Intravenous energy and XXXX in the preterm newborn @entity1 : effects on metabolic rate and potential mechanisms of action.

@entity1 @entity1522 @entity4962 @entity26 @entity1955 @entity1063 @entity1954
The effects of intravenously administered @entity1522 and of varying amounts of energy on metabolic rate were studied and potential mechanisms examined in 19 healthy 4- to 6-day-old preterm (30 to 32 weeks gestation) @entity1 . The @entity1 were randomized to three groups. Group 1 (n = 6) received nonprotein energy 38 kcal/kg/d; group 2 (n = 5), 64 kcal/kg/d; and group 3 (n = 8), 64 kcal/kg/d plus 1 to 2 g/kg/d crystalline @entity1522 . Thirty-six hours after beginning the infusion, @entity26 consumption (VO2) was measured by indirect calorimetry for 5 to 6 hours. Simultaneously, urine was collected for urinary @entity1063 excretion, which was determined using liquid chromatography with electrochemical detection. Serum @entity1955 (T4) and @entity1954 (T3) concentrations were determined by radioimmunoassay. Group 1 had lower VO2 and urinary @entity1063 excretion than did groups 2 and 3, which did not differ. T4 and T3 were not different among the three groups. The demonstrated simultaneous changes in @entity4962 and @entity1063 excretion with varying energy intakes independent of age supports energy intake as a modulator of the sympathetic nervous system, which in turn controls metabolic rate. Moderate amounts of intravenously administered @entity1522 do not appear to play an active role in this process; nor do they alter T3 and T4 valves. When VO2 increased with increasing energy intake, T3 and T4 were unaffected, supporting a passive role for thyroid hormones in diet-induced thermogenesis.
