Abstract
Objectives
To describe changes in renal function of horses after oral and IV administration of sodium bicarbonate (NaHCO3) and to determine whether changes are dose dependent.
Animals
6 Standardbred mares.
Procedure
Blood and urine samples for determination of renal function were collected immediately before and at hourly intervals for 12 hours after administration of each of 3 oral doses (1,500, 1,000, and 250 mg/kg of body weight, in 3 L of water) and 1 IV dose (250 mg/kg, 5% solution) of NaHCO3, or water (3 L orally).
Results
NaHCO3 induced increases in urine flow; electrolyte-free water reabsorption; urine concentrations of sodium and bicarbonate; fractional excretion of sodium, potassium, chloride, and bicarbonate; urinary excretion and clearance of sodium and bicarbonate; urine pH and anion gap; and mean plasma concentration of antidiuretic hormone. NaHCO3 induced attenuation in reduction with time of urine excretion and clearance of potassium, chloride, and osmoles, and induced reduction in urine osmolality. Plasma aldosterone and atrial natriuretic peptide concentrations and glomerular filtration rate were not modified.
Conclusions
Renal responses to NaHCO3 load emphasize conservation of plasma volume and re-establishment of acid-base balance over control of hyperosmolality by means of diuresis, natriuresis, and increased bicarbonaturia. These responses imply a large fluid shift from the extravascular space to the vascular compartment, which was eliminated via diuresis, thus preventing hypervolemia. (Am J Vet Res 1997;58:664–671)
