NUTRITIONAL AND METABOLIC VARIABLES CORRELATE WITH AMINO-ACID FOREARMFLUX IN PATIENTS WITH SEVERE HEAD-INJURY

Objective: To measure the arterial-venous amino acid flux across the f orearm muscle in patients with severe head injury. Design: Prospective , interventional study. Setting: Level I trauma hospital in the neuros urgery intensive care unit (ICU) at a university medical center. Patie nts: Eight nonsteroid-treated patients with severe head injury. Interv entions: Patients were prospectively randomized to receive either stan dard or supplemental intravenous zinc therapy. Measurements and Main R esults: Net forearm alanine, glutamine, tyrosine, phenylalanine, and b ranch-chain amino acid forearm flux were measured and compared with me tabolic markers of energy expenditure and nitrogen excretion. There wa s a significant inverse relationship between the measured energy expen diture/predicted energy expenditure ratio and glutamine flux (r(2)=.62 ; P < .05), The patients with the highest measured energy expenditure/ predicted energy expenditure ratio had the greatest release of glutami ne from forearm muscle. Nitrogen balance was significantly correlated with leucine flux (r(2)=.53;p<.05) and with isoleucine flux (r(2)=.67; p<.05), The patients with the most positive nitrogen balance had the l east release of branch-chain amino acids from skeletal muscle. Tyrosin e flux was highly correlated with net amino acid flux (r(2)=.76; P<.O1 ). Tyrosine flux was therefore indicative of overall muscle catabolism . Four patients had an overall negative flux of amino acids from skele tal muscle. Three patients had an overall negative flux of branch-chai n amino acids. Conclusions: This preliminary descriptive report sugges ts that increased skeletal muscle efflux of amino acids correlates sig nificantly with metabolic variables of hypermetabolism and hypercatabo lism in nonsteroid-treated, head-injured patients.