EDITORIAL CORRESPONDENCE

Fluid and electrolyte intake in preterm infants

To the Editor: The report by Costarino et al. 1 on sodium restriction in very low

birth weight (VLBW) infants addresses important issues about fluid and electrolyte management in premature babies. Unfortu- nately, the article does not mention the weight loss in the two groups, a very important variable to be considered when dealing with fluid balance in VLBW infants. 2

We recently compared the outcome of two groups of VLBW in- fants before and after the introduction of a new protocol of fluid administration. The purpose of this protocol was to prevent exces- sive weight loss (>3% of birth weight per day) in the first 5 days of life. Our previous protocol was exactly that proposed by Costarino et al., with fluid and sodium restriction. The results are shown in the Table.

After the introduction of this new protocol, we also observed a decrease in the time to regain birth weight (16 _+ 5 vs 12 + 3 days; p <0.05). No significant differences were noted with respect to re- nal failure, the incidence of patent ductus arteriosus, intraventric- ular hemorrhage, bronchopulmonary dysplasia, or survival. We observed one case of hypernatremia and one of hyponatremia, both in the new protocol group.

Dr. Costarino's approach of fluid and sodium restriction was more likely to preserve normal serum osmolality. However, we do not know the cost of the approach in terms of weight loss. Previous reports have indicated that weight loss in the first days of life is mainly due to contraction of extracellular volume, and, contrary to Dr. Costarino's findings, sodium excretion can be altered by sodium intake. 3

Our approach to the maintenance of fluid homeostasis is based on preventing excessive extracellular volume contraction and weight loss, with administration of water and sodium in a given proportion. Thus we do not offer water in excess of sodium nor so-

T a b l e

Before After (n = 14) (n = 44)

Birth weight (gm) 831 _+ 127 820 _+ 126 Weight loss~" 17.0 + 5.0 11.5 + 4.8* Fluid intake, day 2 94 _+ 25 130 + 31"

(ml/kg/day) Fluid intake, day 4 117 _+ 21 176 _+ 41"

(ml/kg/day) Sodium intake, day 4 2.6 + 1.5 4.7 + 2.6*

(mEq/kg/day)

Values are expressed as mean _+ SD. *p <0.05. tPereentage of birth weight.

dium in excess of water. Our data, previous published reports, and Costarino's study show that it is possible to manage VLBW infants with different protocols of fluid and electrolyte administration with comparable results with respect to morbidity and mortality rates. 4

Further studies are needed to determine whether preventing weight loss and improving the time to regain birth weight, which reflect smaller changes in body fluid compartments, are beneficial to the long-term outcome of VLBW infants.

Josh M. Lopes, MD Charles S. Odeh, MD

Manoel de Carvalho, MD Newborn Intensive Care Unit Instituto Fernandes Figueira

Av. Rui Barbosa, 716 Flamengo--Rio de Janeiro CEP 22250, Brazil

9/35/39313 REFERENCES

1. Costarino AT Jr, Gruskay JA, Corcoran L, Polin RA, Baum- gart S. Sodium restriction versus daily maintenance replace- ment in very low birth weight premature neonates: a random- ized, blind therapeutic trial. J PEDIATR 1992;120:99-106.

2. Bauer K, Versmold HT, Roithmaier A, G6tz M, Bovermann G, Pr6iss A. Body composition, nutrition, and fluid balance during the first two weeks of life in preterm neonates weighing less than 1500 grams. J PEDtATR 1991;118:615-20.

3. Shaffer SG, Meade VM. Sodium balance and extracellular volume regulation in very low birth weight infants. J PEDtATR 1989;115:285-90.

4. Lorenz JM, Kleinnam LI, Kotaga VR. Water balance in very low birth weight infants: relationship to water and sodium in- take and effect on outcome. J PEDIATR 1982;101:423-32.

Reply

To the Editor: We agree with Dr. Lopes and colleagues that parenteral fluid

regimens modify the rate and total volume of water and salt loss from the extracellular fluid space after birth, and that serial patient weight measurements provide one way to quantify the magnitude of such losses. Data from our subjects indicate that the percentage of daily body weight loss was 2.4% + 3.4% (mean _+ SD) in our sodium-restricted group versus 1.4% +_ 4% in the sodium-supple- mented group: These group differences were not statistically significant because of the large variation within groups.

We omitted weight data from our report because assessment of day-to-day weight change, particularly in such small infants receiving mechanical ventilation, is inaccurate with the techniques commonly employed to Weigh babies in nurseries. The practice in our nursery is to weigh babies every other day on a mechanically tared, off-bed lever-load pan. Body weight obtained with an impre-

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