Controlled pressure reperfusion of rat pulmonary grafts yields improved function after twenty-four-hours' cold storage in University of Wisconsin solution

Background: Pulmonary graft recipients commonly have a degree of pulmonary 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 reperfusion of pulmonary grafts at low pressures may be beneficial. Methods: We used an isolated, ventilated rat lung model, perfused by an extracorporeal veno-venous circuit from a support animal. Three groups of donor lungs (n = 5 each) were flushed with cold University of Wisconsin solution. Group I was reperfused immediately at physiologic pressure to provide control values. Group II grafts were stored at 4° C for 24 hours and reperfused at physiologic pressure. Group III grafts were also stored at 4° C for 24 hours but reperfused according to a protocol of reduced pressure initially, with increments every 15 minutes up to physiologic levels by 60 minutes. Grafts and support animals 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 group II functioned poorly at 2 hours compared with control values: group II: oxygen tension 68 ± 4 mm Hg; pulmonary vascular resistance 2488 ± 675 x 103 dyne · sec/cm5; 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 103 dyne · sec/cm5; peak airway pressure 13 ± 1 mm Hg and wet/dry weight ratio 3.6 ± 0.3; p <0.001 all parameters except pulmonary vascular resistance: p <0.05. In contrast, grafts undergoing controlled pressure reperfusion (group III) achieved function comparable with baseline values at 2 hours: oxygen tension 137 ± 3 mm Hg; pulmonary vascular resistance 132 ± 7 x 103 dyne · sec/cm5; peak airway pressure 13 ± 1 mm Hg; wet/dry weight ratio 4.1 ± 0.3 (p = Not significant). Conclusions: The pressure at which pulmonary grafts are initially reperfused appears to be critical to their subsequent integrity. A protocol of controlled reperfusion may reduce reperfusion injury and improve graft function in clinical practice.