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ABSTRACT & COMMENTARY
Synopsis: A body mass index of 25 or greater was associated with subsequent hospitalization for thromboembolism in patients undergoing total hip arthroplasty.
Source: White RH, et al. N Engl J Med 2000;343:1758-1764.
The three-month incidence of symptomatic thromboembolism after total hip arthroplasty is approximately 3-4%, according to White and colleagues. More than 75% of these events are diagnosed after the patient is discharged from the hospital.1 They noted that the risk factors associated with these events are not well defined.
Using administrative data from the California Medicare records for 1993 through 1996, they identified 297 patients 65 years or older who were rehospitalized for thromboembolism within three months after total hip arthroplasty. They compared demographic, surgical, and medical variables in these patients with 592 unmatched controls.
A total of 89.6% of the patients with thromboembolism and 93.8% of control patients were treated with pneumatic compression, warfarin, enoxaparin, or unfractionated heparin alone or in combination. In addition, 22.2% and 29.7%, respectively, received warfarin after discharge.
White et al concluded that a body mass index (BMI) of 25 or greater was associated with rehospitalization for thromboembolism, with an odds ratio of 2.5. The only prophylactic regimens associated with a reduced risk of thromboembolism were pneumatic compression in patients with a BMI of less than 25 (odds ratio, 0.3) and warfarin treatment after discharge (odds ratio, 0.6).
Comment by Ralph R. Hall, MD, FACP
The last 10-15 years have seen significant improvement in the methods for the management of patients with the potential for thromboembolism. Advanced age, previous deep venous thrombosis, immobility, and the presence of genetic or acquired risk factors, such as antithrombin, protein C abnormalities, protein S deficiencies, factor V Leiden, hyperhomocysteinemia, and others have been recognized as precipitating factors.
There are numerous instances, however, in which none of these factors are present. Obesity and leg varicosities have been suspected causes, but their association with thromboembolism has not been well documented.
Also noted in this study’s results was that ambulation before day 2 after surgery had a protective effect. How important is mobility after the patient is discharged? How active or inactive were these patients after discharge? What other factors may associated with obesity?
Many of the laboratory tests for clotting abnormalities are expensive and complicated and, therefore, have not gained acceptance in clinical practice. Therefore, as White et al point out, we must improve our efforts to focus on improving the effectiveness of in-hospital as well as postdischarge thromboprophylaxis in over-weight patients.
1. Colwell CW, et al. J Bone Joint Surg Am 1999;81: 932-940.