Randomized study of adjusted versus fixed low dose heparin prophylaxis of deep vein thrombosis in hip surgery.

A randomized study of adjusted versus fixed low dose heparin prophylaxis has been conducted in 100 patients undergoing surgery for hip replacement or fractured neck of femur. The two types of patients were randomized independently into the adjusted and fixed dose regimens. Patients in the adjusted group were controlled by an activated partial thromboplastin time method particularly responsive to the anticoagulant effect of heparin. The aim was to maintain the peak value just above the upper limit of the normal range. Adjustment of dosage began 24 h after surgery in the replacement group and 24 h after admission in the fracture group. Significant improvement in protection against postoperative deep vein thrombosis, assessed by venography, was observed in the adjusted group undergoing hip replacement (P = 0.013) and overall in both groups (P = 0.017) compared with a conventional fixed dose subcutaneous regimen (calcium heparin 5000 units, 8-hourly). In most instances, adjustment resulted in increased heparin dosage but this was not associated with any evidence of excessive bleeding.