Does parenteral nutrition influence electrolyte and fluid balance in preterm infants in the first days after birth?

Background: New national guidelines recommend more restricted fluid intake and early initiation of total parenteral nutrition (TPN) in very preterm infants. The aim was study the effect of these guidelines on serum sodium and potassium levels and fluid balance in the first three days after birth.

Methods: Two cohorts of infants <28 weeks gestational age, born at the Leiden University Medical Center in the Netherlands, were compared retrospectively before (2002-2004, late-TPN) and after (2006-2007, early-TPN) introduction of the new Dutch guideline. Outcome measures were serum sodium and potassium levels, diuresis, and changes in body weight in the first three postnatal days.

Results: In the first three postnatal days no differences between late-TPN (N = 70) and early-TPN cohort (N = 73) in mean (SD) serum sodium (141.1 (3.8) vs 141.0 (3.7) mmol/l) or potassium (4.3 (0.5) vs 4.3 (0.5) mmol/l) were found, but in the early-TPN cohort diuresis (4.5 (1.6) vs 3.2 (1.4) ml/kg/h) and loss of body weight were decreased (-6.0% (7.7) vs -0.8% (8.0)).

Conclusions: Initiation of TPN immediately after birth and restricted fluid intake in very preterm infants do not seem to influence serum sodium and potassium levels in first three postnatal days. Further research is needed to see if a decreased diuresis and loss of body weight in the first days is the result of a delayed postnatal adaptation or better energy balance.