title: Oxygen in nitrogen versus nitrous oxide during pediatric general anesthesia.
abstract: BACKGROUND
  Induction of anesthesia decreases lung volumes, giving areas of non-ventilated lung. Nitrogen is a slowly-absorbed gas that could prevent resorption of gases from these closed spaces, preventing atelectasis and improving oxygen saturations during recovery.
  
  
  METHODS
  We evaluated oxygen saturations during emergence after intra-operative administration of 33% oxygen in nitrogen versus 33% oxygen in nitrous oxide in 62 children having elective urologic surgery. Patients were randomly assigned to either group A (2.5 L/min air with 0.5 L/min oxygen) or group N (2 L/min nitrous oxide and 1 L/min oxygen). Flowmeters were covered to maintain blinding. Anesthetic technique was standardized (laryngeal mask airway, caudal, halothane, and deep extubation). Patients breathed room air during emergence, while a blinded observer recorded duration of desaturations by stopwatch for 15 min.
  
  
  RESULTS
  We found similar desaturations in both groups. The difference in desaturations < 94% at an interim 2-min total probably reflects diffusion hypoxia and was not significant at 15 min. The frequency of desaturations < 87% during emergence was significantly greater in children who were crying during induction.
  
  
  CONCLUSIONS
  The intra-operative use of air versus nitrous oxide has no substantial effect on oxygen saturations during emergence from anesthesia in children. These results are consistent with a recently published mathematical model.
authors.affiliation: Department of Anesthesiology, University of Washington School of Medicine & Children's Hospital and Regional Medical Center, Seattle, Washington, USA. telwoo@chmc.org
authors.forename: T
authors.initials: T
authors.lastname: Elwood
authors.forename: E
authors.initials: E
authors.lastname: Hutchinson
mesh_terms: D000768:Anesthesia, General; D002648:Child; D002675:Child, Preschool; D006801:Humans; D007223:Infant; D017214:Laryngeal Masks; D008433:Mathematics; D008954:Models, Biological; D009584:Nitrogen / Q000494:pharmacology*; D009609:Nitrous Oxide / Q000494:pharmacology*; D010100:Oxygen / Q000378:metabolism*
chemical_list: D009609:Nitrous Oxide; D009584:Nitrogen; D010100:Oxygen