Is heparin necessary for extracorporeal circulation?

To explore the possibility of extracorporeal circulation (ECC) without heparin, we performed veno-arterial extracorporeal membrane oxygenator procedures for a five hour period on a total of 15 rabbits in three groups. Blood flow rates were maintained at 125 ml/min with a standard roller pump through 1/4 inch PVC tubing and a 0.4 m2 SciMed membrane oxygenator. The rabbits in Group 1 received a standard dose of heparin, while no form of anticoagulation was used in Group 2. The tubing and membrane surfaces in Group 3 were modified by a glutaraldehyde crosslinked albumin-heparin complex with no systemic heparinization. Blood samples were obtained for activated clotting time, platelet count, and blood gas determinations. Circuits were evaluated for thrombosis, and samples of lung and kidney were examined histologically for emboli. There were no statistically significant differences among the three groups for any of the quantitative parameters. Moderate thrombus formation was visually detected in some areas of stagnation in the nonheparinized systems, while the albumin coating appeared to inhibit thrombus formation in regions of moderate and high blood flow. These results do not reflect any significant benefit of either the albumin-heparin coating or systemic heparinization during short-term ECC.