Original Article

Full Title: The endovascular pre procedural run through and brief: A simple intervention to reduce radiation dose and contrast load in endovascular aneurysm repair

Tim Stansfield a 1, Richard Parker b, Neil Masson c, David Lewis a

a Department of Vascular & Endovascular Surgery, The Royal Infirmary of

Edinburgh, 51 Little France Crescent, Edinburgh, EH16 4SA, United Kingdomb Health Services Research Unit, University of Edinburgh, Centre for

Population Health Sciences, Teviot Place, Edinburgh, EH8 9AG, United

Kingdomc Department of Radiology, The Royal Infirmary of Edinburgh, 51 Little France

Crescent, Edinburgh, EH16 4SA, United Kingdom

Email addresses:

timstansfield@doctors.org.uk

richard.parker@ed.ac.uk

Corresponding Author:

Tim Stansfield

Telephone: +1(916)7690654

Email: timstansfield@doctors.org.uk

Postal Address: Department of Vascular & Endovascular Surgery, The Royal

Infirmary of Edinburgh, 51 Little France Crescent, Edinburgh, EH16 4SA,

United Kingdom1 Present Address: David Grant Medical Center, 101 Boden Circle, Travis

AFB, CA 94535

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What this paper adds

By introducing rigorous quality assurance and utilising the principles of crew

resource management to the EVAR process it is possible to reduce screening

times, contrast use, hospital length of stay and improve endovascular training

opportunities. We believe this straightforward practice should be routinely

performed with EVAR procedures.

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Abstract

Objectives: to assess the impact of a quality assured planning and sizing

process and the endovascular team briefing (pre procedure run through and

brief - PRTB) on the delivery of EVAR in Edinburgh.

Design: Prospective observational study, comparing parameters before and

after the intervention.

Materials: Prospectively collected database recording infrarenal aneurysms

treated with EVAR performed from January 2007 to April 2014 at our

institution. The total screening time, iodinated contrast volume used, radiation

dose, endovascular training opportunities and hospital length of stay were

recorded.

Methods:. A comparison before (January 2007 to November 2011) and after

(December 2011 to April 2014) the introduction of the PRTB was made for

each of these variables. Multiple linear regression analysis was performed to

account for the learning effect.

Results: 61 EVAR cases were performed prior to and 44 EVAR cases after

the introduction of the PRTB. Univariate Mann-Whitney tests suggested a

significant difference between before PRTB introduction and after PRTB

introduction on all outcome variables except procedure time. Multiple linear

regression analysis results showed a statistically significant improvement in

outcomes after the change point for all outcomes except for radiation dose.

Endovascular training opportunities were realised in 12/61 (20%) before

compared to 42/44 cases (95%) after PRTB introduction.

Conclusions: By introducing rigorous quality assurance and utilising the

principles of crew resource management to the EVAR process it is possible to

reduce screening times, contrast use, hospital length of stay and improve

endovascular training opportunities.

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Keywords (MeSH): Endovascular Procedures; Patient Care Team; Radiation;

Contrast Media

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1. Introduction

Endovascular aneurysm repair (EVAR) is an accepted treatment for

abdominal aortic aneurysm. 1-3 EVAR is however documented to have

recognised complications from the use of contrast 4 as well as potential risks

to patients and staff from exposure to ionising radiation. 5 Any intervention to

improve procedural efficiency and safety warrants serious consideration.

Efficient stent graft deployment may facilitate a reduction in radiation

exposure lessening the well recognised deterministic 5 and stochasitic effects.

The principles of crew resource management (CRM) originate from the US

aviation industry. 6,7 CRM is, in essence, team based practice and training

procedure for high value interactions focusing on communication, leadership

and decision making to minimise error and optimise outcomes by the team. 8

The principles and practices of CRM have particular relevance in EVAR; a

complex procedure that in many institutions demands careful multidisciplinary

planning and intraoperative coordination. The WHO surgical safety checklist

can be regarded as a component of CRM and has been shown to reduce

intraoperative error and negligence claims. 9

As part of a quality improvement process aimed at enhancing the service in

our unit, and based on the principles of CRM, we introduced a Pre procedure

run through and brief (PRTB), outlined in Table 1, in December 2011. This

was in addition to the existing practice of performing the WHO surgical safety

checklist pre-anaesthetic, pre-procedure and post procedure. The aim of this

study was to assess the impact of this quality assured planning and sizing

process and the endovascular team briefing on the delivery of EVAR in

Edinburgh.

Abbreviations

PRTB – Pre procedure run through and brief

CRM – Crew resource management

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2. Material and methods

Prospectively collected data regarding elective infrarenal aneurysms treated

with EVAR performed from 01 January 2007 to 01 April 2014 at The Royal

Infirmary of Edinburgh were retrospectively analysed. All procedures were

performed in the non-hybrid intervention suite. All patients’ electronic records

were followed up to 01 August 2014. Primary endpoints recorded included

the total screening time, iodinated contrast volume used, radiation dose

(measured by the imaging equipment kerma area product meter),

endovascular training opportunities and hospital length of stay. We defined an

endovascular training opportunity as an opportunity for the vascular or

interventional radiology trainee to perform a component part of the stent graft

deployment as recorded in the operative note or personal logbook.

Secondary endpoints included mortality (early and late) technical success (no

type 1 endoleak seen on the intraoperative angiogram and no conversion to

open repair), type 1 and 3 endoleaks (early and late), secondary interventions

(early and late), postoperative morbidity (during admission), and other graft

related complications identified during follow-up. Early was defined as within

30 days of implantation and late as after this time period.

A comparison before and after the introduction of the PRTB was made for

each of these variables, with the change point (PRTB introduction) identified.

Firstly, medians and ranges of primary outcome data were calculated within

each group and a (two tailed) univariate Mann Whitney U test was used to test

for a statistically significant difference between the two periods. To investigate

the effect of the introduction of PRTB while accounting for the departmental

learning curve over this period, scatterplots for each variable were

constructed and multiple linear regression models were fitted with interaction

terms included. These interaction models consisted of an intercept term and

three explanatory variables:

(1) a continuous variable representing the timing (in days) at which surgery

was performed centred at the change point;

(2) a binary variable indicating the period (before or after the PRTB

introduction); and

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(3) an interaction term representing the interaction between the two variables,

which allowed the effect of timing of surgery on outcome to vary in the

different periods before and after the intervention. This model specification

allowed the investigation of the change in outcome immediately after PRTB

was introduced while adjusting for the effect of any gradual change in

outcome over time that may have been caused by a learning effect or change

in case-mix. Graphically, the focus is on the intersection of the line of best fit

through the post PRTB introduction data with the change point vertical line on

the scatterplot.

For the length of stay outcome, we additionally included variables for patient

gender and age at surgery to obtain age and gender-adjusted effect

estimates. The resulting model This variable did not show normally distributed

residuals and so two separate models were fitted: for the first model a natural

logarithm transformation was applied to the length of stay outcome prior to

analysis; while for the second, all patient lengths of stay greater than 30 days

were removed from the analysis. All statistical tests were two-tailed and the

significance level was set at 5% throughout. SPSS software version 21 (IBM

Corp. Released 2012. IBM SPSS Statistics for Windows, Version 21.0.

Armonk, NY: IBM Corp.) was used for the statistical analyses. The scatter

plots were produced using R software version 3.1.2. (R Core Team (2014). R:

A language and environment for statistical computing. R Foundation for

Statistical Computing, Vienna, Austria. URL http://www.R-project.org/.).

3. Theory

Studies examining the merits of EVAR planning and preparation have focused

on the technical aspects of this procedure. There are recognised limitations

to EVAR simulation in terms of the dynamic aortoiliac anatomy, contrast flow

dynamics and wire/stent graft stiffness. 10 Three groups have run pilot studies

on patient specific rehearsal for elective EVAR using computer based

simulation with live case, 11 silicone model validation,12 or 3D model rehearsal. 13 The latter group (European Virtual Reality Endovascular Research Team)

intends to perform a Randomised Controlled Trial following the promising

results of their multicentre pilot study. Mehta and colleagues 14 considered the

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team dynamics in emergency EVAR performance. They performed

multidisciplinary moulaging for EVAR of ruptured abdominal aortic aneurysms

from Emergency Department presentation through to completion of the

procedure. Their study went on to show very favourable outcomes for

symptomatic and ruptured aortic aneurysms. A significant reduction in

observed error for combined open/endovascular aortic cases (n=15) after the

introduction of a pre-procedure structured team based mental rehearsal has

also been documented. 15 Cumulative skin radiation dose to the patient

following implementation of improved range radiation reduction strategies

including CRM considerations has been shown for percutaneous coronary

procedures. 16

4. Results

61 EVAR cases were performed prior to and 44 EVAR cases after the

introduction of the PRTB. The minimum follow up period in the latter group

was three months. The profile of these two groups are listed in Table 2.

There were no deaths within 30 days in either group. The before PRTB group

had 11 late deaths (two aneurysm related: one ruptured aortic aneurysm and

one cardiac arrest in theatre during an open repair for a type 1 endoleak) and

the after PRTB group had one late death (not aneurysm related). A technical

success was judged in 57 of the 61 before PRTB group and 42 of the 44 after

PRTB group. There were two early and two late type 1 endoleaks in the

before PRTB group and one early and no late type 1 endoleaks in the after

PRTB group. There were no Type 3 endoleaks observed in either group.

Secondary intervention in the before PRTB included a palmaz stent insertion

on the first post procedural day for one patient and eight patients requiring

late type 2 endoleak inteventions. No early secondary interventions were

performed on the after PRTB group and three late type 2 endoleak

interventions were performed. Morbidity suffered by patients post procedure

included three strokes, four myocardial infarctions, ten acute kidney injuries

and six pneumonias before PRTB and respectively one, two, four and two

after PRTB. There were no access or groin complications recorded in either

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group. Scatterplots of the primary outcomes, with regression lines and

vertical lines indicating the change point for the introduction of PRTB, are

shown in Figure 1a-d. The univariate Mann-Whitney tests suggested a

significant difference between before PRTB introduction and after PRTB

introduction on all outcome variables except procedure time; see Table 3. The

scatterplots graphically illustrate a difference at the change point before and

after the introduction of the Pre procedural brief and run through in terms of

duration of procedure, inpatient stay, amount of contrast used and possibly

also radiation dose. The multiple linear regression analysis results showed a

statistically significant improvement in outcomes after the change point for all

outcomes except for radiation dose; see Table 4. Endovascular training

opportunities were realised in 12/61 (20%) before compared to 42/44 cases

(95%) after PRTB introduction.

5. Discussion

The first EVAR performed in Edinburgh was before 2007, however the

prospectively collected dataset in its current form began in January 2007. We

terminated the study data collection when it became apparent we were

observing a pattern of improvement in performance of EVAR in our unit. We

directly compared the two groups with a non-parametric data analysis tool to

demonstrate statistical difference. Following this we demonstrated through

multiple linear regression analysis, that this was not solely attributable to the

learning curve within the unit, industry involvement, to improvements in EVAR

planning computer software 17 or evolving imaging and stent graft technology.

This matched our clinical suspicion. There are limitations to the regression

models used. They may only partially adjust for changes over time. It is

possible that some residual changes will remain unaccounted for in the model

and thereby influence the results. Further, the sample size is small and

observations occurring near the changepoint are highly influential. Although

the scatterplots show a slight trend of worsening performance following the

improvement observed immediately after introduction of the PRTB, this may

be due to the presence of outlying data points at the very end of the study

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rather than any genuine trend. However, this finding merits further scrutiny of

service within the department.

There are two important potential confounders in this retrospective analysis.

Firstly, although clinicians were unaware they were being studied, they were

not blinded to the intervention. Therefore, changes seen may partly be due to

the Hawthorne effect of applying any intervention (i.e. not just PRTPTB). For

example discharging clinicians may discharge patients sooner simply by being

aware of the intervention, thus confounding the reduction in the length of stay

observed. Secondarily, changes in clinical personnel will have had an impact

on the delivery of the service and may have contributed to the differences

observed at the changepoint. An EVAR competent surgeon joined the

department at incept of the PRTB. However we believe the PRTB was the

substantial component in maximising the benefits of clinical experience,

technical skills and team dynamics. Turning up to a case as an experienced

operator, without prior planning and discussion, does not necessarily allow an

entirely positive influence on the procedure. As indicated above, flux at the

change point is highly influential on such a statistical analysis,

Our primary outcome parameters are clinically and economically relevant in

terms of radiation exposure and hospital length of stay. Radiation dose usage

as measured by the imaging equipment correlates well with personnel

radiation dosage in endovascular procedures, more so than fluoroscopy time. 18 Therefore a reduction in radiation dose as measured by the imaging

equipment reduces the risk to the clinical staff as well as the patient. The

length of procedure time, in our experience, is important in that a lengthy

procedure is more exposed to simple errors through has prolonged

concentration demands, a team fatiguing effect and is more exposed to simple

errors a p. Prolonged anaesthetic time in a generally unfit patient population

may be associated with increased complications.

CRM performance can be objectively measured, for example through the

Mayo High Performance Team Work Scale. 19 We chose to measure outcome

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variables that were clinically relevant rather than measure the team’s

performance per se.

Data recorded regarding endovascular training opportunities were subjective,

relying on operation notes and logbooks, and it is possible that some training

opportunities were not captured by this study. Nevertheless there appeared

to be a trend towards vascular registrars becoming more involved with the

planning and technical aspects of the procedure, having demonstrated that

they had considered the steps of the procedure and were aware of anticipated

difficulties.

We did not analyse patient comorbidity and aneurysm/access vessel

morphology. These are certainly potential confounding factors in all the

outcome variables. Despite this caveat, all graft stent deployments were

planned within the remit of the instructions for use (IFU). There were no

deaths in either group with the first 30 days and there were similar rates of

technical success, early endoleaks and early secondary intervention. This

infers a degree homogeneity between the groups. Nevertheless future

examination of the effects of the PRTB may consider these important

parameters; using for example, the anatomic severity grading score 20 to

objectively confirm the homogeneity of aortic anatomy if within the IFU remit.

Given the scope of anatomical case selection described above a high overall

technical success rate is unsurprising. A modest difference in the late

endoleak and secondary intervention rate will be biased in favour of the

shorter follow-up period for the after PRTB group and may also reflect a

reduced intervention philosophy for type 2 endoleaks over this time frame.

We accept that not every member of the multidisciplinary team is included in

the pre op run through. In order to allow the procedure to start without

significant delay the anaesthetic team were initiating the patient anaesthetic

and invasive monitoring. We have not yet evolved a logistically acceptable

method of involving the anaesthetic team in the PRTB.

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There was a significantly higher proportion of missing contrast use data pre-

PRTB compared to after PRTB (57% versus 16%, p<0.001) which may have

biased our results for this outcome; although we have no reason to suspect

that the probability of missing is related to the amount of contrast.

A generic CRM training package may not deliver the improvements in a

specific clinical context. Clinical simulator training has been shown to

modestly improve objective teamwork assessment scores 21 and some CRM

courses have shown improved compliance with WHO type surgical safety

checklists. 22 However in a Randomised Controlled Trial, final year medical

students did not show any improvement in performance or situational

awareness in severe sepsis resuscitation despite receiving a one and a half

day generic CRM course. 23 We believe a tailored approach is required.

Implementation of new technological developments and strategies relevant in

EVAR planning and preparation, such as 3D aortic printing 24, hybrid suites 25,

error capture tools for team debriefing 26 and patient specific anatomy

simulator training may provide further improvements in CRM based practices.

Given the declining incidence of ruptured aortic aneurysms, Van Herzeele and

colleagues 27 have proposed that simulator training should become de rigour

in order to improve team performance through iteration and allow

maintenance of team competencies.

6. Conclusions

Our data suggest, within the limitations of this study, a measurable advantage

in the EVAR procedure from introduction of a Pre Procedure Briefing and Run

Through. The PRTB is effectively a clearly defined quality assurance step,

utilising the principles of crew resource management, to optimise the team

performance during the real-time EVAR procedure. We have demonstrated

that this gain cannot solely be attributed to the learning curve or evolution of

our unit.

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Conflict of interest statement

Conflicts of interest: none

Acknowledgements

RP was supported in this work by NHS Lothian via the Edinburgh Health

Services Research Unit

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Tables

Timing Immediately before the procedure the surgeon leads a pre

operative run through and brief

Duration: approximately 30 minutes

Location Angiosuite backroom with 3D workstations.

Objectives Complement the WHO safety checklist

Optimise the technical aspects of deployment

Maximise training yield

Discuss potential problems and solutions

Define roles (Who is going to do what)

Personnel Consultant Vascular Surgeon

Trainee Vascular Surgeon

Consultant Interventional Radiologist

Trainee Interventional Radiologist

Industry Technical Support

Radiographer

Checklist Confirm: -

Planning and sizing: neck length, lowest renal artery, infra renal

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(immediately below lowest) aortic diameter, aortic bifurcation

diameter, maximum AP diameter of aneurysm sac, EIA diameter

(left/right), axis (supra renal to neck and neck to sac), any

additional considerations for proximal landing zone, coiling of any

necessary vessels

Probable angulation of the C arm

to optimise imaging of renal arteries and aneurysm neck

to optimise imaging of each internal iliac artery

Additional considerations for distal landing zone

Availability of all endovascular equipment including bale out kit

Run through of the entire procedure using 3D work station as the

basis for discussion

Access: Common Femoral Artery (left/right), Brachial and

Subclavian artery access options

Delegation of tasks during stent graft deployment

Anticipated difficulties and plans to overcome these

Table 1: Components of the Edinburgh preoperative run through and brief

(PRTB)

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Before PRTB

introduction

After PRTB

introduction

Number 61 44

Time frame Jan 2007 to Nov 2011 Dec 2011 to Apr 2014

Mean age at surgery in

years (SD; range)

74.2 (8.38; 52-89) 74.6 (7.75; 58-89)

Sex:

Male

Female

51 (84%)

10 (16%)

27 (61%)

17 (39%)

Minimum follow-up after

admission* (months)

33 3

30 day mortality 0 0

Mortality (all cause) at

Aug 2014

11 (18%) 1 (2%)

Mortality (aneurysm

related) at Aug 2014

2 (3%) 0

*For those patients who did not die before the end of follow-up.

Table 2: Profile of patient groups undergoing EVAR before and after the

PRTB introduction

PRTB: Pre-procedure Run Through and Brief

SD: Standard Deviation

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456

457

458

459

460

461

462

463

464

465

466

467

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Outcome Variable Sample

size N

Median Range U-

value

p-value

Length of hospital

stay (days)

Before PRTB 61 6.0 4 to 219746.5 <0.0001

After PRTB 44 5.0 2 to 29

Procedure time

(hrs)

Before PRTB 61 3.6 2.1 to 9.71174 0.277

After PRTB 44 3.5 1.8 to 7.8

Screening time (s)Before PRTB 61 2039 751 to 8685

1006.5 0.029After PRTB 44 1546 888 to 9218

Dose radiation

(µGym2)

Before PRTB 61 22511 1663 to 167157914 0.005

After PRTB 44 14222 2098 to 63531

Contrast volume

(mls)

Before PRTB 26 277.5 80 to 685148 <0.0001

After PRTB 37 150.0 60 to 440

Table 3: Mann-Whitney test comparison before and after Pre-procedure Run

Through and Brief (PRTB) introduction

PRTB: Pre-procedure Run Through and Brief

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468

469

470

471

472

473

474

475

476

477

478

20

Outcome Variable Adjusted mean

difference*

95% confidence interval

for mean difference

P-value

Duration of Surgery

(hrs)

-1.525 -2.548 to -0.503 0.004

Length of hospital stay

(days; natural log

transformed)

-0.637 -1.162 to -0.111 0.018

Length of hospital stay

(days; excluding

outliers)

-3.487 -6.693 to -0.281 0.033

Radiation dose (µGym2) -15037.62 -34961.50 to 4886.26 0.137

Volume of Contrast

(mls)

-178.42 -293.32 to -63.51 0.003

*After PRTB– Before PRTB

Table 4: Estimated difference in outcome immediately after the pre-surgery

briefing was introduced, adjusted for changes over time due to a learning

effect: changepoint results from a multiple linear regression model

PRTB: Pre-procedure Run Through and Brief

21

479

480

481

482

483

484

485

486

487

488

21

Legend for Figure 1

The vertical line represents the change point at which the pre procedure brief

was introduced.

Each circle represents an individual EVAR procedure.

Lines correspond to models unadjusted for age and sex.

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489

490

491

492

493

494

495

496

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