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Thromboelastographic Assessment
of the Effect of Temperature on
Global Coagulation: A Pilot Study
Amanda K. Rollins
Anthony G. Shackelford DHA, CCP, CCT
Cardiovascular Perfusion Division
Medical University of South Carolina
Charleston, South Carolina

Background: Neurologic Injury
In Open Heart Surgery
• Prevention:
• Using systemic hypothermia (SH) during
cardiopulmonary bypass (CPB)
• causes a reduction in oxygen consumption and results in
an increased neuroprotective effect.
• SH does come with other risks
2

Effects of Hypothermia
and Rewarming
Hypothermia
• Decrease metabolism
and oxygen demand
• Decreases chance for
ischemic injury in
tissues
• Delays the coagulation
cascade and causes
decreasing platelet
function.
• Requires the patient to
be rewarmed.
Rewarming
• Historical strategies
heat the body back to
37°C while causing the
brain to be effectively
warmed to 38 or 39°C.
• The brain rewarms
faster than other
tissues of the body.
• Increased temperatures
can contribute to
neurologic injury.

Hypothermia Paradox
Neurologic Injury
↑ Brain Temperatures
↑ CPB Times
↑ GME
Employ
Hypothermia
> 37°C Arterial
Blood
Temperatures
Employ
Rewarming
4

Balancing the Pros and Cons
Hypothermia
↓ Hemostasis ?
Normothermia
↑ Neurological Injury

Conflicting Evidence
• Bleeding study
• Hypothermia
induces platelet
inhibition.
• Platelet function
normal when
restored to 37°C.
• Fundamental Paper
for normothermic
practice today
Valeri CR, Feingold H, Cassidy G, Ragno G, Khuri
S, Altschule MD. Hypothermia-induced reversible
platelet dysfunction. Ann Surg 1987;205:175-181.
• Separated from CPB
• as low as 34°C
• no differences in
blood loss
• blood product use
was similar between
the groups
Nathan HJ, Wells GA, Munson JL, Wozny D.
Neuroprotective effect of mild hypothermia in
patients undergoing coronary artery surgery with
cardiopulmonary bypass: a randomized trial. 6
Circulation 2001;104:I85-91.

Q: How much must the patient be
rewarmed to achieve adequate
coagulation?
A: The answer is relatively unknown.
Comment: Patients are returned to
normothermia, but is this necessary?

Clinical Significance
of this Study
If hemostasis
restored
< 37°C
•Terminate CPB at
that temperature
Brain not
exposed to:
•higher temperatures
•longer CPB times
(GME).
Could contribute
to a reduction in
the incidence of
neurologic
injury.
8

Background:
Thromboelastography (TEG)
• Point of Care test
• results

TEG Variables
R Time
K-Time and Alpha angle
MA – (Maximum Amplitude)

Hypotheses
• H 0 : It is feasible to use the Thromboelastogram
(TEG) to answer research questions involving
the effect of temperature on global coagulation.
• H 1 : There is no difference in measured TEG
parameters at temperatures of 33°C – 37°C

Methods
12

Verification of Proper
Temperature Manipulation
13

Experimental
Method
TEG WELL 1:
37°C
Citrated
Blood Sample
Kaolin +
CaCl 2
TEG WELL 2:
Experimental
Temp
TEG WELL 3:
37°C
Averages of the various TEG parameters from the
2 experimental temperatures wells for each trial
will be compared to the averages of the normal
temperature TEG parameters.
TEG WELL 4:
Experimental
Temp

Results
R values
Trial 33 Trial 34 Trial 35 Trial 36
37 6.75 8.2 9.6 8.4
temp 7.35 8.85 9.85 8.15
12
10
8
6
4
2
R-Values
percent
change -8% -8% -3% 3%
37
Temp
0
Trial 33 Trial 34 Trial 35 Trial 36

Results
K Values
Trial 33 Trial 34 Trial 35 Trial 36
37 1.75 2.65 2.5 2.25
temp 2.05 2.3 2.55 2.1
percent
change -17% 13% -2% 7%
3
K-Values
2.5
2
1.5
1
37
Temp
0.5
0
Trial 33 Trial 34 Trial 35 Trial 36

Results
MA Values
Trial 33 Trial 34 Trial 35 Trial 36
37 57.45 61.65 63.7 63.7
Temp 61.25 63.05 64.05 61.55
MA Values
percent
change -7% -2% -0.60% 3%
68
66
64
62
60
58
56
54
52
50
Trial 33 Trial 34 Trial 35 Trial 36
37
Temp

Results
LY30
Trial 33 Trial 34 Trial 35 Trial 36
37 1.05 0.25 0.1 0.15
Temp 0.05 0 0 0.35
Percent
Change -95% -100% -100% 133%
1.2
LY30
1
0.8
0.6
0.4
37
Temp
0.2
0
Trial 33 Trial 34 Trial 35 Trial 36

Conclusion
• As a pilot study, significance could not
be declared statistically due to the
sample size. However, the data
suggests that there may be a
temperature below 37°C at which
adequate coagulation is restored.
• Neurologic deficits may be avoided by
not rewarming to such extreme
temperatures.

Limitations of the Study
• Sample size
• Age of the blood
• Mechanical disparities

Future Research
• A study modeled after the methods
used in this pilot study. This study
will involve a large number of subjects
that will be undergoing CPB.

TEG At 37°C
TEG At 34°C
22

Thank you for this
opportunity!
Questions?