Prevention of Fatal Postoperative pulmonary embolism by low doses of heparin. Reappraisal of results of international multicentre trial.

The results of a multicentre trial, designed to assess the efficacy of low-dose heparin in preventing fatal postoperative pulmonary embolism, were published in July 1975. In view of inconsistencies which have now become apparent in the data from one of the twenty-eight centres which took part in the trial, the results of the trial have been re-examined, excluding the data from this centre. Of 4031 patients remaining after exclusion of these data, 2033 were in the control group and 1998 in the heparin group. 170 (4-2%) patients died during the postoperative period, 94 in the control group and 76 in the heparin group; 70-2% of deaths in the control group and 65-7% in the heparin group had necropsy examination. 15 patients in the control group and none in the heparin group were found at necropsy to have died due to acute massive fatal pulmonary embolism (P less than 0-001). Exclusion of data from the one centre did not alter already published significant differences in the total incidence of deep-vein thrombosis, nor in the frequency of operative and post-operative bleeding complications observed in the control group and the heparin group.