Nonpharmacologic circulatory support in the brain-dead animal

A nonpharmacologic technique for providing an artificial peripheral resistance enabled the canine heart to pump blood for 12 hours in a brain- dead (spinal) animal model. The artificial peripheral resistance was provided by binding the body with elastic bandage. The only other support provided was artificial respiration. Following the 12-hour preservation period, the hearts were challenged to pump by the intravenous infusion of saline. Aortic pressure, cardiac output (CO), oxygen uptake, body temperature, arterial Na⁺, K⁺, pH, and HCO₃^-, and transchest ECG were monitored in all five animals studied during the control and 12-hour preservation periods. Mean blood pressure fell to 50-60 mmHg following cervical cord transection, rising to above 100 mmHg when the body was bound with elastic bandage that restored the peripheral resistance. During the 12-hour preservation period the average mean blood pressure fell from 118 to 60 mmHg, at which point the average normalized CO was 34 mL/min/kg. Following the saline challenge, the average CO increased to 1.89 times the value at the end of the preservation period, representing an average normalized value of 64.3 mL/min/kg (a typical value for the normal resting dog is 70 mL/min/kg). Body temperature decreased slightly in four animals and increased slightly in one. Na⁺ was virtually unchanged throughout the control and preservation periods, but K⁺ increased slightly in all animals, exceeding 5 mEq/L in one animal after 8.5 hours and in another after 10 hours. HCO₃^- was almost constant in all animals, as was pH. However, the pH was elevated during the preservation period due to slight overventilation to assure a high oxygen saturation. The transchest ECG revealed a slight axis shift in all animals and a slight peaking of the T wave in some. In no case was there an ST-segment shift. To assess perfusion of myoneural junctions, phrenic-nerve stimulation was performed hourly and in all cases there was a brisk contraction of the diaphragm. The authors conclude that this method of providing an artificial peripheral resistance could reduce the need for pharmacologic support for brain-dead organ donors.