Prophylaxis against postoperative pulmonary embolism and deep-vein thrombosis by low-dose heparin.

The prophylactic effect of low-dose heparin on postoperative fatal and on clinically apparent but non-fatal thromboembolic complications was studied in a double-blind, prospective, randomised study comprising 1296 patients. 16 out of 653 patients in the placebo group had such complications within the treatment period of 1 week, compared with 4 out of 643 in the heparin group. This difference was statistically significant (P less than 0.05). 4 cases in the placebo group and 1 in the heparin group were fatal. After prophylactic treatment had been stopped at the end of the first postoperative week, the rate of thromboembolic complications was equal for the 2 groups. Low-dose heparin prophylaxis is thus effective and should be given routinely in patients aged over 40 years; it should also be given for more than 1 week in patients not ambulant by then.