Restricted versus liberal water intake for preventing morbidity and mortality in preterm infants

Most premature infants are not sufficiently mature physiologically to take all of their required water and nutrients orally, and so they cannot regulate their own water intake. Thus, the caregiver must determine the amount of water to be given each day to such infants.

The objective of this review is to examine the effects of water intake on postnatal weight loss and on the risks of dehydration, patent ductus arteriosus, necrotizing enterocolitis, bronchopulmonary dysplasia, intracranial hemorrhage, and death in premature infants.

Randomized clinical trials were sought that compared the outcomes of interest in groups of premature infants who were given different levels of water intake according to experimental protocol. Such trials were sought in a previous review by one of the authors (Bell EF. Fluid therapy. In: Effective Care of the Newborn Infant, eds JC Sinclair, MB Bracken. Oxford: Oxford University Press, 1992: 59-72), in a list of trials provided by the Cochrane Neonatal Review Group, and in the authors' personal files.

Only randomized clinical trials of varying water intake in premature infants are included. The review was limited to trials that included infants whose water intake was provided mainly or entirely by parenteral means. Studies were included regardless of outcomes examined.

Trials were selected by two reviewers, who also assessed the methodological quality of each trial. Data were independently extracted by the reviewers, and differences were reconciled. The data were then entered into tables using RevMan 3.1 for Windows. The adverse event rates were calculated for the restricted and liberal water intake groups for each dichotomous outcome, and the relative risk was computed. In addition, the maximal weight loss results were recorded, and the weighted mean difference was computed. The analyses (including calculation of relative risk, risk difference, and weighted mean difference) and tests of heterogeneity were accomplished with MetaView 3.1 software and a fixed effects model. No subgroup analyses were conducted.

The analysis of the four studies taken together indicates that restricted water intake significantly increases postnatal weight loss and significantly reduces the risks of patent ductus arteriosus, necrotizing enterocolitis, and death. With restricted water intake, there are trends toward increased risk of dehydration and reduced risk of bronchopulmonary dysplasia, but these trends are not statistically significant.

Based on this analysis, the most prudent prescription for water intake to premature infants would seem to be careful restriction of water intake so that physiological needs are met without allowing significant dehydration. This practice could be expected to decrease the risks of patent ductus arteriosus and necrotizing enterocolitis--and perhaps the overall risk of death--without significantly increased risk of adverse consequences.