Prevalence and Prognostic Significance of Chloride Levels in Patients with Acute Medical Conditions: A Prospective Observational Study

Chloride plays a considerable role in physiology. This study aimed to assess the association between serum chloride and prognosis in the population of adults with acute medical conditions. A prospective cohort study was conducted in an acute medical unit. Chloride levels at admission were the main exposure factor, categorized into hypochloremia, normochloremia, and hyperchloremia. The outcomes were in-hospital mortality and length of hospital stay (LOHS). A total of 798 patients were included. The mean age was 57.3 ± 18.3 years. The prevalence of dyschloremia was 40.9%. Restricted cubic splines revealed a linear association between hypochloremia and in-hospital mortality, as well as between hypochloremia and LOHS. After adjusting for age, sex, heart failure, diabetes, sodium, bicarbonates, creatinine, and diuretic use, hypochloremia was significantly associated with in-hospital mortality (OR = 2.23; 95% CI: 1.29, 3.86, <i>p</i> = 0.006), but not hyperchloremia (<i>p</i> = 0.57). Similarly, it was associated with a longer LOHS (β = 2.19; 95% CI: 0.01, 4.39, <i>p</i> = 0.05), but not hyperchloremia (<i>p</i> = 0.8). The interaction between chloride and sodium levels was not significant (<i>p</i> = 0.61). Subgroup analysis showed that the effect of hypochloremia on in-hospital mortality was consistent across subgroups. The prevalence of dyschloremia in this study was high at 40.9%. Hypochloremia increased the risk of in-hospital mortality and extended the LOHS. Differentiating the effects of chloride levels from those of sodium can enhance clinical risk stratification and enable a more targeted management approach for acutely ill patients. Recognizing this distinction is essential for optimizing prognostic assessment and tailoring treatment strategies accordingly.