title: Oxygen consumption after cardiopulmonary bypass surgery in children: determinants and implications.
abstract: OBJECTIVE
  We sought to assess oxygen consumption and its determinants in children shortly after undergoing cardiopulmonary bypass operations.
  
  
  METHODS
  Twenty children, aged 2 months to 15 years (median, 3.75 years), undergoing hypothermic cardiopulmonary bypass operations were studied during the first 4 hours after arrival in the intensive care unit. Central and peripheral temperatures were monitored. Oxygen consumption was continuously measured by using respiratory mass spectrometry. Oxygen delivery was calculated from oxygen consumption and arterial and mixed venous oxygen contents, which were sampled every 30 minutes. Oxygen extraction was derived by the ratio of oxygen consumption and oxygen delivery. Arterial blood lactate levels were measured every 30 minutes.
  
  
  RESULTS
  There was a correlation between oxygen consumption and age in patients older than 3 months (r = -0.76). Mean oxygen consumption increased by 14.7% during the study. The increase in oxygen consumption was correlated with the increase in central temperature (r = 0.73). Nine patients had an arterial lactate level above 2 mmol/L on arrival. There were no significant differences in oxygen consumption, oxygen delivery, and oxygen extraction between the group with lactate levels between 2 and 3 mmol/L and the groups with normal lactate levels both on arrival and at 2 hours. One patient with a peak lactate level of 6.8 mmol/L had initially low oxygen delivery (241.3 mL. min(-1). m(-2)).
  
  
  CONCLUSIONS
  During the early hours after a pediatric cardiac operation, the increase in oxygen consumption is mainly attributed to the increase in central temperature. Oxygen consumption is negatively related to age. Mild lactatemia is common and does not appear to reflect oxygen delivery or oxygen consumption or a more complicated recovery.
authors.affiliation: Cardiothoracic Unit, Great Ormond Street Hospital for Children NHS Trust, London, UK.
authors.forename: J
authors.initials: J
authors.lastname: Li
authors.forename: I
authors.initials: I
authors.lastname: Schulze-Neick
authors.forename: C
authors.initials: C
authors.lastname: Lincoln
authors.forename: D
authors.initials: D
authors.lastname: Shore
authors.forename: M
authors.initials: M
authors.lastname: Scallan
authors.forename: A
authors.initials: A
authors.lastname: Bush
authors.forename: A N
authors.initials: AN
authors.lastname: Redington
authors.forename: D J
authors.initials: DJ
authors.lastname: Penny
mesh_terms: D000293:Adolescent; D000367:Age Factors; D001831:Body Temperature; D002315:Cardiopulmonary Bypass; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007773:Lactates / Q000097:blood; D008297:Male; D010101:Oxygen Consumption; D011184:Postoperative Period; D013997:Time Factors
chemical_list: D007773:Lactates