Objective: The goal was to analyze the relationship between changes in serum sodium levels during the first month of life and impaired functional outcomes at 2 years of age for very preterm infants.
Methods: All very preterm infants who were born at <33 weeks of gestation between January 1, 2003, and July 31, 2004, were hospitalized in the NICU, and survived to discharge were included in this study. Changes in serum sodium levels were measured, and infants were evaluated at corrected age of 2 years.
Results: The analysis involved 237 patients, for whom 3927 serum sodium determinations were performed during the first month of life. We defined 3 tertiles of changes in serum sodium levels. A total of 84 infants demonstrated small changes in serum sodium levels (<8 mEq/ L), 86 demonstrated large changes (8 -13 mEq/L), and 67 demonstrated very large changes (13 mEq/L). The reference group was represented by the first tertile. At 2 years of age, large and very large changes in serum sodium levels were significantly associated with risk of impaired functional outcomes, after adjustment for gestational age and perinatal and neonatal hospitalization characteristics (large changes: odds ratio: 3.5 [95% confidence interval: 1.1-11.8]; P = .04; very large changes: odds ratio: 5.1 [95% confidence interval: 1.3-13.6]; P = .02).
Conclusions: Although large and very large changes in serum sodium levels may simply reflect the severity of illness and/or the quality of care, a causal relationship with outcomes cannot be excluded. Cautious fluid and electrolyte management is recommended for very premature infants.