Effect of meal viscosity on gastric pH and residual volume in the fasted dog

Abstract

This study was designed to study the gastric handling of various volumes of viscous materials in dog. Based on earlier studies in which small (50 ml) or large (300 ml) volumes showed different patterns of gastric emptying, 50 or 300 ml test meals of varying viscosities were administered to fasted dogs during phase I of the motility pattern. High-viscosity grade hydroxypropylmethylcellulose was used as a viscosity inducing agent to obtain solutions with viscosities of up to 45 000 cps. Gastric residual volume was analyzed by monitoring the concentration and amount of a non-absorbable dye — phenol red in the stomach. As with meals of low viscosity, viscous fluids showed distinctly different patterns of discharge from the stomach for small and large volumes. However, for both volumes of the test meals, the rate of gastric emptying was slower compared with corresponding volumes of water (low viscosity). Small volumes of viscous meals showed longer lag periods between the ingestion of meals and the start of gastric emptying as compared with less viscous meals. 300 ml meals of viscous fluids exhibited a lag phase and linear discharge instead of the first-order discharge usually shown by comparable volumes of low viscosity. For the range of viscosities studied, there appears to be no effect of viscosity on gastric motility in the fasted state. The pH changes associated with gastric processing of viscous materials were not significantly different from those of water.