Thromboelastography (TEG) is a diagnostic test used to evaluate the function of the blood clotting system. It measures the viscoelastic properties of blood clot formation and dissolution in real-time, providing information about the clotting ability of the blood.
During a TEG test, a small amount of blood is collected from the patient and placed in a specialized cup that contains a rotating pin suspended in the blood sample. As the pin rotates, it measures the strength of the clot as it forms and dissolves.
TEG can be used to diagnose bleeding disorders and monitor the effectiveness of anticoagulant therapies. It is commonly used in surgical and trauma patients to guide blood transfusion and hemostatic therapy decisions.
In patients with cirrhosis and liver disease, conventional coagulation measures fall short in accurately predicting bleeding risk. Despite presenting with markedly elevated INR levels, bleeding episodes in these patients are infrequent. Global coagulation tests like TEG, provide a better means of assessing procoagulant and anticoagulant pathways, clot strength, and fibrinolysis as a point-of-care test.
A Rebalance Coagulation State in Liver Disease
Cirrhosis is a medical condition that can lead to changes in the blood clotting process, resulting in a rebalanced state. Specific coagulation factors, including V, VII, IX, X, XI, prothrombin, protein C, and protein S, are reduced in cirrhosis. A decrease in V, VII, IX, X, XI, and prothrombin can reduce coagulation, while a deficiency of protein C and S can promote coagulation. In addition, cirrhotic patients produce increased levels of nitric oxide and prostacyclin, which along with low platelet count, can reduce the function of platelets. Meanwhile, the production of von Willebrand factor (VWF) and factor VIII (FVIII) is increased, leading to the promotion of platelet aggregation.
Reliability of Standard Coagulation Tests in Liver Disease
Standard coagulation tests, namely prothrombin time (PT), activated partial thromboplastin time (aPTT), international normalized ratio (INR), fibrinogen levels, and platelet count are not reliable predictors of bleeding or clotting in liver disease. These tests do not account for cellular elements (i.e., platelets, endothelial cells, inflammatory cells) which play a major role in the coagulation process in liver disease.
In a study conducted by Stravitz et al., hemostasis in patients with acute liver injury was evaluated using thromboelastography. The study revealed that patients exhibited significantly elevated INR levels but maintained normal hemostasis as indicated by TEG [1].
In a review article published in 2022, He et al. found that TEG can reflect the hemostatic status of the liver disease more comprehensively compared to conventional coagulation tests [2].
These findings provide insights to the intensivists caring for patients with liver disease, where abnormal traditional coagulation tests do not necessarily correspond with clinically evident hemostatic failure such as spontaneous bleeding.
The Use of TEG Results in Less Blood Component Transfusion in Liver Disease
A randomized controlled trial published in the journal of Hepatology in January 2020 investigated the use of thromboelastography to guide blood component transfusion in patients with cirrhosis and nonvariceal bleeding. The study found that using TEG-guided transfusion strategy led to significantly lower use of blood components compared to standard-of-care (SOC) transfusion guided by international normalized ratio (INR) and platelet count, without an increase in failure to control bleed, failure to prevent rebleed, and mortality [3].
Another randomized controlled trial compared the effectiveness of TEG-directed blood product transfusion to conventional transfusion in 60 cirrhotic patients with acute variceal bleeding. The study found that the TEG-guided strategy led to a reduced need for blood product transfusion without compromising hemostasis in cirrhotic patients. Rebleeding at 42 days was also significantly less in the TEG group, and 6-week mortality was similar between the groups [4].
In a study published by De Pietri et al in 2015, 60 cirrhotic patients with significant coagulopathy were randomized to receive TEG-guided transfusion or SOC based on INR and platelet count prior to undergoing an invasive procedure. The TEG group had significantly lower blood product use without an increase in bleeding complications. These results suggest that TEG may be a more effective tool for guiding blood transfusion in patients with cirrhosis undergoing invasive procedures [5].
These studies suggest that TEG may be a more accurate tool for assessing the hemostatic status of cirrhotic patients and guiding transfusion decisions. By using TEG to guide transfusion, clinicians may be able to avoid unnecessary blood component transfusions, reduce the risk of adverse events associated with blood product administration, and improve patient outcomes.
In making a decision to transfuse blood components in liver disease patient, which tests would you rely on?
PT and INR
TEG
I have no options other than Pt/INR as TEG is not available
How to Intrepret the Results of TEG
Thromboelastography-based factor replacement is a treatment strategy that guides factor replacement therapy in liver patients with bleeding disorders or before invasive procedures. Fresh frozen plasma is given with prolonged reactive time, cryoprecipitates with decreased alpha angle or prolonged K time, platelet transfusion for decreased MA, and tranexamic acid for increased LY30 (see infographic for details).
In Summary
TEG is a diagnostic test that measures the viscoelastic properties of blood clot formation and dissolution in real-time. It is used to evaluate the function of the blood clotting system, diagnose bleeding disorders, and monitor the effectiveness of anticoagulant therapies. TEG is particularly useful in patients with cirrhosis and liver disease, where conventional coagulation tests are not reliable predictors of bleeding or clotting.
TEG can reflect the hemostatic status of liver disease more comprehensively compared to conventional coagulation tests. TEG-directed transfusion may be a more effective approach to managing coagulopathy in cirrhotic patients, leading to less blood component transfusion without compromising hemostasis or increasing bleeding complications.
REFERENCES:
Stravitz RT, Lisman T, Luketic VA, Sterling RK, Puri P, Fuchs M, Ibrahim A, Lee WM, Sanyal AJ. Minimal effects of acute liver injury/acute liver failure on hemostasis as assessed by thromboelastography. J Hepatol. 2012 Jan;56(1):129-36. doi: 10.1016/j.jhep.2011.04.020. Epub 2011 May 19. PMID: 21703173; PMCID: PMC4944117. Link
He Y, Yao H, Ageno W, Méndez-Sánchez N, Guo X, Qi X. Review article: thromboelastography in liver diseases. Aliment Pharmacol Ther. 2022 Aug;56(4):580-591. doi: 10.1111/apt.17080. Epub 2022 Jun 14. PMID: 35698893. Link
Kumar M, Ahmad J, Maiwall R, Choudhury A, Bajpai M, Mitra LG, Saluja V, Mohan Agarwal P, Bihari C, Shasthry SM, Jindal A, Bhardwaj A, Kumar G, Sarin SK. Thromboelastography-Guided Blood Component Use in Patients With Cirrhosis With Nonvariceal Bleeding: A Randomized Controlled Trial. Hepatology. 2020 Jan;71(1):235-246. doi: 10.1002/hep.30794. Epub 2019 Aug 27. PMID: 31148204. Link
Rout G, Shalimar, Gunjan D, Mahapatra SJ, Kedia S, Garg PK, Nayak B. Thromboelastography-guided Blood Product Transfusion in Cirrhosis Patients With Variceal Bleeding: A Randomized Controlled Trial. J Clin Gastroenterol. 2020 Mar;54(3):255-262. doi: 10.1097/MCG.0000000000001214. PMID: 31008867. Link
De Pietri L, Bianchini M, Montalti R, De Maria N, Di Maira T, Begliomini B, Gerunda GE, di Benedetto F, Garcia-Tsao G, Villa E. Thrombelastography-guided blood product use before invasive procedures in cirrhosis with severe coagulopathy: A randomized, controlled trial. Hepatology. 2016 Feb;63(2):566-73. doi: 10.1002/hep.28148. Epub 2015 Dec 9. PMID: 26340411. Link