Effects of sodium bicarbonate on fluid, electrolyte and acid-base balance in racehorses.

The research article reports on the effects of sodium bicarbonate, given by a nasogastric tube, on the fluid, electrolyte, and acid-base balance in racehorses. The study examined the assumption that sodium bicarbonate, used as a ‘milkshake’, enhances a horse’s racing performance by increasing blood buffering capacity and lactate clearance from skeletal muscles, thereby delaying fatigue.

Methodology

• The study revolves around experiments conducted to analyze the impact on fluid, electrolyte, and acid-base values of a 0.5 g kg-1 dose of sodium bicarbonate.
• The study also aimed to establish whether the simultaneous administration of glucose (0.5 g kg-1) or the withholding of water had any impact on the uptake and elimination of sodium bicarbonate.
• Control values of venous blood, urine and faecal samples were established via collections for 24 hours prior to sodium bicarbonate administration in six Thoroughbred horses, each wearing a urine and faecal collection harness.
• Post sodium bicarbonate administration (0.5 g kg-1) in 2 l of water, samples were then collected at different times over a span of 46 hours.

Key Findings

• Post-administration of sodium bicarbonate, significant increases were observed in water consumption, urine output, and urinary sodium concentration.
• Water consumption increased to a range of 0.5-2.3 l h-1 at two hours post-administration.
• Urine output increased approximately threefold, returning to control levels 18 hours post-administration.
• Urinary sodium concentration increased from 95 +/- 16 mmol l-1 (mean +/- SEM) to peak values of 349 +/- 12 mmol l-1 at 12 hours, while total urinary potassium and chloride excretion did not significantly change.
• In the 24 hours following sodium bicarbonate administration, around 80% of the sodium intake (NaHCO3+feed) was excreted in the urine.
• Although faecal water content did not change, an increase was observed in faecal sodium content.
• The mean increase in venous blood bicarbonate concentration was 7.6 +/- 0.4 mmol l-1 after the 0.5 kg-1 dose.
• Water deprivation for 6 hours after sodium bicarbonate administration, fasting, or the co-administration of glucose did not affect the peak blood bicarbonate concentration or the time to peak concentration.
• However, the withholding of water resulted in a faster rate of decrease in blood bicarbonate concentration when water was reinstated.