Dynamics of Nitroglycerin-induced Exhaled Nitric Oxide After Lung Transplantation: Evidence of Pulmonary Microvascular Injury?

Background In search of real-time molecular correlates to ischemia–reperfusion-induced lung injury, we explored the hypothesis that liberation of nitric oxide (NO) into exhaled breath after pulmonary microvascular bioconversion of nitroglycerin (GTN) is attenuated in clinical lung transplantation. Methods Exhaled NO was measured under basal conditions and after intravenous administration of GTN in patients undergoing lung transplantation. Patients undergoing routine cardiac surgery served as controls. Basal and GTN-induced exhaled NO was also measured in donors before retrieval and after implantation in recipients. Results The characteristic GTN-induced exhaled NO response observed in cardiac surgical patients before cardiopulmonary bypass and in lung transplant and multiple-organ donors was nearly totally abolished in lung transplant recipients. This response was also attenuated to a lesser degree in the routine cardiac surgery patients after cardiopulmonary bypass. Conclusions These results suggest a graded influence of time-factored complete and partial ischemia on GTN-induced evolution of NO into exhaled breath, providing biochemical evidence for a degree of microvascular injury, which can be monitored non-invasively at the bedside.