Comparison Of Thromboelastography (TEG) With Rotational Thromboelastrometry (ROTEM) In Surgical Patients
Authors: Kinard Theresa Nguyen , Christie Alana , Greilich Philip E. , Sarode Ravindra 
Published: October 2019

Abstract

Introduction
Viscoelastic point-of-care coagulation devices have been used in trauma and surgical settings to manage blood component transfusions in bleeding and/or coagulopathic patients. Current technologies are thromboelastography (TEG) and rotational thromboelastometry (ROTEM), which allow for real time in-vitro analysis of the kinetics clot formation, clot strength, and fibrinolysis on whole blood samples. Unlike TEG, ROTEM has four channels with different reagents to detect abnormalities in different components involved in coagulation (Intem- contact activation pathway, Extem- tissue factor pathway, Heptem- neutralization of heparin, Fibtem- the contribution of fibrinogen to clot formation). The values of analogous TEG and ROTEM parameters are not interchangeable but provide similar interpretations.
TEG has been used at our institution in surgical procedures to guide blood component transfusion in bleeding patients. We evaluated performance characteristics of TEG and ROTEM, compared suggested blood product for transfusions based on algorithms for TEG and ROTEM, and correlated those results with conventional laboratory tests.

Methods
Laboratory data from all patients undergoing surgical intervention between February 2013 to March 2013 who had TEG and ROTEM performed along with conventional laboratory measures (fibrinogen, platelet count, prothrombin time (PT), and activated partial thromboplastin time (PTT)) were analyzed. TEG (reaction time (R), K-value, angle, maximum amplitude (MA)) was compared to Intem or Heptem (clotting time (CT), clot formation time (CFT), alpha, maximum clot firmness (MCF)) for concordance. The local TEG decision tree and a published, but unvalidated ROTEM algorithm were used to determine recommended blood product transfusions. The guidelines for transfusing blood components based on concurrent conventional laboratory tests (cryoprecipitate if fibrinogen<100 mg/dL, platelets if platelet count <50 K/uL, fresh frozen plasma (FFP) if PT or PTT were 1.5 times greater than the upper limit of normal) were compared to TEG and ROTEM transfusion algorithm recommendations. The time to clinical decision was determined by the time to maximum amplitude (TMA) for TEG and time to A10 (amplitude at 10 minutes after clot formation) for ROTEM and compared using the paired t-test.

Results
Forty-one patients (mean age 58 years; 78% males) were eligible for analysis. There were 41 surgical procedures (2 lung transplants, 2 liver transplants, 1 partial nephrectomy, and 36 cardiac surgeries). The mean number of intra-procedure tests was 2.2 (total 91, range: 1-4). There was good agreement with no statistical difference when comparing TEG to Intem or Heptem parameters. The best overall agreement was seen with MA and MCF (70.7%), followed by R and CT (67.2%), K and CFT (65.5%) and lastly, angle and alpha values (58.6%). When comparing suggested blood products using our TEG decision tree and an Intem based decision tree, both devices had the best agreements on transfusion of no products as guided by conventional tests, but lower agreement with abnormal conventional tests that would have resulted in blood component transfusion based on low fibrinogen levels (TEG and ROTEM- 0%), low platelets (TEG 44.4%, ROTEM 54.5%), or elevated PT or PTT (TEG 0%, ROTEM 22.2%). When comparing TEG to ROTEM, with additional information from Extem and Fibtem, there was overall agreement with transfusion of no products from both devices when conventional laboratory values were normal; there was less agreement with both devices when products were indicated based on abnormal conventional laboratory values. ROTEM had greater sensitivity to low fibrinogen (ROTEM 100%, TEG 0%) and better sensitivity to abnormal PT or PTT than TEG (ROTEM 40%, TEG 0%). TEG had better sensitivity to low platelet counts (TEG 100%, ROTEM 0%). The average time to a clinical decision was significantly faster with ROTEM (Intem- 13 minutes) as compared to TEG (26 minutes, p<0.0001).

Conclusions
TEG and ROTEM are comparable devices. TEG and ROTEM appear to prevent unnecessary blood component transfusions. Although the parameters of TEG and ROTEM (Intem) were not statistically different, slight disagreements in the values may result in transfusion of different products. Given that both devices provide similar information, ROTEM may be better in the surgical setting because of faster turn-around time.

Disclosures:
No relevant conflicts of interest to declare.