This study retrospectively reviewed 591 patients who were diagnosed of sepsis and admitted to the intensive care unit (ICU) of Beijing Friendship Hospital from January 2009 to December 2014. Patients who were hospitalized in ICU for less than 24 h, pregnant, and suffering from diseases causing elevated serum sodium were excluded. According to the concentration of serum sodium, the 591 patients were further divided into three groups: normal group, hyponatremia group and hypernatremia group (Figure 1).
Clinical data of patients were collected, including age, gender, BMI (Body Mass Index), body temperature, respiratory rate, heart rate, SBP (Systolic Blood Pressure), DBP (Diastolic Blood Pressure), pH, PaO2 (Arterial partial pressure of oxygen), PaCO2 (Arterial partial pressure of carbon dioxide), concentration of HCO3-, K+, Na+, Cl-, Ca2+, ALT (Alanine aminotransferase), AST (Aspartate aminotransferase), D-BIL (Direct bilirubin), T-BIL (Total bilirubin), albumin, hemoglobin, D-Dimer, lactic acid, CK (Creatine Kinase), CK-MB, UA (Uric Acid), UpH (Uric pH), BUN (Blood Urea Nitrogen), Creatinine , APACHE score, SOFA score and Glasgow score.
Previous history of nephropathy, diabetes, hyperlipidemia, hypertension, coronary heart disease, chronic heart failure, COPD (Chronic Obstructive Pulmonary Disease), cirrhosis, tumor, smoking and drinking were recorded. Infection site was also recorded, including lung, biliary tract, urinary system, skin and soft tissue, abdominal and pelvic cavity.
Organ dysfunctions including respiratory system dysfunction, circulatory system dysfunction, liver dysfunction, kidney dysfunction, and coagulation system dysfunction were recorded as well.
Normal serum Na+ ranged from 135 to 145 mmol/L. Hypernatremia was defined as the concentration of Na+ more than 145 mmol/L. Hyponatremia was defined as the concentration of Na+ less than 135 mmol/L.
Definition of sepsis was according to “Surviving Sepsis Campaign (2012)” as the presence of infection together with systemic manifestations.
Definition of AKI was referred to the diagnostic criteria of AKIN (Acute Kidney Injury Network) and KDGIO (the Kidney Disease Improving Global Outcomes)[12, 13].
Continuous variables were expressed as mean ± SD. Date with abnormal distribution were expressed as median (interquartile range). Chi-square test were used for comparison. Univariate analysis was performed first, followed by multivariate analysis for hypernatremia, AKI and death. The ROC (receiver operating characteristic) curve was used in analyzing predictive ability of Na+ for AKI and death. P<0.05 was regarded as significant difference.