Echocardiographic effects of high and low volumes of maintenance fluid administration in low-birth-weight infants

Abstract

Serial M-mode echocardiograms were performed during days 3-20 of life in 73 low-birth-weight infants randomized on day 3 of life to 'high' (n = 40) and 'low' (n = 33) fluid regimens designed to give significantly different maintenance fluid intakes (172 +/- 25 and 121 +/- 13 ml/kg/day, mean +/- SD, respectively, p less than 0.001). The groups were comparable with respect to birth weight, gestational age, incidence of respiratory distress syndrome and mean number of serial echocardiograms performed per infant (9 and 9), respectively. Calorie and electrolyte intake were not controlled in the study design. Cumulative echocardiographic data were compared by unpaired t test. Left ventricular end diastolic diameter, right ventricular end diastolic diameter, septal excursion, left ventricular posterior wall excursion and left atrial to aortic root ratio were slightly but statistically significantly larger in the 'high' fluid group. Comparison of regression coefficients showed that left ventricular end-diastolic diameter tended to rise with postnatal age in the 'high' group and fall with postnatal age in the 'low' group. Left atrial to aortic root ratio tended to fall with postnatal age in the 'low' group relative to the 'high' group. These differences in echocardiographic measurements may reflect adaptation of the circulation to a degree of chronic volume overload in low-birth-weight infants.