PATHOGENETIC MECHANISMS OF ALKALEMIA IN ACUTE-RENAL-FAILURE PATIENTS

Patients with acute renal failure (ARF) commonly develop a high anion gap metabolic acidosis. However, sporadic cases with alkalemia have been described. We present 3 patients admitted to our hospital with ARF (2 patients had non oliguric ARC) and alkalemia. Two patients had ARF due to aminoglycoside toxicity and one acute tubular necrosis due to severe hypovolemia. Arterial blood pH was 7.47-7.52, PCO2 40-46 mmHg, serum HCO3- 31-36 mmol/L and serum Cl- 82-91 mmol/L. Despite the alkalemia these pa-tients had a mixed acid-base disturbance (metabolic alkalosis plus high anion gap metabolic acidosis) which could be suspected from the coexistence of high anion gap with increased (greater than or equal to 2) ratio of Delta AG/Delta HCO3-. The causes of metabolic alkalosis were vomiting and hypovolemia in all 3 patients and hypokalemia due to prior diuretic treatment in one patient with non-oliguric ARF. The main reasons which contributed to the maintenance of metabolic alkalosis were the impaired HCO3- excretion because of the decreased GFR, hypovolemia and hypochloremia. In conclusion, alkalemia may be present in ARF patients and could mask the underlying metabolic acidosis.