The Role of Thromboelastography Testing in the Emergency Medicine, Trauma Center, and Critical Care Environments
- 6 Downloads
Purpose of Review
Thromboelastography (TEG) has been gaining attention for its potential use in a variety of disease of states to guide therapies and determine prognosis. This review will explore recent research specifically regarding the use of thromboelastography in the emergency, trauma, and critical care clinical environments.
Thromboelastography has its drawbacks. TEG has wide operator and machine variability. Known coagulopathic states may exhibit normal viscoelastic results, indicating inconsistent results. Thromboelastography has shown to decrease transfusion of blood products in traumatic hemorrhage. In sepsis, both hypercoagulable and hypocoagulable states occur. Patients with certain neurological conditions may have disparate results on viscoelastic testing. Patients with intracranial bleeding and hematoma expansion were found to be hypocoagulopathic, whereas acute ischemic stroke patients tend to have hypercoagulopathic results.
The bottom line is that thromboelastography requires further study before standard utilization for emergency and critical care departments.
KeywordsThromboelastography (TEG) Guide therapies Prognosis discovery Emergency
Compliance with Ethical Standards
Conflict of Interest
The author declares the she has no conflicts of interest.
Human and Animal Rights and Informed Consent
This article does not contain any studies with human or animal subjects performed by any of the authors.
Papers of particular interest, published recently, have been highlighted as: • Of importance •• Of major importance
- 1.• Da Luz L, Nascimento B, Shankarakutty A, Rizoli S, Adhikari N. Effect of thromboelastography (TEG®) and rotational thromboelastometry (ROTEM®) on diagnosis of coagulopathy, transfusion guidance and mortality in trauma: descriptive systematic review. Crit Care. 2014;18(5). Predictive performance not superior to routine testing. Some early coagulopathies found that cannot be seen on routine testing. A ROTEM-based transfusion protocol decreased need for blood products but not associated with lower mortality rates. Google Scholar
- 2.•• Kreitzer N, Bonomo J, Kanter D, Zammit C. Review of thromboelastography in neurocritical care. Neurocrit Care. 2015;23(3):427–33. Limitations to the use of TEG—Patients who have serial TEG studies should be run on the same machine with the same activator. This requires calibration two to three times per day by personnel who are trained in the maintenance of TEG. TEG values reported at one institution do not represent values reported at another institution. Another drawback may be in the use of kaolin. Kaolin is a standardized agent that activates clotting through the contact activation (intrinsic) pathway. Monoanalysis with kaolin does not distinguish coagulopathy secondary to dilution from that of thrombocytopenia. Thus, algorithms based on the use of kaolin alone may lead to unnecessary transfusion of platelets. TEG is unable to provide information such as a platelet count, so the combination of aggregometric and viscoelastic methods is recommended for completeness. CrossRefPubMedGoogle Scholar
- 3.• Quarterman C, Shaw M, Johnson I, Agarwal S. Intra- and inter-centre standardisation of thromboelastography (TEG®). Anaesthesia. 2014;69(8):883–90. Thromboelastography (TEG®; Haemonetics, Braintree, MA, USA) is one point-of-care method of assessing coagulation. A sample of whole blood is pipetted into a cup into which a torsion wire is suspended. The cup oscillates, and as the blood begins to clot, the oscillation is conducted to the wire. With increasing clot strength, there is increasing conduction of oscillation. The kinetics of the change in the oscillation of the wire are recorded graphically as the thromboelastograph (Fig. 1) . The TEG is considered to reflect the process of clotting and fibrinolysis, as well as the availability and function of clotting factors, platelets, and fibrinogen. R time and K time has significant variability of results when performed by a single or multiple operators. Blood in citrated form had better consistency of results. Maxamplitude and alpha angle were consistent throughout. Variability may be due to mixing with kaolin. CrossRefPubMedGoogle Scholar
- 6.ROTEM® analysis: Thromboelastometry. 2017. https://www.rotem.de/en/methodology/rotem-delta-and-sigma-analysis/. Accessed 19 Sept 2017.
- 8.• Müller M, Meijers J, Vroom M, Juffermans N. Utility of thromboelastography and/or thromboelastometry in adults with sepsis: a systematic review. Crit Care. 2014;18(1):R30. Results of TEG in sepsis are widely varied and show both hypercoagulable and hypocoagulable states consistent with comsumption coagulopathy. May also relate to clinical status, as changes were more pronounced in severe sepsis patients. Degree of hypocoagulation seemed related to severity of organ failure. Hypocoagulation was seen more in the acute phase of sepsis and returned to normal levels as patients neared discharge from ICU. Hypercoagulable states seen in cases of endotoxemia, where there were higher circulating prothrombin fragments. The combination of reaction times, maximum amplitude, and alpha angle may help diagnose DIC. “A score to detect DIC with the use of thromboelastometry has been developed, including prolonged reaction and K times and decreased α angle and maximum amplitude. This score was validated in patients with an underlying disease known to be associated with DIC and with an ISTH DIC score of more than 5. However, to date, this score has not been validated in critically ill patients with sepsis, and included studies in this review consisted of relatively small patient groups.” Timing of TEG in sepsis greatly affected results. Also, reference values for septic patient are not well established. CrossRefPubMedPubMedCentralGoogle Scholar
- 9.• Whiting P, Al M, Westwood M, Ramos I, Ryder S, Armstrong N, et al. Viscoelastic point-of-care testing to assist with the diagnosis, management and monitoring of haemostasis: a systematic review and cost-effectiveness analysis. Health Technol Assess. 2015;19(58):1–228. Studies generally found that a positive result on each of the TEG or ROTEM parameters or on SLTs was associated with an increased risk of transfusion (RBC, any blood component and massive transfusion) and death. There was no clear difference between ROTEM, TEG, or SLTs. However, none of the studies provided a direct comparison between TEG and ROTEM. The presence of hyperfibrinolysis was the strongest predictor of mortality. Cost effectiveness, VE testing showed greater cost saving when compared to standard coag testing, but that was due to decreased blood given based on results. If the same amount of blood was given despite results, then not cost effective. CrossRefGoogle Scholar
- 11.• Dias J, Norem K, Doorneweerd D, Thurer R, Popovsky M, Omert L. Use of thromboelastography (TEG) for detection of new oral anticoagulants. Arch Pathol Lab Med. 2015;139(5):665–73. Thromboelastography can provide a quick determination of the effects of dabigatran, rivaroxaban, and apixaban using either the rTEG or citrated kaolin assays. Both illustrate prolongation of the enzymatic phase of coagulation with prolonged TEG ACT in the rTEG assay and a long R time in the kaolin assay. In trauma patients who may present with hemorrhagic shock and are either suspected or known to have taken NOACs, the persistence of the long R time/ACT following resuscitation and correction of surgical bleeding can demonstrate persistent NOAC effects. Can differentiate between apixiban and other NOACs due to ability to test for direct thrombin inhibition when compared to XA inhibition. CrossRefPubMedGoogle Scholar
- 12.• Kane I, Ong A, Orozco F, Post Z, Austin L, Radcliff K. Thromboelastography predictive of death in trauma patients. Orthop Surg. 2015;7(1):26–30. Normal R value is 6 in healthy volunteers. But in those with pelvic fractures, TEG R of 6 was associated with higher rates of mortality. The concern is that healthy volunteers, not undergoing trauma, do not have active hemorrhage or trauma affecting clinical status. This indicates that what is considered normal in one clinical state may be innately change by the change in clinical states. Therefore, normal values have to be recalibrated based on the state they are in. Abnormally low R times were also not correlated to mortality but showed trends toward worsening mortality than those in the moderate R range. TEG R may predict mortality. CrossRefPubMedGoogle Scholar
- 13.• Veigas P, Callum J, Rizoli S, Nascimento B, da Luz L. A systematic review on the rotational thrombelastometry (ROTEM®) values for the diagnosis of coagulopathy, prediction and guidance of blood transfusion and prediction of mortality in trauma patients. Scand J Trauma Resusc Emerg Med. 2016;24(1). Many studies used in these systematic reviews involved varying cut off values for current coagulation studies. There is no golden standard test for this. The studies also used various cutoffs of the ROTEM values to guide treatment. “abnormal EXTEM and FIBTEM clot amplitude (CA5, CA10, CA20) and MCF are capable of diagnosing Acute coagulopathy of trauma/shock (compared to Standard coag tests), predict the need for massive transfusion, and predict mortality”. Google Scholar
- 14.• Wikkelsø A, Wetterslev J, Møller A, Afshari A. Thromboelastography (TEG) or thromboelastometry (ROTEM) to monitor haemostatic treatment versus usual care in adults or children with bleeding. Cochrane Database Syst Rev. 2016. Trials involving elective cardiac surgery patients have shown Teg/ROTEM reduce the need for blood products and improve mortality. In the review, they examined articles regarding acute bleeding from post-surgical complications (cardiac surgery, burn excision, livertransplantation) and found a decreased mortality by using TEG-guided transfusion. However, the numbers are too small to ensure accurate numbers. But a trend toward improve mortality cannot be excluded. “No trials included in this review compare a TEG- or ROTEM-guided treatment with a ratio based 1:1:1 transfusion strategy in cases of severe life-threatening haemorrhage.” TEG/ROTEM trend toward reduced mortality and decreased need for transfusion products. No difference in need for surgical re-intervention. No difference in proportion having excessive bleeding episodes or massive transfusion. However, large heterogeneity, low number of events, imprecision and indirectness bias the studies involved. Google Scholar
- 15.• Hunt H, Stanworth S, Curry N, Woolley T, Cooper C, Ukoumunne O et al. Thromboelastography (TEG) and rotational thromboelastometry (ROTEM) for trauma-induced coagulopathy in adult trauma patients with bleeding. Cochrane Database Syst Rev. 2015. No evidence on accuracy of TEG and limited evidence of accuracy of ROTEM. Google Scholar
- 16.• Haase N, Ostrowski S, Wetterslev J, Lange T, Møller M, Tousi H, et al. Thromboelastography in patients with severe sepsis: a prospective cohort study. Intensive Care Med. 2014;41(1):77–85. Any trend toward hypocoagulability was associated with increased mortality, even when values were within reference range. TEG values were correlated with bleeding risk and degree of organ failure. Only fibrinogen max amplitude increased in the 5 days of observation; other variables remained constant. Unable to confirm that hypercoagulability was associated with mortality. CrossRefPubMedGoogle Scholar
- 17.Arruda VR, High KA. Coagulation disorders. In: Kasper D, Fauci A, Hauser S, Longo D, Jameson J, Loscalzo J, editors. Harrison’s principles of internal medicine. New York: McGraw-Hill; 2014. p. 19e.Google Scholar
- 18.• Kiliç Y, Topçu İ, Bambal H, Çivi M. Thromboelastography in the evaluation of coagulation disorders in patients with sepsis. Turk J Med Sci. 2014;44(2):267–72. In anesthesiology and surgical ICU patients, those with SIRS-sepsis had lower R times, K times, and alpha angles consistent with hypercoagulopathy. CrossRefPubMedGoogle Scholar
- 19.• Figueroa S, Merriman-Noesges K. Utility of thromboelastography in traumatic brain injury and the neuroscience intensive care unit. J Neurosci Nurs. 2014;46(2):66–70. Coagulopathy after TBI is thought to be due to release of tissue factor, which activates the extrinsic pathway. Patient are thought to be immediately hypercoagulable, a brief period of hypocoagulable, then back to be hypercoagulable. They are at increased risk of VTE. Adverse reactions to ppx can possibly be anticipated by TEG. Manitol reduces clot strength. Hypertonic saline disrupts fibrin formation and platelet function. CrossRefPubMedGoogle Scholar
- 20.• Rowe A, Greene C, Snider C, Carroll R, Wiseman B, Henry J, et al. Thromboelastographic changes in patients experiencing an acute ischemic stroke and receiving alteplase. J Stroke Cerebrovasc Dis. 2014;23(6):1307–11. A total of seven patients were included in the analysis. At baseline, thromboelastogram parameters of all patients were within the normal range. The maximum inhibition of fibrin buildup was seen at 30 min after the start of alteplase infusion, and the lowest clot strength was observed at 60 min after initiation of alteplase. Most patients return to near baseline parameters within 150 min of alteplase initiation; however, two patients did not return to their baseline values within the 150-minute time frame. CrossRefPubMedGoogle Scholar
- 21.• Elliott A, Wetzel J, Roper T, Pivalizza E, McCarthy J, Wallace C, et al. Thromboelastography in patients with acute ischemic stroke. Int J Stroke. 2015;10(2):194–201. Stroke patients had greater clotting activity. They had a shorter R time, greater alpha angle, and shorter K time. Some patients created clots with a stronger platelet matrix. TPE results in decreased clot strength but there was a significant variation in results. TOA did not affect the kinetics of clot formation. Instead, it affected lysis of an already formed clot and strength of the formed clot. White clots, with platelet and fibrin, took higher doses of tpa, and red clots with fibrin and blood took lower doses of tpa to lyse. CrossRefPubMedGoogle Scholar
- 22.• McDonald MM, Wetzel J, Fraser S, Elliott A, Bowry R, Kawano-Castillo J, et al. Thromboelastography does not predict clinical response to rtPA for acute ischemic stroke. J Thromb Thrombolysis. 2016;41(3):505–10. They believe that measuring TEG of venous blood does not correlate to clot in arterial blood, such as in strokes. Hypocoagulability found on TEG is associated with increased risk of bleeding. Prolonged delta was associated with hemorrhagic transformation. Delta represents maximum rate of thrombus generation and measure enzyme kinetics. Future research should prospectively explore whether a subset of tPA-eligible patients with a significantly prolonged delta have more HT and should be the target of experimental therapies to prevent post tPA bleeding or even lower doses of tPA. CrossRefPubMedGoogle Scholar