title: Intramucosal-arterial PCO2 gap fails to reflect intestinal dysoxia in hypoxic hypoxia.
abstract: BACKGROUND
  An elevation in intramucosal-arterial PCO2 gradient (DeltaPCO2) could be determined either by tissue hypoxia or by reduced blood flow. Our hypothesis was that in hypoxic hypoxia with preserved blood flow, DeltaPCO2 should not be altered.
  
  
  METHODS
  In 17 anesthetized and mechanically ventilated sheep, oxygen delivery was reduced by decreasing flow (ischemic hypoxia, IH) or arterial oxygen saturation (hypoxic hypoxia, HH), or no intervention was made (sham). In the IH group (n = 6), blood flow was lowered by stepwise hemorrhage; in the HH group (n = 6), hydrochloric acid was instilled intratracheally. We measured cardiac output, superior mesenteric blood flow, gases, hemoglobin, and oxygen saturations in arterial blood, mixed venous blood, and mesenteric venous blood, and ileal intramucosal PCO2 by tonometry. Systemic and intestinal oxygen transport and consumption were calculated, as was DeltaPCO2. After basal measurements, measurements were repeated at 30, 60, and 90 minutes.
  
  
  RESULTS
  Both progressive bleeding and hydrochloric acid aspiration provoked critical reductions in systemic and intestinal oxygen delivery and consumption. No changes occurred in the sham group. DeltaPCO2 increased in the IH group (12 +/- 10 [mean +/- SD] versus 40 +/- 13 mmHg; P < 0.001), but remained unchanged in HH and in the sham group (13 +/- 6 versus 10 +/- 13 mmHg and 8 +/- 5 versus 9 +/- 6 mmHg; not significant).
  
  
  CONCLUSIONS
  In this experimental model of hypoxic hypoxia with preserved blood flow, DeltaPCO2 was not modified during dependence of oxygen uptake on oxygen transport. These results suggest that DeltaPCO2 might be determined primarily by blood flow.
authors.affiliation: Cátedra de Farmacologia, Facultad de Ciencias Médicas, Universidad Nacional de La Plata, Argentina. adee@infovia.com.ar
authors.forename: Arnaldo
authors.initials: A
authors.lastname: Dubin
authors.forename: Gastón
authors.initials: G
authors.lastname: Murias
authors.forename: Elisa
authors.initials: E
authors.lastname: Estenssoro
authors.forename: Héctor
authors.initials: H
authors.lastname: Canales
authors.forename: Julio
authors.initials: J
authors.lastname: Badie
authors.forename: Mario
authors.initials: M
authors.lastname: Pozo
authors.forename: Juan P
authors.initials: JP
authors.lastname: Sottile
authors.forename: Marcelo
authors.initials: M
authors.lastname: Barán
authors.forename: Fernando
authors.initials: F
authors.lastname: Pálizas
authors.forename: Mercedes
authors.initials: M
authors.lastname: Laporte
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D015415:Biomarkers; D002245:Carbon Dioxide / Q000097:blood*; D000860:Hypoxia / Q000175:diagnosis* / Q000503:physiopathology; D007413:Intestinal Mucosa / Q000098:blood supply* / Q000378:metabolism*; D010101:Oxygen Consumption; D010313:Partial Pressure; D012039:Regional Blood Flow; D012756:Sheep; D014065:Tonometry, Ocular
chemical_list: D015415:Biomarkers; D002245:Carbon Dioxide