Neonatal intestinal oxygen consumption during arterial hypoxemia

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Abstract
In 12 chronically catheterized neonatal lambs, we determined intestinal tract blood flow (Qi) and O2 consumption (VO2i) at O2 contents of arterial blood (CaO2) ranging from 15.3 to 3.2 ml O2/dl blood. We measured Qi with the radioactive microsphere technique and computed intestinal O2 delivery (DO2i), VO2i, and O2 extraction (VO2i/DO2i) using the Fick principle. In lambs breathing air, mean Qi = 214 ml X min-1 X 100 g intestine-1, DO2i = 27.0 ml O2 X min-1 X 100 g-1, O2 extraction = 21%, and VO2i = 5.6 ml O2 Xmin-1 X 100 g-1. During reductions in CaO2, Qi and DO2i decreased. Intestinal O2 extraction increased sufficiently, however, so that VO2i was maintained over the range of CaO2 from 15.3 to about 6.5 ml O2/dl blood. VO2i was independent of Qi at Qi greater than 160 ml X min-1 X 100 g-1. When CaO2 was reduced below values of 6.5 ml O2/dl blood, corresponding to Qi less than 160 ml X min-1 X 100 g-1, VO2i fell in association with increases in the H+ concentration difference between mesenteric venous and arterial blood. These data indicate that the intestinal tract of the neonatal lamb can meet its oxygen requirements when O2 supply varies over a wide range. When O2 availability reaches a critically low level, intestinal anaerobic metabolism develops as the O2 supply to the neonatal intestinal tract becomes inadequate for the O2 demand.

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