The relationship between hyponatremia and mortality in patients receiving nutrition support.

Background & Aims: Hyponatremia is frequently seen in clinical practice, but most cases are mild and asymptomatic and therefore often go unmanaged. In recent years, it has been reported that the onset or improvement of hyponatremia, even in mild cases, has an impact on mortality and that hyponatremia is directly related to increased mortality. In addition, it has been reported that patients with Nutrition Support Team (NST) are more likely to develop hyponatremia than the general hospitalized population. This study aimed to determine the association between the development and amelioration of hyponatremia and mortality in patients with NST.

Methods: A total of 1553 patients who underwent initial NST intervention from April 1, 2013 to March 31, 2017 were included. Hyponatremia was defined as hyponatremia <138 mEq/L and normal serum sodium level was defined as 138-145 mEq/L based on the laboratory reference values of our hospital. Hyponatremia was defined as L and normal sodium as N. Based on sodium levels at the start and end of the intervention, the population was classified into four groups, L-L, N-L, L-N, and N-N (sodium level at the start of intervention - sodium level at the end of intervention), and the 5-year survival rate curve and hazard ratio for death for each group were calculated. Multivariate analysis adjusted for age, sex, and body mass index.

Results: Analysis revealed that the L-L group with persistent hyponatremia (hazard ratio (HR) = 3.47, vs N-N, p < 0.0001) had the highest risk of death, while the L-N group with improved hyponatremia (HR = 2.19, vs N-N, p < 0.0001) had a significantly lower risk than the L-L group. The risk of death was also increased in the L-N and N-L groups (HR = 1.97, vs. N-N, p << 0.0001) after even one episode of hyponatremia compared to the N-N group.

Conclusion: The results of this study indicate that hyponatremia is associated with poor survival in patients undergoing NST. Future randomized controlled trials are needed to determine whether correction of hyponatremia leads to improved survival in patients undergoing NST to clarify the need for prevention and management of hyponatremia.