Efficacy and safety of low-molecular-weight heparin (CY216) in preventing postoperative venous thrombo-embolism: a co-operative study.

The efficacy and safety of a low-molecular-weight (LMW) heparin fraction in preventing postoperative venous thrombo-embolism, was assessed in a double blind, randomly allocated trial, and in an 'open' study. Of 395 patients included in the double blind trial, 199 received unfractionated (UF) calcium heparin, and 196 the LMW heparin fraction. The data were analysed on an 'intention to treat' basis. The two groups were well matched for risk factors which could predispose to the development of venous thrombosis. Fifteen (7.5 per cent) of one hundred and ninety-nine patients receiving UF heparin, and five (2.5 per cent) of one hundred and ninety-six patients in the LMW heparin group developed DVT (P less than 0.05). There was no significant difference between the two groups in terms of excessive incisional or total blood loss during surgery, postoperative drainage or wound haematoma formation. Of 910 patients included in the 'open' study who received a single injection of LMW heparin every day, 30 (3.2 per cent) died during the postoperative period; in none of the autopsied patients were pulmonary emboli detected. Thirty-one (3.4 per cent) patients developed isotopic DVT; twenty-seven (2.9 per cent) were receiving prophylaxis at the time the DVT was diagnosed. Thirty-six (3.9 per cent) patients developed wound haematoma; twenty-five (12.4 per cent) of those were in the two hundred and one undergoing surgery for gynaecological conditions, and eleven (1.5 per cent) in the seven hundred and nine patients having general abdominal surgery. This difference is statistically significant (P less than 0.001). The results of a double blind trial indicate that a single daily injection of 1850 APTT units (7500 antifactor Xa units) of a LMW heparin is more effective than 10 000 APTT units of commercially available UF heparin in preventing postoperative DVT. The findings of the 'open' study suggest that this regimen also provides an effective prophylaxis against post-operative major pulmonary embolism.