Hemodynamic and perioperative management in two different preclinical pig-to-baboon cardiac xenotransplantation models

Background The perioperative phase of preclinical cardiac xenotransplantations significantly affects the experimental outcome. Moderate or even severe hemodynamic and respiratory impairment occurs frequently in baboons after receiving a cardiac transplant. The perioperative management of such postoperative instability is very demanding, especially in the experimental setting. We compared perioperative changes of hemodynamic and laboratory findings during orthotopic and heterotopic thoracic cardiac xenotransplantations and describe our monitoring, treatment and intensive care. Methods Twenty-eight pig-to-baboon cardiac xenotransplantations were performed using either the orthotopic (oHTx, n=5) or heterotopic thoracic (htHTx; n=23) technique. In both techniques, cardioplegia and an intraoperative cardiopulmonary bypass (CPB) were required. Preoperatively, intensive care (eg, transfusions, catecholamine therapy) was provided and fast extubation was targeted. A central venous catheter, a femoral arterial thermodilution catheter, a telemetric pressure transmitter and transthoracic echocardiography were used to monitor the animal. Baboon jackets with a tethering system were used to continuously apply medication postoperatively and permit blood sampling, also after extubation of the animal and transfer into the cage. Perioperative survival, hemodynamics, catecholamine doses, respiratory function and weaning from respirator were compared. Perioperative organ damage was evaluated based on laboratory findings 12 hours after transplantation. Results Recipients could be weaned from CPB in the 20 htHTx and all five oHTx experiments, and three htHTx procedures were terminated during the operation. The time of cardiopulmonary bypass was significantly lower in the heterotopic group (oHTx median 171 [157-193] minutes; htHTx median 144 [100-190] minutes; P=.02). In 17 htHTx procedures, no inotropics were used, whereas epinephrine had to be administered in four of the five oHTx experiments; the mean time of catecholamine support was longer in the oHTx group (oHTx 972±348 minutes vs htHTx 111±92 minutes; P<.01). After htHTx, weaning off the respirator was possible in 19 of 20 cases (one died due to pneumothorax). After oHTx, three of the five baboons could be weaned off the respirator; in these cases, the arterial saturation was higher compared with the extubated baboons after htHTx (oHTx 99±1% vs htHTx 91±4%, P=.01). Intraoperative blood loss was similar between the two groups, and hemostasis was impaired after all procedures, but relevant postoperative bleeding never occurred. Conclusion Intensive intra- and postoperative monitoring and care is required in both transplantation techniques as a requirement for successful weaning from CPB and respirator. After htHTx, the animals needed less catecholamines and were hemodynamically more stable. Even though pulmonary function was often impaired after htHTx, weaning from the respirator and extubation was more successful in this group.