Prolonged open-chest total cardiopulmonary bypass in calves.

Utilizing currently popular techniques for clinical cardiopulmonary bypass on 10 consecutive 70- to 80-kg calves, open-chest total cardiopulmonary bypass was carried out for 4 hours with 100 percent survival. However, all animals demonstrated serious intraoperative and postoperative alterations in blood gas, blood chemistry, and hematology parameters, grossly abnormal cardiovascular hemodynamics, and altered renal function. Therefore, a modified bypass technique and procedural protocol was developed, based on observations of more than 2000 clinical human and experimental canine bypass procedures, plus selected pilot experiments on calves. These modified techniques were then utilized in 12 consecutive 70- to 80-kg calves for 8 hours of open-chest total cardiopulmonary bypass. There were no deaths, and all physiologic parameters tested remained in a satisfactory (near normal) range during and after the prolonged bypass procedure. Details of the technique and the specific data collected during and after bypass are presented. The data suggest that important fallacies may exist in currently popular concepts about the harmful effects of cardiopulmonary bypass, particularly as they relate to steady flow arterial perfusions, methods of extracorporeal oxygenation, techniques of heparinization, and etiology of oozing tendencies associated with prolonged perfusions and dilution perfusions.