The effectiveness of 3 X 5000 IU s. c. heparin daily (starting preoperatively) for the prevention of postoperative deep vein thrombosis was evaluated in a prospective, controlled, randomized study including general surgical and urological patients. 125I-fibrinogen test was performed daily in all patients. 2. 178 patients fulfilled the conditions of the protocol. 35.8% of the 95 patients in the control group developed deep vein thrombosis, but only 13.3% of 83 subjects in the heparin group did so. The difference is statistically highly significant (p less than 0.001). 3. The vast majority of all thrombi in both groups appeared before the 3rd postoperative day. 4. With 1 exception, all deep vein thrombi in the heparin group started in the mid-calf region. In the control group 5 deep thrombi originated in the popliteal vein. 5. Heparin displays a better effect in males (n = 34; p less than 0.01) than in females (n = 49; p less than 0.025). 6. In patients undergoing surgery for malignant disease heparin does not reduce the incidence of deep vein thrombosis. 7. Heparin is far more effective in patients under 60 years of age than in those over 60 (p less than 0.005). 8. Heparin is more effective in obese patients than in those of normal body build. 9. Heparin prophylaxis also reduces the incidence of deep vein thrombosis in patients who exhibit predisposing factors. In patients of the control group with preexisting disease of the venous system, there were significantly more deep vein thrombi (p less than 0.01) than in those without predisposing factors. 10. In the heparin group 29% of all thrombin time determinations show a definite prolongation of more than 26 sec (normal value 15 sec). 11. In 14 patients (=16.9%) of the heparin group, 21 side effects or complications were seen. Bleeding complications were the main problem, comprising 5 wound hematomas and hematomas at the injection site, 4 postoperative bleeding episodes and 2 reoperations. There were no complications in the control group. 12. According to the results of 10 well controlled studies, there is no doubt that in general surgery small doses of subcutaneous heparin, commencing preoperatively, do reduce the incidence of postoperative deep vein thrombosis to a significant degree. However, whether this form of prophylaxis is also effective in patients with fractures of the hip and in elective hip surgery cannot, on the evidence available, be decided. In the fields of gynecological surgery and urology as well, more data are needed before this form of heparin prophylaxis can be recommended.
