Splanchnic and overall cardiovascular hemodynamics during eating and digestion.

The cardiovascular system responds to feeding in two distinctly different phases. During anticipation and ingestion of food, cardiac output, heart rate, aortic pressure, and vascular resistance in various vascular beds are altered in a pattern that mimics an increase in sympathetic neural activity. Myocardial oxygen consumption and adenosine concentration increase. Cardiovascular responses to exercise performed during this period are similar to those that occur during fasting except that the exercise-induced skeletal muscle hyperemia is smaller during the ingestion phase. Within 5-30 min after a meal, all cardiovascular responses to feeding subside except that blood flow to the digestive organs increases while that to skeletal muscle decreases in resting animals. The times of onset, duration, and localization of the hyperemia in the digestive organs appear to be related to the feeding-induced changes in tissue and organ activities. Exercise performed during the digestion phase does not affect intestinal hyperemia but severe excitement can actually decrease intestinal blood flow. Digestion is accompanied by an increase in total body, splanchnic, and intestinal oxygen consumption. The increase in oxygen consumption, however, is proportionally greater than the increases in splanchnic and intestinal blood flow.