title: Peritoneal pH during laparoscopy is dependent on ambient gas environment: helium and nitrous oxide do not cause peritoneal acidosis.
abstract: BACKGROUND
  Little is know about the effects of different insufflation gases on peritoneal pH during laparoscopy. However, these changes may influence the intracellular signalling system, resulting in altered cell growth or adhesiveness. The aim of this study was to determine the effects of carbon dioxide (CO(2)), nitrous oxide (N(2)O), and helium (He) on parietal and visceral peritoneal pH. The effect of different intraabdominal pressures on parietal and visceral peritoneal pH was also examined.
  
  
  METHODS
  We conducted both an ambient gas study and a pressure study. For the ambient gas study, 20 pigs were divided into the following four groups: (a) CO(2), (b) He, (c) N(2)O, and (d) abdominal wall lift (Lift) laparoscopy. Parietal and visceral peritoneal pH were measured at 15 min intervals for 180 min. For the pressure study, 15 pigs were divided into the following three groups: (a) CO(2), (b) He, (c) N(2)O laparoscopy. Baseline values were established for parietal and visceral peritoneal pH. Intraabdominal pressure was then increased stepwise at 1-mmHg intervals to 15 mmHg. After pressure was maintained for 15 min at each setting, parietal and visceral peritoneal pH were measured.
  
  
  RESULTS
  Ambient gas environment was the major determinant of parietal peritoneal pH. Carbon dioxide caused parietal peritoneal acidosis. Helium, N(2)O, and Lift caused alkalotic parietal peritoneal pH. Intraabdominal pressure had a minor effect on parietal peritoneal pH. At higher intraabdominal pressure (12-15 vs 5-8 mmHg), CO(2) caused a slight decrease in parietal peritoneal pH, whereas N(2)O and He caused a slight increase in parietal peritoneal pH. Visceral peritoneal pH remained relatively unaffected during all studies.
  
  
  CONCLUSIONS
  Parietal peritoneal pH during laparoscopy was highly dependent on the ambient gas environment. The effect of intraabdominal pressure on parietal peritoneal pH was of minor significance. Carbon dioxide caused a slight worsening of parietal peritoneal acidosis at higher intraabdominal pressure, whereas, N(2)O, He, and Lift did not cause parietal peritoneal acidosis.
authors.affiliation: Department of General surgery, Lahey Clinic Medical Center, Burlington, MA, USA. yewtohwong@hotmail.com
authors.forename: Y T
authors.initials: YT
authors.lastname: Wong
authors.forename: P C
authors.initials: PC
authors.lastname: Shah
authors.forename: D H
authors.initials: DH
authors.lastname: Birkett
authors.forename: D M
authors.initials: DM
authors.lastname: Brams
mesh_terms: D000818:Animals; D002245:Carbon Dioxide / Q000494:pharmacology*; D006371:Helium / Q000494:pharmacology*; D006863:Hydrogen-Ion Concentration; D007432:Intraoperative Period; D010535:Laparoscopy; D009609:Nitrous Oxide / Q000494:pharmacology*; D010537:Peritoneum / Q000187:drug effects* / Q000378:metabolism*; D011312:Pressure; D013552:Swine
chemical_list: D002245:Carbon Dioxide; D006371:Helium; D009609:Nitrous Oxide