Predictors of rehospitalization for symptomatic venous thromboembolism after total hip arthroplasty.

Background: Recent studies have shown that symptomatic venous thromboemboli sm after total hip arthroplasty most commonly develops after the patient is discharged from the hospital. Risk factors associated with these symptomat ic thromboembolic events are not well defined. Methods: Using administrative data from the California Medicare records for 1993 through 1996, we identified 297 patients 65 years of age or older who were rehospitalized for thromboembolism within three months after total hi p arthroplasty. We compared demographic, surgical, and medical variables po tentially associated with the development of thromboembolism in these patie nts and 592 unmatched controls. Results: A total of 89.6 percent of patients with thromboembolism and 93.8 percent of control patients were treated with pneumatic compression, warfar in, enoxaparin, or unfractionated heparin, alone or in combination. In addi tion, 22.2 percent and 29.7 percent, respectively, received warfarin after discharge. A body-mass index (the weight in kilograms divided by the square of the height in meters) of 25 or greater was associated with rehospitaliz ation for thromboembolism, with an odds ratio of 2.5 (95 percent confidence interval, 1.8 to 3.4). In a multivariate model, the only prophylactic regi mens associated with a reduced risk of thromboembolism were pneumatic compr ession in patients with body-mass indexes of less than 25 (odds ratio, 0.3; 95 percent confidence interval, 0.2 to 0.6) and warfarin treatment after d ischarge (odds ratio, 0.6; 95 percent confidence interval, 0.4 to 1.0). Conclusions: In patients who underwent total hip arthroplasty, a body-mass index of 25 or greater was associated with subsequent hospitalization for t hromboembolism. Pneumatic compression in patients with a body-mass index of less than 25 and prophylaxis with warfarin after discharge were independen tly protective against thromboembolism. (N Engl J Med 2000;343:1758-64.) (C ) 2000, Massachusetts Medical Society.