Postnatal urinary conductance measurement in preterm infants

The aim of this study was to determine whether serial urinary conductance measurements can be used to estimate reliably the end of the transition period of negative sodium balance in preterm infants. The relationship between urine conductance, measured by a conductance meter, and urine sodium concentration was determined in 109 pooled samples of urine obtained from 14 preterm infants during the transitional period of fluid balance. It was shown by linear regression analysis that urine sodium concentration (mmol l(-1)) = 0.78 x urine conductance - 1.25. Urine sodium concentrations derived from the above formula were concordant with urine sodium measured directly when used to calculate daily sodium balance in all 14 infants.

Urine conductance can be accurately measured at the cotside by neonatal nurses and used to identify the timing of the postnatal transition from negative to positive sodium balance in preterm infants. These findings can help in making decisions on the introduction of postnatal sodium administration to preterm infants.