We examined the relationship between obesity, a recognized risk factor for venous thromboembolism (VTE), and practices in the provision of VTE prophylaxis. Study subjects were enrolled in the International Medical Prevention Registry on Venous Thromboembolism (IMPROVE).
Beginning in July 2002, consecutive patients were enrolled who were ≥18 years old and hospitalized for ≥3 days for an acute medical illness. Body weight was categorized according to Body Mass Index (BMI; kg/m2) as morbidly obese (BMI >40), obese (BMI >30-40), overweight (BMI >25-30), normal weight (BMI 18.5-25), or under weight (BMI <18.5).
Data are presented for 2,745 patients enrolled through March 31, 2004 at 31 hospitals, in 9 countries. Compared to other patients, obese and morbidly obese patients were younger, had a shorter stay in hospital, were more often female, more often US residents (all p<0.0001), and less likely to die in hospital (p=0.01). Morbidly obese and obese patients were more likely to receive pharmacological prophylaxis than normal weight or under weight patients (40%, 40% and 32% respectively, p=0.001; figure 1) with the main differences observed for unfractionated heparin (UFH) use (28%, 19% and 12%, p<0.0001). Of 332 patients who received UFH, the use of q8h dosing increased significantly with increasing BMI category (p=0.01 for linear trend; figure 2).
Consistent with published reports, obesity is more prevalent in US patients than other countries. Obese patients were more likely to receive prophylaxis in hospital than non-obese patients. Physicians increased the dose of UFH prophylaxis with increasing BMI, perhaps due to concerns that use of a standard q12h or q8h UFH dosing schedule may lead to heparin overdosing in under weight and under dosing in overweight patients.
Given the significant proportion of obese medical patients in the IMPROVE registry, and the variation in practice patterns for providing VTE prophylaxis, this population should be studied further to understand their risk of VTE.
V.F. Tapson, IMPROVE is funded by an unrestricted educational grant