Twenty-four hour membrane oxygenation in dogs without anticoagulation.

Is systemic heparinization or heparin-bonded circuitry better than no anticoagulation during 24 hours of cardiopulmonary bypass? We compared blood pressure, coagulation state, oxygenator function, and scanning electron microscopic appearance of the circuits. There were three groups of five dogs each: Group I had no anticoagulants; Group II received systemic heparization; Group III perfusions utilized heparin-bonded circuits. Group I animals all survived, whereas 80 percent (four fifths) in Group II and 20 percent (one fifth) in Group III survived. Arterial pressures were better maintained in Group I as compared to Groups II and III. The coagulation parameters were similar in all groups. Oxygenator function was maintained at normal in all groups. No thrombi were present in any of the circuits following perfusion. The surfaces in Group I had less debris on them compared to Groups II and III. Animals that died had fibrin thrombi present in tissues examined histologically. Systemic heparinization had no advantage over no heparin in this study. The striking similarity of the coagulation state between Groups I and II and better preservation of the surfaces in Group I were unexpected. Heparin-bonded circuits were unsatisfactory when compared to no anticoagulation and systemic heparinization. Additional experiments with various species with and without anticoagulation must be done to determine the best guidlines for human cardiopulmonary bypass.