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29 Comparison aPTT Values
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Transcript of 29 Comparison aPTT Values
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