Changes in the body composition of the surgical infant in the early postoperative period

Abstract

The purpose of this study was to evaluate the effects of postoperative nutritional management on the body composition of infants after major surgery. We studied 13 full-term surgical infants (mean initial weight 2.88 +/- 0.19 kg; mean days postsurgery 5.0 +/- 0.5). Ten infants were receiving total parenteral nutrition and three were orally fed (mean caloric intake 84 +/- 4 kcal/kg/d; mean fluid intake 145 +/- 4 mL/kg/d). Total body water (TBW) was measured by isotope dilution using heavy oxygen (18O) labeled water (H2(18)O). Total body fat (TBF) was estimated from anthropometric data. Lean body mass (LBM) was calculated as follows: LBM = weight--TBF. Protein, fat, and carbohydrate accretion were determined by energy and macronutrient balance in conjunction with open-circuit indirect calorimetry. Body composition was reevaluated after an interval of seven days. Body weight increased from 2.88 +/- 0.19 to 3.00 +/- 0.19 kg, representing a mean growth velocity of 5.9 g/kg/d. Increments were observed in all body compartments but only the increase in TBF reached statistic significance (12.9 v 14% of body weight, P less than .05). TBW ranged from an initial value of 76.2 +/- 1.4% to a value of 75.5 +/- 1.4% at the end of the study. Protein, fat, and carbohydrate accretion (g/kg/d) during the seven-day study period were 1.62 +/- 0.13; 1.44 +/- 0.41, and 0.96 +/- 0.70, respectively. These data indicate that in the early postoperative period, the weight gain is secondary to both water and solid tissue accretion. Fat represents the major form of energy storage in the new tissues synthesized.(ABSTRACT TRUNCATED AT 250 WORDS)