Effect of composition of gastric contents on resistance to emptying of liquids from stomach in humans.

Experiments were conducted in normal healthy volunteers to investigate whether factors other than the intragastric pressure induced by tonic contraction of the gastric fundus could regulate the gastric emptying of liquids. The emptying of solutions of different osmolality and composition from the stomach was measured, while maintaining the intragastric pressure constant with a barostat system that employed an external reservoir. Preliminary experiments showed a linear relationship between intragastric pressure and emptying rate, but indicated that a normal intragastric pressure of 7 cm water would be insufficient by itself to maintain normal emptying. When intragastric pressure was maintained at 20 cm water, an isotonic solution of 30 mM glucose in saline (278 mosm/kg) emptied at a rate of 49.9 +/- 0.5 ml/min (mean +/- SEM, N = 11). Milk (284 mosm/kg) and a hyperosmolar solution of 30 mM glucose in saline (586 mosm/kg) significantly reduced the emptying rate. These results suggest that factors other than the intragastric pressure induced by fundic contraction regulate the rate at which liquids empty from the stomach and that the slower emptying of hyperosmotic solutions or solutions containing fat could be brought about in part either by an increased resistance of the pylorus and possibly the duodenum or a reduction in the effectiveness of an antroduodenal pump.