Methods for detecting local intestinal ischemic anaerobic metabolic acidosis by PCO2

Ranna A. Rozenfeld, Michael K. Dishart, Tor Inge Tønnessen, Robert Schlichtig*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

63 Scopus citations


Gut ischemia is often assessed by computing an imaginary tissue interstitial pH from arterial plasma HCO3 and the PCO2 in a saline-filled balloon tonometer after equilibration with tissue PCO2 (Pti(CO2). Pti(CO2) may alternatively be assumed equal to venous PCO2 (Pv(CO2)) in that region of gut. The idea is that as blood flow decreases, gut Pti(CO2), and Pv(CO2), will increase to the maximum aerobic value, i.e., maximum respiratory Pv(CO2) (Pv(CO2rmax)). Above a 'critical' anaerobic threshold, lactate (La-) generation, by titration of tissue HCO3, should raise Pti(CO2) above Pv(CO2 rmax). During progressive selective whole intestinal flow reduction in six pentobarbital-anesthetized pigs, we used PCO2 electrodes to test the hypotheses that critical Pti(CO2) is achieved earlier in mucosa than in serosa and that Pv(CO2 rmax), computed using an in vitro model, predicts critical Pti(CO2). We defined critical Pti(CO2) as the inflection of Pt(CO2)-Pv(CO2) vs. O2 delivery (Q̇O2) plots. Critical Q̇O2 for O2 uptake was 12.55 ± 2 ml · kg-1 · min-1. Critical Pti(CO2)) for mucosa and serosa was achieved at similar whole intestine Q̇O2 (13.90 ± 5 and 13.36 ± 5 ml · kg-1 · min-1, P = NS). Critical Pti(CO2) (129 ± 24 and 96 ± 21 Torr) exceeded Pv(CO2rmax) (62 ± 3 Torr). During ischemia, La- excretion into portal venous blood was matched by K+ excretion, causing Pv(CO2) to increase only slightly, despite Pti(CO2) rising to 380 ± 46 (mucosa) and 280 ± 38 (serosa) Torr. These results suggest that mucosa and serosa become dysoxic simultaneously, that ischemic dysoxic gut is essentially unperfused, and that in vitro predicted Pv(CO2rmax) underestimates critical Pti(CO2).

Original languageEnglish (US)
Pages (from-to)1834-1842
Number of pages9
JournalJournal of applied physiology
Issue number4
StatePublished - Oct 1996


  • acidosis
  • carbon dioxide
  • hypercarbia
  • ischemia
  • strong ion difference

ASJC Scopus subject areas

  • Physiology (medical)
  • Physiology


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