Failure of low dose heparin to prevent pulmonary embolism after hip surgery or above the knee amputation.

In a randomized, double-blind trial, 5,000 USP units of sodium heparin or saline were give subcutaneously at least two hours before surgery and at 12 hour intervals thereafter to patients requiring total hip replacement, surgical correction of hip fracture, or major lower extremity amputation for vascular insufficiency. Lung perfusion scans were performed before surgery and at weekly intervals during the postoperative period. Pulmonary arteriograms were requested in patients developing new perfusion defects on serial scans. Two hundred twelve patient hospitalizations were analyzed. We diagnosed acute pulmonary embolism by serial lung perfusion scans or at autopsy in 37 patients. The incidence of pulmonary embolism in 40 patients with below the knee amputation was too low to warrant conclusions. The incidence of acute pulmonary embolism in 94 patients undergoing above the knee amputation was 25% in patients receiving heparin and 27% in patients receiving saline. The incidence of acute pulmonary embolism in 78 patients undergoing hip surgery was 13% in patients receiving heparin and 12% in patients receiving saline. We conclude that the regimen used had no significant effect on the incidence of acute pulmonary embolism in patients undergoing hip surgery or above the knee amputation.