title: Hypothermic cardiopulmonary bypass alters oxygen/glucose uptake in the pediatric brain.
abstract: OBJECTIVE
  Neurologic morbidity related to cardiac surgery has been recognized as a major morbidity. A variety of causes related to cardiopulmonary bypass, including microemboli, nonpulsatile flow, hemodilution, and inflammatory mediation, have been proposed. Because oxygen and glucose are the predominant metabolic substrates for the brain, we sought to examine the uptake of these substrates by the pediatric brain during hypothermic cardiopulmonary bypass.
  
  
  METHODS
  Eleven children (median age 5 months, range 1 day-17 years) undergoing a variety of cardiac surgical procedures with the use of hypothermic cardiopulmonary bypass were studied. Cerebral arteriovenous differences for oxygen, glucose, and lactate were obtained before, during, and after bypass. On the basis of the predictable stoichiometric relationship for the oxidation of glucose, the relationship of substrate uptake was expressed as the oxygen/glucose index.Oxygen/glucose index (%) = (arteriovenous oxygen difference [micromol/mL]/arteriovenous glucose difference [micromol/mL] x 6) x 100
  
  
  RESULTS
  All children survived with no obvious neurologic sequelae. During cooling on cardiopulmonary bypass, the oxygen/glucose indexes fell significantly from prebypass values (53% +/- 19% at 28 degrees C and 54% +/- 25% at 24 degrees C vs 117% +/- 70%; P <.05, analysis of variance). This decline resulted from decreased oxygen uptake with stable glucose uptake (P <.05). Although oxygen and glucose uptake both increased with rewarming, the net effect was only a slight increase in oxygen/glucose index (62% +/- 16%). Postbypass oxygen/glucose index exceeded prebypass values (149% +/- 83%).
  
  
  CONCLUSIONS
  Hypothermic cardiopulmonary bypass alters the relationship between oxygen and glucose uptake in the pediatric brain. The relationship of these findings to bypass-related neurologic morbidity remains to be explored.
authors.affiliation: Division of Cardiothoracic Surgery, 2 Main, Children's Hospital of Pittsburgh, Pittsburgh, PA 15213, USA. pigulaf@heart.chp.edu
authors.forename: F A
authors.initials: FA
authors.lastname: Pigula
authors.forename: R D
authors.initials: RD
authors.lastname: Siewers
authors.forename: E M
authors.initials: EM
authors.lastname: Nemoto
mesh_terms: D000293:Adolescent; D001786:Blood Glucose / Q000378:metabolism; D001921:Brain / Q000378:metabolism*; D002315:Cardiopulmonary Bypass / Q000009:adverse effects* / Q000379:methods; D002675:Child, Preschool; D005260:Female; D005947:Glucose / Q000378:metabolism*; D006801:Humans; D007036:Hypothermia, Induced / Q000009:adverse effects*; D007223:Infant; D008297:Male; D010100:Oxygen / Q000378:metabolism*; D017694:Rewarming
chemical_list: D001786:Blood Glucose; D005947:Glucose; D010100:Oxygen