Graduated compression stockings in the prevention of postoperative venous thromboembolism. A meta-analysis.

BACKGROUND The effectiveness of graduated compression stockings in prophylaxis of postoperative venous thromboembolism is unclear to many physicians. Surveys show there is considerable variability in their use and their perceived effectiveness. We undertook to establish, by a systematic overview of the literature, the effectiveness of graduated compression stockings in the prophylactic setting of postoperative venous thromboembolism. METHODS Studies published between 1966 and June 1992 were identified through the MEDLINE database, with a search in all languages, through reviews of Current Contents, and including references cited in identified articles. Articles were selected for initial analysis if they assessed the use of graduated compression stockings for the prophylaxis of venous thromboembolism, and if the stocking group was compared with an untreated or unconfounded control group. Criteria were established a priori, to select only studies with sound methods. On the basis of these criteria, 12 studies were identified for the combined analysis. Each eligible study was independently analyzed for the risk of development of deep venous thrombosis in the control and stocking groups, and this was expressed as an odds ratio. Odds ratios were combined across studies by means of the Mantel-Haenszel chi 2 procedure. The data were analyzed separately for orthopedic surgery because of its high risk for venous thromboembolism. RESULTS Eleven of the 12 studies were in moderate-risk surgery (abdominal, gynecologic, and neurosurgery); the summary odds ratio was 0.28, which translates into a risk reduction of 68% (95% confidence interval, 53% to 73%), which is statistically significant (P < .0001). In the one study in orthopedic surgery that was eligible for inclusion, the odds ratio was 0.50 (95% confidence interval, 0.19 to 1.29; P = .17). CONCLUSIONS The use of graduated compression stockings for prophylaxis of venous thromboembolism after moderate-risk surgery results in a significant risk reduction. It is unknown whether the use of graduated compression stockings in combination with other forms of prophylaxis results in further risk reduction. The efficacy of graduated compression stockings in orthopedic surgery has been assessed by only one study that used sound methods, hence no definitive conclusions can be made in these high-risk patients.