Abstract P230: Risk of Venous Thromboembolism in Acutely Ill Medical Patients and the Influence of Timely Ambulation

Abstract

Background: Ambulatory status is often considered a criterion for stopping prophylaxis for venous thromboembolism (VTE) in medically ill patients. Methods: A subgroup analysis of the Prophylaxis in Medical Patients with Enoxaparin (MEDENOX) trial was performed according to ambulatory status. Ambulatory status was defined as the ability to attain autonomous walking distance of > 10 meters assessed at visit day 10 ± 4. Incidence of VTE and bleeding was evaluated. Results: The majority of patients (607 of 1084) were ambulatory at visit day 10 ± 4, with a mean time to ambulation of 4.4 days. Thromboprophylaxis was provided for a mean of 7.3 days in the ambulatory subgroup and 7.9 days in the non-ambulatory subgroup. Main results are displayed in the graph. Major bleeding was not significantly different between enoxaparin 40 mg once daily versus placebo in the ambulatory (1 of 212 vs 1 of 190, respectively) or non-ambulatory subgroups (5 of 146 vs 3 of 169). In a multivariate logistic regression model to assess which factors influenced the probability of individual patients becoming ambulatory, ambulatory patients were less likely than non-ambulatory patients to be aged > 75 years (OR 0.57; 95% CI 0.43-0.75; P < 0.0001) and to have a previous history of VTE (OR 0.61; 95% CI 0.38-0.95; P = 0.03). Provision of VTE prophylaxis or placebo did not affect ambulatory status. Conclusions: Despite timely mobilization, medically ill patients who become ambulatory in hospital remain at substantial risk of VTE and have significant VTE risk reduction with enoxaparin 40 mg once daily, as also observed in non-ambulatory patients. Ambulatory status is significantly influenced by baseline characteristics.