Effects of hypercalcemia on serum concentrations of magnesium, potassium, and phosphate and urinary excretion of electrolytes in horses.

This medical study investigates the relationship between hypercalcemia and serum concentrations and urinary excretion of various electrolytes in horses. The researchers hypothesized that hypercalcemia, a condition marked by abnormally high calcium levels in the blood, could impact the levels of other crucial electrolytes, including ionized magnesium, sodium, potassium, and phosphate.

Methods

• The study focused on 21 clinically healthy mares.
• Various experimental procedures were employed. These included inducing hypercalcemia with calcium gluconate or calcium chloride, infusing dextrose solution, infusing sodium gluconate, and infusing saline solution.
• All procedures except hypercalcemia induction lasted for 2 hours.
• Blood samples were collected to measure serum concentrations of electrolytes, creatinine, parathyroid hormone, and insulin.
• Urine samples were collected to assess the fractional excretion of ionized electrolytes.

Findings

• The administration of calcium gluconate or calcium chloride led to a decrease in serum ionized magnesium, potassium, and parathyroid hormone concentrations.
• Concurrently, it increased phosphate concentration, but it did not affect sodium, chloride, and insulin levels in the serum.
• The induction of hypercalcemia escalated the urinary excretion of all tested electrolytes.
• There was an increase in urine output and a decrease in urine osmolality and specific gravity.
• Dextrose administration increased insulin levels in the serum but decreased levels of ionized magnesium, potassium, and phosphate. Additionally, it reduced the urinary excretion of ionized magnesium.
• Sodium gluconate increased the excretion of ionized calcium, sodium, and potassium.

Conclusions

• The study concludes that hypercalcemia causes hypomagnesemia (low magnesium levels), hypokalemia (low potassium levels), and hyperphosphatemia (excess phosphate).
• Hypercalcemia also increased urinary excretion of several electrolytes and induced diuresis, a condition that increases urination and the removal of electrolytes and wastes from the body.
• These findings are significant because they indicate that hypercalcemia and excessive administration of calcium can potentiate a significant increase in the urinary excretion of electrolytes, especially ionized magnesium, and can cause volume depletion.