title: Lack of effect of ranitidine on gastric luminal pH and mucosal PCO2 during the first day in the ICU.
abstract: BACKGROUND
  Histamine(2) (H(2))-blocking agents can attenuate intragastric CO(2)-production by reducing gastric acid secretion and preventing the interaction between H(+) and bicarbonate. However, gastric acid production may be impaired in acute circulatory failure due to poor mucosal perfusion, and H(2)-blockade could further impair mucosal perfusion.
  
  
  METHODS
  Forty patients with acute circulatory and/or respiratory failure, age 61 +/- 16 years (mean +/- SD), APACHE II score 21 +/- 7, and SOFA score 8 +/- 3, received randomly either ranitidine, 50 mg (R) or placebo (P) every 8 h. Gastric intraluminal pH (gpH; antimony probe with external reference electrode) and mucosal pCO(2) (prCO(2), semicontinuous air-tonometry) were measured during 24 h, and blood gases were taken at 6-h intervals.
  
  
  RESULTS
  Gastric intraluminal pH was 4.3 +/- 2.4 in P and 5.1 +/- 1.6 in R (NS). Mean prCO(2) was 6.8 +/- 2.7 kPa in P and 7.4 +/- 2.1 kPa in R, and mucosal-arterial pCO(2) gradient (Delta pCO(2)) was 2.2 +/- 2.9 kPa and 2.4 +/- 2.4 kPa, respectively (NS). Within-patient variabilities of gpH and prCO(2) were not influenced by ranitidine. A posthoc analysis revealed that non-survival in R was associated with a low mucosal pHi after 24 h (P = 0.002). This was explained by a low arterial pH but not by differences in gpH or prCO(2).
  
  
  CONCLUSIONS
  In acute respiratory and circulatory failure, H(2) blockade has an inconsistent impact on gpH and does not reduce variabilities of gpH or prCO(2).
authors.affiliation: Department of of Anaesthesiology and Intensive Care Medicine, Kuopio University Hospital, Kuopio, Switzerland. stephan.jakob@insel.ch
authors.forename: S M
authors.initials: SM
authors.lastname: Jakob
authors.forename: I
authors.initials: I
authors.lastname: Parviainen
authors.forename: E
authors.initials: E
authors.lastname: Ruokonen
authors.forename: A
authors.initials: A
authors.lastname: Uusaro
authors.forename: J
authors.initials: J
authors.lastname: Takala
mesh_terms: D000208:Acute Disease; D001784:Blood Gas Analysis / Q000379:methods; D002245:Carbon Dioxide / Q000378:metabolism*; D003422:Critical Care; D005260:Female; D005745:Gastric Acidity Determination; D005750:Gastric Juice / Q000737:chemistry / Q000187:drug effects*; D005753:Gastric Mucosa / Q000098:blood supply* / Q000187:drug effects*; D006635:Histamine H2 Antagonists / Q000009:adverse effects / Q000494:pharmacology*; D006801:Humans; D006863:Hydrogen-Ion Concentration / Q000187:drug effects; D008297:Male; D008365:Manometry / Q000379:methods; D008875:Middle Aged; D011899:Ranitidine / Q000009:adverse effects / Q000494:pharmacology*; D012131:Respiratory Insufficiency / Q000188:drug therapy / Q000378:metabolism; D012769:Shock / Q000188:drug therapy / Q000378:metabolism; D013997:Time Factors
chemical_list: D006635:Histamine H2 Antagonists; D002245:Carbon Dioxide; D011899:Ranitidine