Increased extracellular water volume associated with hyponatremia at birth in premature infants

Clinical implications of postnatal alterations in body water distribution

Substantial alterations take place in the quantity and distribution of body water compartments after birth. Clinical management must be tailored to the pace of postnatal adaptation, and the neonatal physician must be aware of these alterations in order to promote both normal physiological change and growth.

Regulation of extracellular fluid volume in neonates

This review summarises mechanisms of control of extracellular fluid volume in the neonatal period. 'Normal' body fluid distribution and methods of its measurement are discussed as well as regulatory mechanisms with particular emphasis on hormonal and renal aspects.

Fecal sodium and potassium losses in low birth weight infants

We measured 24-hour fecal losses of sodium (Na) and potassium (K) in immediate post natal period of preterm neonates to determine the role of this route in the electrolyte imbalances seen in such infants. The values from preterm infants were compared to a group of age matched term infants. Eleven studies were done on unfed extremely low birth weight infants (group I, birth weight < 1200 gms), seven on fed preterm infants (group II, birth weight 1201-2500 gms) and nine on fed term infants (group III, birth weight 2501-4000 gms). Measured and derived variables compared between the groups were 24 hour fecal volume, total fecal electrolyte contents, Na or K lost per kg of body weight and per gm. of stool and Na or K losses as percent of intake. Although 24 hour fecal volume was lowest in group I, none of the variables related to Na differed between groups I and II whereas all of them were significantly lower in group I when compared with group III. Groups II and III differed only in terms of Na loss/gm stool which was lower in the previous group. Conversely K loss/gm of stool was significantly higher in group I when compared with both groups II and III and the only variable that differed between groups II and III was a higher fecal K content as fraction of intake. Fecal K/Na ratio was highest in group I, and decreased progressively with advancing gestational age, whereas creatinine clearance was lowest in group I and increased along with gestational age.(ABSTRACT TRUNCATED AT 250 WORDS)

Relationship between nutrition, weight change, and fluid compartments in preterm infants during the first week of life

This study was conducted to investigate the redistribution of fluid compartments and to examine the factors contributing to the variability of early weight loss in premature infants. Fourteen preterm infants (mean +/- SD: birth weight, 1473 +/- 342 gm; gestational age, 30.7 +/- 2.4 weeks) were studied at 1 and 7 days of age. Total body water was measured by deuterium oxide dilution, extracellular volume by bromide dilution, and intracellular volume by the difference between total body water and extracellular volume. There were significant changes in body fluid distribution per concurrent weight from birth to age 1 week. Extracellular volume decreased by 11%, and intracellular volume increased by 8.5% with no change in total body water. Infants were then grouped according to postnatal weight loss (group 1 (n = 7) > 10% and group 2 (n = 7) < 5% of birth weight). In group 1 there was a significant loss of both weight (mean +/- SD: 15.6% +/- 3.7%) and extracellular volume (15.9% +/- 9% of birth weight), with no change in intracellular volume. In group 2 there was no significant weight loss (1.4% +/- 1.8%), but a significant loss of extracellular volume (13.0% +/- 5.4% of birth weight) and a significant increase in intracellular volume. Other differences between the groups were a lower energy intake in group 1 than in group 2 (mean +/- SD: 177 +/- 46 vs 269 +/- 45 kilojoules/kg per day; p < 0.005) and a higher physiologic stability index in group 1 (p < 0.05). We conclude that significant postnatal weight loss as a result of the contraction of the extracellular compartment occurs only in less stable infants whose energy intake is inadequate. With adequate energy intake, weight loss is minimal because of the expansion of the intracellular compartment, which may be related to the onset of growth.

Estimation of extracellular fluid volume by bromide dilution in infants less than 1000 grams birth weight

We measured extracellular fluid volume by bromide dilution within 12 h of birth in 32 infants less than 1000 g birth weight. Mean (+/- S.D.) birth weight and gestational age were 763 +/- 123 g and 26 +/- 1 week, respectively. Mean extracellular fluid volume was 360 +/- 86 ml (477 +/- 107 ml/kg). These results are similar to extracellular fluid volume estimates from previous carcass analysis data. Wide variability is observed with both methods suggesting that biologic variability may be important.

Mineral balance studies in sick preterm intravenously fed infants during the first week after birth. A guide to fluid therapy

Mineral balance studies were performed in 61 sick preterm infants given parenteral fluids only. Their gestational ages varied from 24 to 35 weeks, and 50 required mechanical ventilation. Two consecutive balance studies were performed; the first from admission to 48 hours in all babies given maintenance fluids of 10% Dextrose, and the second from 48 hours to 7 days in those babies given intravenous feeding (IVN). At the beginning and end of each balance period, the baby was weighed and an arterial blood sample taken for blood gases, electrolyte, urea, creatinine and protein determinations. During the balance period all urine was collected and analysed for electrolyte, urea, and creatinine composition, and all fluid intake was recorded. The balance of a mineral was calculated as the difference between parenteral intake and urine output. Infants requiring IVN were allocated alternatively to regimen X or regimen Y, which had the same calcium content of 9.5 mmol/L, but different phosphate contents, regimen X containing 7.3 mmol/L and regimen Y 11.6 mmol/L. In those infants requiring prolonged IVN, 12-24 hour balance studies were performed at weekly intervals after day 10. 1. Phosphate deficiency developed in infants given regimen X, who had higher urine calcium excretion, lower percentage calcium retention and lower plasma phosphate levels than those given regimen Y. These differences were apparent by day 7 and persisted after day 10. In infants given regimen Y, mean calcium retention from admission to day 7 was 3.9 mmol/kg, and after day 10 was 0.9 mmol/kg/day. 2. In the first 48 hours, urine output and creatinine clearance varied widely and were lower in infants with higher oxygen requirements at 48 hours. Ten babies had severe oliguria with outputs less than 10 mL/kg/day. Creatinine clearance was directly related to gestational age, mean arterial blood pressure, and plasma protein concentrations on admission. After 48 hours, urine output and creatinine clearance increased considerably. 3. In the first 48 hours, metabolic acidosis was produced by increased plasma non-protein metabolisable acid concentrations, which were associated with low creatinine clearances, and were thought to be due to lactic acid accumulation in response to decreased tissue perfusion. At 7 days, metabolic acidosis was of similar severity but was produced by decreased plasma non-metabolisable base concentrations, caused by increased urine loss of net base, and not directly by IVN.(ABSTRACT TRUNCATED AT 400 WORDS)

Postnatal changes in total body water and extracellular volume in the preterm infant with respiratory distress syndrome

Body water compartment changes were assessed during postnatal weight loss in 14 infants with respiratory distress syndrome. Total body water and extracellular volume were measured by dilution methods on the first day of life and again between the third and sixth days of life. Extracellular volume changes were calculated between the first and second determinations by measurement of chloride balance. Fluid therapy was prescribed to allow negative net water balance and a 1% to 3% reduction in body weight per day. All infants had concurrent reductions in body weight, total body water, and extracellular volume. Progressive daily extracellular volume reduction concurrent with weight loss was also apparent from chloride balance data. The correlation of changes in body weight with extracellular volume in individual subjects was poor (r = 0.05). We speculate that variations between sodium and free water balance in the sick preterm infant may be responsible for variability in the distribution of postnatal body water losses. Assessment of hydration in the newborn infant should include consideration of sodium balance and alterations of serum osmolality, and changes in body weight.