Background: The inhibition of cellular metabolism induced by hypothermia obviates the possibility of substantial reparative processes occurring during organ preservation. The aim of this study was to develop a technique of extended (12-hour) ex vivo lung perfusion (EVLP) at normothermia for assessment and protective maintenance of the donor lung.
Methods: Six double-lung blocks from 35-kg pigs and 5 single human lungs were subjected to 12 hours of normothermic EVLP using acellular Steen Solution. In the animal studies, the left lung was transplanted into recipients at the end of EVLP and reperfused for 4 hours to evaluate the impact of prolonged EVLP on post-transplant lung function. A protective mode of mechanical ventilation with controlled perfusion flows and pressures in the pulmonary vasculature were employed during EVLP. Lung oxygenation capacity (DeltaPo(2)), pulmonary vascular resistance and airway pressures were evaluated in the system. Red blood cells were added to the perfusate to a hematocrit of 20% at the end of human lung EVLP to study lung functional assessment with and without cells.
Results: Lung function was stable during 12 hours of EVLP. This stability during prolonged normothermic EVLP translated into excellent post-transplant lung function (Pao(2)/Fio(2): 527 +/- 22 mm Hg), low edema formation (wet/dry ratio: 5.24 +/- 0.38) and preserved lung histology after transplantation. The acellular perfusion assessment of lung function accurately correlated with post-transplant graft function.
Conclusions: Twelve hours of EVLP at physiologic temperatures using an acellular perfusate is achievable and maintains the donor lungs without inflicting significant added injury. This system can be used to assess, maintain and treat injured donor lungs.