Intramucosal-arterial PCO2 gap fails to reflect intestinal dysoxia in hypoxic hypoxia.
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.
Dubin
Arnaldo
A
Cátedra de Farmacologia, Facultad de Ciencias Médicas, Universidad Nacional de La Plata, Argentina. adee@infovia.com.ar
Murias
Gastón
G
Estenssoro
Elisa
E
Canales
Héctor
H
Badie
Julio
J
Pozo
Mario
M
Sottile
Juan P
JP
Barán
Marcelo
M
Pálizas
Fernando
F
Laporte
Mercedes
M
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
D015415:Biomarkers; D002245:Carbon Dioxide