Intestinal blood flow and oxygen uptake in the neonatal piglet during reduced perfusion pressure.

The effect of reduced perfusion pressure on neonatal intestinal blood flow, vascular resistance, arterio-venous oxygen content (a-v O2), and oxygen uptake was studied in nine fasted newborn piglets, aged 5-6 days. Successive reductions of intestinal perfusion pressure were achieved by a clamp on the thoracic aorta. Intestinal blood flow decreased after each reduction of perfusion pressure. Intestinal vascular resistance increased and Gf, a measure of flow control, was negative after all but the final, most severe reduction of perfusion pressure. However, intestinal a-v O2 increased after each pressure reduction and intestinal oxygen uptake was thus maintained at greater than or equal to 95% of its baseline value until perfusion pressure was reduced to less than or equal to 70% of its base-line value. The neonatal intestine maintains tissue oxygen uptake during moderate hypotension, and this is accomplished by regulation of a-v O2, rather than by regulation of blood flow.