Context.—Plasma anti-Xa and anti-IIa activities correlate with the dose of low-molecular-weight heparin, and D-dimer and thrombin-antithrombin complexes are markers of procoagulant activity.
Objective.—To investigate the relationship between plasma coagulation parameters and patient characteristics, including renal function, thromboprophylaxis, and incidence of venous thromboembolism (VTE) in the MEDENOX study population.
Design.—Controlled, multicenter, double-blind, randomized study.
Patients.—Two hundred twenty-four acutely ill medical patients.
Interventions.—Either 20 or 40 mg of enoxaparin administered subcutaneously or a placebo once daily for 10 (±4) days.
Main Outcome Measures.—VTE and plasma anti-Xa and anti-IIa activities, D-dimer, and thrombin-antithrombin levels in blood collected before prophylaxis was given (day 0) and after the last injection of the study drug.
Results and Conclusions.—Anti-Xa activity correlated with the dose of enoxaparin. In patients with mild or moderate renal impairment, there was no significant relationship between anti-Xa activity and the creatinine clearance rate. D-dimer concentrations were lower at day 10 (±4) in the 40-mg group, which had a 63% lower VTE incidence, than at day 0. No venographically confirmed thromboses were found in patients with a normal D-dimer concentration (<0.5 μg/mL [0.5 mg/L]). D-dimer levels were higher in patients with VTE than in those without VTE, but no predictive value could be demonstrated for individual patients.