POSTNATAL WEIGHT LOSS AND REGAINING OF BIRTH WEIGHT IN VLBW INFANTS REFLECT EXTRACELLULAR VOLUME CHANGES AND NOT NUTRITIONAL STATUS

Abstract

Do initial weight changes under the usual restrictive fluid therapy in premature infants reflect water balance or nutritional status? We studied in 8 premature infants (GA 26-29 wks, on respirator) total body water TBW (D2O space),body solids (weight-TBW), extracellular volume ECV (sucrose space) and intracellular volume ICV (TBW-ECV) at birth, at maximal weight loss and when birth weight was regained. Weight (-79g), TBW (-95ml) and ECV (-80ml) initially decreased (p<:*0.01;**0.001), body solids and ICV did not change. During subsequent weight gain there was a trend of TBW and ECV to return to initial levels. Caloric intake was borderline to meet basal metabolic needs, but even at study end not sufficient for growth.Conclusion: Postnatal weight loss is loss of body water from the ECV, subsequent weight gain is restauration of fluid volumes towards initial levels.