Hypernatremia is associated with mortality in severe elderly sepsis patients
Authors: Liu Xu , Hong Yalin , Li Bingchen , Xu You , Wang Nianci , Liu Han , Liu Ying 
Published: November 2024

Objective
To explore the relationship between hypernatremia and 28-day mortality in elderly sepsis patients.

Methods
A total of 179 elderly patients (age ≥65 years) with elevated serum sodium admitted to the Department of Critical Care Medicine of Nanjing Hospital affiliated with Nanjing Medical University from September 2021 to September 2022 were included in this retrospective observational study. The clinical data of all patients were collected, and the patients were divided into septic group and nonseptic groups according to the Sepsis 3.0 definition. The clinical features, acute physiological and chronic health II score (APACHE II score), mechanical ventilation time, serum sodium value and duration of serum sodium elevation were compared between the two groups. ROC curves were drawn to evaluate the predictive value of each index on the prognosis of sepsis patients, and Kaplan‒Meier survival analysis was carried out on patients with different serum sodium peaks.

Results
(1) The changes in serum sodium within 48 hours after admission in the sepsis group were small and statistically significant compared with those in the nonsepsis group (P = 0.039); however, the serum sodium elevation duration was longer (P = 0.018). (2) Compared with nonseptic patients, the 7-day mortality of septic patients was higher (15.8 vs. 7.7, P<0.001). The 28-day mortality of septic patients was higher than that of nonseptic patients, but there was no significant difference between the two groups (P = 0.086). (3) The serum sodium level in the sepsis group was higher than that in the nonsepsis group on the 1st, 3rd, 5th and 7th days (P<0.001). There was no significant difference in mechanical ventilation time or duration of stay in the ICU between the two groups. (4) The ROC curve analysis showed that the peak value of serum sodium had predictive value for the prognosis severity of elderly patients with sepsis. The area under the curve (AUC) was 0.753, the 95% confidence interval (95% CI) was 0.639~0.867, and the best cut-off value was 154.9 mmol/L. (5) According to the best cut-off value of the serum sodium peak, the septic patients were divided into two groups: the peak value of serum sodium was ≥154.9 mmol/L (group A), and the peak value of serum sodium was <154.9 mmol/L (group B). Among them, the case fatality rate was higher at 7 days and 28 days when the peak value of serum sodium was ≥154.9 mmol/L (group A) (22.0% vs. 8.6%); the χ2 value was 35.379, P<0.05; 75.6% vs. 37.1%, χ2 = 14.21, P = 0.003). There was no significant difference in mechanical ventilation time or duration of stay in the ICU between the two groups. (6) Kaplan‒Meier survival analysis showed that the median survival time of patients with a serum sodium peak ≥154.9 mmol/L (group A) was significantly shorter than that of patients with a serum sodium peak < 154.9 mmol/L (group B) (16.7±1.4 d vs. 24.8±1.2 d, P <0.05).

Conclusions
The serum sodium increase in elderly sepsis patients lasts for a long time, and the serum sodium fluctuation is relatively small. The serum sodium peak value has predictive value for 28-day mortality.