Abstract
The ability of the LBW infant to control water balance during the first 5 days of life was studied prospectively in 68 infants. Matched AGA infants with birth weights (BW) of 750-1500 g were randomized to either Group I -- fluids managed to allow loss of 1-2% of BW per day to a maximum loss of 8-10%, or Group II -- fluids managed to allow loss of 3-5% of BW per day to a maximum loss of 13-15%. All infants were cared for in convectively heated incubators with 80-95% relative humidity and abdominal skin temp maintained at 35.5-36.0°C. Mean fluid inputs were as follows:
Group I lost a mean of 80 g/kg and Group II 125 g/kg over 5 days. Mean cumulative caloric input in Group I was 216±10 Cal/kg and in Group II 143±5 Cal/kg (p<.01). When weight loss was corrected for caloric loss (assuming caloric expenditure of 45 mg/kg/day and 4.8 cal/gm dry tissue metabolized), cummulative water loss was 78±6 g/kg in Group I and 110±10 g/kg in Group II (p<0.02). A 230 ml/kg difference in fluid input was required to produce a mean difference in total body water of only 32 g/kg. Thus the LBW infant is able to maintain water balance within a comparatively narrow range over a broad range of fluid inputs by regulating water excretion. This ability to handle higher fluid inputs relatively well allows higher caloric input.
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Lorenz, J., Kleinman, L. & Kotagal, U. 1362 ABILITY OF LOW BIRTH WEIGHT (LBW) INFANTS TO MAINTAIN FLUID HOMEOSTASIS. Pediatr Res 15 (Suppl 4), 670 (1981). https://doi.org/10.1203/00006450-198104001-01391
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DOI: https://doi.org/10.1203/00006450-198104001-01391