Intestinal blood flow and O2 uptake during hypoxemia in the newborn piglet

Previous work has indicated that the neonatal intestinal circulation responds to hypoxemia with vasoconstriction and subsequent intestinal ischemia. This work was carried out in newborn lambs, a ruminant species, and may not be representative of all newborns. Therefore, we measured intestinal blood flow, vascular resistance, tissue O2 uptake, and cardiac output during normoxemia and varying degrees of hypoxemia in newborn piglets, a nonruminant species. Hypoxemia was induced by adding N2 gas to the inspired gas mixture, and measurements were obtained over a wide range of arterial O2 contents (2.2-15.6 ml O2 X dl-1). Intestinal blood flow increased in response to moderate hypoxemia and decreased in response to severe hypoxemia. The changes in intestinal blood flow were primarily due to change in intestinal vascular resistance, not cardiac output. Intestinal O2 was independent of arterial O2 content until the latter decreased below approximately 6.5 ml O2 X dl-1. These data indicate that the response of the neonatal intestinal circulation to hypoxemia is species specific and that the nonruminant neonatal intestine is capable of vasodilation in response to moderate hypoxemia.