Further Studies on Microdose Intravenous Heparin in the Prevention of Postoperative Deep Vein Thrombosis

Following in-vitro observations of heparin activity, which demonstrated that sodium heparin was stable in 0.9% saline but not in dextrose solutions, a clinical trial was undertaken to assess the effectiveness of i.v. microdose (I u/kg/h) heparin in preventing postoperative deep vein thrombosis and to find out whether subsequent s.c. low-dose (5000 u/12 hourly) offered additional prophylaxis. Eighty-six patients undergoing major surgical operation received i.v. microdose heparin for mean 4.1 days. Patients were then randomly allocated to one of two groups. Forty received s.c. heparin (5000u/12 hourly) when i.v. fluids were discontinued for an additional mean 4.3 days and 46 received no further prophylaxis. Deep vein thrombosis was detected by ¹²⁵I-fibrinogen uptake in five patients, with no significant difference between the two groups.