One hundred five patients over age 40 undergoing various major operations were randomly divided into control and treated groups; all were treated by subcutaneous injection containing either 5,000 international units aqueous heparin sodium or a placebo one hour prior to operation and every 12 hours thereafter for eight days. Deep vein thrombosis (DVT) was detected by daily 125I-fibrinogen injection and leg scanning, and confirmed by ascending phlebography.
Both groups were comparably distributed by age, sex, variety of operation, incidence of previous thromboembolism, and myocardial and cerebrovascular disease. Blood loss was not increased in the treated group. Incidence of DVT was 8.6% for the total group, 7.5% in the heparin-treated group (four of 53), and 9.6% in the control group (five of 52), including one control patient with a normal scan who later had a pulmonary embolus.
Covey TH, Sherman L, Baue AE. Low-Dose Heparin in Postoperative PatientsA Prospective, Coded Study. Arch Surg. 1975;110(8):1021-1026. doi:10.1001/archsurg.1975.01360140165032