Background: Arginine is the substrate for the synthesis of nitric oxide (NO), a potent vasodilator in both the systemic and pulmonary circulation. Case reports have suggested a role for the L-arginine-nitric oxide pathway in neonatal blood pressure regulation (Acta Pediatr, 1995;84:460-2). Objective: To examine the possible relationship between plasma arginine levels and systemic BP in premature babies with RDS.Design: Twenty premature babies with birthweight (BW) ≤ 1250 g requiring mechanical ventilation were studied. Gestational age, 26.5±1.6 weeks; BW, 880±150 g (mean ± SD). Plasma arginine levels and mean systemic BP were measured on days 3, 7, 14 and 21. A random-effects model for longitudinal data (Biometrics, 1982;38:963-74) was used to analyze the influence of the following on BP: plasma arginine levels, use of vasopressors, gestational age, oxygenation index, daily sodium intake and difference between daily fluid intake and diuresis. Results: Use of dopamine was the only significant factor in this model and was negatively correlated with BP (p < 0.01). A positive correlation between plasma arginine levels and BP was suggested but did not reach statistical significance (p=0.056). Conclusion: Plasma arginine levels may be related to BP in premature babies with RDS but after adjusting for the influence of other factors this relation does not reach statistical significance. Speculation: Activation of NO synthetase in babies with RDS may utilize arginine producing lower systemic BP. Alternatively, lower plasma arginine levels may be a manifestation of increased catabolism in babies with lower BP.
