Systemic, renal, and colonic effects of intravenous and enteral rehydration in horses.
Authors: Lester G D, Merritt A M, Kuck H V, Burrow J A
Journal: Journal of veterinary internal medicine
Summary
# Editorial Summary: Systemic, Renal, and Colonic Effects of Intravenous and Enteral Rehydration in Horses Lester and colleagues investigated how different rehydration routes and rates affect intestinal hydration, renal function, and electrolyte balance in dehydrated horses—a clinically relevant question given that IV and nasogastric fluid therapy are cornerstone treatments in equine practice, yet their physiological trade-offs remain poorly characterised. Using a crossover design, six Thoroughbreds were subjected to water deprivation then treated with either constant-rate IV polyionic isotonic fluids at 50, 100, or 150 mL/kg/day or equivalent volumes of plain water administered as four nasogastric boluses over 24 hours. Both IV fluids at 100 and 150 mL/kg/day successfully restored faecal water content to baseline, but escalating from 100 to 150 mL/kg/day provided no additional intestinal benefit whilst significantly increasing urine output and urinary sodium loss—a concerning trade-off that suggests higher rates impose unnecessary renal stress. Nasogastric plain water achieved greater intestinal hydration with substantially lower urine production, indicating superior efficiency for restoring colonic water when enteral administration is feasible. Practitioners should reconsider the dogma of aggressive IV rehydration rates; 100 mL/kg/day appears optimal for intestinal recovery, and prioritising oral or nasogastric water when clinically possible minimises unwanted electrolyte losses and post-treatment complications.
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Practical Takeaways
- •IV fluids at 100 mL/kg/day are as effective as 150 mL/kg/day for restoring intestinal hydration; using the lower rate reduces unnecessary urine losses and electrolyte depletion
- •When safe enteral access is available, intragastric water boluses outperform IV fluids for intestinal rehydration and should be preferred to minimize electrolyte losses
- •Reserve high-rate IV fluid therapy for cases where oral/nasogastric administration is contraindicated; monitor for excessive urine output and electrolyte disturbances with rates above maintenance
Key Findings
- •IV fluids at 100 and 150 mL/kg/d restored fecal hydration equally; increasing from 100 to 150 mL/kg/d provided no additional intestinal benefit but significantly increased urine production and sodium loss
- •Equivalent 24-hour volumes of intragastric plain water achieved greater intestinal hydration with less urine output than IV administration
- •IV polyionic isotonic fluids can hydrate intestinal contents when enteral fluids are impractical, but three times maintenance dosing is not more efficacious
- •Bolus dosing of intragastric water restores intestinal water content with minimal adverse effects