Prospective comparison of three enoxaparin dosing regimens to achieve target anti‐factor Xa levels in hospitalized, medically ill patients with extreme obesity

Abstract

Enoxaparin is commonly used to prevent venous thromboembolism (VTE) [1, 2] but has not been well-studied in patients with extreme obesity, a population at high risk for VTE. We prospectively compared three enoxaparin dosing regimens for the achievement of goal peak anti-Factor Xa levels in medically-ill patients (n=31) with extreme obesity (body mass index (BMI) ≥ 40 kg/m2). Patients were assigned to receive fixed-dose (FD) enoxaparin 40mg daily (QDay, n=11), weight-based, lower-dose (LD) enoxaparin 0.4 mg/kg QDay (n=9), or weight-based, higher-dose (HD) enoxaparin 0.5 mg/kg QDay(n=11). The average BMI and weight of the entire cohort was 62.1 kg/m2 (range 40.5-82.4) and 176 kg (range 115-256 kg) and did not differ between groups. Peak anti-Factor Xa levels were significantly higher in the HD group compared to either LD or FD groups. Patients in the HD group achieved target anti-Factor Xa levels more frequently than the LD and FD groups (p<0.05). Peak anti-Factor Xa levels did not correlate with age, weight, BMI, or creatinine clearance, demonstrating the predictability of weight-based enoxaparin dosing. There were no adverse events (e.g. bleeding, thrombosis, thrombocytopenia). To our knowledge, this is the first prospective comparative study demonstrating that in extremely obese, medically-ill patients enoxaparin 0.5 mg/kg QDay is superior to fixed-dose and lower-dose enoxaparin for the achievement of target anti-Factor Xa levels.

Canadian Consensus Recommendations on the Management of Venous Thromboembolism in Patients with Cancer. Part 1: Prophylaxis

“…Compared with the lower weight-based dose or fixeddose groups, the higher weight-based dose group more frequently achieved target factor Xa levels (p < 0.05). No adverse event (bleeding, thrombosis) occurred in any group 74 .…”

A systematic review of venous thromboembolism prophylaxis strategies in patients with renal insufficiency, obesity, or on antiplatelet agents

“…The subgroup analysis by Kucher et al 11 showed effect attenuation of dalteparin when given at a fixed dose of 5000 IU/mL to patients with a BMI of >40 kg/m 2 . The Freeman study 12 showed that extremely obese patients (average BMI >62.1 kg/m 2 ) who are given a fixed dose of enoxaparin achieved target anti-factor Xa levels significantly less often than those who received a higher dose of enoxaparin. The 2 separate findings, although not conclusive, lend some credence to the current ACCP guidelines.…”

“…12 The average BMI of the entire cohort was 62.1 kg/m 2 (range, 40.5-82.4). All patients had anti-factor Xa levels drawn on the day of enrollment and daily for 3 days ( Table 2).…”

Challenges in the surgical management of spine trauma in the morbidly obese patient: a case series

“…On a weight-adjusted basis, morbidly obese patients should receive the same dose of LMWH, although there is evidence that twicedaily dosing of 1 mg/kg is safer for patients with a BMI greater than 35 or a weight greater than 150 kg (330 lbs). 21 …”

“…21 However, initiation of LMWH prophylaxis is often delayed because of injury-related intracranial, intraspinal, or other bleeding, as well as deferment associated with planned operative intervention. On a weight-adjusted basis, morbidly obese patients should receive the same dose of LMWH, although there is evidence that twicedaily dosing of 1 mg/kg is safer for patients with a BMI greater than 35 or a weight greater than 150 kg (330 lbs).…”