Introduction

CONTINOUS HEPARIN INFUSIONS require monitoring

aPTT values. Blood samples can be collected from a central

venous access device (CVAD) if present or from a peripheral

vein (PV). If heparin is infusing through a CVAD, how

should aPTTs be collected?

• Peripheral specimen required/desired?

• From CVAD acceptable? Desired port?

• Turn off infusion? How long? Flush first? Waste

amount?

Comparison of aPTT values from venipuncture and central venous access device specimens in hospitalized adult patients

receiving continuous heparin infusions Mary Sue Dailey APN-CNS, Fortunata Dabu, RN, BSN, Sue Durkin, APN- CNS,

Barbara Kohn, MTRN, BSN, Barbara Berger, PhD, RN

Recommendations

Results

Relevant Literature

Venipuncture vs Heparinized Arterial Line •Alzetani (2004)( n=49) Arterial aPTT unreliable

•Heap ( 1997) (n=79) Arterial aPTT valid 96% of time

Venipuncture vs Heparinized CVAD without continuous

heparin infusion •Humphries and Baldwin (2012)( n=30) Power =.71

•0.99 correlation between PICC and VP specimens

•Rondina (2007) (n= 41)

•No significant difference between CVAD and VP specimen

•Hinds (2002) (n=53 pediatric patients with tunneled CVAD )

•Tunneled CVAD results inaccurate but as discard volume

increased paired results closer ( tested 6,9,12mL discards)

Venipuncture vs CVAD-with continuous heparin infusion •Bellmunt. P, et al. (2000) (n=74)

•Significant difference in aPTT between CVAD and venipuncture

specimens with either a 10 or 20mL discard -- the difference was

slightly lower with 20mL discard (10.6 sec aPTT difference with

20mL discard vs. 12.7 sec with 10mL discard)

.

Discrepancies at Start of Study

Nursing and Lab Policies

Previous Studies

Actual RN Practice

Manufacturers Guidelines

Professional Standards

Policies

Lab: Turn off infusion

•Waste depends on dead space – 5-12mL

Nursing: No mention of stopping infusion first

•No mention of “desired port”

•Waste first 6 mL

Professional Standards -- Infusion Nursing Society (INS)

(2006)

Manufacturer’s Guidelines

.

Study Design & Methods Paired blood specimens (CVAD & peripheral venipuncture)

from 74 patients receiving a continuous heparin infusion

through a CVAD. Specimens were collected simultaneously

by a research RN and a phlebotomist

• Protocol: turn off infusions for at least 1 minutes, flush

line with 10 ml., wait 1 minute, draw and discard 10ml,

then draw aPTT specimen.

• Power = .80 with alpha=.05

Actual RN practice at Good Samaritan Hospital

134 respondents completed an online survey in 2009

•82% flushed prior to obtaining sample

•50% wasted 10 mL

•56% collected the coagulation specimen first

•94% stopped the infusion

Purpose

Is there a clinically significant difference between the aPTT

results from a CVAD specimen and a peripheral venipuncture

(VP) when the patient is receiving continuous heparin

through the CVAD?

Collect aPTT specimen from peripheral venipuncture if possible

If CVAD specimen necessary:

• Collect from port without a heparin infusion

• Follow INS guidelines-turn heparin off 5 minutes prior to

specimen collection

Designate port for heparin infusion- proximal port is preferred as

blood flow diffuses drug into circulation.

Thanks to data collectors:

Colleen O’Leary, APN, Karen Calimlim, RN, Carrie Bauman, RN,

Barbara Gulczynski,APN, Karen Hagemaster, RN, Joy Kennedy, RN,

Cindy Zaletel, APN

ATTENTION

PHLEBOTOMIST:

PLEASE SEE RN BEFORE ____BLOOD DRAW

THANKS

FROM THE RESEARCH TEAM

Discussion

0

5

10

15

20

25

30

35

CVAD vs peripheral specimens

aPTT difference in seconds

Sample Characteristics Age: mean = 67.5 yrs (SD 13.8), median = 70, range 26 to 94

Sex: 36 females (49%), 38 males (51%)

Race: 63 white (85%), 11 other (15%)

PTT values between CVAD & peripheral specimens were

significantly different if sample was drawn from heparin infusion

port; there was no difference between peripheral & CVAD

specimens if sample was drawn from port either proximal or distal

to heparin infusion port.

For nurses, compatibility of infusates was of greater concern than

which port of the CVAD was used for the infusion, resulting in no

standard approach to “which drug should be infused where.”

After study began, the INS (2011) issued standards recommending

coagulation studies not be drawn from lines with any exposure to

heparin.

Institution policies were recently revised to recommend peripheral

specimens for coagulation studies.

N=74

Arrow ( TLC) Bard ( PICC) Use proximal port Turn off distal infusions for at least one minute Discard volume varies from priming volume (dead space) to 3-10mL

Flush per hospital protocol Waste 2-6 X the priming volume 5mL = 6x the priming volume of all nontunneled PICC

variable n mean (SD) Test statistic p-value

PTT (seconds) From central line From venipuncture

74 74

82.1 (47.2) 74.0 (42.0)

PTT difference (seconds) (CVAD – venipuncture) 74 8.1 (34.6) t73 = -2.017 .047

PTT difference (seconds) n mean (SD) Test statistic p-value

By line type PICC

Other central line

55

19

-16.7 (55.0)

-5.2 (24.1) t20.4= -0.881 .389

By indication DVT / PE

Cardiac

Other

34

32

8

-2.0 (29.6)

-11.9 (35.0)

-18.8 (50.7)

F2,71 = 1.099 .339

Additional infusions Heparin only

Heparin + fluids

Heparin + meds

24

19

25

-5.1 (29.4)

2.7 (25.5)

-20.4 (44.7)

F2,65=2.534 .087

By collection

method

Syringe

Vacutainer

53

21

-7.6 (32.6)

-9.4 (40.2) t72 = 0.205 .838

By additional

specimens

Yes

No

7

67

-27.1 (52.0)

-6.1 (32.3) t72 = 1.538 .128

By time infusion off 1 minute

>1 minute

55

19

-11.2 (38.8)

0.8 (15.2) t72 = -1.307 .196

PTT difference (seconds) by relative position of specimen port to heparin infusion port

n mean (SD) Kruskall

Wallis test p-

value

Specimen from heparin port 15 -31.0 (43.8)

X22=13.007 .001

Specimen from a port proximal to heparin port

27 -3.0 (24.7)

Specimen from a port distal to heparin port

25 -1.4 (37.3)

•Stop infusion

•Flush with 3-5 mL saline

•Distal lumen preferred

•Discard volume = to 1.5-2 times the fill volume

of the CVAD PTT difference by relative position of sampling

port