Variability in serum sodium concentration and its prognostic significance in severe burn injuries: A retrospective study

Dysnatremia is a common electrolyte disturbance in severe burn patients and may significantly impact prognosis. This study investigated the association between serum sodium variability and mortality in adults with extensive burn injuries. In this retrospective cross-sectional study, 300 adult burn patients with burns involving more than 20% of total body surface area (TBSA) and at least second-degree depth were included. Patients were admitted to Velayat Burn and Plastic Surgery Center (Rasht, Iran) between March 2018 and March 2020. Serum sodium was measured daily during hospitalization. Hypernatremia and hyponatremia were defined as serum sodium >145 mmol/L and <135 mmol/L, respectively. Sodium variability was quantified as the standard deviation (SD) of daily sodium measurements. Multivariate logistic regression was used to identify independent predictors of in-hospital mortality. Of the 300 patients (mean age: 47.5 ± 13.5 years; mean TBSA: 39.8 ± 21.9%), 21.3% of the patients had hypernatremia, and 33 (11%) developed hyponatremia. Overall mortality was 36.7%. Non-survivors had significantly higher mean serum sodium levels (143.2 ± 8.9 vs. 138.6 ± 3.0 mmol/L; P < 0.0001) and greater sodium variability. Multivariate analysis identified age (Odds ratio (OR): 1.15; P = 0.004), TBSA (OR: 1.24; P = 0.002), mechanical ventilation duration (OR: 1.38; P < 0.001), inhalation injury (OR: 23.5; P = 0.003), and sodium variability (OR: 1.12; P = 0.004) as independent predictors of mortality. Dysnatremia—particularly hypernatremia—and greater serum sodium variability are strongly associated with increased mortality in patients with severe burns. These findings underscore the prognostic importance of sodium monitoring and suggest that minimizing sodium fluctuations may improve outcomes in critically ill burn patients. Further prospective studies are warranted to validate these associations and inform clinical management strategies.