Fluid overload worsens respiratory failure; conversely, fluid restriction has been associated with a higher survival rate without chronic lung disease. We therefore hypothesised that fluid restriction in the perinatal period might improve lung function in ventilated, prematurely born infants of very low birthweight. As a consequence, we compared in a randomised trial the effect of two fluid regimes on perinatal lung function. On one regime infants were to receive 60 ml/kg on day 1, increasing to 150 ml/kg by day 7, and on the other regime approximately 25% less fluid was to be prescribed. Lung function was assessed by measurement of functional residual capacity (FRC) and compliance. Measurements were made daily on days 1 to 5 and then on day 7. Ninety infants, median gestational age 28 weeks (range 23-33), were included in the study. There were no significant differences between the two groups regarding their gestational age or birthweight, or in the proportions who received antenatal steroids or postnatal surfactant. The infants on the restricted regime received significantly less fluid (P < 0.01). The only significant differences in lung function between the two groups, however, were that the infants on the restricted regime had a higher mean compliance on day 3, but thereafter the difference was reversed. Colloid intake, however, unfavourably affected lung function, total colloid intake being negatively correlated with both the area under the curve of birth-adjusted FRC (P=0.003) and compliance (P=0.001).
Conclusion: We conclude that early fluid restriction appears to have very little impact on perinatal lung function.