and distress was taken. In five (45.45%)

studies, a combination of two or more of the above mentioned

rneasures was used. The most common rneasure of anxiety, mood,

and distress was the scores on Spielberger State-Trait Anxiety

Inventory which was used in 6 (54.55%) studies. Other

measurements were used in the following frequency: Palmer

Sweat Index (n=l) , Profile of Mood States (n=l) , Multiple

Affect Adjective List (n=2) , Postoperative A£ fect Scale (n=l) ,

another adjective checklist (n=l) , scores on various

researcher-created subjective or objective rating scales

63

(n=5), heart rate (n=l), and doses of sedatives or anxiolytics

(n=l) - In the primary studies, the measurements of anxiety were

taken at various points in the perioperative time period.

Theçe varied from prior to, during, or after the surgery.

Those measurements that were obtained prior to or during the

surgery cannot be considered as postoperative outcome

measurements of anxiety. In some other studies, the scores of

the anxiety measures were given only as the percentage of

anxiety decrease from preoperative to postoperative. Further,

rnocd, distress, apprehension, psychological well-being, and

depression were al1 grouped under anxiety. The measures varied

from the doses of anxiolytics, to physiological measures such

as pulse rates, to various anxiety scales, to various mood

scales. Although the reliability and validity of the anxiety

measurements have been provided in most studies, because of

the above mentioned inconsistencies in measurement,

postoperative anxiety was not further examined in the

quantitative analysis.

V V

Studies varied in the number of outcomes measured, and in

the number of measures taken per outcome. The steps given

below were used in calculating individual effect sizes for

each study.

F i r s t , i n t h o s e s t u d i e s w i t h a s i n g l e measure of a n

outcome, t h a t measure w a s used t o o b t a i n a n e f f e c t s i z e f o r

t h a t outcome r e p r e s e n t i n g t h a t s t u d y . Second, i n t h o s e s t u d i e s

w i t h m u l t i p l e measures o f t h e same outcome, e f f e c t s i z e s w e r e

c a l c u l a t e d u s i n g e a c h o f t h e s e measures . These e f f e c t s i z e s

w e r e t h e n ave raged t o o b t a i n a s i n g l e e f f e c t size t h a t

r e p r e s e n t e d e a c h s t u d y . For example, i f p a i n was measured i n a

s t u d y u s i n g s e v e r a l measures, such a s t h e number of doses of

IM a n a l g e s i c s r e c e i v e d , t h e number o f d o s e s o f o r a l a n a l g e s i c s

r e c e i v e d , and s u b j e c t s c o r e s on t h e M c G i l l p a i n s c a l e , t h e n ,

a n e f f e c t s i z e was c a l c u l a t e d f o r each measure and t h o s e

e f f e c t s i z e s w e r e ave raged t o o b t a i n a s i n g l e e f f e c t s i z e f o r

t h a t study. Taking t h e ave rage o f t h e s e e f f e c t s i z e s is

j u s t i f i a b l e b a s e d on t h e p r i n c i p l e t h a t t h e v a r i o u s measures

are i n d i c a t o r s o f t h e same concept (Devine & Cook, 1986;

Devine, 1992; Hedges & Olkin, 1 9 8 5 ) .

Second, e f f e c t s i z e v a l u e s w e r e a s s i g n e d a p o s i t i v e s i g n

when r e s u l t s i n d i c a t e d a b e n e f i c i a l e f f e c t . For example, i f

p a t i e n t s i n t h e e x p e r i m e n t a l group had less p a i n o r s h o r t e r

l e n g t h o f h o s p i t a l s t a y compared t o t h o s e i n t h e c o n t x o l

group, a p o s i t i v e s i g n was a s s i g n e d , A n e g a t i v e s i g n w a s u sed

when t h e r e v e r s e w a s t h e case.

T h i r d , t h e f i n a l weighted a v e r a g e e f f e c t size v a l u e f o r

e a c h outcome w a s t h e n c o n s i d e r e d u s i n g Cohen's (1969)

c l a s s i f i c a t i o n s o f p o p u l a t i o n e f f e c t s i z e v a l u e s , t h a t is ,

65

values of 5 0.30 correspond to small effects, 0.40 to 0.70 to

medium effects, and values of r 0.80 to large effects.

PART II

Results of the Quantitative Analysis

This section reports the results of the frequency count

for the outcomes of LOS and pain followed by the results of

the statistical analysis of data across studies for those two

outcomes. Owing to the inconsistencies in the rneasurements of

anxiety that were mentioned in the previous chapter, anxiety

outcome was excluded from the quantitative analysis.

The frequency count approach was used as a preliminary

strategy in identifying patterns or trends in the

relationships between the postoperative outcomes and the

characteristics of the study participants, This strategy

allowed the inclusion of al1 20 studies in the analysis. - The significance of the postoperative outcome of length

of hospital stay (LOS) was tabulated against the categories of

each demographic characteristic of the study participants

(Tables 7-10).

Table 7

Aae

Mean Age Signif icance Yes no

ppppp

18-40 yrs - - 41-50 yrs 2 3 51-60 yrs 1 2 > 60 yrs 1 1 not given - 1

t o t a l 4 7

Table 7 dezonstrates that none of the studies included

patients whose mean age was in the category of 18 to 40.

However, there were five studies that included patients whose

mean age was in the category of 41-50. Of these, two studies

reported significant effect of preoperative teaching on LOS

and three studies had no significant results. Of the three

studies with patients with a mean age of 51-60 years, one

study reported a significant LOS outcome compared to the two

studies that reported non-significant outcomes. In the two

studies that included patients with mean age of > 60 yrs, one

study had significant outcomes and the other, non-significant

outcomes. Overall, the number of studies with a significant

effect did not differ much from the number of studies with

non-significant findings across the age categories, suggesting

that age did not affect the LOS outcome. However, there is a

tendency for a non-significant effect to be reported in the

younger age group.

Table 8

Gender

Gender Signif icance Yes no

a l 1 male 1-508 female 51-75% female 76-100% female

total

As seen from Table 8, al1 the studies that examined LOS

as one of the outcomes of preoperative teaching also reported

the gender distribution of their study participants, Of these,

three studies had al1 male patients and two of these studies

reported a non-significant outcome. There were no studies that

included 1 - 50% women among the participants of their

studies. Of the two studies that included 51-758 women in

their study samples, one had a significant and the other had a

non-significant outcome, Six studies included >76% female

patients in their studies. Of these six, only two studies had

a significant effect of preoperative teaching on LOS outcomes.

Overall, no clear pattern relating gender to LOS outcome of

preoperative teaching could be seen.

Table 9

Educational level -- p~

Signif icance Yes no

elementary ( d / 8 1 secondary (8-13) 6. higher not given

total

This table shows that seven studies did not provide the

educational level or the number of years of schooling of the

participants of their studies. Of the four studies that

reported such information, al1 included patients whose average

level of education was at the secondary or higher level. Of

these, three had non-significant outcornes and only one

reported a significant outcome. Overall, there was a tendency

for patients with high education to have no significant change

in their LOS outcome following preoperative teaching.

Table 10

Ethnici Signif icance YeS no

a l 1 non-white 1-50% white 51-75% white 76-100% white not given

total

69

The ethnicity of the study participants was not reported

in eight studies (see table above). Of the thxee studies that

reported such information, only one study reported a

significant outcome and two reported non-significant findings

with regard to the length of hospital stay. Overall, no clear

pattern of influence of ethnicity on the LOS outcome was

f ound.

Ou-

The frequency count tabulations of the significance of

the pain outcome against the categories of each demographic

characteristics of the study participants are provided below

in Tables 11-14.

Table 11

Bae

Mean Age Significance Ye* no

18-40 yrs 41-50 yrs 51-60 yrs > 60 yrs not given

total

Among the studies that examined pain as an outcome of

preoperative teaching, none included patients whose mean age

was in the 18 to 40 category (Table 11). However, six studies

included patients with a mean age in the category of 41-50.

These studies were equally divided in terms of the

significance of the pain outcome. The two studies with

patients whose mean age was in the category of 51-60 reported

a non-significant outcome. Similarly, the only study with

patients whose mean age of > 60 years reported a non-

significant outcome. Two remaining studies did not report

mean age of its participants. Overall, there was no clear

pattern, although a tendency for a non-significant effect

older age groups was noted.

Table 12

Gender

Gender -

Signif icance

a l 1 male 1-25% female 26-50% female 51-75% female 76-100% female not given

total

the

in

As seen from this table, only one study did not report

the gender distribution of its study participants; that study

had a significant outcome. Two studies with non-significant

outcomes included al1 male patients in the samples of their

studies. Eight out of the 11 studies that examined the pain

outcome included more women than men. Of these, two studies

included 51-75% women in their study samples, one had a

significant outcome, and the other had a non-significant

outcome. The remaining six studies included >76% female

patients in their studies and the studies were divided equally

with regard to the significance of the pain outcome. No clear

pattern of the relation between gender and pain outcome was

found; however, there was a tendency for studies with al1

males to have non-significant effect.

Table 13

Educational level Significance Y e s no

elementary ( < 7 /8) - secondary (8-13) & higher 1 not given 4

total 5

Nine studies did not provide data about their

participants' educational level or the number of years of

schooling (see table above). Of the two studies that reported

information regarding the patientsf educational level, one had

significant outcomes and the other non-significant outcomes.

No studies included patients whose average level of education

fell below secondary level. No clear pattern regarding the

relation of level of patient education to pain outcome was

discerned.

Table 14

Ethnicity Significance YeS no

al1 non-white 1-25% white 26-50% white 51-75% white 76-100% white not given

total

As seen from Table 14, ethnicity of the study

participants was not reported in eight studies, Al1 three

studies that reported information regarding ethnicity had a

significant pain outcorne. Only one of these three studies

included a 51-75% of white patients and the other two studies

included 76-100% white patients in their study samples. These

results indicate that overall al1 the studies with white

patients had significant pain outcomes.

In conclusion, the results of the frequency count

approach indicated that the patientsq characteristics of age,

gender, level of education, and ethnicity did not affect the

LOS and pain outcomes of preoperative teaching. To confirm

these results, additional quantitative analyses were conducted

on the subsample of the 20 studies for which the effect sizes

could be calculated.

The effect size estimates of preoperative teaching on the

two postoperative outcornes, length of hospital stay, and pain,

based on the meta-analytic techniques described in Chapter 2

are given in this section. In each case, a least variant

estimate of the population effect size was obtained using the

two different numerical procedures: (1) A Quick Estimate and

(2) Iterative Procedure, described in Appendix A. Tt was found

that the effect size results from these two methods of

calculations were in agreement up to three decimal places.

This shows that the method of a quick estimate is a very

useful and valid numerical technique that can often be used

instead of the time consuming iterative procedure.

U S Of the 11 studies that examined LOS outcome, eight

(72.73%) studies provided sufficient information to calculate

the ES, however, one study had to be excluded due to its small

sample size (<IO). Therefore, the final sample size for the

outcome of length of hospital stay was seven (63.64%).

The effect sizes for the outcome of LOS from the seven

studies ranged from 0.04 to 1.17. The least variant estimate

of the population effect size for the outcome LOS, is 0.46

with a variance of 0.016. Thus, a 95% confidence interval for

the population effect size is 0.206 to 0.708.

Further, the assumption that these studies share a common

population effect size for the outcorne LOS was confirmed by

7 4

the homogeneity test ( Q= 12,279, degree of freedom (df) = 6,

p= 5-10% ) .

Pain, Of the 11 studies that examined pain outcome, nine

(81.82%) studies provided sufficient information to calculate

the ES, however one study had to be excluded due to its small

sample size (<IO). Therefore, the final number of studies

included, when calculating the ES of length of hospital stay,

was eight (72 -73%) . The effect sizes for the outcome of pain from eight

studies ranged from -0.23 to 0.93. The least variant estimate

of the population effect size for the outcome of pain is 0.39

with a variance of 0.008. Thus, a 95% confidence interval for

this population effect size is 0.220 to 0,570. The assumption

that these studies share a common population effect size was

confirmed here as well by the homogeneity test ( Q= 6.600,

df= 7, p= 25-50% )

The fact that the magnitude of the effects are of

moderate-size and the confidence intervals do not contain zero

or negative numbers mearis that these studies provide reliable

evidence that preoperative teaching does have a positive

effect on the aforementioned outcornes. The fact that the

studies are homogenous precludes motivation for separating the

studies into further subgroups sharing common characteristics

and calculating the effect sizes for subgroups(Hedges & Olein,

1985). As a result, effect sizes of subgroups on the basis of

age, gender, educational and cultural background on

postoperative outcome achievement were not calculated. - The results of the descriptive analysis of the 20 primary

studies are as follows: (a) the majority of the studies

reported the age and gender, but not the education and

ethnicity of the participants; (b) the average age of the

participants of most studies was in the 41-50 years range and

the majority of the studies included more women than men; (c)

the average education of the participants was above secondary

level; and (d) al1 studies consisted mostly of white, English

speaking patients,

The results of the frequency count analysis indicated

that the number of studies with significant findings did not

differ much £rom the number of studies with non-significant

findings across the age, gender, educational, and ethnic

groups for both LOS and pain outcornes. These results are

consistent with those of the homogeneity tests conducted in

the quantitative meta-analysis.

Statistical techniques used in the quantitative analysis

resulted in an ES of 0.46 for LOS and 0.39 for pain outcome.

An ES for anxiety w a s not calculated due to inconsistencies

and inaccuracies in measurements, conceptual definitions, and

construct validity of the primary studies. The effect sizes

were found to be homogenous indicating that no further

subgroupings of the studies were necessary. Therefore, an

evaluation of the subgroups of studies in relation to the

demographic characteristics of the patients participating in

the studies on postoperative outcornes was not conducted. The

importance and implications of these findings will be

addressed in the next chapter.

CHAPTER 4:

DISCUSSION

This cbapter presents a discussion of the characteristics

of the studies included in this meta-analysis first, followed

by a discussion of the findings in relation to the research

questions of this meta-analysis as well as the findings of the

other meta-analyses.

Characteristics of the Studies

1 P u c a t i o n T v n e - daçi F m

The 20 primary research studies included in the sample of

this meta-analysis were published within the period extending

from 1956 to 1997; the majority of the studies were published

£rom 1970 to 1989, There were seven previously published meta-

analyses on preoperative psychoeducational interventions

(Mumford et al., 1982; Smith & Naftel, 1984; Devine & Cook,

1983 and 1986; Hathaway, 1986; Suls & Wan, 1989; Devine,

1992). The sample of this meta-analysis differed from the

samples of the majority of these meta-analyses in several

ways. The sample in this meta-analysis: (1) included only

published studies; (2) consisted of a smaller sample size;

(3) consisted of only adult patients; (4) examined only the

preoperative teaching intervention; and (5) included most

recent studies . First, the sample of this meta-analysis differed from

that of the seven meta-analyses in the publication form of the

primary studies included. For the purpose of this meta-

analysis, only the published studies were examined. Six of the

seven previously published meta-analyses included both

published and unpublished studies in their samples. The only

meta-analysis that excluded unpublished studies was conducted

by Suls & Wan (1989). Exclusion of the unpublished studies in

the present study reduced the sample size and limited the

representativeness of this meta-analysis results to the

published studies only.

Second, this meta-analysis differed from the other meta-

analyses in the sample size. Only one other study, (Suls &

Wan, 1989), consisted of a small sample size of 21 studies.

The sample sizes of the rernaining six meta-analyses varied

form 34 to 191. However, the differences in sample size are

related not only to the publication form of the studies

included (as described above), but also to the inclusion

criteria set for each of these meta-analyses. In most of the

meta-analyses, studies that sampled children and studies that

evaluated psychological preoperative interventions in addition

to the educational interventions were included. As explained

below, in this meta-analysis, studies that were recently

published, that sampled only adults, and that evaluated only

the educational interventions were included.

Third, this meta-analysis differed £rom three of the

othex meta-analyses (Mumford et al,, 1982; Smith & Naftel,

79

1984; S u l s & Wan, 1989) in the type of patients examined. As

was mentioned above, this study included only adults

undergoing surgery whereas the three other meta-analyses

included children as well.

Fourth, the present meta-analysis differed £rom the other

meta-analyses in that it included more recent studies,

published from 1989 until 1997. These were expected to

increase the likelihood of including studies with more women

and/or more patients of different ethnic backgrounds. Details

of these are presented later in this chapter in the discussion

of the first research question,

The fifth difference between this study and the other

meta-analyses relates to the intervention of interest. The

differences in the interventions of interest are addressed in

detail later in this chapter ic the discussion of the second

research question.

R - e a J r h &s&R

Al1 20 (100%) studies included in this meta-analysis used

either an experimental or quasi-experirnental research design.

The purpose of experimental and quasi-experimental research

designs is to examine causality, that is, the causal effect of

preoperative teaching on outcomes, Although the experimental

design is better in maintaining the validity of this causal

relationship, the quasi-experimental design is an alternative

design that can be used in situations where complete control

80

is not possible. In this sense, the research designs allow the

understanding of the true effects of the intervention, and can

effectively reduce threats to the validity of the conclusions

(Burns & Grove, 1993). The other meta-analyses also included

studies with experimental and quasi-experimental research

designs.

Random assignment to treatment condition was used in 13

(65%) studies and non-random assignment in seven (35%)

studies. Since it is important to have an initial equivalence

between the experimental and control groups by using random

assignment, non-random assignment may lead to differences in

experimental and control groups in terms of extraneous

variables. If, for example, people with higher levels of

education were in the experimental group compared to those

with lower levels of education in the control group, then the

results would be inflated. Thus, in the seven studies with

non-random assignment, the interna1 validity would be

affected, and this in turn, would lead to inaccurate

conclusions in the meta-analysis.

Furthemore, the extent of equivalence among the groups

should be examined since random assignment does not guarantee

equivalence. It only increases the "probability that subjects

with various levels of extraneous variables are equally

dispersed in treatment and control groups" (Burns & Grove,

1993, p.274). However, in the studies included in the sample

of this meta-analysis, any comparison of characteristics of

the control and the experirnentaf groups was rarely mentioned.

This may have influenced the interna1 validity of the primary

s tudies.

Moreover, the rate of participation among eligible

patients and the characteristics of those who participated

versus those who declined to participate were rarely reported

in the primary studies. Burns and Grove (1993) stated that

those who participate in studies may be volmteers, or "do-

gooders" (p.270). In this case, the sample may be limited and

biased because only certain types of individuals may have

agreed to participate. If such information is not provided, it

then precludes further attempts to examine whether those who

participated share conunon characteristics that may not be

applicable to surgical patients in general. Therefore,

generalizing the findings to al1 patients undergoing surgery

cannot be justified.

Additionally, information that would permit calculation

of attrition rates were not reported in 70% of the studies

comprising the sarnple of this meta-analysis. The results of

the primary studies may be questionable, for example, if the

attrition rate is more than 20% since the sarnple is likely to

be biased (Burns 6 Grove, 1993). The lack of such information

in research reports prevents any attempts to determine the

validity of the results of these studies.

82

The type of control group that was employed varied in the

20 studies: usual or routine preoperative preparation,

placebo-type, and in some studies, both types. The usual care

involved the provision of some information about the surgery

that may have included some aspects of actual preoperative

teaching contents, and in other cases, no information at all.

In the first case, the actual ES obtained would be lower

(Sidani h Braden, 1998). Similarly, in one study, a historical

control group was used, and if this control group was exposed

to certain factors causing them to respond better, the effect

of the treatment outcome would be reduced. In other cases,

placebo-type control group preparation varied from providing

attention only, providing global information such as hospital

facts and information, to providing no information at all. Al1

the above mentioned variations in control groups in primary

studies can cause differences in outcome achievements in each

study. These variations in turn can affect the final averaged

ES in this meta-analysis.

Although the possible effects of the designs of the

studies on the results were acknowledged, this was not

examined further since the results of homogeneity tests did

not warrant further examination of the potential influence of

methodological and substantive factors on the Ess.

The First Research Question

The first research question of this study was: "What are

the demographic characteristics of patients who participated

in the studies that examined the effectiveness of preoperative

patient teaching on postoperative outcomes?"

The demographic characteristics of interest in this meta-

analysis were age, gender, level of education, and ethnicity-

The results of the descriptive analysis indicated that the

only demographic characteristics that were reported with any

regularity were age, reported in 80% of the studies, and

gender, reported in 90% of the studies. In cornparison, the

information regarding the level of education and ethnicity of

the study participants was reported only in 33% of the

studies .

Acxe

The average age of the participants in the majority of

studies was in the 41-60 years category. Thus, the findings of

this meta-analysis may be more applicable to those in that age

category. For example, Brown (1992) found a statistically

significant inverse relationship between the age and knowledge

outcomes in patients with diabetes receiving psychoeducational

interventions. Similarly, age is known to affect outcomes of

preoperative teaching (Lundeman et al., 1990; Payne, 1992) . Therefore, the findings may not be applicable to the younger

or the older patients undergoing surgery.

Gender

Two-thirds of the studies included more women compared to

one-third of the studies that included more men in their

samples. Al1 (100%) studies that were published in the 1989-

1997 period included women. In comparison, in the studies

published prior to 1989, only 66% of the studies included

wornen. This indicates an increase in inclusion of women in

studies over time, and this increase may be as a result of the

recent criticisms researchers have received regarding the lack

of, or the insufficient inclusion of, women in research

studies . Fdtuzation

The average educational level of the participants in al1

of the studies that reported this information was at or above

the secondary level, In addition, another 25% of studies

excluded those patients who were not proficient in English,

could not understand consent forms, or could not read or

write. This indicates the exclusion of patients from these

preoperative teaching effectiveness studies if English was not

their first language, or if they have not had at least grade 5

to 8 level of education.

Therefore, the results of this meta-analysis are mostly

applicable to those with above secondary level education or

for those who are proficient in English. This conclusion

indicates that the effectiveness of preoperative teaching may

85

not have been examined in patients who have no education or

minimal education, as well as in patients who cannot speak

English proficiently. Individuals who fit these descriptions

in Canada and the United States may amount to several million,

There is a lack of research based evidence to support the

effectiveness of preoperative teaching to such individuals.

Although an increase in the inclusion of women in recent

studies w a s found, this was not the case for ethnicity. There

was no evidence to indicate an increase in inclusion of

patients of different ethnic backgrounds in recent research

studies, The samples of al1 the primary studies reviewed

consisted mostly of white patients. Thus, the findings of this

study indicate that primary research studies continue to

include mostly white patients, and that results of this meta-

analysis are applicable only to white patients undergoing

surgery, That is, research-based evidence that indicate the

effectiveness of preoperative teaching to patients from

different ethnic backgrounds is lacking,

In addition, none of the previously published meta-

analyses reported the level of education and/or the ethnicity

of the participants of the studies included in their meta-

analyses. Thus, the findings of these meta-analyses also

cannot be generalizable to people of different educational or

ethnic backgrounds.

Also of importance with regard to ethnicity is that

primary studies rarely described the ethnic backgrounds of the

white patients. This lack of detail prevents further

understanding of the demographic characteristics of the

participants of the studies and the applicability of the

findings of these studies even to the white patients. A sample

of white patients, in general, rnay include people who speak

French or English. In addition, among those who speak English,

there may be people who are Canadian, British, Irish, or even

South Africans. As such, reporting skin colour (white or

black) or race (Caucasian) instead of ethnicity, and making

generalizations based on skin colour or race are

inappropriate.

Race refers to physical appearance, determined by

ancestry, and rnost often perceived as a permanent genetic or

biological state (Fernando, 1991; Lipson, 1996). Although the

original categories, Caucasoid, Negroid, and Mongoloid are not

in frequent use in academe and research (Lipson, 19961, the

use of skin colour to identify and characterize individuals

continues to be common. In comparison to the concepts such as

race or skin colour, ethnicity provides a basis for

identifying and defining groups of individuals. Ethnic group

refers to a socially, culturally, and politically constructed

group of individuals that share characteristics such as a

common ancestry, a sense of historical continuity, common

language, and religion (Lipson, 1996) . Ethnicity and culture influence one's decisions, choices,

and preferences with regard to care, treatment, and

therapeutic interventions. Culture and ethnicity also

influence people's learning, learning patterns, and the

importance given to knowledge regarding illness, treatment,

and interventions. Hanna (1997) stated that if the patients of

diverse cultural backgrounds are to "benefit from the

statistically proven benefits of preoperative teaching, the

nurse educator must be aware of the cultural differences

inherent in that patient population" (p. 57) . Thus, paying

attention to the culture and ethnicity of the study

participants in research studies is important in understanding

and improving care to al1 patients undergoing surgery.

Another related issue is that the majority of the

preoperative teaching studies were conducted in the United

States. In Canada as compared to the United States, not only

is the ethnic distribution and average level of education

different, but so. are socioeconomic status, immigration

status, cost of health care, and access to insured health

services. The influence of these factors on postoperative

outcornes can affect the findings of the studies in these two

countries differently. For example, lack of insured health

services may have an effect on LOS outcome in the studies

conducted in the United States. Therefore, more Canadian

studies examining preoperative teaching effectiveness are

necessary. In addition, researchers should consider inclusion

of relevant studies that were conducted in countries other

than the US, UK, and Canada. The cost of accessing and

translating studies need to be considered in applying for

funding for such studies.

The Second Research Question

The second research question that was defined in Chapter

2 was: "What are the effects of the selected dernographic

characteristics on the outcornes of preoperative teaching

intervention?" In addressing this research question, a short

discussion about the results of the frequency counts will be

presented first, followed by a detailed discussion about the

effect of preoperative teaching on LOS, anxiety, and pain as

well as a discussion about the components of preoperative

teaching and the reliability and validity of the outcome

measurements.

Pes11)ts of t h e Fr- Crlllllts ADDTc>=KL

Frequency counts approach was used as a preliminary

strategy to answer the second research question. For this

purpose, the demographic characteristics were tabulated

against the reported level of significance of the outcome of

LOS and pain. Anxiety as an outcome indicator was not explored

due to the reasons provided in Chapter 3.

The results of the frequency counts approach showed that

89

the number of studies with significant findings did not differ

much from the number of studies with non-significant findings

across the age and gender groups for both outcomes indicating

that age and gender did not affect these two outcomes-

However, there was a tendency for younger age groups and

groups with higher education to have non-significant effects

of LOS outcome. No clear pattern w a s noted between ethnicity

and LOS outcome.

In cornparison, there was a tendency for non-significant

pain outcomes to be associated with al1 male groups. No clear

pattern was noted between the level of education and pain

outcome, although in terms of ethnicity, there was a tendency

for white patients to have significant pain outcomes.

In sumrnary, no significant patterns of the influence of

the selected demographic characteristics on the outcome of

preoperative teaching were noted across the 20 studies

included in the sample of this meta-analysis, The results of

the frequency counts were confirmed by the homogeneity test

when aggregated under each of the outcome variables,

E f f e c t sizes aggregated by the dependent variable

indicators of LOS and pain, resulted in values of 0.46 and

0.39 respectively. As was mentioned previously in Chapter 3,

postoperative anxiety as an outcome indicator was not explored

and the effect magnitude for that outcome was not obtained due

90

to problems in construct and interna1 validity. In the context

of the general guidelines suggested by Cohen (1977), the

results obtained for the LOS and pain outcomes indicated a

moderate beneficial effect of preoperative teaching.

The variances associated with the population estimate of

the effect sizes for LOS and pain remained fairly narrow

(0.016, and 0.008) and the 95% confidence intervals did not

include zero or negative values. Such confidence intervals

indicate that preoperative teaching does have favourable and

reliable effects on these two outcomes. The fact that the

effect size results were homogenous across studies in this

meta-analysis showed that the effect size values corne from the

same population and that no further subgroupings of the

primary studies were necessary.

In summary, the results of this meta-analysis

demonstrated the effectiveness of preoperative teaching on the

postoperative outcomes of pain and length of hospital stay.

Overall, these findings are consistent with the previously

published preoperative psychoeducational meta-analyses. A

detailed comparison is given below,

of the nrevynus - meta - d v s e q -

Three meta-analyses examined the effect of

psychoeducational interventions on the LOS outcome, In

comparison to the ES of 0 - 4 6 (SD=0.13, n=ll) obtained in the

present meta-analysis for the outcome of LOS, the ESs in the

91

other meta-analyses were: 0.36 (SD=N/A, n=49) in Devine and

Cook (1983); 0.46 in Hathaway (1986) ; and 0.42 (SD=0.43,

n=40) in Devine and Cook (1986).

Pain as an outcome was examined in two previously

published meta-analyses. In comparison to the ES of 0.39 that

was found in the present meta-analysis, these two meta-

analyses reported the following ESs for the pain outcome:

Devine & Cook (1986), an ES of 0.34 (SD=0.49, n=35), and

Devine (1992) reported an ES of 0.38 for 82 primary studies.

In comparison, the effect sizes reported for both LOS and

pain outcornes in the previously published related meta-

analyses (Devine & Cook, 1986; Hathaway, 1986; and Devine,

1992) were consistent with the results of the present meta-

analysis regardless of the differences in the interventions of

interest, the sample sires, patient populations, and time and

form of publication.

. . Timina, Of the various components of preoperative

teaching, the timing of teaching was the easiest to extract

£rom al1 primary studies. The majority of the studies included

in the sample of this meta-analysis employed post-admission

teaching. In comparison, pre-admission teaching had been

explored as early as 1976 in the sample of this meta-analysis,

however, only 19% of the studies published prior to 1989

employed pre-admission teaching compared to the 50% of the

92

studies published after 1989. This rnay be due to the increase

in preoperative teaching in pre-admission clinics as a result

of the increase in pressure, in recent years, to reduce LOS

for patients undergoing surgery and to contain cost.

Content, The interventions used in these 20 preoperative

teaching studies provided patients with sensory, procedural,

behavioural information or a combination of these. The

majority of the studies used a combination of al1 three types

of content followed by various combinations of two types. This

indicated that most primary studies included in this meta-

analysis employed a combination of information rather than a

single content, Multiple contents of information, in

cornparison to a single content, may have met the needs of many

patients, which may, in turn, have accounted for the

favourable outcornes that was found in this meta-analysis.

Calculation of average effect sizes of single versus

multiple contents was not feasible in this meta-analysis due

to the resulting smaller sample sizes when aggregated by the

n d e r and the type of content. However, three previously

published meta-analyses (Devine & Cook, 1983; 1986; Suls &

Wan, 1989) examined the differences in average effect sizes

depending on the number of contents, Results of the first two

meta-analyses showed that multiple psychoeducational contents

provided moderate values with low variances, compared to

single psychoeducational content that provided both extremely

93

high and low values associated with large variances. Suls and

Wan (1989) meta-analysis which examined the effects of only

preoperative teaching concluded that the sensory-procedural

combination was better for patients in cornparison to the

sensory or the procedural alone. These results indicate that

multiple contents are better when compared to single content,

which is also consistent with the findings of the present

meta-analysis. Although more studies are needed to draw

definite conclusions, results of the meta-analysis indicated

that multiple contents are more beneficial for most of the

patients.

Meth& Various methods of information delivery were

used in the 20 studies of this meta-analysis sample including

audio-video, booklets, one-to-one teaching, home visits, and

group teaching. The majority of the studies used either

audiovisual or written materials. Also, the majority of the

studies ernployed a single method to convey preoperative

information. Although audiovisual or written rnaterials can be

an asset when there is little time available for teaching,

these rnaterials, specially the use of audiovisual rnaterials,

may not be as productive to somebody who has never operated

audio-video equipment. This may cause unnecessary anxiety and

stress for some.

Similarly, the readability level of the written materials

may be too high for some patients. Many of the studies that

were conducted in the United States have shown that the

readability level in most of the written information materials

in hospitals or clinics are written at a higher level than the

average educational level of the people in general in the

country (Dixon & Park, 1990; Stephens, 1992; Miller & Bodie,

1994). No Canadian studies that addressed this issue were

found. In summary, regardless of the methods used in primary

studies, the results of this meta-analysis indicated reliable

and favourable effects of preoperative teaching on

postoperative outcomes,

The other components of

preoperative teaching of interest in this study were

presentation and structure of teaching, Preoperative teaching

can be presented either on an individual or group basis. Only

six studies reported information about presentation, of which

only two studies employed group teaching. Explicit information

about the presentation of preoperative teaching was not

reported in most of the studies. Further research is needed to

assess whether the benefits of group teaching are reliable and

consistent since group teaching can be cost effective

(Crabtree, 1978; Miner, 1990) and efficient (Lindeman, 1973)

and is an important consideration when nursing time spent per

patient has been reduced,

In terms of the structure, preoperative teaching can be

presented either in a structured or non-structured manner,

95

Only two of the studies explicitly reported using structured

teaching, However, most of the studies appear to have

presented information in a structured and consistent rnanner as

indicated by the use of written materials.

. . v - & V-tv - of t h e 0 i i t c ~ ~ e . s M e - r n e n t ~

The three outcome indicators that were examined in this

meta-analysis were LOS, anxiety, and pain, As was mentioned in

Chapter 1, these were also the most prevalent postoperative

measures used in the 20 studies to assess the recovery,

psychological, and psycho-physiological outcomes,

respectively. Issues related to the reliability and the

validity of the measurements of these three outcomes are

discussed below.

~ , e n g t h of Hns-1 S t a v , In the seven studies that

provided definitions of LOS, it was measured starting either

1) the day of admission to the hospital; 2) the day of

surgery; or 3) the day following surgery,

The total hospital stay, as is the case in the first

definition, is not an appropriate measure of the postoperative

outcome of LOS. Further, this measure can cause

inconsistencies even within the same study since the number of

hospital days prior to the surgery may Vary for each patient

due to unforseen reasons such as delay of chest X-rays,

hematology results, CT scan, or other complications.

96

Therefore, variability in LOS is not only related directly to

preoperative teaching, but also to other extraneous factors

which threaten the validity of conclusions regarding its

ef fectiveness.

Even when LOS was measured as a postoperative outcorne, as

is the case in the latter two definitions, the reliability of

rneasurements is low. For example, when the day of, or even the

day after, the surgery is considered as the first day, a

patient who finished the surgery at 0800 hours rnay not be

comparable to one who finished the surgery at 2300 hours on

the same day. The existing time gap may cause inaccurate

measures of LOS even within the same study. This inconsistency

may have been avoided by using a measure such as the total

number of hours £rom the end of the surgery to, for example,

1200 hours on the day of discharge regardless of actual

discharge time. This would also have avoided the differences

that may occur in LOS due to differences in discharge time in

each unit. Another method would have been to measure the total

number of hours starting with the time the patient left the

postoperative recovery room.

These inconsistencies in the measurements of LOS may

affect the construct validity of primary studies, and in turn,

the validity of the conclusions of this meta-analysis. In

fact, these variations may have contributed to some of the

97

variations encountered among the effect sizes for LOS in the

primary studies. A single more accurate measure of LOS would

have increased the consistency of measurernents within and

across studies.

Pain, The most common indicator of pain was the doses of

analgesics given to patients. The routes and the timing of

analgesics administration varied among these studies. For

example, the analgesics were given as either oral, injectable,

or intravenous. Further, the doses of oral, IM, and IV

analgesics were simply totalled in some studies with no

attention paid to the equivalency of oral versus IM or IV

doses. These variations in calculation made comparison

inappropriate since the effectiveness of analgesics can Vary

depending on the route of administration and the dose. For

example, oral Codeine is approxirnately 60% as effective as

injectable Codeine (Jaffe, 1971; in Anderson, 1987).

Similarly, the effectiveness of different analgesics can Vary,

for example, Pethidine 80mg = Morphine lOmg = Codeine 120mg,

hydromorphine 1.5mg = Oxycodone lOmg (Jaffe h Martin, 1980; in

Weis et al., 1983). This indicates that if different

analgesics or different routes of analgesic administration

were employed within the same sample, then the measurernents

for that study were inconsistent unless these differences were

taken into consideration.

Also, the timing or the length of analgesics

administration varied among the primary studies. In other

words, the time period during which the outcornes changes were

measured varied among studies- In the studies that reported

the time period, the total analgesic use was measured either

(a) during the first 24 hours, (b) from surgery to discharge,

or (c) from midnight on the day of surgery to midnight in the

third postoperative day. In the first two cases, the beginning

of the time period needs to be more specified, since the

current definition rnay cause inconsistencies even within the

same study. In the third case, the measure of analgesics from

midnight on the day of surgery to midnight on the third

postoperative day was also not accurate since a patient who

may have had the surgery at 2300 hours rnay not be comparable

to a patient who had the surgery at 0800 hours. Using a

single, well-defined method such as starting the count at the

patient's transfer from the surgical intensive care unit

(Anderson, 1987) may provide consistency within and among

s tudies.

These inconsistencies indicate a possible lack of

reliability and validity in the outcome measures used, which

in turn, could pose threats to construct validity. These

threats may have influenced the effect s i z e s in individual

studies leading to inaccurate conclusions in the individual

studies, and in turn, to inaccurate conclusions in this meta-

analysis. As was the case in LOS, some of the variations found

99

in the effect sizes for pain among the primary studies may be

attributable to these inconsistencies in the primary studies.

Of the seven studies that

provided operational definitions, postoperative anxiety was

measured with various methods and scales. These were:

1) State-Trait Anxiety Inventory, 2) Palmer Sweat Index,

3) Profile of Mood States, 4) Multiple Affect Adjective List,

5) Postoperative Affect Scale, 6) adjective check list,

7) Persona1 Orientation Inventory, 8) varigus investigator-

developed subjective or objective rating scales, and 9) heart

rates and doses of sedatives or anxiolytics.

Some of these instruments measure different phenornena

that are related to, but not necessarily, the same outcome

concept of anxiety. In other words, some of these instruments

measure mood, distress, apprehension, psychological well-

being, and depression. For example, in a study by Anderson and

Masur (1989), anxiety was rneasured using the Adjective Check

List which is part of the depression check list. The persona1

Orientation Inventory measures "values, attitudes, behaviours

relevant to Maslow's concept of self-actualizing person", but

does not accurately measure the concept of anxiety (cited in

Felton et al., 1976). Also heart rate was used in some studies

to measure anxiety; increase in heart rate may even occur

because of the anxiety in participating in a study, thus not

necessarily measuring the postoperative anxiety. Additionally,

100

investigator-developed subjective or objective rating scales

may not accurately measure postoperative anxiety. Sidani

(1996) stated that "using instruments with no established

construct validity may lead to difficulty in interpreting

results" (p. 88) . These inconsistencies and inaccuracies in measurement

pose a threat to the statistical conclusions and construct

validity in individual studies. Such errors in measurement

V I ... increase variability in the distribution of scores for subjects in the experimental groups, leading to increased

within-group variance". As a result, this "... reduces the statistical power to detect significant intervention effects,

increasing the potential for erroneous conclusions regarding

the effectiveness of the intervention in achieving the

expected outcornes" (Lipsey, 1990, Stucliffe, 1980, cited in

Sidani 1996, p . 8 9 ) . These inconsistencies may also be related

to the lack of well-developed frameworks or theories in

guiding most of the primary studies used in this meta-

analysis.

In addition, these measurements were taken at various

points in the perioperative period. These varied from prior

to, during, or after the surgery. Those measurements that were

obtained prior to or during surgery cannot be considered as

postoperative outcome measurements of anxiety. The outcome

variable of interest in this meta-analysis is the

postoperative anxiety and ,therefore, these studies that

measured anxiety before and during procedures were excluded

from the study, Measurement time points need to be carefully

chosen to match when the intervention is most likely to

produce a measurable effect of the intended outcome

(Strickland, 1997) . In some of the studies, the anxiety scores were given

only as the percentage of anxiety decrease from preoperative

to postoperative measurement. As such, the means and the

standard deviations of the control and the experimental groups

were not available. Therefore, the studies that reported only

the percentage increase or decrease in anxiety were also

excluded £rom the quantitative data analysis.

Limitations

The first major criticism of meta-analyses is the "file

drawer" problem (Graney & Engle, 1990), which is also referred

to as the publication bias. Some researchers have stated that

the studies with statistically significant results are more

likely to be submitted and accepted for publication by

refereed journals (Glass, McGaw, & Smith, 1981; Greenwald,

1975; Rosenthal, 1978; Wolf, 1986) . They have further suggested that including only the published studies, as is the

case in this meta-analysis, may result in inflated effects of

the intervention (Wolf, 1986) . However, other researchers have concluded that there have

102

been no significant difference between the effect sizes of the

published and unpublished studies in most meta-analysis

(Devine & Cook, 1992; Lipsey & Wilson, 1993; Preiss 6 Allen,

1995). In fact, several meta-analyses which examined the

effectiveness of psychoeducational interventions have

demonstrated that the differences of the effect sizes of the

postoperative outcomes between published and unpublished

studies were not considerably large (Devine & Cook, 1983,

p. 270; Devine & Cook, 1986; Mumford et al., 1982) . Further, the most recent meta-analysis of the effectiveness of

psychoeducational interventions by Devine (1992) cited that

beneficial effects are not '.. . attributable to a publication bias" (p.135). In addition, the effect sizes obtained in this

meta-analysis were in agreement with the effect sizes found in

the other meta-analyses that examined both published and

unpublished studies. These reasons indicate that the 'file

drawer" problem is not a significant concern in this meta-

analysis.

The second concern is that the results of any meta-

analysis depend on the quality of data that can be extracted

£rom primary studies and the completeness with which the

primary studies provide relevant information. If sufficient

data are not available, a problem of aggregating enough

primary studies together to produce convincing results occurs,

which is known as the "file folder" issue, For example, the

103

sample for this research was limited to 20 studies. Although

other related meta-analyses (Mumford et al., 1983; Suls & Wan,

1989) have also had similar sarnple sizes, having a small

sarnple size introduces low power to the statistical test of

the study. Power is the "capacity of the study to detect

differences in relationships that actually exist in the

population" (Burns & Grove, 1993, p.247).

Further, the problem of missing demographic

characteristics of the participants in the primary studies was

a significant cause for concern in this meta-analysis. The

authors of these studies were not contacted in order to

retrieve missing data not only due to financial and time

constraints, but also because of the fact that the majority of

the studies were conducted over 10 years ago and that very

little new information about the study participants could

iikely be obtained even if the authors were contacted.

The third concern noted in this meta-analysis is the

weaknesses and inconsistencies of the measurements and the use

of instruments in the primary studies. The details xelated to

this limitation were addressed elsewhere in this thesis. Lack

of cornmon measurement timing, common metric with regard to the

outcomes, and concerns regrading the reliability and validity

were most apparent in the case of the LOS and pain outcomes.

Although previous literature on reliability and validity of

the measurements of postoperative anxiety was available, many

104

inconsistencies regarding the construct validity were noted in

the studies that examined anxiety.

Summarv

This chapter presented a discussion of the results of

both the descriptive and quantitative analysis of data in this

meta-analysis. The first sections of this chapter presented a

comparison of the samples of the meta-analyses. In comparison

to the previously published meta-analyses, the present meta-

analysis included studies that were published r e c e n t l y , that

sampled adults only, and that evaluated educational

interventions only.

Various components of preoperative teaching that were

used in the 20 primary studies were then addressed,

Preoperative teaching has been conducted mostly after patients

were admitted to a hospital and using audiovisual or written

materials. The majority of primary studies employed a

combination of information rather than a single content,

however, explicit information regarding the presentation and

structure of preoperative teaching was not provided in most of

the primary studies.

The next sections of this chapter examined the

reliability and validity of the measurements of the outcome

variables of interest in this meta-analysis. Many

inconsistencies related to the reliability and validity of the

measurements and conceptual definitions were noted. Also, the

105

relevance of these problems to the effect sizes obtained in

this meta-analysis was discussed.

The last sections of the chapter addressed the

limitations of this meta-analysis. The main limitations

considered were the inclusion of the published studies only,

small sample size, and inability to calculate an ES for

anxiety due to the above mentioned problems in the primary

studies . Regardless of these limitations, the findings of this

meta-analysis dernonstrated favourable effects that are

consistent with the findings of the previously published

related meta-analyses, T h e s e results confirm the continuing

effectiveness of the preoperative teaching intervention in

adult patients undergoing surgeries. Implications of these

results for practice, theory, ând research are discussed in

next chapter.

CHAPTER 5

SUMMARY, IMPLICATIONS, AND CONCLUSIONS

Suxnmary

A meta-analysis of 20 primary research studies that were

published in journals from 1970 to 1996 was conducted to

examine: 1) the demographic characteristics of the patients

participating in the studies examining the effectiveness of

preoperative teaching; and 2) the influence of the selected

demographic characteristics, such as age, gender, education,

and ethnicity of the patients on the postoperative outcomes of

LOS, anxiety, and pain.

A descriptive synthesis of data was used to examine the

demographic characteristics of those who participated in the

preoperative teaching effectiveness studies. Although the

majority of the studies reported information regarding the age

and gender of the patients who participated in their studies,

this was not the case for education and ethnicity. Of the

studies that reported the relevant information, the majority

of the patients appeared to be white females of 41-60 years of

age with above secondary level of education.

Therefore, the findings of this meta-analysis, similar to

that of the previously published meta-analyses, are

generalizable only to the white English speaking patients

undergoing surgery. However, this conclusion is limited

because most of the primary studies have reported the race

instead of the ethnicity of the patients in the primary

research reports. The description of the race (for example,

white patients or South Asians) instead of the ethnic,

cultural, or the religious affiliation of the patients (for

exarnple, white Quebec Francophone, or Sri Lankan Tamil Hindus)

limits the ability to determine the specific target population

to which the results of this meta-analysis can be generalized.

A frequency count approach was used as a preliminary

strategy in examining variations in the LOS and pain outcomes

in relation to each of the four demographic characteristics of

the patients who participated in the studies. The results

indicated that, overall, the n d e r of studies with

significant findings did not differ much from the rider of

studies with non-significant findings across the age, gender,

education, and ethnic groups for both LOS and pain outcomes.

Postoperative anxiety as an outcome indicator was not explored

in the quantitative analysis due to the inconsistencies and

inaccuracies in measurements, conceptual definitions, and

construct validity of the primary studies.

The results of the frequency count approach were

confirmed by analysing a subsample of the 20 studies using a

meta-analytic technique introduced by Hedges & Olein (1985).

This technique was used to examine the effect of preoperative

teaching on three postoperative outcomes. The results

confirmed a moderate-sized beneficial effect of preoperative

teaching on the outcomes of LOS and pain, Overall, these

findings were consistent with the previously published related

meta-analyses as well as the results of the frequency count

approach.

Implications

The results of this study have implications for nursing

practice, theory, and research. The use of meta-analytic

techniques in a systematic rnanner to review many primary

studies enabled the researcher to gain a broader perspective

of the effectiveness of preoperative teaching. The

recommendations derived from this understanding for further

improvement in practice, theory, and research are given below.

Prac+i-=

The findings of this meta-analysis confirm the importance

of preoperative teaching in improving postoperative outcomes

in patients undergoing surgery. However, these results need to

be critically examined in order to assess the extent of the

applicability of these findings to the patients seen in each

practice setting. -For exarnple, the participants in these 20

studies are not representative of the population of Toronto

where the majority of the downtown hospitals are frequented by

people of various ethnic backgrounds. Thus, these results

cannot be generalizable to al1 people undergoing surgery in a

city like Toronto.

Culture and ethnicity in combination with the other

demographic characteristics such as age, gender, level of

education can directly or indirectly influence teaching-

learning interventions (Sidani 6 Braden, 1998). Evaneshko

(cited in Tripp-Reimer, 1989) pointed out, that the "majority

of health education programs have been one of two types: those

developed by whites for use with white patients, or pre-

existing white programs adapted to an etnnic group by layering

a thin veneer of cultural information over the white-based

format" (p.613). Furthermore, the same nursing intervention

presented by the same nurse to individuals £rom two different

ethnic or cultural backgrounds rnay have different outcornes.

Tripp-Reimer (1989) stated that one patient rnay be persuaded

by the teaching, whereas the other person rnay be

"disillusioned, fearful", or perceive that the information

given was not applicable to his or her situation. Thus,

standardized care rnay not be effective across diverse cultural

groups; and in fact, rnay not equally be effective even within

one cultural group (Masi et al., 1993). Each patient is unique

and preoperative teaching needs to be tailored accordingly.

Further, each patient's preference for information and

behavioural involvement in care, as well as the best method,

the content, timing, presentation and the structure of

teaching for each patient, rnay Vary. These issues have not

been addressed sufficiently in research studies in order to

make definite conclusions, Therefore, it is important to pay

110

attention to various components when implementing preoperative

teaching in each practice setting or when applying research

findings £rom studies like the ones in the meta-analysis.

Theorv

Research findings can be used not only for practice

recommendations but also for theory development. Theories that

are emerging from research findings can be tested and refined

through further research in order to enhance their

applicability to practice (Burns & Grove, 1993). For example,

the framework that was used to guide this research can be

tested in further research to examine the influence of various

demographic characteristics of patients on preoperative

teaching. If further reseaxch confirms what is proposed in

this framework, then it rnay become a starting point in

developing theories that relate to the effectiveness of

preoperative teaching and the direct or the indirect influence

of the demographic characteristics on the outcomes of these

interventions. Other theories such as Leininger's (1991) or

Kleinman's (1988) that examine the impact of and importance of

ethnicity and culture in care, treatment, and outcomes may be

integrated in this inductive reasoning process.

Furthemore, theories and frameworks guiding primary

studies will reduce problems that were encountered in the

primary studies of this meta-analysisl sample in terms of

construct validity and conceptual definitions.

Reçearch

The maximum contribution of this meta-analysis rests on

its ability to indicate gaps in research and to provide

recommendations for further research accordingly.

First, the findings demonstrate the need for research to

examine the effect of demographic characteristics on

preoperative teaching. Without gaining such knowledge, the

effectiveness of preoperative teaching in al1 patients

undergoing surgery is questionable. For example, is

preoperative teaching effective in patients who do not speak

English, or who have very little knowledge of English? 1s the

written information effective in patients who use story

telling as the method of comcnication and information giving?

It is important to examine how to measure the effectiveness of

preoperative teaching

religious cultural

way of punishing self

important to find out

preoperative teaching

on the pâin outcome in patients whose

beliefs require them to endure pain as a

to deal with karma? Similarly, it is

how to measure the effectiveness of

on the early adulation indicator of

recovery outcome category in patients whose religious or

cultural beliefs require them to be passive to Save energy for

healing purposes. Therefore, research examining how various

demographic characteristics can alone or in combination affect

various aspects of preoperative teaching is needed in order to

make accurate statements and conclusions regarding the

effectiveness of preoperative teaching for patients of diverse

demographic characteristics.

Second, further research is also needed to assess the use

of instruments and scales that are commonly used in research

such as STAI and POMS and their cultural and linguistic

appropriateness to patients from different ethnic backgrounds.

The extent of the accuracy, appropriateness, and difficulties

with these measurements and scales have been avoided in the

studies included in this meta-analysis by excluding those

patients who are not proficient in English, or those who could

not understand the consent forms, or those who do not have the

reading or writing s k i l l s .

Third, there appears to be a gap in the research

literature in terms of the number of studies conducted in

Canada. As mentioned elsewhere in this study, the population

undergoing surgery in Canada is not the same as the population

of interest in the United States. Various characteristics such

as ethnicity, level of education, and socio-economic factors

such as poverty, cost of health care, or the availability of

insured services can differently influence these t w o

populations, Therefore, more Canadian studies exarnining

preoperative teaching effectiveness are necessary.

Fourth, future research should respond to the importance

of reporting details about: 1) the rate of participation among

113

eligible patients; 2) characteristics of those participating

versus those declining to participate; 3) attrition rates; and

4) the demographic characteristics of the study participants.

Such information would aid in detedning the

representativeness of the study samples and the population to

which these results can be applied.

Fifth, research examining various aspects of preoperative

teaching is needed to make accurate statements and conclusions

regarding the effectiveness of preoperative teaching. The

components of teaching, specifically single versus multiple

content, the effect of various methods, timing, presentations

and structures are important in determining the extent of the

effectiveness of preoperative teaching needed to guide the

design and implementation of preoperative teaching in everyday

practice.

Sixth, the use of consistent measures with documented

validity and reliability in primary studies is recommended to

increase the construct validity of their studies. The timing

of measurements and the time frame of the rneasures need to be

consistently used within and across studies and the rationale

for these timings also needs to be carefully employed and

reported, Furthermore, the use of theories and frameworks to

link interventions and outcomes conceptually is recommended in

primary studies to reduce the inconsistencies and inaccuracies

in conceptual definitions and construct validity (as was

apparent in the case of postoperative anxiety).

Conclusion

Although there is a large number of studies on the

effectiveness of preoperative teaching on postoperative

outcomes, these studies are limited in the demographic

representativeness of the their samples. As a result, the

findings of this meta-analysis as well as the results of the

previously published related meta-analyses are not

generalizable to al1 patients undergoing surgery, specifically

not for patients with less t h a n secondary level of education

or of var ious ethnic backgrounds. Therefore, further research

examining the influence of age, gender, education, and

ethnicity of patients on the outcomes of preoperative teaching

is needed.

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Part 1 of this appendix gives a detailed description of

the statistical theories and formulas behind the meta-analytic

techniques used in this thesis. The statistical methods used

in extracting information from individual studies that did not

explicitly report pertinent information are given in Part 2.

A rigorous development and definition of the population

effect size parameter followed by the derivation of its least

variant linear combination estimator is given here. This is

based on the Fixed Effect Structural Mode1 and closely follows

Hedgesls original paper (1981) and the methods outlined in

subsequent books by Hedges and Olkin (1985) and Cooper and

Hedges ( 1 9 9 4 ) .

Let us suppose a number of different studies examined the

effect of an intervention on the same dependent variable using

different units or scales to measure this dependent variable-

If the results of these studies were to be combined in any

meaningful way, it is essential that these measurements first

be converted into a common scale. One method of accomplishing

this would be to calculate Glass's Effect Size g, which

standardizes the difference between the mean scores from the

experimental and control groups. T h u s , E f f e c t Size g £ r o m a

particular study given by:

- - where Y. and Y, are the mean scores of the experimental and

control groups, respectively, from that study. Although Glass

originally proposed using the control group standard deviation

for S, for reasons that will become clear in the next section,

it has become common practice to use the pooled standard

deviation, Sp, from the experimental and the control groups

for S. Since the mean scores and the standard deviation have

the same units of masurement, g is unitless and hence, scale

free. Thus,

where ,

Sp = J { ( n.4 )se2 + ( - 1 s / (ne + n, - 2) and ne, n, are the sarnple sizes, and Se, Sc are the standard

deviations of the experirnental and control groups,

respectively.

Let us consider a hypothetical list of all possible

studies that are similar to the study mentioned above in a l 1

the characteristics, but differed only in the selection of

study subjects. The scores Yens and Y,'s of the particular

study considered earlier are nothing but samples from these

hypothetical populations of al1 possible experimental and

control scores of similar studies, Suppose these populations

of experimental and control group scores are independently

normally distributed with means p, and p,, respectively.

Further, suppose these two populations share the same standard

deviation 0. Then, it is possible to define a population

counterpart to the sample effect size g -- a population effect

size parameter 6 for this list of studies -- given by:

Let us consider now, an additional list of hypothetical

studies that differed from those on the above list on yet

another aspect -- the studies that used a common unit of measurement but one that is different from the unit used in

studies of the first list. The scores £rom these studies

cannot be assumed to be in the populations considered above

because the corresponding means will be certainly different

from p, and p, owing to the different units of measurements.

However, we can consider two new populations of scores with

means p,' and p,' and cornrnon standard deviation a' , and define

a new population effect size parameter 6' for this list of

studies in the same manner as before:

Since effect sizes are unitless, it is entirely possible

to make the assumption that 6 = 6', even though the two lists

of studies used different units of measurements. In fact it is

possible to extend this argument to cover al1 hypothetical

s t u d i e s that differed f r o m the initially mentioned study in

only two aspects: the subjects selected to participate, and

the unit of measurements used- These hypothetical studies can

be divided into subgroups where al1 the studies in any one

subgroup used the same unit of measurement and define 6, 6',

6' ' . - - as above and make the assumption

The common value 6 defined above is called the population

effect size parameter for a group of studies under the Fixed

E f f e c t structural Model,

It would seem that a n estimate of 6 can be obtained by

calculating an average of the sample effect sizes across the

studies- However, if the aim here is to accomplish this with

as much precision as possible, then it becomes essential to

examine the sampling distribution of g first.

If the scores Y,'s and Ycls a l 1 corne from normal

140

distributions with a common standard deviation, then the

sampling distribution of g will be a non-central t-variate

except for a constant multiplicative factor (Hedges 19811. The

mean of this distribution is given by:

where, m is the degree of freedom of Sp:

and J(m) is a mathematical function derived from the Gamma

function, and depends only on m, the degree of freedom

(Hedges, 1981) , Further, J(m) < 1 for al1 values of m and

J(m) - 1 as m - There are tables such as the one in

Hedges (1981) that gives values of J(m) for different integer

values of m.

If ne = n,, then as m - am, the above distribution

approaches a normal distribution with a mean 6. This suggests

that if the sample sizes in each of the studies are

sufficiently large, then the g values £rom the studies can be

used to estimate 6, The question of how large the sample sizes

ne and n, should be in order to estimate 6 with a certain

precision can be answered with the aid of J(m) values.

Suppose ne = n, = 10.

Then, m = 18 and J(m) = 0.95765.

Hence, 1 / J ( m ) = 1,044 and the corresponding mean

E ( g ) = 1.044 '-6.

In other words, if w e are using studies with sample sizes

of 10, the error introduced in the 6 estimate would be at

least 4%. For sample s i z e s less than 10 , J ( m ) would be even

smaller and the error would be even greater. The error

introduced in this manner i s often referred t o as a srna11

sample bias, However, s i n c e t h i s error or bias depends only on

t h e sample sizes of the study, it is possible to eliminate

this error entirely by making a modification to g.

If t h e effect s i z e g is modified and a new sample

statistic d is d e f i n e d as :

then, it follows that d will have a ' non-cen t ra l t' sampling

distribution with a mean

Therefore, t h e s t a t i s t i c d f r o m a series of studies can b e

averaged t o o b t a i n a n estimate of 6 , It should be no ted t h a t

although there exists an approximate formula f o r calculating

J ( m ) f r o m m that is accurate enough for m o s t practical

142

purposes, it is most useful only in simple software routines

where looking up a table might be memory intensive. In hand

calculations, looking up at a table such as the one in Hedges

& Olein (1985) is faster.

Suppose the d values from a collection of k studies are

linearly combined as follows:.

where di comes from study number j and w j ' s are weights yet to

be determined. If we were to present our D value with as tight

a confidence interval as possible, then we should strive to

minimize the variance of D. It follows from the above

expression that for fixed values of the weights, the variance

of D is a linear combination of the variances of the djls with

the same weights. Therefore, the variance of D will be a

minimum when the weights wjls are inversely proportional to

the variance of djVs. In other words,

where v, i.c variance of the dj estimate from the j-th study.

Hence, before proceeding with the linear combination

estimate, an explicit expression for the variance of the

sample statistic d should be obtained.

As

mentioned earlier, the sampling distribution of the modified

effect size d is a non-central t-variate with a mean 5 .

Unfortunately, the formula of the variance of this

distribution, is too complicated for use in any manual

calculations. However, when ne and n, each is greater than 10,

t h i s distribution can be closely approximated by a normal

distribution with mean 6 and a variance v given by

Here, the variance of the estimator d is used i n the pooled

estimate for the unknown 6, depends on 6 itself.

There are two different methods of getting around this

problem. The first involves a very reasonable approximation to

v that does not involve 6, and the second one involves an

iterative procedure for obtaining successive approximations

for the estimate of 6.

A-k estimate, In most cases where the effect is of

moderate to small size, the value of 6, and the values ne and

n, are such that,

For example, c o n s i d e r 6 = 0.5 and ne = 20 and n, = 20.

62 / 2 (ne + n,) = 0.003 and (ne + n,) / (ne n,) = 0 . 100

T h e r e f o r e , t h e v a r i a n c e v c a n be approximated as f o l l o w s :

v = (ne + n c ) / (ne * n c ) .

T h a t is , 1 / v = (ne * n,) /(ne + n,)

Thus, W j = 1 / TT, = (ne, * n,) / (nej + na)

And t h e e s t i m a t o r f o r 6 i s given by k

D = { C w j * d j ) / C w j j=I

In t h i s method, t h e ci v a l u e

from e a c h study i s u s e d as a f i r s t approx imat ion for 6 i n t h e

fo rmula f o r t h e v a r i a n c e v, That is ,

Vj = (ne!+ n,,) / ( n ) + d j 2 / 2 (ne j + n,)

and wj = 1 / v j .

T h e s e w e i g h t s are now used t o cornpute a f i rst estimate f o r d

a s f o l l o w s k

d+, = { C w j d j 1 / W j

j=l

T h e d,l c a l c u l a t e d t h i s way i s now u s e d i n p l a c e o f t h e d ' s

e a r l i e r f rom t h e i n d i v i d u a l s t u d i e s , t o c a l c u l a t e v i n t h e

fo rmula above:

New weights wjgs are calculated using the above vj's and a

second estimate of 6, namely d+2r is obtained.

These iterative steps are continued until the difference

between the successive a's becomes negligible for practical

purposes .

ce m e r u a l , When the sample sizes are

sufficiently large, the distribution of bj tends to be normal

with a variance:

where vifs are the variances of the djls from which d+ was

calculated (Hedges & Olein 1985) . However, recalling that the weights wjgs were chosen such

Wj = l / v j , v(d , ) can be calculated using the formula

Thus, a 95% confidence interval

where the number 1.96 came fxom

standard normal distribution.

for 6 can be obtained as

1 I

the two-tail 5% cut-off in the

The chi square distribution

that is often used in the primary analysis to test if two sets

146

of data belong to the same distribution, can be used here to

test if al1 the studies share a common population effect size

6 . Each study produced a d value and we have an estimate of 6,

in d+. Therefore, each d value is compared to 4 and the mean

squared difference of individual dus with respect to the d, is

computed.

Under the null hypothesis that each study cornes from the

same population with effect size d,, the resulting statistic Q

given by

has a chi square distribution with degree of freedom k-1.

Hence, the above null hypothesis is rejected if the

probability associated with Q value obtained above is too

small (such as less than 5%). Otherwise the observed

differences between the individual d s and the population d+

are attributed to chance alone. That is, the studies are

considered to share a common population effect size.

If the homogeneity tests fails, then performing effect

size calculation over subgroups of studies that share common

characteristics may provide a better understanding of the

effect of the intervention.

Ln order to calculate the effect size g for a study, the

sample sizes, means, and the standard deviations of both the

experimental and control groups were extracted from that

study. However, a conunon difficulty encountered in doing so is

that many studies do not report the control and experimental

group standard deviations explicitly. In these instances, a g

value was calculated indirectly from the t-statistic or ANOVA

statistics that were reported in the study using the

appropriate statistical techniques.

When a two sample t-statistic between the experimental

and control group was reported, the following method was used

to calculate g. The student t-statistic for the two sample

difference of independent means is given by:

Therefore, g = t * J ( l / n e + ~ n , ) -

When statistics from a One-Way-Analysis of Variance

(ANOVA) conducted across the groups were reported, the

following method was used to calculate the effect size g.

First, observe that the statistic Mean Sum of Squares

within the groups (MSSUi,,,) from the ANOVA is no th ing but the

pooled variance across al1 groups. The square root of MSS,,,,,,

is the pooled standard deviation across al1 groups, In the

absence of any further information, the pooled standard

deviation across al1 groups can be used to approximate the

pooled standard deviation Sp across the two groups of

interest, Thus, if a study has reported MSS,,,,,,, then Sp is

calculated as follows:

In some studies, MSSWicm, is not reported, but an F-value

and the group means are reported. In this case, a Mean Sum of

Squares between the groups (MSSbetween) was first calculated

using the group means- T h i s MSSbe,,,,, together with the F-value

reported, is now used to calculate the MSS,,,,, a s follows:

The square root of MSS,,,,,, is now used to approximate Sp as

mentioned abooe.

I I I

First Aulhor

Christopherson, B.

Dziurbejko, M.M,

Fel ton, G .

"

Fortin, F.

ticgyviry S.T

lfill, B.J,

hlcthod of trrching

!ducrlioarl t v t l : ange, nean, SD

rrbaic brck !round

igc: range mcan

SD

trperim«itrl

nndom wlgnment

individuil imchin8 iàmily taching

LOS numbcr of rnrlgeoics imbulai ion podop cornpliath ilemiindingncss r-h

v w , bodtlcc of WOJ, individual taching

LOS psychologiccil mllbcing inxkty dccraw pulmocrciry compllcrth

LOS comfbrt rlf-niing ovcnll albbction numbcr of rnrlgtslcs tima until mum Io work

hospiml l l- ncirlly mixcd ll2 J9I60- white, O-blrck

booklei, individu1 taching

LOS complication numbcr of rnilgeoics

enpcrimcnlrl nndom rssignmcni

I I I I I I I I I

I I I I I I I I I

I I I

Characteristic Frequency Percentage

Publication form

Journal

First author

Nursing

Anesthesia

Pharmacology

Psychology

Cardiology

could not be determined

Publication date

< 1960 1961-1970

1971-1980

1981-1990

> 1991

Setting

United States

United Kingdom

Canada

Characteristic Frequency Percentage

Type of surgery

abdominal

thoracic

orthopedic

GYNE/GU

combination of surgeries

other surgeries/cataract

tes ts/procedures

Mean/Average age

18-40 yrs

4 1-50 yrs

51-60 yrs

> 60 yrs

not given

Gender

al1 male

1-253 female

26-50% female

51-75% female

76-99% female

al1 female

not given

Educational level

elementary (<7/8 1

secondary 18-13)

college/university

not given

Ethnicity

al1 non-white

1-25% white

26-505 white

51-75% white

76-995 white

al1 white

not given

Table 5

Characteristic Frequency Percentage

Manner of assigrunent to groups

random

non-xandom

Type of control group

usual care

placebo-type

placebo & usual care

Number of experimental groups

1 preop teaching group

>1 preop teaching groups

>1 intervention groups 6

1 preop teaching group

Table 6

Review of the 20 studies

Hill, BJ.

Johnson. J E . 1974

Johnson 1.E- 1978

Mikulanincc. CE- 1987

Wallace. L.M. LIL

II_ wacicïns, Lo.