Lasting beneficial effect of short-term inhaled nitric oxide on graft function after lung transplantation

Abstract

The combination of ischemia and reperfusion after lung transplantation is characterized by endothelial damage, neutrophil sequestration, and decreased release of endothelial nitric oxide. Because nitric oxide has been shown to selectively dilate the pulmonary vasculature, abrogate neutrophil adherence, and restore endothelial dysfunction, we hypothesized that inhaled nitric oxide given for 4 hours during initial reperfusion might attenuate reperfusion injury in a porcine model of left single-lung transplantation. We tested hemodynamic and gas exchange data, lung neutrophil sequestration, and pulmonary artery endothelial dysfunction after 4 and 24 hours of reperfusion in 12 pigs randomly assigned to nitric oxide and control groups. Harvested lungs were preserved in normal saline solution for 24 hours at 4º C. During transplantation, inflatable cuffs were placed around each pulmonary artery to allow separate evaluation of each lung by occluding flow. Compared with the transplanted lungs in the control group, transplanted lungs in pigs treated with inhaled nitric oxide significantly improved gas exchange, pulmonary vascular resistance, shunt fraction, and oxygen delivery at 4 and 24 hours after reperfusion. Neutrophil sequestration, as measured by the neutrophil-specific enzyme myeloperoxidase and the alveolar leukocyte count per light microscopic field, was significantly lower at 24 hours after reperfusion in the transplanted lungs of the nitric oxide group. The nitric oxide–treated native right lungs exhibited significantly reduced increase in neutrophil accumulation compared with that in control native right lungs. After 24 hours of reperfusion, endothelium-dependent relaxation to acetylcholine was similarly and severely altered in both groups. We conclude that short-term inhaled nitric oxide given during the first 4 hours of reperfusion after lung transplantation significantly attenuates reperfusion injury, improving graft function as long as 24 hours after operation. This effect is probably mediated by a decrease in neutrophil sequestration. A protective effect on the contralateral lung was also observed. Inhaled nitric oxide may be a suitable agent when an acute reperfusion phenomenon is anticipated. (J T HORAC C ARDIOVASC S URG 1996;112:590-8)