Excessive sodium supplementation but not fluid load is correlated with overall morbidity in extremely low birth weight infants.

Objectives: Sodium homeostasis in extremely low birth weight (ELBW) infants is critical. While a lack of sodium delays growth, excessive supplementation increases morbidity. Methods: We performed a single-center retrospective study on sodium and fluid management during the first 2 weeks of live including all ELBW infants born between June 1, 2017 and May 31, 2019. Results: Forty-seven patients (median GA 26 + 6 weeks, median BW 845 g) were included. Mean sodium intake was above the ESPGHAN recommendation, 4.58 mmol/kg/day during the first 2 days and 1.99 mmol/kg/day during the following period. Incidence of PDA, IVH, and ROP was directly associated with sodium intake (OR 1.6, 1.3, and 1.4, respectively), but not with fluid supplementation. No association to BPD was found. The most important source for inadvertent sodium intake were 0.9% saline given by arterial lines. Sodium supplementation did not correlate directly with serum sodium levels, but a linear regression model combining sodium intake and fluid supplementation was able to predict serum sodium changes 24-48 h in advance (correlation coefficient of 0.294, Conclusions: Sodium application substantially exceeded ESPGHAN recommendations in ELBW infants. An excess in sodium was associated with an overall increased morbidity, justifying increased efforts to identify inadvertent sodium sources in these patients with the aim to decrease sodium excess.