Effect of cardiopulmonary bypass on urea cycle intermediates and nitric oxide levels after congenital heart surgery.
OBJECTIVE
To test the hypothesis that cardiopulmonary bypass used for repair of ventricular septal defects and atrioventricular septal defects would decrease availability of urea cycle intermediates including arginine and subsequent nitric oxide availability.


METHODS
Consecutive infants (n = 26) undergoing cardiopulmonary bypass for repair of an unrestrictive ventricular septal defect or atrioventricular septal defect were studied. Blood samples were collected immediately before surgery, immediately after surgery, and 12 hours, 24 hours, and 48 hours after surgery. Urea cycle intermediates, including citrulline, arginine, and ornithine, were measured by amino acid analysis. Nitric oxide metabolites were measured by means of the modified Griess reaction.


RESULTS
Cardiopulmonary bypass caused a significant decrease in the urea cycle intermediates arginine, citrulline, and ornithine at all postoperative time points compared with preoperative levels. The ratio of ornithine to citrulline, a marker of urea cycle function, was elevated at all postoperative time points compared with preoperative values, indicating decreased urea cycle function. Nitric oxide metabolites were significantly decreased at all postoperative time points except for 48 hours, compared with preoperative levels.


CONCLUSIONS
Cardiopulmonary bypass significantly decreases availability of arginine, citrulline, and nitric oxide metabolites in the postoperative period. Decreased availability of nitric oxide precursors may contribute to the increased risk of postoperative pulmonary hypertension.
Barr
Frederick E
FE
Department of Pediatrics, Vanderbilt University School of Medicine, Nashville, Tennessee, USA.
Beverley
Heidi
H
VanHook
Kristin
K
Cermak
Emma
E
Christian
Karla
K
Drinkwater
Davis
D
Dyer
Karrie
K
Raggio
Noel T
NT
Moore
Jason H
JH
Christman
Brian
B
Summar
Marshall
M
D001120:Arginine / Q000097:blood; D001806:Blood Urea Nitrogen; D002315:Cardiopulmonary Bypass; D002956:Citrulline / Q000097:blood; D005260:Female; D006330:Heart Defects, Congenital / Q000097:blood* / Q000601:surgery*; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D009569:Nitric Oxide / Q000097:blood*; D009952:Ornithine / Q000097:blood; D014508:Urea / Q000097:blood*
D002956:Citrulline; D009569:Nitric Oxide; D014508:Urea; D001120:Arginine; D009952:Ornithine