IMMEDIATE COMMENCEMENT OF AMINO-ACID SUPPLEMENTATION IN PRETERM INFANTS - EFFECT ON SERUM AMINO-ACID-CONCENTRATIONS AND PROTEIN KINETICS ONTHE FIRST DAY OF LIFE

To determine whether the general reluctance to begin amino acid admini stration to preterm infants from birth onward might lead to loss of le an body mass and impairment of growth, we measured amino acid levels a nd protein kinetics in 18 preterm infants, Nine infants received amino acids (1.15 +/- 0.06 gm . kg(-1). day(-1)) and glucose (6.05 +/- 1.58 gm . kg(-1). day(-1)), whereas the other nine infants received only g lucose (6.48 +/- 1.30 gm . kg(-1). day(-1)) from birth onward, Protein kinetics on the first postnatal day were measured with a stable isoto pe dilution technique with (1-C-13)leucine as a tracer, No statistical ly significant differences were noted in blood pH, base excess, urea c oncentration, or glucose levels, Both total amino acid concentration a nd total essential amino acid concentration were significantly lower a nd were below the reference range in the nonsupplemented group, Plasma amino acid levels of five essential amino acids (methionine, cystine, isoleucine, leucine, arginine) were below the reference range in the nonsupplemented group, whereas only cystine was below the reference ra nge in the supplemented group, Nitrogen retention was improved signifi cantly by the administration of amino acids (-110 +/- 44 mg nitrogen p er kilogram per day in the glucose-only group vs +10 +/- 127 mg nitrog en per kilogram per day in the group given glucose and amino acids; p = 0.001); leucine oxidation was not significantly increased in the sup plemented group (41 +/- 13 mu mol . kg(-1). hr(-1) vs 46 +/- 16 mu mol . kg(-1). hr(-1)). Leucine balance also improved significantly (-41 /- 13 mu mol . kg(-1). hr(-1) vs -8 +/- 16 mu mol . kg(-1). hr(-1); p = 0.01) because of a combination of an increased amount of leucine bei ng used for protein synthesis and a lower amount of leucine coming fro m protein breakdown, Plasma cystine concentration, the only amino acid below the reference range in the supplemented group, was highly predi ctive for protein synthesis in that group. We conclude that the admini stration of amino acids to preterm infants from birth onward seems saf e and prevents the loss of protein mass.