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Electrolyte abnormalities in preterm neonates receiving electrolyte-free versus standard parenteral nutrition solutions: a two-centre retrospective study

Presented at the Neonatal Society 2017 Autumn Meeting.

Lee KY1, Mulla S2, Mardare R1, Hoodbhoy S1, Paul P2

1 Rosie Maternity Unit, Cambridge University Hospitals NHS Foundation Trust, Cambridge, UK
2 Neonatal Unit, Norfolk and Norwich University Hospitals NHS Foundation Trust, Norwich, UK

Background: There is current debate as to whether “electrolyte-free” parenteral nutrition (PN) solutions should be used for preterm infants during the first days of PN provision. Electrolyte-free PN does not contain Na+, K+, Cl, Ca2+, PO4, or Mg2+ and is preferred by some to restrict early Na+ intakes during the postnatal transitional period of extracellular fluid contraction and physiological weight loss. Yet sufficient early electrolyte supplementation is needed for adequate protein accretion when delivering higher amounts of amino acids[1]. In the East of England region some centres routinely use electrolyte-free PN while others use electrolyte-supplemented PN from birth. We compared the incidence of electrolyte disturbances of Na+, K+, Ca2+ and PO4 in preterm infants according to whether they received electrolyte-free PN or standard (electrolyte-supplemented) PN. Our hypothesis was that there would be no difference in incidences of hypernatraemia or hyperkalaemia during the first postnatal week.

Methods: Retrospective cohort study done at two UK tertiary-level neonatal units. Centre 1 routinely uses electrolyte-free PN in the first 48-72h after birth, while centre 2 routinely uses standard PN. We included preterm neonates <36 weeks’ gestational age who started on PN within 24 hours of birth within two discrete 6-month epochs. Outcome measures were first-week peak and nadir serum Na+, K+, Ca2+, and PO4 concentrations; and proportions with hypernatraemia (Na+ >150 mmol/L), hyponatraemia (Na+ <130 mmol/L), hyperkalaemia (K+>7.0 mmol/L), hypokalaemia (K+ <3.5 mmol/L), hypercalcaemia (Ca2+ >3.0 mmol/L), and hypophosphatemia (PO4 <1.5 mmol/L).

Results: A total of 81 patients (n=43 centre 1; n=38 centre 2) were included. Median (IQR) gestational age was 27.1 (25.7-29.2) weeks and mean (SD) birth weight was 986 (321) g, with no significant demographic differences between centres. More babies who received electrolyte-free PN in the first week (centre 1) had hyperkalaemia (12% vs 0%, p=0.03), hyponatraemia (28% vs 3%, p=0.001), hypokalaemia, (77% vs 40%, p=0.001), and hypophosphataemia (81% vs 37%, p=0.002) compared with standard PN babies (centre 2). Nadir Na+, K+, and PO4 concentrations were also significantly lower in babies who received electrolyte-free PN. Comparative rates of hypernatraemia (16% vs 34%, p=0.06), hypercalcaemia (18% vs 21%, p=0.8), and median peak Na+ (147 mmol/L vs 148 mmol/L, p=0.6) and Ca2+ (2.9 mmol/L vs 2.8 mmol/L, p=0.3) concentrations were similar.

Conclusion: Use of electrolyte-free PN within the first 2-3 days after birth was not associated with significantly lower rates of first-week hypernatraemia, but was instead associated with higher rates of hyponatraemia, hyperkalaemia, hypokalaemia and hypophosphataemia. Routine use of electrolyte-free PN solutions may not be optimal for preterm neonates in the first week. A formal randomised controlled trial is now indicated to address the issue.

Corresponding author: kyl@doctors.org.uk

References
1. Moltu SJ, et al. Clin Nutr 2013;32:207–12

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