The utility of thromboelastography in monitoring low molecular weight heparin therapy in the coronary care unit.

Low molecular weight heparins (LMWHs) are used for prevention and management of vascular thrombosis. In general, monitoring of anticoagulant activity is not required, however, certain populations may be susceptible to overdosing or underdosing. As anti-activated factor X(anti-Xa) activity testing is not readily available, it was our aim to investigate the usefulness of thromboelastography (TEG; Haemoscope Corporation, Skokie, Illinois, USA) for the assessment of coagulation in patients on LMWH. All patients admitted to the coronary care unit on therapeutic dose of enoxaparin were included (1 mg/kg twice daily). Blood samples were collected 4 h after the morning dose of enoxaparin once the participant had received at least three doses. When anti-Xa activity was classified as low (0-0.5), correct (0.5-1.0) or high (>1.0), the distribution of reaction time (R) and dose per kg showed little association with anti-Xa activity. The difference between mean R for the high anti-Xa group and the correct anti-Xa group was statistically nonsignificant using two-sample t-test (P = 0.26). A linear regression model showed no evidence of association between dose per kg and anti-Xa (P = 0.95). However, there was evidence of positive association between dose per kg and R (P = 0.011) wherein a 10% increase in dose per kg was associated with an increase in R of 2.7 (95% confidence interval 0.6-4.7). There was no evidence of association between R and anti-Xa (P = 0.38). TEG was unable to be used to predict anti-Xa activity. However, TEG R was prolonged in more than 90% patients and correlated with dose of enoxaparin. As enoxaparin dose correlated poorly with anti-Xa activity, a more global test might be necessary to adjust dosing of LMWH in sick, hospitalized patients.