1518 IMPROVED TECHNIQUE FOR ASSESSING URINARY ACIDIFICATION

Abstract

Ammonium chloride (NH₄Cl) loading to evaluate urinary acidification often is poorly tolerated because of severe side effects. Indeed it may produce severe uncompensated metabolic acidosis in infants (J Peds. 1977, 91:263). We have developed an alternate protocol utilizing the intravenous infusion of arginine hydrochloride (HC1) and have studied this in 22 children, of whom 4 had distal renal tubular acidosis (dRTA), 2 had proximal renal tubular acidosis (pRTA), 14 had recovered from glomerulonephritis and 2 had no evidence of renal disease. Arginine HC1 was infused over 2.0 to 2.5 hours in a dose equivalent to between 100 to 150 mEq [H⁺] per m² SA in patients with RTA or decreased GFR and between 150 to 200 mEq [H⁺] per m² in the remainder. This resulted in a systemic acidosis sufficient to separate patients with dRTA from the remainder. In no one with dRTA was urine acidified below pH 5.50, lowest values being seen at 5 to 6 hr after starting the infusion. Urine pH was reduced to between 4.65 and 5.35 in all remaining subjects, values below 5.50 occurring in each within 3 hr of starting the infusion. In no instance did the systemic acidosis become excessive or induce symptoms. The procedure was well tolerated by the patients: the severe nausea, vomiting and cramping abdominal pain frequently associated with NH₄C1 loading did not occur. We recommend that arginine HC1, rather than NH₄C1 be used to study urinary acidification because of the safety, reliability, and better patient acceptance of the test.

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