Correlation between Heparin Anti-Xa Activity and Thromboelastography in Adult Critically Ill COVID-19 Patients

Abstract

Specific Aims: Identify the relationship between therapeutic heparin anti-Xa activity and TEG R times in adult COVID-19 intensive care unit (ICU) patients. Methods: Baseline will be defined as the patient day which continuous infusion therapeutic unfractionated heparin (UFH) was initiated. The normal reference range of standard TEG parameters will be consistent with previously published reports (Supplement Appendix Table S1). The coagulation index (CI) will be calculated based on TEG findings as follows: –0.2454 (R time) + 0.0184 (K time) + 0.1655 (MA) – 0.0241 (α) – 5.0220.8 A normal CI is considered between -3.0 to 3.0. Thus, hypercoagulable and hypercoagulable states will be defined as a CI > 3.0 and < -3, respectively. The therapeutic range of UFH at the study site is defined as an anti-Xa of 0.3-0.7 units/mL. Subtherapeutic and supratherapeutic anti-Xa will be defined as <0.3 and >0.7 units/mL, respectively. Heparin resistance will be classified in patients with therapeutic or supratherapeutic UFH anti-Xa levels, elevated TEG reaction time, but hypercoagulable CI. Main Results: The overall incidence of agreement (subtherapeutic, therapeutic, supratherapeutic) between concurrent coagulation index and anti-Xa was 63.9%. Significant differences among several TEG parameters were observed including the following: R time, K time, Alpha angle, and Maximum amplitude. The median heparin anti-Xa found between the agreement and no agreement groups were 0.54, 0.42-0.63 vs. 0.41, 0.14-0.61, respectively, p<0.0001. Conclusions: The poor level of correlation between TEG and anti-Xa modest level of agreement on therapeutic categorization of TEG in COVID-19 remains unknown.