Body water content of extremely preterm infants at birth

Abstract

Background-Preterm birth is often associated with impaired growth. Small for gestational age status confers additional risk. Aim-To determine the body water content of appropriately grown (AGA) and small for gestational age (SGA) preterm infants in order to provide a baseline for longitudinal studies of growth after preterm birth. Methods-All infants born at the Hammersmith and Queen Charlotte's Hospitals between 25 and 30 weeks gestational age were eligible for entry into the study. Informed parental consent was obtained as soon after delivery as possible, after which the extracellular fluid content was determined by bromide dilution and total body water by H 2 18O dilution. Results-Forty two preterm infants were studied. SGA infants had a significantly higher body water content than AGA infants (906 (833-954) and 844 (637-958) ml/kg respectively; median (range); p = 0.019). There were no diVerences in extracellular and intracellular fluid volumes, nor in the ratio of extracellular to intracellular fluid. Estimates of relative adiposity suggest a body fat content of about 7% in AGA infants, assuming negligible fat content in SGA infants and lean body tissue hydration to be equivalent in the two groups. Conclusions-Novel values for the body water composition of the SGA preterm infant at 25-30 weeks gestation are presented. The data do not support the view that SGA infants have extracellular dehydration, nor is their regulation of body water impaired. (Arch Dis Child Fetal Neonatal Ed 2000;83:F56-F59)

Association between early postnatal weight loss and death or BPD in small and appropriate for gestational age extremely low-birth-weight infants

“…[7][8][9] This observation is consistent with the notion that in intrauterine growth restricted or SGA infants, the higher body water content is due to a lower lean body mass and fat content when expressed as percent birth weight. 10 Thus, it is somewhat counterintuitive to have a lower incidence of EPWL in SGA infants since the expectation is that a larger body fluid content 3,4 would result in more fluid loss after birth with greater accompanying weight loss.…”

“…Previous studies [7][8][9] have shown that small for gestational age (SGA) infants have a different body composition when compared with appropriate for gestational age (AGA) infants. Because SGA infants have less lean body mass and fat when expressed per kilogram body weight, their body water content is higher than their AGA counterparts.…”

Modeling the glucose regulatory system in extreme preterm infants

“…In particular, the extra-cellular fluid compartment is a much higher percentage of total body weight [39][40][41]. It can also decrease over time as very preterm neonates can pass through a diuretic stage in the first few days of life [40,42], and this contraction of the extra-cellular fluid compartment may be a major contributor to weight loss in infants of this gestation and postnatal age [43].…”

The Newborn Drug Development Initiative

“…Similarly, the distribution of water-soluble drugs may be increased in low birth weight infants because of their larger extracellular volume compared with term infants. 13 Low renal blood flow 14 and patent ductus arteriosus 15 during the first few days can markedly influence drug distribution through the body. Moreover, the low glomerular filtration rate in low birth weight infants 16 may lead to the accumulation of those drugs that are eliminated primarily by the kidneys, necessitating dose adjustment.…”