Furosemide and sodium bicarbonate-induced alkalosis in the horse and response to oral KCl or NaCl therapy

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SUMMARY Metabolic alkalosis was induced in 10 clinically normal horses by administration of furosemide (1 mg/kg of body weight, im) followed 4.5 hours later by sodium bicarbonate (NaHCO3; 500 g in 8 L water) via nasogastric tube. Furosemide diuresis resulted in a mean weight loss of 21.1 kg, which was associated with small, but significant, increases in venous blood pH, bicarbonate, and plasma protein concentrations (P < 0.001), while plasma potassium, chloride, and calcium concentrations declined significantly (P < 0.001). Oral administration of the hypertonic NaHCO3 solution resulted in clinical evidence of hypovolemia, which was accompanied by a marked increase (P < 0.001) in plasma protein concentration. Seven of the 10 horses developed signs of neuromuscular excitability, as evidenced by muscle fasciculations, and 5 of the horses developed diaphragmatic flutter. Hypernatremia was transiently induced, but it resolved as the horses were allowed access to water. The alkalosis induced by furosemide and NaHCO3 was profound and persisted for a 24-hour period and was associated with marked hypochloremia and hypokalemia. Partial replacement of the electrolyte deficits and correction of the metabolic alkalosis was attempted, using 1,000 mEq of NaCl or KCl given as an isotonic solution via nasogastric tube. In the KCl-treated group, there was a prompt and significant decline in venous blood pH and bicarbonate concentration (P < 0.001) accompanied by a significant increase in plasma potassium concentration (P < 0.001). Reductions in sodium concentration and increases in chloride concentration followed the KCl therapy, but these responses were variable and less significant (P < 0.05). In the NaCl-treated group, there was a slight reduction in venous blood pH (P < 0.05), but no significant changes in plasma bicarbonate or potassium concentrations. Plasma chloride concentration was slightly increased 2 and 5 hours after NaCl therapy (P < 0.05).