title: Reliable gastric tonometry after coronary artery surgery: need for acid secretion suppression despite transient failure of acid secretion.
abstract: OBJECTIVE
  To study the need for suppression of gastric acid secretion for reliable intragastric partial pressure of carbon dioxide (PCO2) tonometry by evaluating the effect of an oral dose of sodium bicarbonate before and after administration of the H2-blocker ranitidine to mimic CO2 generation following the buffering of acid by bicarbonate in patients after cardiac surgery.
  
  
  METHODS
  Prospective, open, non-randomized clinical study.
  
  
  METHODS
  Cardiothoracic intensive care unit at a university hospital.
  
  
  METHODS
  10 patients after elective coronary artery bypass surgery.
  
  
  METHODS
  An oral dose of 500 mg sodium bicarbonate before and after acid secretion suppression by 100 mg ranitidine as an intravenous bolus given at approximately 3 h after surgery (day 0) and on the first postoperative day (day 1).
  
  
  RESULTS
  Intragastric PCO2 (iPCO2; tonometry), gastric juice pH (aspirate) and arterial blood gas values were measured. On day 0, the iPCO2 was 25 +/- 5 mmHg before and 31 +/- 5 mmHg after the bicarbonate dose, 29 +/- 5 mmHg after ranitidine infusion, and 31 +/- 5 mmHg after the bicarbonate dose following the ranitidine infusion (NS). On day 1, the basal iPCO2 was 32 +/- 4 mmHg and it increased to 56 +/- 25 mmHg following bicarbonate (p < 0.01). After ranitidine, the iPCO2 was 33 +/- 4 mmHg before and 40 +/- 14 mmHg after bicarbonate (NS). Basal gastric juice pH was > 4 in nine of ten patients on day 0 and > 4 in seven of ten patients on day 1.
  
  
  CONCLUSIONS
  Pharmacological suppression of gastric acid secretion is mandatory for reliable iPCO2 tonometry after cardiopulmonary bypass surgery, even when gastric acid secretion is transiently inhibited. In fact, gastric acid secretion was inhibited immediately after surgery, but returned on the first postoperative day in most patients, as judged from the bicarbonate back titration of gastric acid, even when gastric juice pH was relatively high.
authors.affiliation: Department of Cardiopulmonary Surgery, State University of Groningen, The Netherlands. Hans_Bams@csi.com
authors.forename: J L
authors.initials: JL
authors.lastname: Bams
authors.forename: J J
authors.initials: JJ
authors.lastname: Kolkman
authors.forename: M P
authors.initials: MP
authors.lastname: Roukens
authors.forename: D P
authors.initials: DP
authors.lastname: Douma
authors.forename: B G
authors.initials: BG
authors.lastname: Loef
authors.forename: S G
authors.initials: SG
authors.lastname: Meuwissen
authors.forename: A B
authors.initials: AB
authors.lastname: Groeneveld
mesh_terms: D000284:Administration, Oral; D000897:Anti-Ulcer Agents / Q000627:therapeutic use*; D002245:Carbon Dioxide / Q000032:analysis*; D001026:Coronary Artery Bypass; D005260:Female; D005744:Gastric Acid / Q000378:metabolism*; D005745:Gastric Acidity Determination; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007275:Injections, Intravenous; D007413:Intestinal Mucosa / Q000737:chemistry*; D008297:Male; D008991:Monitoring, Physiologic / Q000379:methods*; D011182:Postoperative Care / Q000379:methods; D011446:Prospective Studies; D011899:Ranitidine / Q000627:therapeutic use*; D015203:Reproducibility of Results; D017693:Sodium Bicarbonate / Q000627:therapeutic use*
chemical_list: D000897:Anti-Ulcer Agents; D002245:Carbon Dioxide; D011899:Ranitidine; D017693:Sodium Bicarbonate