Origins of hyperphenylalaninemia in burn patients

Plasma phenylalanine concentrations were measured on the seventh postburn day in patients with burn surface areas ranging from 1 to 39%. Hepatic function (glutamate-pyruvate transaminase, prothrombin time) and protein breakdown (nitrogen balance, urine 3-methylhistidine/creatinine ratio) were evaluated in parallel. Plasma phenylalanine concentrations in patients with normal hepatic function and those with hepatic failure were similar. A correlation was shown between phenylalaninemia and nitrogen balance for all patients but phenylalaninemia only correlated with the urine 3-methyl-histidine/creatinine ratio in patients with burn surface areas under 20%. Taken as a whole, the data suggest that the determination of plasma phenylalanine concentration is a valuable test to assess the nitrogen balance in burn patients. This test, when performed on day 7, is particularly relevant in patients with normal hepatic function and either slight or moderate burn injury.