Predictors of Rehospitalization for Symptomatic Venous Thromboembolism After Total Hip Arthroplasty.

Predictors of Rehospitalization for Symptomatic Venous Thromboembolism After Total Hip Arthroplasty White RH, Gettner S, Newman JM, et al (Division of General Medicine, Department of Medicine and Department of Orthopedic Surgery, University of California, Davis, Sacramento; California Medical Review Inc, San Francisco, Calif), N Engl J Med. 2000;343: 1758-1764.

According to several studies, symptomatic venous thromboembolism following total hip arthroplasty (THA) most commonly develops after the patient is discharged from the hospital. The risk factors associated with this phenomenon are not well known. The purpose of this study was to pinpoint the risk factors for the development of symptomatic thromboembolism after a THA and to determine if the incidence of this condition is reduced as the result of extended prophylaxis.

Subjects were chosen using Medicare records from 1993 to 1996. The authors identified 297 subjects (mean age= 74.8 [+ or -] 6.0 years) who met the inclusion criteria and who were readmitted to the hospital for thromboembolism within 3 months of a THA. The researchers also created a group of 592 unmatched control subjects (mean age=74.3 [+ or -] 5.8 years) who met the inclusion criteria. Physicians who did not know the purpose of the study were trained to use a computerized tool to abstract the required information from the hospital records. A positive laboratory finding (pulmonary arteriography, ventilation-perfusion lung scans, venography of the legs, venous ultrasonography, or impedance plethysmography) was required to document the presence of a thromboembolism.

Of the 297 patients who were hospitalized with a diagnosis of postoperative venous thrombosis, 94 (31.6%) had venous thrombosis with pulmonary embolism, whereas 203 (68.4%) had an isolated venous thrombosis. An odds ratio (OR) of 2.5 (95% confidence interval [CI]=1.8-3.4) for thromboembolism was associated with a body mass index of 25 or greater. The study found that use of pneumatic compression was associated with a significant reduction in the risk of thromboembolism, but only in patients with a body mass index of 25 or less (OR=0.3, 95% CI=0.2-0.6). Following multivariate analysis, the independent predictors for thromboembolism were: (1) an age of 85 or greater (OR=2.1, 95% CI=1.1-3.9), (2) female sex (OR= 1.4, 95% CI=1.0-1.9), (3) history of thromboembolism (OR=3.4, 95% CI=1.7-7.0), and (4) a body mass index of 25 or higher (OR=1.8, 95% CI=1.1-2.9). The authors thought that the finding that in-hospital prophylaxis therapy (standard heparin, enoxaparin, or warfarin) did not reduce the risk of thromboembolism after discharge could have been the result of a type II statistical error, especially because relatively small numbers of patients received each of the prophylactic interventions.

The authors concluded that a reduced risk of thromboembolism was associated with: (1) initial ambulation before day 2 after surgery (OR=0.7, 95% CI= 0.5-0.9), (2) use of pneumatic compression (OR=0.3, 95% CI=0.2-0.6), and (3) use of warfarin after discharge (OR=0.6, 95% CI=0.4-1.0). They also suggested that efforts should be made to increase the effectiveness of thromboprophylaxis in people who are overweight (body mass index [is greater than] 25).

Brad Stockert, PT, PhD
University of the Pacific
Stockton, Calif