RESUMO
OBJECTIVE: The objective of this study is to discern patterns of serum sodium in a broad cohort of extremely low birth weight (ELBW) infants and associate those patterns with hospital outcomes. STUDY DESIGN: Retrospective cohort study of ELBW infants from 323 neonatal intensive care units (NICUs) discharged from 2004 to 2014. We included patients who survived at least 7 days and had daily sodium levels available, and categorized infants by their minimum and maximum sodium levels. RESULTS: We identified 26,871 infants of whom 12,428 met inclusion criteria. Only 1964 (15.8%) maintained eunatremia for the first week. We found most dysnatremias to be associated with increased overall mortality compared with eunatremic patients including moderate hyponatremia (12.9% vs. 8.6%, p < 0.05) and severe hypernatremia (34.8% vs. 8.6%, p < 0.001). Most of these associations were maintained after regression modeling for mortality. CONCLUSION: Sodium fluctuations occurring within the first week of life are associated with increased mortality.