June 5 2015 What is TEG TEG is a functional assay which measures the bloods ability to form a clot Measures clot formation via the tensile strength of fibrinpolymerplatelet complex First developed in Germany in 1948 ID: 933075
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Slide1
Thromboelastography in Trauma
June 5, 2015
Slide2What is TEG?
TEG is a functional assay which measures the blood’s ability to form a clotMeasures clot formation via the tensile strength of fibrin-polymer-platelet complexFirst developed in Germany in 1948
Slide3How does it work?
The patient’s whole blood sample is placed in a small cup at 37° CA metal pin goes into the center of the cup
The machine slowly spins the cup
As the clot forms, it connects the inside of the cup with the metal pin, and the energy used to move the cup is transferred to the pin
A wire connected to the pin measures the strength of the clot and creates a computerized tracing
J Periop US App Tech. 2012;1(1).
Slide4http://emmedonline.com/emergency_medicine/thromboelastogram
Slide5Parameters
R (reaction time): Time from activation of the clotting cascade to the formation of fibrinDepends on coagulation factors
Treat short R with
coumadin
Treat prolonged R with coagulation factor replacement/ FFP
Slide6Parameters
k: Time from formation of fibrin to a defined amplitudeRepresents speed of clot formation
Slide7Parameters
α (angle): Measures the speed of fibrin build-up and cross-linking
Depends on fibrinogen
Treat a low angle with fibrinogen
replacement/ cryoprecipitate
Slide8Parameters
MA (maximum amplitude): Represents strength of the fibrin clot correlated to platelet function (80% platelets/20% fibrinogen)Depends on platelets
Treat a low MA with
platelets
Treat an increased MA with ASA/Plavix
Slide9Parameters
LY30: Percentage decrease in amplitude 30 minutes after the MA is measuredMeasures degree of
fibrinolysis
May consider treatment with
antifibrinolytics
or anticoagulants (primary vs. secondary)
Slide10Examples
Int
J
Periop
US
Appl
Tech. 2012;1(1).
Slide11J Periop US App Tech. 2012;1(1).
Slide12Types of TEG
Standard TEGCoagulation initiated with kaolinRapid TEG
Coagulation initiated with tissue factor; ACT (activated clotting time) instead of
r-value
Heparinase
cup
TEG is run twice, once with
heparinase and once without; compare two curves and if no change then no effect from heparinPlatelet mappingBaseline TEG compared to two additional patient samples with maximal stimulation of platelets with AA and ADP; computer calculates difference in MA as % inhibition
Slide13Trauma induced coagulopathy
1981 to ̴2007: “Bloody vicious cycle" Acidosis from tissue injury and shock, hypothermia from fluid infusions and exposure, and
hemodilution
from blood and fluid
administrations (“lethal triad”)
Leads to secondary development of trauma induced coagulopathy
https://www.aacc.org/publications/cln/articles/2014/july/coagulation
Slide14Trauma induced coagulopathy
2007: Distinct primary
disorder, cell-based model
Initiation (tissue factor on cells), amplification (platelet activation), propagation (thrombin generation)
H
ypoperfusion
leads to excess activation of protein C, which inhibits thrombin generation, impairs clot formation, and degrades any clots that have
formed
Inten Care Med. 2011;37.
Slide15Trauma induced coagulopathy
Occurs in 30% of trauma patientsMost common preventable cause of postinjury mortality
Associated with:
8x increased 24 hour mortality
4x increased total mortality
longer ICU and total hospital stay
increased
risk for renal insufficiency and multiple organ failurelonger need for ventilatory support
tendency
towards increased lung injury
Classical coagulation tests (PT/PTT) are only weakly predictive of bleeding in trauma patients, do not predict extent of bleeding, and results are not available rapidly enough
Inten Care Med. 2011;37.
Slide16Trauma induced coagulopathy
J Trauma. 2003;54(6).
Slide17Guidelines
We recommend that routine practice to detect post-traumatic coagulopathy include the measurement of international normalised ratio (INR), activated partial thromboplastin
time (APTT), fibrinogen and platelets. INR and APTT alone should not be used to guide
haemostatic
therapy (Grade 1C). We suggest that
thrombelastometry
also be performed to assist in characterising
the coagulopathy and in guiding haemostatic therapy (Grade 2C).
Crit Care. 2010;14:R52.
Slide18TEG in trauma induced coagulopathy
Turn around timeDiagnosis of TICPrediction of blood product use Prediction of mortality
Critical
Care. 2014;18.
Slide19Turn around time
Slide20Turn around time
J Trauma. 2009 Apr;66(4
).
Slide21Turn around time
Prospective study of 272 trauma patientsEarly r-TEG (activated clotting time, k-time) available within 5 minutesLate r-TEG (
α
angle, MA) within 15 minutes
Standard clotting tests (PT/INR/PTT/platelet count) within 48 minutes (p=<0.001)
J Trauma. 2011;71(2).
Slide22Diagnosis of trauma induced coagulopathy
Slide23Diagnosis of trauma induced coagulopathy
Observational study of 69 blunt trauma patients
7
hypocoagulable
by TEG (mean ISS 28.6)
1
hypocoagulable by PT/PTT
6/7 hypocoagulable patients received blood45 hypercoagulable by TEG (mean ISS 13.1)17 normal by TEG (mean ISS 3.7)
Only ISS and TEG were predictive of blood product use in the first 24 hours (p=<0.05)
J Trauma. 1997;42(4).
Slide24Diagnosis of trauma induced coagulopathy
20 traumatic brain injury patients versus 10 healthy controlsTBI patients have a lower platelet count (180,000 per microliter vs 256,000 per microliter in healthy controls, p<0.005) and reduced platelet response to AA on platelet mapping (mean 22% vs 73% in healthy controls, p<0.001)
J Neurotrauma. 2007;24(11).
Slide25Diagnosis of trauma induced coagulopathy
Review from 1970 to 2013 to determine diagnostic accuracy of TEG or ROTEM for diagnosing TIC3 studies using ROTEM and 0 studies using TEG
300, 90, and 40 patients
Clot amplitude was the only potential indicator
5 min: 70-96% sensitivity and 86-58% specificity
10 min: 100% sensitivity and 70% specificity
15 min: 88% sensitivity and 100% specificity
TIC was defined as INR of 1.2 or greater or 1.5 or greater
Cochrane Library. 2015;2.
Slide26Prediction of blood product usage
Slide27Prediction of blood product usage
Observational study of 69 blunt trauma patientsTEG, PT, PTT, revised trauma score, ISS6 patients received transfusion in first 24 hours
Only ISS and TEG were predictive of blood product use in the first 24 hours (p=<0.05)
J Trauma. 1997;42(4).
Slide28Prediction of blood product usage
Retrospective study of 44 penetrating trauma patientsINR, PT, and PTT were increased in 39%, 31%, and 37% but did not correlate with use of blood products (p>0.05)
MA correlated with blood product use as well as platelet count (p,0.01)
Patients with reduced MA (23) used more blood products and had lower platelet counts and hematocrit.
J Trauma. 2008;64(2).
Slide29Prediction of blood product usage
Prospective study of 272 trauma patientsRapid TEG available in trauma bayACT predicted RBC (p < 0.001), plasma (p < 0.001) and platelet (p <0.001) transfusions within 2 hours of arrival
ACT > 128 sec predicted massive transfusion > 10 units in first 6 hours (p = 0.01)
ACT < 105 sec predictions patients who did not receive any transfusions in first 24 hours (p = 0.04)
J Trauma. 2011;71(2).
Slide30Mortality
Slide31Mortality
23 trauma patients5 patients with hyperfibrinolysis H
igher injury severity score (75 vs 20, p<0.05)
Higher INR (8.2 vs 1.3, p<0.05)
Lower fibrinogen (0.0 vs 2.2 g/L, p<0.05)
Higher mortality rate (100% vs 11%, p<0.05)
Br J Anaesth. 2008;100(6).
Slide32Mortality
Prospective study of 795 major trauma patientsElevated Ly30 was an independent predictor of mortalityCombined with GCS ≤ 8, SBP ≤ 90mmHg,
Hgb
< 11g/
dL
, and BE < -6mEq/L to create 5-variable 24 hour mortality predictive model (AUROC 0.88, HL goodness-of-fit 0.90)
All parameters available within 30 minutes.J Trauma
. 2014 May;207(5).
Slide33Mortality
Retrospective review 131 trauma patients with pelvic fractureTEG R > 6 was independently associated with death independent of injury severity (OR 16, P=0.0001); death rate 52%No significant association between traditional coagulation tests (PT/INR/PTT) and death rate
Orthopedic Surgery 2015;7(1).
Slide34Additional points
Slide35Additional points
What about hypercoagulable TEG results? What does this mean in the trauma setting?
Slide36Hypercoagulable TEG in cardiac surgery patients
124 patients scheduled for CABGDivded
into two groups: TEG-
hypercoagulable
and TEG-
normocoagulable
3 months post-op, all had CT to evaluate graft patency
359 grafts, 186 TEG-HC and 173 TEG-NCNo difference in bypass graft occlusion (p=0.9)Rate of major adverse cardiovascular and cerebral events significantly higher in TEG-HC (30% vs 9%, p=0.004)
Scandinavian Cardiovascular Journal 2013;47(2).
Slide37TEG-based blood administration algorithms
Studies in other populations (cardiac surgery) have found some benefit to TEG-based blood administration algorithms, does this apply to trauma patients?
Slide38TEG-guided transfusions in pediatric surgery patients
78 pediatric cardiac surgery patientsConventional transfusion vs algorithm/TEG guided transfusion for 12 hours post-op
TEG-guided transfusion significantly reduced post-op bleeding (9 vs 16 mL/kg, p<0.001), PRBC transfusion requirement (11 vs 23 mL/kg, p=0.005), and ICU stay (60 vs 71 h, p=0.014)
Platelet and plasma transfusions were similar, but occurred earlier in TEG-guided group
Brit J Anesth. 2015;114(1).
Slide39Special populations
Slide40Special populations
Effect of differing baseline TEG results in special populations, and potential impact during trauma:NeonatesAlcohol intoxication
Use of newer anticoagulants
Uremia
Slide41Neonates
Limited data in neonates, particularly no data on premature neonatesSmall number of healthy infants showed age dependent accelerated initiation and propagation of coagulation despite prolonged standard coagulation tests; clot firmness and fibrinolysis similar to adults
J Maternal-Fetal and Neonatal Med 2012;25(s4).
Slide42Effect of alcohol
35-50% of trauma patients are acutely intoxicated Alcohol has little effect on standard coagulation tests, transfusion requirements, or outcome, but does affect TEG results:
Prolonged R time (5.91 vs 4.43 min, p=0.013)
Decreased angle (66.5 vs 70.2 degrees, p=0.001)
Trend toward decreased MA (63.44 vs 64.93 mm, p=0.063)
J Trauma Acute Care Surg 2014;77(6).
Slide43Newer anticoagulants
It is unclear how newer anticoagulants may or may not affect TEG parameters
Slide44Uremia
Baseline TEG r-time, k-time, α angle, and MA are hypercoagulable in uremic patients compared to controls (p<0.05), and fibrinolysis was decreased in uremic patients
J Clin Anesth. 1997;9(6).
Slide45Summary
Many small, single center, observational studies of TEG in traumaTEG results are available more rapidly than standard coagulation testsSome evidence to suggest TEG may allow for early diagnosis of trauma induced coagulopathy and may predict blood product usage and mortality, but associations with specific parameters are variable
Randomized trials are lacking
It’s unclear how baseline differences in TEG in various populations might impact TEG results during trauma