Plasma L-Arginine and Metabolites of Nitric Oxide Synthase in Patients With Left-To-Right Shunt After Intracardiac Repair

Study objective: Human plasma L-arginine serves as a substrate pool for endothelial-derived nitric oxide (NO) synthase. In this pilot study, we tested the hypothesis that plasma L-arginine and other metabolites of the L-arginine NO pathway could correlate with postoperative pulmonary hypertension after cardiopulmonary bypass (CPB). Design: Forty-two patients (median age, 0.5 years; range, 0.1 to 28 years) with atrial septal defect (n = 15), ventricular septal defect (n = 18), atrioventricular canal (n = 8), and aortopulmonary window (n = 1) were enrolled. The influence of patient age, preoperative pulmonary hypertension, duration of CPB, plasma L-arginine, guanosine 3′, 5′-cyclic monophosphate (cGMP), and nitrate on postoperative pulmonary hypertension during the first 24 h after CPB was studied by logistic regression. Results: Nineteen of 42 patients were found to have preoperative pulmonary hypertension. Thirteen of 42 patients showed persistent pulmonary hypertension after intracardiac repair with a mean pulmonary artery pressure (PAP) of 38 mm Hg (range, 23 to 55 mm Hg) at 24 h after CPB. L-arginine concentrations in plasma were significantly lower 24 h after CPB than before: 52 μmol/L (range, 18 to 95 μmol/L) vs 79 μmol/L (range, 31 to 157 μmol/L). Plasma cGMP levels were higher and plasma nitrate levels were lower immediately after weaning from CPB (p < 0.0033). On logistic regression analysis, only patient age (p = 0.02) and preoperative PAP (p = 0.01) were related to postoperative pulmonary hypertension. Conclusion: Low plasma L-arginine does not relate to persistent pulmonary hypertension in patients with left-to-right shunt after CPB and intracardiac repair.