A 2-year-old Friesian mare was examined because she had been sluggish For a few weeks. Blood biochemistry showed that concentrations of creatinine (136 mu mol.L(-1)) and urea nitrogen (6.1 mmol.L(-1)) in plasma were within their normal limits. Severe metabolic acidosis was apparent; the venous pH was 7.154 and the bicarbonatr: concentration was 13 mmol.L(-1). The base excess amounted to -15.3 mmol.L(-1) and the venous pCO(2) measured 5.1 kPa. Plasma sodium was normal (135 mmol.L(-1)) and plasma chloride(113 mmol.L(-1)) was slightly elevated, but there was a hypokalaemia (2.9 mmol.L(-1)). The urine had a specific gravity of 1.030 and a pH of5. These findings indicated type 2 renal tubular acidosis. The blood values returned to normal 3 days after treatment with sodium bicarbonate as a 4.2 per cent solution (3.2 mol in total) and additional bicarbonate (125 g) and potassium chloride (100 g) administered orally.
