Plasma amino acid concentrations during late rehabilitation in patients with traumatic brain injury

Abstract

Objectives: To investigate whether the basal plasma amino acid concentrations in patients with traumatic brain injury (TBI) have returned to levels found in healthy controls at about 17 months postinjury and to determine the effect of intake of a mixture of essential amino acids (EAA) on plasma amino acid concentrations in TBI versus healthy controls.

Design: Peripheral venous amino acid concentrations in subjects with TBI were compared with concentrations in healthy controls both at rest and for 1 hour after intake of 7g of EAA.

Setting: Postacute brain injury rehabilitation center.

Participants: Six men with TBI (age +/- standard deviation, 27+/-6y; months postinjury, 17+/-4) and 6 healthy men (age, 43+/-7y).

Intervention: Intake of a drink consisting of 7g of EAA.

Main outcome measures: Individual and total plasma amino acid concentrations.

Results: Total amino acid concentration was about 12% lower in TBI versus controls (P=.022). Valine was reduced by 33% in the TBI group versus controls (P=.003), whereas the other EAA did not differ between groups. After intake of the EAA drink, plasma non-EAA increased to a significantly higher level in controls versus TBI subjects (P=.017).

Conclusions: Plasma total amino acid concentration is still reduced 17 months postinjury in patients with TBI versus healthy controls, mainly because of a lower valine level. This may be of importance for both brain and muscle metabolic functions, and warrant further study. Further, ingested EAA are apparently not as readily converted to non-EAA in TBI patients as in healthy controls, suggesting that in recovery from TBI, certain non-EAA may become provisionally essential.