Treatment of episodic hyperammonemia in children with inborn errors of urea synthesis

Abstract

Although normal plasma ammonium levels can be maintained in children with inborn errors of ureagenesis, these children are vulnerable to episodic hyperammonemia often resulting in coma and death. To treat such episodes, we designed a therapeutic protocol that included prompt recognition of hyperammonemia, therapy with intravenous sodium benzoate, sodium phenylacetate, and arginine, and nitrogen-free intravenous alimentation. Dialysis was performed if the hyperammonemia was unresponsive to drug therapy. Twelve episodes of hyperammonemia in seven children deficient in carbamyl phosphate synthetase, ornithine transcarbamylase, or argininosuccinic acid synthetase were treated; one patient died and the others recovered. In two patients measurement of the distribution of urinary nitrogen revealed that hippurate nitrogen and phenylacetylglutamine nitrogen together accounted for 60 per cent of "effective" urinary waste nitrogen. Successful therapy of episodic hyperammonemia plays an important part in the long-term management of disorders of the urea cycle.