title: Nitrogen accumulation during closed circuit anesthesia depends on the type of surgery.
abstract: OBJECTIVE
  The aim of this study is to test the hypothesis that the amount of nitrogen that accumulates within the closed breathing system would be greater during open abdominal surgery than during superficial surgery with small wounds.
  
  
  METHODS
  Prospective, comparative study.
  
  
  METHODS
  Operating rooms of a university hospital.
  
  
  METHODS
  Fourteen American Society of Anesthesiologists physical status I and II adult patients scheduled for abdominal surgery (n = 7) or tympanoplasty (n = 7).
  
  
  METHODS
  After induction of anesthesia and endotracheal intubation, the patients were denitrogenated for 30 minutes using 100% oxygen at a fresh gas flow of 10 L/min. The breathing system was then closed and patients were anesthetized using 60% xenon in oxygen, supplemented with epidural anesthesia in the abdominal surgery group and sevoflurane in the tympanoplasty group.
  
  
  METHODS
  Nitrogen concentration in the breathing system was determined by gas chromatography immediately before and 2 hours after the breathing system was closed.
  
  
  RESULTS
  The median (range) increase in nitrogen concentration during the 2-hour period of closed circuit anesthesia was greater in the abdominal surgery patients than in the tympanoplasty patients (6.5% [4.0%-10.2%] vs 2.5% [1.4%-8.4%], P = 0.035, Mann-Whitney U test).
  
  
  CONCLUSIONS
  The amount of nitrogen accumulation during closed circuit anesthesia is greater during open abdominal surgery than in superficial surgery such as tympanoplasty. We postulate that during open abdominal surgery, nitrogen in the ambient air enters the body across the peritoneum and then diffuses into the alveoli to be exhaled.
authors.affiliation: Department of Anesthesiology and Surgical Intensive Care Medicine, University Hospital Schleswig-Holstein, Campus Kiel, Schwanenweg 21, D-24105 Kiel, Germany.
authors.forename: Pia
authors.initials: P
authors.lastname: Hanne
authors.forename: Takahisa
authors.initials: T
authors.lastname: Goto
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Nakata
authors.forename: Yoshiki
authors.initials: Y
authors.lastname: Ishiguro
authors.forename: Shigeho
authors.initials: S
authors.lastname: Morita
mesh_terms: D000005:Abdomen / Q000601:surgery*; D000328:Adult; D000368:Aged; D000764:Anesthesia, Closed-Circuit; D000769:Anesthesia, Inhalation; D001794:Blood Pressure / Q000187:drug effects; D004432:Ear, Middle / Q000601:surgery*; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D008297:Male; D008875:Middle Aged; D009584:Nitrogen / Q000378:metabolism*; D011446:Prospective Studies; D014433:Tympanoplasty
chemical_list: D009584:Nitrogen