The body clearance of 10 plasma
amino acids (AA) was determined from the rate of compared muscle-released AA and AA administered by infusion of
total parenteral nutrition (TPN) compared to their estimated extracellular (ECW) pool in patients with
multiple trauma with (n = 10) or without (n = 16)
sepsis at 8-hour intervals. In both nonseptic and septic
trauma, increasing TPN increased the mean clearance rate of all infused AA. When the individual AA clearance rates were normalized by the total AA infusion rate, regression-covariance analysis revealed that patients with
sepsis had relatively impaired clearances of
alanine (p less than 0.01) and
methionine,
proline,
phenylalanine, and
tyrosine p less than 0.05 for all). In contrast, the clearances of branched-chain AA (BCAA)
valine and
isoleucine were maintained, and the clearance of
leucine was higher (p less than 0.05) in
trauma patients with
sepsis than in those without. At any AA infusion rate, compared with surviving patients with
sepsis (p less than 0.05), patients who developed fatal
multiple organ failure syndrome (MOFS) showed increased clearances of all BCAA with further impaired clearance of
tyrosine. The clearance ratio of
leucine/
tyrosine was increased in MOFS at any AA infusion rate (p less than 0.0001), was an
indicator of severity, and, if persistent, was a manifestation of a fatal outcome. Because
tyrosine metabolism occurs almost entirely in the liver while
leucine can be utilized by viscera and muscle, these data suggest early and progressive septic impairment of the pattern of hepatic uptake and oxidation of AA with a greater body dependence on BCAA, especially
leucine, as septic MOFS develops.