Mortality Trends Involving Cardiac Arrest and Fluid, Electrolyte, and Acid–Base Disorders in U.S. Adults, 2004–2024

Background/Objectives: Cardiac arrest and fluid, electrolyte, and acid–base disorders frequently coexist in critically ill patients and are associated with poor clinical outcomes. However, long-term population-level trends in mortality involving both conditions remain poorly characterized. This study evaluated temporal trends and demographic disparities in mortality involving cardiac arrest and fluid, electrolyte, and acid–base disorders among U.S. adults from 2004 to 2024. Methods: We conducted a retrospective population-based study using the Centers for Disease Control and Prevention Wide-Ranging Online Data for Epidemiologic Research (CDC WONDER) Multiple Cause of Death database. Adults aged ≥25 years with cardiac arrest (ICD-10: I46) and fluid, electrolyte, and acid–base disorders (ICD-10: E87) listed anywhere on the same death certificate between 2004 and 2024 were included. Age-adjusted mortality rates (AAMRs) were calculated using the 2000 U.S. standard population. Joinpoint regression was used to estimate annual percent change (APC) and average annual percent change (AAPC), with analyses stratified by demographic and geographic characteristics. Results: A total of 152,937 deaths involved both cardiac arrest and fluid, electrolyte, and acid–base disorders during the study period. The AAMR nearly doubled, increasing from 2.06 (95% CI, 2.00–2.13) in 2004 to 4.08 (95% CI, 4.00–4.16) in 2024, corresponding to an overall AAPC of 3.42% (95% CI, 2.58–4.26; p < 0.001). Mortality remained consistently higher among males, adults aged ≥65 years, and non-Hispanic Black individuals, with significant increases observed across all demographic groups. The West demonstrated the highest regional mortality burden (AAPC, 3.75%; p < 0.001). Urbanization analyses (2004–2020) showed higher mortality in non-metropolitan than metropolitan areas (AAPCs, 5.36% vs. 4.13%; both p < 0.001). Mortality increased through 2021 before declining modestly during 2021–2024. Conclusions: Mortality involving both cardiac arrest and fluid, electrolyte, and acid–base disorders increased substantially in the United States over the past two decades, with persistent disparities in age, sex, race/ethnicity, and geography. These findings identify populations at increased risk and support targeted public health strategies, equitable healthcare access, and improved recognition and management of metabolic disturbances in patients at risk for cardiac arrest.