[Low molecular weight heparin in extracorporeal circulation. 1st clinical applications]

The haemorrhagic complications inherent to the use of heparin during cardiac surgery led us, after a pilot experimental study, to try out a low molecular weight heparin (LMWH), PK 10169, which has weaker haemorrhagic effects in vitro. Our initial experience was confined to 23 patients with differing pathologies, undergoing cardiopulmonary bypass lasting 30 to 165 minutes. The modes of injection of YK 10169 varied according to the results, especially with respect to the limitation of peaks of anti-Xa activity; 8 patients were given one bolus intravenous injection, 9 were given a bolus injection and a continuous infusion, and 6 were only given the continuous infusion. Biological monitoring of anticoagulation was based on anti-Xa activity. Analysis of the biological results showed that the principal feature was the partial correction, and occasionally the non-correction of anti-Xa activity by protamine sulphate, with no correlation between this anti-Xa activity and postoperative bleeding. The authors report cases of severe postoperative bleeding despite the supposed theoretical and experimental weakly haemorrhagic properties of LMWH, and also discuss the inefficacy of protamine sulphate. The indications for LMWH for cardiopulmonary bypass which were retained, were the rare cases of heparin-induced thrombocytopaenia. In conclusion, it is possible to use LMWH during cardiac surgery but we do not advise using it routinely as its theoretical advantages are not confirmed in practice.