The effects of tonicity, glucose concentration and temperature of an oral rehydration solution on its absorption and elimination.

The research investigates the impact of tonicity, glucose concentration, and temperature of oral rehydration solution (ORS) on its absorption and elimination rates in resting horses. It finds that fluid tonicity plays a significant role while glucose concentration and fluid temperature show minimal effects.

Research methodology

• The effect of different tonicities, glucose concentrations and temperatures of oral rehydration solution (ORS) was studied on resting horses.
• The simulated fluid and electrolyte deficits were similar to those seen during prolonged exercise. The deficits were induced by administering frusemide, 3 hours prior to the ORS.
• The fluid was inserted through a nasogastric tube at a volume equal to 4% of the bodyweight of the horses, mirroring the diuretic-induced losses.
• The fluid uptake was determined by changes in haematocrit (PCV) and plasma total protein concentration (TP). These parameters are used to study the fluid’s impact on the body’s blood and protein levels.
• To study the changes in electrolyte balance, measurements of plasma and urinary electrolyte concentrations were taken. Meanwhile, the body weight changes, urine volume, and faecal water content were considered to gauge the retention of the inserted fluids.
• Venous blood bicarbonate values were used to assess the changes in the horse’s acid-base status.

Findings

• The tonicity of the fluid was found to largely determine the uptake and elimination of the ORS. Specifically, hypertonic fluid (628 mOsm/kg bwt) was less rapidly absorbed and led to more rapid fluid and electrolyte excretion than isotonic (314 mOsm/kg bwt) and hypotonic (water) fluids.
• Adding glucose didn’t show any significant effect on the absorption of the ORS. However, fluids with higher concentrations of electrolytes resulted in faster elimination of fluid in urine.
• A direct relationship was discovered between higher concentrations of sodium in the ORS, plasma sodium values, and osmolality. As the sodium concentration in the ORS increased, so too did plasma sodium values and osmolality.
• The temperature of the fluid (5, 21 and 37 degrees Celsius) showed no noticeable effect on the absorption of the ORS or the elimination of fluids post administration.

Implications of Findings

• The findings underline the importance of fluid tonicity in the uptake and elimination of orally administered fluid. In particular, hypertonic fluids absorb more slowly and subsequently lead to faster fluid and electrolyte excretion.
• The research suggests that glucose concentration and fluid temperature have little to no impact on fluid absorption and elimination, refuting commonly held practices in ORS administration.
• Overall, these findings hold relevance for situations involving ORS administration, providing insights for exercise-related hydration, veterinary care, and other scenarios where rapid and effective hydration is essential.