Failure of Aspirin and Dipyridamole to Influence the Incidence of Leg Scan Detected Venous Thrombosis after Elective Hip Surgery

Drugs known to affect platelet function have been shown to be effective in the prevention of venous thrombosis after surgery. A double-blind randomized trial of aspirin plus dipyridamole was carried out to investigate the prophylactic value of the drug combination in the prevention of venous thrombosis detected by 125 Iodine-labelled fibrinogen leg-scanning after elective hip surgery. Aspirin 900 mg plus dipyridamole 100 mg were given once pre-operatively and twice daily for 10 days postoperatively, or until the patient was fully ambulant. 43 patients were entered into the trial, 22 in the control group and 21 in the treated group. Both groups were similar with respect to age, sex and factors known to predispose towards venous thrombosis. 8 patients (36.7%) in the control group and 8 patients (38.1% ) in the treated group developed leg scan-detected deep vein thrombosis. The thrombi were detected between the 1st and 17th post-operative day and were found as frequently in the operated limbs as in the non-operated limbs in both groups. It is concluded that prophylaxis with aspirin 900 mg and dipyridamole 100 mg twice daily does not influence the incidence of leg scan-detected deep vein thrombosis after elective hip surgery.