Effects of inhaled nitric oxide following lung transplantation

Abstract

Background: Lung transplantation offers an established therapeutic option for end-stage lung disease. It is associated with several complications, and early allograft failure is one of the most devastating among all. Different studies are focused on an attempt to minimize these complications, especially transplant failure. We aimed to evaluate the effects of inhaled nitric oxide (iNO) treatment in patients receiving lung transplantation. Methods: Nine patients (six female, three male; mean age 42.9 +/- 15.8) requiring lung transplantation for end-stage pulmonary disease-chronic obstructive pulmonary disease (three patients), cystic fibrosis (three patients), scleroderma and systemic sclerosis (two patients), Eisenmenger's syndrome (one patient), and treated with iNO were included in this retrospective study. Hemodynamic data (mean arterial pressure, mean pulmonary arterial pressure, heart rate) and respiratory parameters were analyzed. Pretreatment data were compared with the post-iNO treatment data at 6-8 hours and 12-14 hours. Results: The inhalation of nitric oxide was started with an initial dose of 40 parts per million (ppm) and the dose was gradually decreased until hemodynamic and pulmonary stability was achieved. Six patients underwent double-lung transplantation and three single-lung transplantations were performed. Cardiopulmonary bypass was used in seven patients. The iNO therapy was started before transplantation in five patients, after the procedure in four patients. Mean iNO therapy duration was 83.2 +/- 74.4 hours. The administration of iNO resulted in a significant reduction in mean pulmonary arterial pressure (36.8 +/- 15.8 mm Hg to 22 +/- 6.8 mm Hg at 6-8 hours and 22.8 +/- 7.96 mm Hg at 12-14 hours). Mean systemic arterial pressure slightly increased at 6-8 hours and significantly increased at 12-14 hours (70.2 +/- 6.3 mm Hg to 90.1 +/- 11.96 mm Hg). Heart rate was not significantly affected with the treatment. Arterial oxygenation improved with the treatment. All patients except one showed improvement of overall respiratory functions. The mean duration of mechanical ventilation was 12.8 +/- 10.9 days. Mortality occurred in one patient due to neurologic injury. NO2 and methemoglobin levels were closely monitored during the treatment. Methemoglobinemia did not occur and NO2 levels remained between 0.1 and 0.4 ppm. Conclusion: Nitric oxide inhalation for the prevention and treatment of early allograft failure in lung transplant recipients is encouraging. It is superior to other vasodilators with its selectivity to the pulmonary vasculature, while having no significant side effects on systemic circulation. It appears to improve gas exchange and oxygenation properties. Further prospective randomized studies will aid to standardize inhalation nitric oxide therapy.