1. Thromboelastography in Trauma
June 5, 2015

2. What is TEG?
TEG is a functional assay which measures the blood’s ability to form a clot
Measures clot formation via the tensile strength of fibrin-polymer-platelet complex
First developed in Germany in 1948

3. How does it work?
The patient’s whole blood sample is placed in a small cup at 37° C
A 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). 

5. Parameters
R (reaction time): Time from activation of the clotting cascade to the formation of fibrin
Depends on coagulation factors
Treat short R with coumadin
Treat prolonged R with coagulation factor replacement/ FFP

6. Parameters k: Time from formation of fibrin to a defined amplitude
Represents speed of clot formation

7. Parameters
α (angle): Measures the speed of fibrin build-up and cross-linking
Depends on fibrinogen
Treat a low angle with fibrinogen replacement/ cryoprecipitate

8. Parameters
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

9. Parameters
LY30: Percentage decrease in amplitude 30 minutes after the MA is measured
Measures degree of fibrinolysis
May consider treatment with antifibrinolytics or anticoagulants (primary vs. secondary)

10. Examples
Int J Periop US Appl Tech. 2012;1(1).

11. J Periop US App Tech. 2012;1(1). 

12. Types of TEG Standard TEG Rapid TEG Heparinase cup Platelet mapping
Coagulation initiated with kaolin
Rapid 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 heparin
Platelet mapping
Baseline TEG compared to two additional patient samples with maximal stimulation of platelets with AA and ADP; computer calculates difference in MA as % inhibition

13. Trauma 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

14. Trauma induced coagulopathy
2007: Distinct primary disorder, cell-based model
Initiation (tissue factor on cells), amplification (platelet activation), propagation (thrombin generation)
Hypoperfusion 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. 

15. Trauma induced coagulopathy
Occurs in 30% of trauma patients
Most 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 failure
longer 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. 

16. Trauma induced coagulopathy
J Trauma. 2003;54(6). 

17. Guidelines
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.

18. TEG in trauma induced coagulopathy
Turn around time
Diagnosis of TIC
Prediction of blood product use
Prediction of mortality
Critical Care. 2014;18.

19. Turn around time

20. Turn around time
J Trauma. 2009 Apr;66(4).

21. Turn around time Prospective study of 272 trauma patients
Early r-TEG (activated clotting time, k-time) available within 5 minutes
Late 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).

22. Diagnosis of trauma induced coagulopathy

23. Diagnosis 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 blood
45 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). 

24. Diagnosis of trauma induced coagulopathy
20 traumatic brain injury patients versus 10 healthy controls
TBI 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). 

25. Diagnosis of trauma induced coagulopathy
Review from 1970 to 2013 to determine diagnostic accuracy of TEG or ROTEM for diagnosing TIC
3 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. 

26. Prediction of blood product usage

27. Prediction of blood product usage
Observational study of 69 blunt trauma patients
TEG, PT, PTT, revised trauma score, ISS
6 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). 

28. Prediction of blood product usage
Retrospective study of 44 penetrating trauma patients
INR, 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). 

29. Prediction of blood product usage
Prospective study of 272 trauma patients
Rapid TEG available in trauma bay
ACT 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).

30. Mortality

31. Mortality 23 trauma patients 5 patients with hyperfibrinolysis
Higher 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). 

32. Mortality Prospective study of 795 major trauma patients
Elevated Ly30 was an independent predictor of mortality
Combined 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 May;207(5). 

33. Mortality
Retrospective review 131 trauma patients with pelvic fracture
TEG 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). 

34. Additional points

35. Additional points
What about hypercoagulable TEG results? What does this mean in the trauma setting?

36. Hypercoagulable TEG in cardiac surgery patients
124 patients scheduled for CABG
Divded 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-NC
No 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). 

37. TEG-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?

38. TEG-guided transfusions in pediatric surgery patients
78 pediatric cardiac surgery patients
Conventional 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). 

39. Special populations

40. Special populations
Effect of differing baseline TEG results in special populations, and potential impact during trauma:
Neonates
Alcohol intoxication
Use of newer anticoagulants
Uremia

41. Neonates
Limited data in neonates, particularly no data on premature neonates
Small 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). 

42. Effect 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 mm, p=0.063)
J Trauma Acute Care Surg 2014;77(6). 

43. Newer anticoagulants
It is unclear how newer anticoagulants may or may not affect TEG parameters

44. Uremia
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). 

45. Summary
Many small, single center, observational studies of TEG in trauma
TEG results are available more rapidly than standard coagulation tests
Some 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