Association Between Serum Sodium and Long-Term Mortality in Critically Ill Patients with Comorbid Chronic Obstructive Pulmonary Disease: Analysis from the MIMIC-IV Database

Abstract

Liming Fan,1,* Deyang Sun,1,* Jia Yang,1 Xiawei Shi,1 Fenglin Shen,1 Ke Chen,1 Junchao Yang1,2 1The First Clinical College, Zhejiang Chinese Medical University, Hangzhou, People’s Republic of China; 2Department of Pulmonary and Critical Care Medicine, The First Affiliated Hospital of Zhejiang Chinese Medical University, Hangzhou, People’s Republic of China*These authors contributed equally to this workCorrespondence: Junchao Yang, Department of Pulmonary and Critical Care Medicine, The First Affiliated Hospital of Zhejiang Chinese Medical University, 54 Youdian Road, Shangcheng District, Hangzhou City, Zhejiang Province, People’s Republic of China, Tel [phone], Email [email protected]: The purpose of our study was to investigate the relationship between serum sodium levels and 1-year and 3-year mortality in critically ill patients with comorbid chronic obstructive pulmonary disease using real-world data.Methods: The data of this study were collected from the Medical Information Mart for Intensive Care-IV (MIMIC-IV) database. First of all, we used the Kaplan–Meier curves and multivariable Cox regression analyses to measure the relationship between serum sodium levels and 1-year and 3-year mortality for critically ill patients with comorbid COPD. Next, a restricted cubic spline was used to analyze non-parametrically the relationship between mortality and serum sodium as a continuous variable. In addition, we also analyzed the mortality of different subgroups.Results: A total of 5540 eligible subjects were extracted. Compared to normal serum sodium levels, adjusted multivariable Cox regression analysis confirmed that hyponatremia and hypernatremia were still significantly associated with 1-year mortality (HR = 1.551, 95% CI = 1.333∼ 1.805, P< 0.001; HR = 1.683, 95% CI = 1.317∼ 2.151, P< 0.001, respectively) and 3-year mortality (HR = 1.507, 95% CI = 1.302∼ 1.744, P< 0.001; HR = 1.612, 95% CI = 1.269∼ 2.048, P< 0.001, respectively). In patients with or without adjustment variables, there was an obvious U-shaped non-linear relationship between serum sodium levels and 1-year and 3-year mortality with a reference level of 139 mmol/L, which indicated that patients in both hyponatremia and hypernatremia had higher mortality than normal serum sodium levels.Conclusion: This study showed that both hyponatremia and hypernatremia were related to increased 1-year and 3-year mortality in critically ill patients with comorbid COPD, which provides a new reference for the control strategy of correcting serum sodium levels.Keywords: serum sodium, chronic obstructive pulmonary disease, intensive care unit, MIMIC-IV

Keywords

• serum sodium
• chronic obstructive pulmonary disease
• intensive care unit
• mimic-iv