Effect of an indwelling nasogastric tube on gastric emptying rates of liquids in horses

Objective-To evaluate the effect of an indwelling nasogastric tube on gastric emptying of liquids in horses. Animals-9 healthy adult horses. Procedure A randomized block crossover design was used. For treatment group horses, a nasogastric tube was placed and 18 hours later, acetaminophen was administered; the nasogastric tube remained in place until the experiment was complete. For control group horses, a nasogastric tube was passed into the stomach, acetaminophen was administered, and the nasogastric tube was removed immediately. Serial blood samples were collected 15 minutes before and after administration of acetaminophen. Serum concentration of acetaminophen was determined by use of fluorescence polarization immunoassay. The variables, time to maximum acetaminophen concentration (T-max) and the appearance constant for acetaminophen (K-app), were determined. The values for K-app and T-max in horses with and without prolonged nasogastric tube placement were compared. Results-No significant difference was found in K, between horses with and without prolonged nasogastric tube placement; the median difference in Kapp was 0.01 min(-1) (range, -0.48 to 0.80 min(-1)). No significant difference was found in T-max between horses with and without prolonged nasogastric tube placement; the median difference in T-max was 5 minutes (range, -30 to 50 minutes). Reanalysis of data following the removal of possible outlier values from 1 horse resulted in a significant difference in T-max between horses with and without prolonged nasogastric tube placement. Conclusions and Clinical Relevance-Although no clinically important impact of 18 hours of nasogastric intubation was found on gastric emptying in healthy horses, considerable variability in Kapp and Tmax was found among horses.