title: Gastric air tonometry during laparoscopic cholecystectomy: a comparison of two PaCO2 levels.
abstract: OBJECTIVE
  Pneumoperitoneum can cause disturbances in acid-base balance and splanchnic perfusion. We studied the effect of ventilation on acid-base balance and gastric mucosal tonometric values in patients undergoing laparoscopic cholecystectomy.
  
  
  METHODS
  Twenty-four patients (ASA I-II) were randomly allocated into two groups. In the fixed ventilation group, ventilation was constant allowing free increase in PCO2, while in the constant CO2 group end-tidal PCO2 was fixed with ventilatory adjustment. Intraabdominal pressure was limited to 12 mmHg. Arterial acid-base balance, automated air tonometric variables and gastric mucosal to arterial PCO2 gap were determined frequently from anesthesia induction until three hours postoperatively.
  
  
  RESULTS
  During pneumoperitoneum, in the fixed ventilation group arterial PCO2 changed from 5.0 +/- 0.2 to 6.6 +/- 0.4 kPa and pH from 7.43 +/- 0.03 to 7.33 +/- 0.04, tonometric PCO2 from 5.1 +/- 0.5 to 6.9 +/- 0.4 and pH from 7.44 +/- 0.04 to 7.33 +/- 0.04. In the constant CO2 group these variables remained at control levels (P < 0.01 between groups). The PCO2 gap remained unchanged without any differences between the groups. In the recovery room all measured variables were within normal range in both groups.
  
  
  CONCLUSIONS
  Despite inter-group differences in arterial and tonometric PCO2 and pH values during CO2 pneumoperitoneum, the patients did not develop splanchnic hypoperfusion detectable by air tonometric method, as indicated by normal PCO2 gap in both groups throughout the study.
authors.affiliation: Department of Anaesthesia and Intensive Care Medicine, Meilahti Hospital, University of Helsinki, Finland. marja-tellervo.makinen@hus.fi
authors.forename: M T
authors.initials: MT
authors.lastname: Mäkinen
authors.forename: P O
authors.initials: PO
authors.lastname: Heinonen
authors.forename: U M
authors.initials: UM
authors.lastname: Klemola
authors.forename: A
authors.initials: A
authors.lastname: Yli-Hankala
mesh_terms: D000136:Acid-Base Equilibrium; D001831:Body Temperature / Q000502:physiology; D002245:Carbon Dioxide / Q000097:blood*; D017081:Cholecystectomy, Laparoscopic; D005260:Female; D005753:Gastric Mucosa / Q000502:physiology; D006439:Hemodynamics / Q000502:physiology; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008297:Male; D008875:Middle Aged; D011027:Pneumoperitoneum / Q000503:physiopathology; D011184:Postoperative Period; D012121:Respiration, Artificial; D013152:Splanchnic Circulation / Q000502:physiology; D013270:Stomach / Q000502:physiology*; D014065:Tonometry, Ocular
chemical_list: D002245:Carbon Dioxide