CONTROLLED REPERFUSION OF CARDIAC GRAFTS FROM NON-HEART-BEATING DONORS

Background. Hearts harvested from non-heart-beating donors sustain sev ere injury during procurement and implantation, mandating intervention s to preserve their function. We tested the hypothesis that limiting o xygen delivery during initial reperfusion of such hearts would reduce free-radical injury. Methods. Rabbits sustained hypoxic arrest after v entilatory withdrawal, followed by 20 minutes of in vivo ischemia. Hea rts were excised and reperfused with blood under conditions of high ar terial oxygen tension (PaO2) (approximately 400 mm Hg), high pressure (80 mm Hg), and low pressure (40 mm Hg), with or without free-radical scavenger infusion. Non-heart-beating donor groups were defined by the initial reperfusion conditions: high PaO2/high pressure (n = 8), low PaO2/high pressure (n = 7), high PaO2/low pressure (n = 8), low PaO2/l ow pressure (n = 7), and high PaO2/high pressure/free-radical scavenge r infusion (n = 7). Results. After 45 minutes of reperfusion, low PaO2 /high pressure and high PaO2/low pressure had a significantly higher l eft ventricular developed pressure (63.6 +/- 5.6) and 63.1 +/- 5.6 mm Hg, respectively) than high PaO2/high pressure (40.9 +/- 4.5 mm Hg; p < 0.0000001 versus both). However, high PaO2/high pressure/free-radica l scavenger infusion displayed only a trend toward improved ventricula r recovery compared with high PaO2/high pressure. Conclusion. Initiall y reperfusing nonbeating cardiac grafts at low PaO2 or low pressure im proves recovery, but may involve mechanisms other than decreased free- radical injury.