Gastrointestinal blood flow and oxygen consumption in the newborn lamb: effect of chronic anemia and acute hypoxia.

The purpose of this study was to investigate the compensatory change in circulation and oxygenation of the newborn lamb gastrointestinal (GI) tract in response to anemic and hypoxic hypoxemia. Radiolabeled microspheres were used to measure blood flow. We subjected the newborn lamb to a 30-35% reduction in hematocrit 4 d before study and to a 10% oxygen environment for 30 min during the study to induce chronic anemic and acute hypoxic hypoxemia, respectively. The circulatory and oxygenation responses were measured 1 h after a standard milk feeding in all cases. During the experimental periods, no change in total GI blood flow was observed. Because of a failure to augment blood flow during hypoxemia, O2 delivery to the GI tract decreased significantly. Despite this, GI O2 consumption was not compromised because tissue O2 extraction by the GI tract rose significantly. The response of the newborn lamb GI tract to hypoxemia after feeding is augmentation of O2 extraction. The newborn's GI tract did not regulate local GI blood flow.