Systemic, renal, and colonic effects of intravenous and enteral rehydration in horses.

This research investigates the effects of different methods of rehydration (specifically intravenous and intragastric) on horses who’ve been dehydrated. They found that both methods can successfully rehydrate the horses, but there might be disproportionate urine production and sodium loss with increased intravenous dosage, and comparatively less water loss through urine with intragastric rehydration.

Objective and Methods

In this experimental study, the university researchers aimed to understand how different methods of rehydration affect horses’ digestive and renal systems. They used six Thoroughbred geldings and experimented on them using a Latin square design investigation. First, these horses were dehydrated by depriving them of water. Then, for rehydration, they were subjected to intravenous (IV) fluid administration at different rates (50, 100, and 150 mL/kg/d) over 24 hours. Others were given the same volume of water intragastrically (IG), divided into four bolus doses over 24 hours.

Results

• Water deprivation among test subjects led to a significant decline in the water content of their feces, and increases in osmolality (a measure of the total number of solute particles per kilogram of water) in their serum and urine.
• IV fluids administered at rates of 100 and 150 mL/kg/d successfully restored fecal hydration. However, there were no additional benefits to the intestines when the rate was ramped up from 100 to 150 mL/kg/d. On the contrary, a higher rate resulted in more urine production and sodium loss.
• When given equivalent 24-hour volumes of plain water intragastrically, the intestinal water levels rose more, while there was less urine output.

Conclusions

This study concludes that both methods of rehydration can effectively hydrate the intestines of dehydrated horses. However, administering IV fluids at higher rates can potentially lead to increased urine production and sodium loss, without providing any additional benefit to intestinal hydration.

IV polyionic isotonic fluids are recommended when the administration of enteral fluids is not possible. But, doses greater than three times the maintenance rate might bring no additional advantages, and could even be associated with adverse physiological effects after withdrawal. Bolus dosing of IG water, however, results in improved intestinal hydration and minimizes adverse effects.