CONTROLLED PRESSURE REPERFUSION OF RAT PULMONARY GRAFTS YIELDS IMPROVED FUNCTION AFTER 24-HOURS COLD-STORAGE IN UNIVERSITY-OF-WISCONSIN SOLUTION

Background: Pulmonary graft recipients commonly have a degree of pulmo nary hypertension. Immediate reperfusion of stored pulmonary grafts at supraphysiologic or even physiologic pressures may be detrimental to subsequent function. We wished to test the hypothesis that initial rep erfusion of pulmonary grafts at low pressures may be beneficial. Metho ds: We used an isolated, ventilated rat lung model, perfused by an ext racorporeal veno-venous circuit from a support animal. Three groups of donor lungs (n = 5 each) were flushed with cold University of Wiscons in solution. Group I was reperfused immediately at physiologic pressur e to provide control values. Group II grafts were stored at 4 degrees C for 24 hours and reperfused at physiologic pressure. Group III graft s were also stored at 4 degrees C for 24 hours but reperfused accordin g to a protocol of reduced pressure initially, with increments every 1 5 minutes up to physiologic levels by 60 minutes. Grafts and support a nimals were ventilated with room air. Graft function was assessed over a 2-hour period with regard to oxygenation, vascular resistance, peak airway pressure, and the wet/dry weight ratio. Results: Grafts in gro up II functioned poorly at 2 hours compared with control values: group II: oxygen tension 68 +/- 4 mm Hg; pulmonary vascular resistance 2488 +/- 675 x 10(3) dyne . sec/cm(5); peak airway pressure 32 +/- 1 mm Hg and wet/dry weight ratio 9.1 +/- 0.8; group I: oxygen tension 136 +/- 2 mm Hg; pulmonary vascular resistance 120 +/- 3 x 10(3) dyne . sec/c m(5); peak ainvay pressure 13 +/- 1 mm Hg and wet/dry weight ratio 3.6 +/- 0.3; p < 0.001 all parameters except pulmonary vascular resistanc e:p < 0.05. In contrast, grafts undergoing controlled pressure reperfu sion (group III) achieved function comparable with baseline values at 2 hours: oxygen tension 137 +/- 3 mm Hg; pulmonary vascular resistance 132 +/- 7 x 10(3) dyne . sec/cm(5); peak airway pressure 13 +/- 1 mm Hg; wet/dry weight ratio 4.1 +/- 0.3 (p = Not significant). Conclusion s: The pressure at which pulmonary grafts are initially reperfused app ears to be critical to their subsequent integrity. A protocol of contr olled reperfusion may reduce reperfusion injury and improve graft func tion in clinical practice.