Heart preservation with metabolic inhibitor, hypothermia, and hyperbaric oxygenation.
The effect of metabolic inhibitor, hypothermia (4 degrees C) and hyperbaric oxygenation (3 atm) on prolonging survival of the canine anoxic heart has been evaluated. Donor hearts were obtained from small mongrel dogs by giving the pre-cooled perfusate of 2 per cent magnesium sulfate (MgSO4), 5 per cent low molecular weight dextran (LMWD) and 2 per cent glucose into the right atrium. Excised hearts were kept at 4 degrees C in a hyperbaric chamber pressurized to 3 atm. After 18 to 48 hours the preserved hearts were transplanted to the neck of recipients by the methods of Marcus. The viability of the preserved hearts were evaluated with functional, biochemical and histologic parameters. Of 29 hearts preserved for 18 to 36 hours, 27 hearts returned to a strong coordinated beat and could maintain function for over 4 hours. Of 5 hearts preserved for 48 hours, 4 showed a coordinated ventricular beat, however, failed to maintain cardiac work over 4 hours. The hearts with 18 to 36 hours storage showed no significant abnormalities on myocardial metabolism and morphology as compared to the control group of the immediately transplanted hearts. The protective action of magnesium is probably related to a number of factors, including metabolic depression and stabilizing effect on membrane permeability of cells to potassium, which would tend to maintain a more normal membrane potential and sub-cellular particles. These studies indicate that viability of the mammalian anoxic hearts can be extended to 36 hours by the combined use of metabolic blockade, hypothermia and hyperbaria suggesting a practical approach to procurement and preservation of cadaver organs.