title: Effect of carbon dioxide on systemic oxygenation, oxygen consumption, and blood lactate levels after bidirectional superior cavopulmonary anastomosis.
abstract: OBJECTIVE
  We sought to assess the effects of four different CO2 tensions on systemic oxygenation, oxygen consumption, and arterial blood lactate levels early after bidirectional superior cavopulmonary anastomosis.
  
  
  METHODS
  Prospective study.
  
  
  METHODS
  Quaternary pediatric cardiac critical care unit.
  
  
  METHODS
  Nine children aged 2-23 months (median, 7 months).
  
  
  METHODS
  All patients were sedated, muscle relaxed, and mechanically ventilated. Baseline Paco2 was adjusted to 35 mm Hg by changing tidal volume. CO2 was added via the inlet port of the ventilator to maintain the Paco2 at 45 and 55 mm Hg. Measurements were repeated after discontinuing additional CO2 gas at a Paco2 of 40 mm Hg. Arterial blood gases and lactate were measured at each level of Paco2. We measured oxygen consumption continuously by respiratory mass spectrometry.
  
  
  RESULTS
  Mean (95% confidence interval) Paco2 increased from 35 (34-36) to 45 (44-46) to 55 (54-56) mm Hg (4.7 [4.5-4.9] to 6 [5.7-6.3] to 7.3 [7.2-7.4] kPa), arterial pH decreased from 7.43 (7.39-7.47) to 7.35 (7.31-7.39) to 7.28 (7.24-7.32). Pao2 increased from 36 (32-40) to 44 (40-48) to 50 (45-55) mm Hg (4.8 [4.3-5.3] to 5.9 [5.4-6.4] to 6.7 [6.2-7.2] kPa), and oxygen saturation increased from 72% (67-79%) to 77% (73-81%) to 80% (76-84%). Oxygen consumption decreased significantly, with each increase in Paco2, from 146 (125-167) to 132 (112-152) to 126 (107-145) mL.min.m (p = .0001), and lactate decreased from 1.5 (1-2.0) to 1.2 (0.8-1.6) to 0.8 (0.5-1.1) mmol/L (p < .01). These changes returned toward baseline at a Paco2 of 40 mm Hg.
  
  
  CONCLUSIONS
  Moderate hypercapnia with respiratory acidosis improved arterial oxygenation and reduced oxygen consumption and arterial lactate levels, thus improving overall oxygen transport in children after bidirectional superior cavopulmonary anastomosis.
authors.affiliation: Division of Cardiology, The Hospital for Sick Children, Toronto, Ontario, Canada.
authors.forename: Jia
authors.initials: J
authors.lastname: Li
authors.forename: Aparna
authors.initials: A
authors.lastname: Hoskote
authors.forename: Chantal
authors.initials: C
authors.lastname: Hickey
authors.forename: Derek
authors.initials: D
authors.lastname: Stephens
authors.forename: Desmond
authors.initials: D
authors.lastname: Bohn
authors.forename: Helen
authors.initials: H
authors.lastname: Holtby
authors.forename: Glen
authors.initials: G
authors.lastname: Van Arsdell
authors.forename: Andrew N
authors.initials: AN
authors.lastname: Redington
authors.forename: Ian
authors.initials: I
authors.lastname: Adatia
mesh_terms: D002245:Carbon Dioxide / Q000008:administration & dosage / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D005260:Female; D018610:Heart Bypass, Right; D006801:Humans; D007223:Infant; D015278:Intensive Care Units, Pediatric; D019344:Lactic Acid / Q000097:blood*; D008297:Male; D010101:Oxygen Consumption / Q000187:drug effects*; D011182:Postoperative Care; D012121:Respiration, Artificial
chemical_list: D002245:Carbon Dioxide; D019344:Lactic Acid