Plasma L-arginine concentration, oxygenation index, and systemic blood pressure in premature infants.
OBJECTIVE
To determine the relationships between plasma L-arginine concentrations and the severity of respiratory distress syndrome (RDS) or systemic blood pressure in premature infants.


METHODS
Prospective, observational study.


METHODS
Neonatal intensive care, tertiary referral hospital.


METHODS
Fifty-three premature infants.


METHODS
We measured arginine and nutritional intake, plasma arginine concentration, total amino acid concentrations, and blood pressure on days 3, 7, 14, and 21 of life. In 33 infants who received assisted ventilation, oxygenation index could be calculated to reflect the severity of RDS. The relationships between plasma arginine and oxygenation index or blood pressure were analyzed using multiple linear regression.


RESULTS
On day 3, plasma arginine concentrations were decreased compared with normal published values. Arginine concentrations increased with the day of life of measurement (p < .001) and with arginine intake (p < .001). After adjusting for arginine intake and day of life, an inverse relationship was found between oxygenation index and plasma 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 RDS, are associated with a decrease in plasma arginine concentration. This finding may reflect arginine consumption by the nitric oxide synthase pathway in the lungs of premature infants with RDS, or may be explained by increased arginine catabolism. The lack of a similar relationship between total plasma amino acids and oxygenation index supports the first interpretation.
Division of Gastroenterology, University of Calgary, AB, Canada.
S A
SA
Zamora
H J
HJ
Amin
D D
DD
McMillan
G H
GH
Fick
J D
JD
Butzner
H G
HG
Parsons
R B
RB
Scott
D000596:Amino Acids / Q000097:blood; D001120:Arginine / Q000097:blood*; D001794:Blood Pressure; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D007234:Infant, Premature / Q000097:blood; D015931:Intensive Care, Neonatal; D016014:Linear Models; D008297:Male; D009569:Nitric Oxide / Q000097:blood; D010100:Oxygen / Q000097:blood*; D011446:Prospective Studies; D012127:Respiratory Distress Syndrome, Newborn / Q000378:metabolism*; D012720:Severity of Illness Index; D013997:Time Factors
D000596:Amino Acids; D009569:Nitric Oxide; D001120:Arginine; D010100:Oxygen