Exhaled nitric oxide and impaired oxygenation in cirrhotic patients before and after liver transplantation

Background: Nitric oxide may be involved in the impaired oxygenation of cirrhotic patients, a condition that improves in most patients after liver transplantation. Objective: To compare oxygenation and nitric oxide concentrations before and after liver transplantation. Design: Before-and-after observational study. Setting: Academic medical center. Patients: 18 patients with cirrhosis and no obvious cardiopulmonary disease who underwent successful orthotopic liver transplantation. Intervention: Orthotopic liver transplantation. Measurements: Blood gas analysis, measurement of exhaled nitric oxide, contrast-enhanced echocardiography, and pulmonary function tests. Results: Before transplantation, the mean (+/- SD) exhaled nitric oxide concentration was higher in patients than in normal controls (13 +/- 4.9 parts per billion [ppb] compared with 5.75 +/- 1.9 ppb; P < 0.001). After transplantation, the alveolar-arterial oxygen gradient significantly decreased (from 17.3 +/- 7.1 mm Hg to 9 +/- 5.2 mm Hg; P < 0.001), as did the exhaled nitric oxide concentration (from 13 +/- 4.9 ppb to 6.2 +/- 2.8 ppb; P < 0.001). The decrease in the exhaled nitric oxide concentration was significantly correlated with the decrease in the alveolar-arterial oxygen gradient (r = 0.56; P = 0.014). Five patients met the criteria for the diagnosis of the hepatopulmonary syndrome before transplantation; the syndrome was cured by transplantation. Conclusions: The correlation between the decrease in exhaled nitric oxide concentration after liver transplantation and the improvement in oxygenation reinforces the hypothesis that nitric oxide is an important mediator of impaired oxygenation in patients with cirrhosis.