Resus: Thromboelastography (TEG) in Trauma Resuscitation

UH has TEG! But now what do we do with it? (And what even is TEG to begin with?)

Thromboelastography (TEG) and Rotational thromboelastography (ROTEM) are the major types of Viscoelastic Tests (VETs, also referred to as a Viscoelastic Hemostatic Assays or VATs). These tests assess the viscoelastic properties (i.e. the ability to initially form and then subsequently breakdown an clot) of whole blood. The single assessment from TEG can provide a synthesized version of information typically gathered from a collection of individual lab tests, including PT, PTT, thrombin time, fibrinogen, and platelet count. With this information, TEG and ROTEM may be used to efficiently assess a patient’s real-time hemostasis and thus change management regarding hemorrhage and resuscitation. (1) (2) (3)

The result from TEG includes measurement of 5 parameters, as well as a coagulation index (CI) which combines several of the individual measurements into a calculation that describes overall coagulation status. For the coagulation index, normal values range from -3.0 to +3.0. A CI of greater than +3.0 corresponds to a hypercoagulable state, while a CI of less than -3.0 indicates coagulopathy. The 5 individual parameters are described below:

FROM REZAIE, S. REBEL REVIEW #54 THROMBOELASTOGRAM (TEG). HTTP://REBELEM.COM/REBEL-REVIEWS/

The TEG results are also depicted in the form of a thromboelastogram, which is the graphical representation of these parameters:

FROM REZAIE, S. REBEL REVIEW #54 THROMBOELASTOGRAM (TEG). HTTP://REBELEM.COM/REBEL-REVIEWS/

The combination of the parameter values and the visual thromboelastogram provide significant insight into the patient’s current coagulation status. For instance, if the shape of the thromboelastogram is has a shorter amplitude than normal, but maintains the overall normal length and shape, this would correspond with the decreased alpha angle and decreased MA – which would indicate a problem with platelets (thrombocytopenia and/or platelet dysfunction) and would guide towards therapy with platelets or DDVAP (depending on the diagnosis based on the rest of the clinical scenario). Examples of these variations are below:

FROM KREITZER, N.P., BONOMO, J., KANTER, D. ET AL. REVIEW OF THROMBOELASTOGRAPHY IN NEUROCRITICAL CARE. NEUROCRIT CARE 23, 427–433 (2015). HTTPS://DOI.ORG/10.1007/S12028-015-0187-9

TEG has been widely used to guide resuscitative management in cardiopulmonary bypass and cardiac and transplant surgeries. Rapid TEG (rTEG) is a variation of TEG that can provide results within 15 minutes, and therefore may offer an adjunct to clinical decision-making when it comes to resuscitation in the setting of acute trauma and hemorrhage.  

A 2016 study looked at TEG in comparison to common coagulation tests (CCTs) in the setting of trauma-induced coagulopathy (TIC). (4) Approximately 25% of patients admitted to the ED with severe traumatic injuries are found to have coagulopathy. Given that there are multiple theories about the etiology of TIC, involving various aspects of platelet function, tissue factor release, and dysfunctional prothrombotic and fibrinolytic pathways (to name a few of the prevailing theories), there is a need to be able to assess patients for these potential sources of dysfunction to appropriately intervene. This is where TEG may play a unique role. TIC and other coagulopathies are typically diagnosed with CCTs – which includes PT/INR, aPTT, platelet count, and fibrinogen. However, CCTs represent a more static look at hemostasis and are based on the coagulation cascade model of clotting – meaning that they do not fully take into account the complexities of hemostasis (i.e. considering the interplay between cell-based interactions, propagation of clotting, subsequent fibrinolysis, etc.). Alternatively, TEG assesses a sample of whole blood (thus involving most of the “players” in the clotting and breakdown process) and provides a dynamic analysis from initial un-clotted blood sample to formation of a clot to breakdown of the clot. TEG may therefore be able to provide an overall more complete picture of a trauma patient’s hemostasis with the potential for targeted trauma resuscitation and improved outcomes for trauma patients, particularly those who develop TIC.(4)

So, has TEG been shown to be as great as it sounds? A 2012 study in the Annals of Surgery analyzed 1974 major trauma activations at a level I trauma center, with the hypothesis that rTEG would more reliably predict blood component transfusions compared to CCTs. All patients who met the center’s criteria of the highest-level trauma activation were included and had rTEG and CCTs obtained within upon ED admission. They compared rTEG parameters (ACT, R, K, α angle, MA, LY30) to corresponding 5 CCT values (PT, aPTT, INR, platelet count, fibrinogen), and assessed both rTEG and CCT for their correlation with patients’ transfusion requirements. Their results demonstrated that rTEG parameters better predicted transfusion requirements compared to the 5 CCTs, and rTEG was shown to identify patients with increased risk of early RBC, plasma, and platelet transfusions – and rTEG results were faster and of similar or lower cost to patients. Their conclusion was that rTEG can replace admissions CCTs for these severe trauma patients (and they note changing their hospital guidelines to utilize admission rTEG, foregoing the traditional CCTs, based on these results).(5)

TEG seems to be the clear winner here, so why haven’t we all switched over? Well, not every study has shown such a clear-cut benefit. The 2020 ITACTIC study was an RCT which included 411 adult trauma patients across multiple major trauma centers in Europe. ITACTIC similarly compared transfusion strategy augmented by %% (VHA, i.e. TEG and ROTEM) versus CCTs, with primary outcomes of number of patients alive and free of massive transfusion at 24 hours. Their results showed no significant different in the proportion of patients alive and free from massive transfusion at 24 hours in VHA versus CCT (OR1.15, 95% CI 0.76-1.73). They also showed no significant difference in secondary outcomes, or in most sub-group analyses. There was a significantly reduced 28-day mortality in a single sub-group – severe TBI – with VHA vs. CCT (44% vs. 74%, p=0.016); the conclusions remained that VHA (TEG) did not improve overall outcomes when compared to CCT. (6)(7)

So where does that leave us (or in other words, TL;DR): TEG is a valuable tool for assessing real-time coagulation status and guiding management in resuscitation. We still need more evidence to determine whether it has a significant benefit over conventional coagulation tests, particularly in the setting of acute trauma. For now, we can expect TEG to become more frequently discussed and utilized in a variety of clinical settings, including the trauma bay. And when in doubt about what to do when you’re handed a thromboelastogram, here’s a quick visual aid:

FROM: @DocXology

POST BY: ALEXANDRIA GERBER, MS4

FACULTY EDITING BY : COLIN MCCLOSKEY, MD

Resources

  1. Zehnder, JL. Clinical Use of Coagulation Tests. UpToDate. (Accessed on April 1, 2023). https://www.uptodate.com/contents/clinical-use-of-coagulation-tests?search=viscoelastic%20testing%20of%20hemostasis&source=search_result&selectedTitle=3~80&usage_type=default&display_rank=3#H1279919076

  2. Cohen, M and Kutcher, ME. Coagulopathy in Trauma Patients. UpToDate. (Accessed on April 1, 2023.) https://www.uptodate.com/contents/coagulopathy-in-trauma-patients?sectionName=Thromboelastography&search=viscoelastic%20testing%20of%20hemostasis&topicRef=1368&anchor=H3046566855&source=see_link#H3046566855

  3. Shaydakov ME, Sigmon DF, Blebea J. Thromboelastography. [Updated 2022 Apr 14]. In: StatPearls [Internet]. StatPearls Publishing. https://www.ncbi.nlm.nih.gov/books/NBK537061/#:~:text=Thromboelastography%20(TEG)%20or%20thromboelastometry%20(,adults%20or%20children%20with%20bleeding.

  4. K Bader M, et al. Targeted Thromboelastographic (TEG) Blood Component and Pharmacologic Hemostatic Therapy in Traumatic and Acquired Coagulopathy. Current Drug Targets 2016; 17(8) . https://dx.doi.org/10.2174/1389450117666160310153211

  5. Holcomb, JB. et al. Admission Rapid Thrombelastography Can Replace Conventional Coagulation Tests in the Emergency Department: Experience With 1974 Consecutive Trauma Patients. Annals of Surgery 256(3):p 476-486, September 2012. https://journals.lww.com/annalsofsurgery/pages/articleviewer.aspx?year=2012&issue=09000&article=00010&type=Fulltext

  6. Walker, G. The Bottom Line: ITACTIC. October 2020. https://www.thebottomline.org.uk/summaries/icm/itactic/

  7. Baksaas-Aasen, K, et al. Viscoelastic haemostatic assay augmented protocols for major trauma haemorrhage (ITACTIC): a randomized, controlled trial. Intensive Care Med 2020. https://doi:10.1007/s00134-020-06266-1

  8. Rezaie, S. Rebel Review #54 Thromboelastogram (TEG). http://rebelem.com/rebel-reviews

ResusLauren McCaffertyteg, thromboelastogram, clotting, coagulation, coags, trauma, thromboelastography, transfusion, clotting cascade