Breath Hydrogen Reflects Canine Intestinal Ischemia

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Abstract
Summary: The relationship between breath hydrogen excretion and intestinal ischemia was investigated in nine mechanically ventilated dogs under pentobarbital anesthesia. An ileal segment was isolated in situ, ligated at each end, and insufflated with hydrogen. Expired air was collected at intervals. Blood volume was reduced 30% by three successive equivalent hemorrhages 10 min apart. Local bowel ischemia was produced by clamping the blood supply to the isolated segment for 10 min. Graded hemorrhage produced stepwise reductions in breath hydrogen concentration, to 77 ± 13, 66 ± 15, and 35 ± 8% (mean ± S.E.) of baseline after the first, second, and third hemorrhages, respectively. These reductions correlated highly (r = 0.84; P < 0.01) with declines in mean aortic blood pressure. Occlusion of blood supply caused a significant (P < 0.025) decrease in breath hydrogen concentration and excretion to 39 ± 14% of baseline. Termination of occlusion was followed within 2 min by a 7-fold increase in breath H2 concentration above the original baseline, probably reflecting reactive hyperemia. Breath hydrogen measurements appear to reflect functional (hemorrhagic shock-induced) and mechanical (vascular occlusion induced) enteric ischemia in dogs. Speculation: Monitoring of breath Hz excretion in the infant at risk for necrotizing enterocolitis may indicate the development of enteric hypoperfusion. Inhibition of transfer of Hz into the portal circulation in the presence of reduced mesenteric blood flow may contribute to distention of the bowel in necrotizing enterocolitis and further impede intestinal perfusion.