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. 2002 Dec;6(6):514-20.
doi: 10.1186/cc1813. Epub 2002 Aug 28.

Intramucosal-arterial PCO2 gap fails to reflect intestinal dysoxia in hypoxic hypoxia

Arnaldo Dubin  1 , Gastón Murias, Elisa Estenssoro, Héctor Canales, Julio Badie, Mario Pozo, Juan P Sottile, Marcelo Barán, Fernando Pálizas, Mercedes Laporte
Affiliations

Intramucosal-arterial PCO2 gap fails to reflect intestinal dysoxia in hypoxic hypoxia

Arnaldo Dubin et al. Crit Care. 2002 Dec.

Abstract

Introduction: 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).

Discussion: 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.

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Figures

Figure 1
Figure 1
Systemic and intestinal oxygen supply dependence. (a) Relationship between systemic oxygen transport and consumption during ischemic and hypoxic hypoxia, and in the sham group. (b) Relationship between intestinal oxygen transport and consumption during ischemic and hypoxic hypoxia, and in the sham group. Data are expressed as means ± SEM. *P < 0.05 versus basal oxygen consumption. §P < 0.05 versus sham group.
Figure 2
Figure 2
Relationship between intestinal oxygen transport and intramucosal–arterial PCO2 difference during ischemic and hypoxic hypoxia, and in the sham group. Data are expressed as means ± SEM. *P < 0.05 versus basal intramucosal–arterial PCO2 difference. § P < 0.05 versus hypoxic hypoxia and sham group.
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