Acute increase in serum tonicity following exchange transfusion. Increased risk for the very low birthweight infant during the first 48 hours of life.

We analysed the data of difference in serum sodium (DIFNA) and glucose (DIFGLU) concentrations and difference in serum tonicity (DIFTON) following exchange transfusion (ET) with CPD blood during 122 consecutive procedures performed in 82 newborn infants. Mean (+/- SE) gestational age (GA) was 30.8 +/- 0.45 weeks, mean birthweight was 1,568.6 +/- 81.4 g. and mean age at time of ET (AGEH) was 60.6 +/- 4.3 h. Following the ET, mean serum sodium concentration increased in 110 cases, by 5.4 +/- 0.7 mmol/l, and the mean DIFTON rose by 14.6 +/- 1.46 mOsm/kg H2O. Mean DIFGLU rose in 11 cases by 3.8 +/- 0.3 mmol/l. Significant correlations were found between DIFNA and AGEH (p less than 0.02), and between DIFTON and AGEH (p less than 0.02). ET performed less than 48 h after birth produced higher DIFTON values than later transfusions (21.2 vs. 8.2 mOsm/kg H2O, p less than 0.001) particularly in the VLBW infants (31.1 in less than 28 weeks vs. 15.1 mOsm/kg H2O in greater than 28 weeks). VLBW neonates appear to be at greatest risk of developing extreme increments in serum tonicity following ET performed within the first 48 h of life.