Thromboelastography for the monitoring of the antithrombotic effect of low-molecular-weight heparin after major orthopedic surgery.

Objective: Low-molecular-weight heparins (LMWHs) are commonly used to prevent and manage postoperative thromboembolism. In general, monitoring of anticoagulant activity by anti-Xa testing is not done properly. Thromboelastography (TEG) evaluates the viscoelastic properties of blood during coagulation. The clinical application of TEG variables in monitoring LMWH treatment is not yet well defined.

Methods: This prospective study was designed to systematically examine the correlation between anti-Xa and basic TEG parameters in monitoring LMWH treatment. We furthermore evaluated for the first time the usefulness of a composite TEG parameter, coagulation index (CI). Thirty patients undergoing unilateral or bilateral total knee replacement, admitted to the intensive care unit on a therapeutic dosage of subcutaneous enoxaparin (30-mg injections administered twice daily), were included into the study. TEG parameters and anti-Xa levels were measures at baseline and 4, 12, and 24 hours after the injection.

Results: This study demonstrates a significant correlation between CI and plasma anti-Xa activity in surgical patients treated with enoxaparin. Although the correlation was significant between r time and anti-Xa level only at Hour 4, CI was significant for each time interval (p<0.05). CI increased immediately after T0, peaking at Hour 4, and remained elevated (relative to baseline) at Hour 24 but still did not return to admission levels.

Conclusion: The current study may be an important first step in order to use CI to measure LMWH activity. Meanwhile, the value and usefulness of TEG in predicting bleeding or thrombotic complications following major orthopedic surgery merit further investigation.