Metabolism of intravenous fat emulsion in the surgical newborn.

The metabolism of an intravenous (IV) fat emulsion was investigated by the combination of chemical balance and computerized indirect calorimetry techniques in 21 newborns (birth weight, 3.0 +/- 0.1 kg; mean +/- SE). All babies were appropriate for gestational age and received total parenteral nutrition after a major surgical procedure. The study was divided into two consecutive periods. Phase 1 consisted of infusion of 10% glucose and 2% amino acid solutions for 24 hours, and phase 2 involved the "Intralipid utilization test" (isocaloric and isovolemic infusion of Intralipid 10% for four hours). The caloric intake was 67.1 +/- 1.9 kcal/kg/d during both phases of the study. The resting energy expenditure was 44.8 +/- 1.6 and 46.5 +/- 1.8 kcal/kg/d during phases 1 and 2 respectively. During glucose/amino acid infusion, 12 patients oxidized endogenous fat, and de novo lipogenesis from glucose was observed in nine. During the Intralipid infusion, there was a significant and progressive decrease of carbon dioxide production, respiratory quotient, and carbohydrate utilization (oxidation plus conversion to fat). Net lipogenesis ended and fat utilization significantly increased. By the second hour of Intralipid infusion, 58% of energy expenditure was derived from fat oxidation. The drop in carbon dioxide production correlated positively with the decrease in carbohydrate utilization (r = .07; P less than .001). During the third and fourth hours of phase 2, the percentage of fat utilized was negatively correlated with the amount of fat given (r = -.07; P less than .01). The surgical neonate showed rapid metabolic adaptation to Intralipid infusion.(ABSTRACT TRUNCATED AT 250 WORDS)