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.