Postprandial hemodynamics and oxygenation in developing piglet intestine.

Age-related differences in the intestinal hemodynamic and oxygenation responses to feeding were studied in 1-day- (never-nursed and nursed-fasted), 3-day-, 2-wk-, and 1-mo-old piglets. A distal branch of the superior mesenteric vein draining an isolated loop of jejunoileum was used to measure intestinal blood flow, arteriovenous oxygen content difference, venous pressure, and capillary pressure. Calculations of oxygen uptake and vascular resistance were performed from the measured variables. Radioactive microspheres were used to measure fractionated flow. After luminal instillation of a cow milk-based formula, postprandial oxygen uptake increased to a similar extent in all age groups. In never-nursed newborns the increase was achieved by a dramatic rise in oxygen extraction with no change in total flow, while all other groups demonstrated a combined increase in blood flow and oxygen extraction. Mucosal blood flow increased to a similar extent in all age groups, but in never-nursed newborns it was at the expense of muscularis-serosa flow. Thus, because oxygen extraction and mucosal blood flow appear to be near maximal during feeding alone, newborn intestine may be at risk for tissue hypoxia and subsequent mucosal injury in the presence of a superimposed cardiovascular stress.