LOW HEPARINIZATION WITH HEPARIN-BONDED BYPASS CIRCUITS - IS IT A SAFESTRATEGY

Background. The use of heparin-bonded cardiopulmonary bypass circuits with reduced doses of heparin sodium has been shown to give hemostatic benefits to the patient. However, fears persist that the use of less heparin may put the patient at risk for thrombotic events. This work t ested the hypothesis that heparin-bonded circuits per se are effective in preserving cells and reducing thrombin generation when a reduced d ose of heparin is used in vitro. Methods. Simulated extracorporeal cir culation was carried out using the same unit of fresh heparinized (1.1 U/mL) human blood to simultaneously perfuse a heparin-bonded circuit and a nonbonded circuit. Samples were taken at 30, 60, 120, and 360 mi nutes and analyzed for markers of cell activation and thrombin generat ion. Results. The concentrations of platelet and white blood cell acti vation markers were found to be significantly lower in the heparin-bon ded circuits compared with the nonbonded circuits. In addition, marker s of thrombin generation were significantly lower in bonded circuits. Scanning electron microscopy revealed fewer adherent cells and less de bris on the bonded surface compared with the nonbonded surface. Conclu sions. Cell activation and thrombin generation were significantly redu ced as a result of the presence of immobilized heparin in a system of cardiopulmonary bypass with reduced plasma heparin. However, evidence of contact activation in the bonded circuits was found after 120 minut es, indicating that anticoagulation in the system was not adequate. Th is becomes more important clinically where the extrinsic pathway of co agulation is also involved. (C) 1997 by The Society of Thoracic Surgeo ns.