Unlocking the secrets of electrolytes: the prognostic value of sodium-to-chloride ratio in intensive care unit patients with myocardial infarction

Background Electrolyte imbalances are commonly observed in individuals diagnosed with myocardial infarction (MI). The levels of serum sodium have been linked to unfavorable outcomes in relation to MI. Additionally, there exists a correlation between serum sodium and serum chloride, although the combined influence of these electrolytes on the prognosis of MI patients has not been extensively studied. Consequently, our study aimed to examine whether an autonomous association exists between the sodium-to-chloride (Na/Cl) ratio and mortality rates during hospitalization among patients admitted to intensive care unit (ICU) with MI. Methods A retrospective cohort study analysis was conducted on the Na/Cl ratio within the ICU from 2008 to 2019. Patients diagnosed with MI were divided into two groups based on a predetermined cutoff value for the Na/Cl ratio. Various statistical models, including the Cox proportional hazard model, generalized additive model, and two-piecewise linear regression model, were employed to assess the relationship between the initial Na/Cl ratio upon admission and the likelihood of in-hospital mortality while accounting for other relevant covariates. Results After adjusting for all other factors, the study revealed that the Na/Cl ratio exhibited an independent association with in-hospital mortality (HR = 1.28; 95% CI: 1.11-1.47, P < 0.001). Further analysis indicated a nonlinear relationship between the Na/Cl ratio and in-hospital mortality among patients with MI, with a threshold at approximately 1.37. Specifically, if the Na/Cl ratio exceeded 1.37, there was a significant and progressively increasing likelihood of mortality during hospitalization (HR = 1.46; 95% CI: 1.20-1.77). Conclusion The in-hospital mortality of patients admitted to ICU with MI is predicted independently by the ratio of sodium to chloride (Na/Cl). A curvilinear correlation was observed between the Na/Cl ratio and in-hospital mortality, with a statistically significant threshold identified at 1.37.