Extracorporeal membrane oxygenation without anticoagulation: a study using quantitative scanning electron microscopy.

In current clinical applications of extracorporeal circulation (ECC) of blood, heparin is administered to prevent thrombosis in the circuit and to eliminate thromboembolism in the patient. Systemic heparinization, however, causes impairment of normal coagulation properties and significantly increases the risks of major bleeding complications. It has been observed in the past that ECC may be performed in the absence of any systemic anticoagulants or material surface treatments. In this study, short-term extracorporeal membrane oxygenation (ECMO) was performed on rabbits in three groups. The animals in the first group received standard clinical dosages of heparin. No form of anticoagulation was used in the second group. The ECMO circuits in the third group were treated with an albumin-heparin complex surface-coating. Thrombosis in the extracorporeal circuit was evaluated by using quantitative scanning electron microscopy. The results indicated very few statistically significant differences between the three experimental systems in the amounts of blood components adhering to the surface. Considerably more platelet activation and attachment was noted in the systemic heparin group. These experiments failed to demonstrate any benefit of systemic heparinization in short-term ECMO. The findings from these experiments suggest that the current levels of systemic heparinization may be unwarranted, and they indicate that more controlled studies must be performed to determine optimal levels of anticoagulation for different applications of ECC.