ACID-BASE STATUS IN DIETARY TREATMENT OF PHENYLKETONURIA

Abstract

Blood acid-base status, serum electrolytes and urine-pH were examined in 64 PKU-patients receiving 3 different low-phenylalanine protein hydrolysates and 2 synthetic amino acid mixtures. The different formulae caused significant differences in acid-base status, K and Cl in blood-and in urine-pH. Metabolic acidosis seemed to be correlated to an excess of anions (Cl⁻) and a high content of the sulphur containing amino acids. Balance studies were done in two children. In 6 balance periods 4 formulae were given. Formula A had an excess of cations, whereas formula B₁ showed an excess of anions. Both were commercially available products. Formulae B₂-B₃ were modifications of formula B₁ with a reduction in the content of Cl, cystine and methionine. We found an increasing metabolic acidosis from A(blood-pH 7.45, serum HCO₃ 25.8 mval/L) to B₃(7. 41, 24.0), B₂(7. 39, 19. 3) and B₁(7.36, 17.0). Urine-pH dlcreased( A 7.25, B₃6.22, B₁ 5.65, B₁ 5.6) and total H excretion in urine increased ( A 0.3, B₃ 2.7, B₂ 3.3, B₁ 4.4 mEq/Kg/24h). In the formulae B₃, B₂ and B₁ the difference in total H⁺excretion correlated with the different Cl⁻ and S⁻ content of the diet and the different Cl⁻ and SO₄⁻ content of the urine. We propose that formulae should have an excess of cations and that organic sulphur intake should not exceed 1mMS/Kg/24h.

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