Neonatal body water turnover: a putative index of perinatal morbidity

The water metabolism of 46 newborn babies was determined during a 10 day period by means of an isotope dilution technique, and correlations were sought with the clinical assessment of the babies by multiple obstetric and pediatric clinical criteria. The babies, 48 to 72 hours of age, were given a single oral dose (2 ml/kg) of deuterated water (D2O), a nonradioactive tracer, and the urinary excretion rate was followed by means of infrared spectrophotometry. After a period of equilibration of the D2O with body water (20 hours), the rate of D2O clearance was found to be a single exponential decay process, thus allowing the fraction of total body water lost each hour (the rate constant) to be calculated for each baby. The median values of the rate constants X 10(4)(h-1) for 14 growth-retarded babies ws 104 (98% confidence limits, 97.8 to 122) compared with 76.3 (67.0 to 80.2) for 16 normal mature babies and 82.1 (73.4 to 90.6) for 16 normal premature babies. These data indicate that, compared with normal mature or normal premature babies, growth-retarded infants have a significantly (P less than 0.05) faster turnover of water during the first 10 days of postnatal life. Since there was little overlap in results between the normally grown and the retarded infants, the measurement of water turnover may provide a useful index of perinatal morbidity.