The antithrombotic effect of low-dose heparin has been ascertained clinically. The postoperative activation of the coagulation factors must be decreased, without increasing any bleeding tendencies. In order to determine the optimal dosage in low-dose heparin prophylaxis we examined the RCT, PTT, TT, Factor Xa, AT III and heparin concentrations in 400 patients prior to and following emergency surgery. Any thrombotic or haemorrhagic complication was registered. All 100 cases
received one of the following treatment plans: 1) 5000 U heparin s.c. TID, 2) 7500 U heparin s.c. TID, 3) 100 U heparin/kg s.c. BID, 4) 150 U heparin/kg s.c. BID. Only plans 2 and 4 achieved a measureable heparin effect without increasing the risk of bleeding. The PTT did not shorten in either of these 2 groups and the thrombin time rose only occasionally to the upper normal limits. All other values remained within normal limits. The thrombo-embolic incidence amounted to 1% in groups 2 and 4, 2% in groups 3 and 5% in the first group.
