Effects of posture on gastric emptying of nonnutrient liquids and antropyloroduodenal motility

Abstract

The effects of posture on gastric emptying, intragastric distribution, and antropyloroduodenal motility after ingestion of a nonnutrient liquid have been evaluated. In seven healthy volunteers antropyloroduodenal pressures were measured for 30 min after ingestion of 150 ml of normal saline in two different positions: sitting and left lateral. Saline drinks were radiolabeled and ingested both before and after intravenous atropine (4 micrograms/kg). Rates of emptying from both the total (P < 0.05) and the proximal (P < 0.05) stomach were faster in the sitting position than in the left lateral position. There were more long (> 6 cm) antropyloric pressure waves (P < 0.05) and isolated pyloric pressure waves (P < 0.05) in the sitting position. Intravenous atropine slowed emptying in both positions (P < 0.05) and in the sitting position decreased (P < 0.05) the number of antropyloric pressure waves. After atropine, gastric emptying was also faster in the sitting compared with the decubitus position (P < 0.05), although there was no difference in antropyloric or isolated pyloric pressure waves between the two postures. We conclude that the effects of gravity on gastric emptying of nonnutrient liquids are likely to reflect changes in both antropyloric motility and intragastric distribution.

Influence of posture on pharmacokinetics

“…Despite the force of gravity being the same for both kinds of liquids, corresponding studies confirmed this difference [6,7]. Whereas intragastric volume and gravity appear to be the driving forces controlling gastric emptying of nonnutrient liquids [2,5,8], for nutrient liquids, feedback from small intestinal "nutrient" receptors is the decisive factor. These receptors, which are sensitive to, for example, carbohydrates and digestion products of fat, mediate the slowing of gastric emptying [2,4,5,8].…”

“…This is also reflected in the emptying pattern, which is predominantly linear for nutrient liquids and exponential for nonnutrient ones [2]. Consequently, nutrient liquids are emptied slower, and the process is largely independent of posture [2,5] (see results of Burn-Murdoch et al, Table 1). In terms of the effects of posture on the gastric emptying of solid food, conflicting results have been published.…”

“…These receptors, which are sensitive to, for example, carbohydrates and digestion products of fat, mediate the slowing of gastric emptying [2,4,5,8]. This is also reflected in the emptying pattern, which is predominantly linear for nutrient liquids and exponential for nonnutrient ones [2]. Consequently, nutrient liquids are emptied slower, and the process is largely independent of posture [2,5] (see results of Burn-Murdoch et al, Table 1).…”

“…For nonnutrient liquids, the mechanisms by which posture affects gastric motility and gastric emptying were clarified by Anvari et al [2]. These researchers examined the effects of posture (sitting vs. left lateral) on gastric emptying, intragastric distribution and antropyloroduodenal motility following ingestion of 150 ml saline, both with and without coadministration of intravenous atropine (see Table 1).…”

“…Whereas intragastric volume and gravity appear to be the driving forces controlling gastric emptying of nonnutrient liquids [2,5,8], for nutrient liquids, feedback from small intestinal "nutrient" receptors is the decisive factor. These receptors, which are sensitive to, for example, carbohydrates and digestion products of fat, mediate the slowing of gastric emptying [2,4,5,8]. This is also reflected in the emptying pattern, which is predominantly linear for nutrient liquids and exponential for nonnutrient ones [2].…”