Thromboelastography


Coagulation disorders can lead to intra- or postoperative bleeding associated with increased morbidity and mortality. The transfusion of blood products to correct coagulopathy disorders is guided by clinical judgement, standard laboratory testing (PT, PTT, platelets, bleeding time, etc.), and thromboelastography testing. Thromboelastography (TEG) is a viscoelastic hemostatic assay, a functional test of clot formation and degradation performed on whole blood, at a point of care (emergency department, intensive care units or operating room) for clotting system deficiency that analyzes each phase of the coagulation process. Blood from a patient is mixed with citrate and placed in a cup of the TEG machine connected to a computer. The cup oscillates and the coagulation process occurs. This testing rapidly generates numeric and graphic results that can lead to guided-directed intervention for correct of coagulation disorders. Five variables are measured using thromboelastography. They are: R (reaction time) quantify as the time until measurable clot is formed, usually between five and 10 minutes. Should the patient have a prolonged R time then management is with fresh frozen plasma transfusion. K time - time since initial clot formation until it has a 20 mm fixed strength, normally one to 3 minutes. An abnormal K-time means low fibrinogen levels and is managed with cryoprecipitate. Alpha angle - is the speed of fibrin accumulation, similarly affected by fibrinogen levels. Normal alpha angle is 53-72 degrees. Again, an abnormal alpha angle is managed with cryoprecipitate. Maximum amplitude (MA) - consist of the highest vertical amplitude of the TEG tracing. MA reflects the strength of the clot normally reaching 50-70 mm. A narrow maximum amplitude is managed with platelets infusion. LY30 percentage - represent 30% decrease in the amplitude of the TEG tracing thirty minutes after maximum amplitude is obtained. It is a measure of fibrinolysis normally being zero and 8%. A higher than normal LY30 is indicative of a hypercoagulable state and may be managed with antifibrinolytics such as aminocaproic acid. TEG is superior to conventional coagulation testing in detecting early trauma coagulopathy reducing mortality. TEG should be available in trauma level I and  II centers.     

References:
1- Wasowicz M, Srinivas C, Meineri M, et al: Technical report: analysis of citrated blood with thromboelastography: comparison with fresh blood samples. Can J Anaesth 55(5): 284-9, 2008
2- Chan KL, Summerhayes RG, Ignjatovic V, et al: Reference values for kaolin-activated thromboelastography in healthy children. Anesth Analg 105(6): 1610-3, 2007
3- Rusell RT, Maizlin II, Vogel AM. Viscoelastic monitoring in pediatric trauma: a survey of pediatric trauma society memebers. J Surg Res. 214: 216-20, 2017
4-  Wikkelso¸ A(1), Wetterslev J, Moller AM, 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 Aug 22;(8):CD007871. doi:10.1002/14651858.CD007871.pub3.
5- Figueiredo S, Tantot A, Duranteau J: Targeting blood products transfusion in trauma: what is the role of thromboelastography? Minerva Anestesiol. 82(11):1214-1229, 2016
6- Nogami K: The utility of thromboelastography in inherited and acquired bleeding disorders. Br J Haematol. 174(4):503-14, 2016

6- Kouri AM, Wilson AC, Nailescu C: A malfunctioning peritoneal dialysis catheter: Questions. Pediatr Nephrol. 32(3):439-440, 2017


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