PLASMA L-ARGININE CONCENTRATION, OXYGENATION INDEX, AND SYSTEMIC BLOOD-PRESSURE IN PREMATURE-INFANTS

Objective: To determine the relationships between plasma L-arginine co ncentrations and the severity of respiratory distress syndrome (RDS) o r systemic blood pressure in premature infants, Design: Prospective, o bservational study, Setting: Neonatal intensive care, tertiary referra l hospital, Subjects: Fifty-three premature infants, Interventions: We measured arginine and nutritional intake, plasma arginine concentrati on, total amino acid concentrations, and blood pressure on days 3, 7, 14, and 21 of life, In 33 infants who received assisted ventilation, o xygenation index could be calculated to reflect the severity of RDS, T he relationships between plasma arginine and oxygenation index or bloo d pressure were analyzed using multiple lineary regression, Measuremen ts and Main Results: On day 3, plasma arginine concentrations were dec reased compared with normal published values. Arginine concentrations increased with the day of life of measurement (p <.001) and with argin ine intake (p <.001), After adjusting for arginine intake and day of l ife, an inverse relationship was found between oxygenation index and p lasma arginine concentrations: (p = .025), No similar relationship was found between oxygenation index and the concentration of total amino acids, A weak positive relationship was found between plasma arginine concentration and systemic blood pressure. Conclusions: Increments in the oxygenation index, reflective of an increased severity of Pus, are associated with a decrease in plasma arginine concentration. This fin ding may reflect arginine consumption by the nitric oxide synthase pat hway in the lungs of premature infants with RDS, or may be explained b y increased arginine catabolism. The lack of a similar relationship be tween total plasma amino acids and oxygenation index supports the firs t interpretation.