The effect of sedation on D(+)-xylose absorption tests in 6 normal horses

Abstract

Reasons for performing study: D(+)-xylose absorption tests are commonly performed when investigating suspected small intestinal malabsorption in the horse. The test involves the administration of a D(+)-xylose solution via a nasogastric tube followed by serial blood sampling to determine its rate of absorption. In some horses, nasogastric intubation cannot be safely performed without prior administration of a sedative. Due to its short duration of action, the α 2 agonist xylazine is commonly used for this purpose. However, α 2 agonists have also been reported to influence the rate of gastric emptying as well as small intestinal motility patterns. Objective: To evaluate if prior sedation with xylazine would influence the rate of absorption of D(+)-xylose in 6 normal Standardbred horses in a randomised cross-over study. Methods: D(+)-xylose was administered by nasogastric intubation at a dose rate of 0.5g/kgbwt given as a 10% solution with water while xylazine was administered iv at a dose rate of 0.5mg/kgbwt. A heparinised blood sample was collected prior to administration of D(+)-xylose (and xylazine when used) and then at 30, 45, 60, 75, 90, 120, 150, 180 and 240 min following administration. Samples were immediately analysed using a modified colorimetric micro method. The cumulative amount of D(+)-xylose absorbed at each time point with and without prior sedation were. The significance rate was set at P<0.05. Results: The study failed to demonstrate a statistically significant difference in the amount of D(+)-xylose absorbed between sedated and unsedated animals, although there was a tendency for a less rapid initial uptake with prior sedation. Conclusion: This study suggests that prior sedation with xylazine will not significantly affect the result of a D(+)-xylose absorption test in the normal horse. © 2011 EVJ Ltd.