Efficacy of low-dose heparin in prevention of extensive deep-vein thrombosis in patients undergoing total-hip replacement.

In a prospective trial, the prophylactic efficacy of low-dose heparin was investigated in 84 consecutive patients undergoing total-hip replacement. 52 of these were randomly allocated to receive heparin or a combination of heparin and dihydroergotamine (D.H.E.); the remaining 32 patients, who were operated on by one orthopaedic team and did not receive prophylaxis, acted as a control group. The frequency of deep-vein thrombosis (D.V.T.), determined by the 125I-fibrinogen test and venography, was 69% in the control group, 32% in the patients receiving heparin alone, and 16% in those receiving heparin and D.H.E. The difference between the control group and each group receiving prophylaxis was statistically significant. The frequency of femoral-vein thrombi, demonstrated by venography, was analysed separately because of its frequent association with major pulmonary embolism. Femoral-vein thrombi developed in 17 (53%) in the control group, while they developed in only 4 patients (8%) in the prophylaxis group (P less than 0.01). 1 patient in the control group died due to massive pulmonary embolism; in another patient, again in the control group, clinical features suggestive of major non-fatal pulmonary embolism developed. This complication was not observed in patients receiving prophylaxis. There was no difference in the amount of operative or postoperative blood-loss in the three groups. In 3 patients in the entire series wound haematomata developed; all 3 were controls and haematomata developed after the administration of streptokinase or large doses of heparin for the treatment of extensive femoral-vein thrombi. By use of a sensitive assay, heparin could be detected in the plasma in 67% of samples in patients in whom D.V.T. did not develop. In contrast, in those patients in whom D.V.T. developed, heparin could be detected in only 21% of blood-samples (P less than 0.01). It is concluded that in patients undergoing total-hip replacement, low-dose heparin prophylaxis is effective in reducing the frequency of life-threatening extensive thrombi in the femoral vein. Prophylaxis using a combination of heparin and D.H.E. requires further evaluation.