Abstract: Objective  To explore the risk factors of pre-dialysis chronic hyponatremia in maintenance hemodialysis (MHD) patients.  Methods  We retrospectively analyzed the 152 MHD patients treated in the Blood Purification Center of Peking University International Hospital from August 2017 to June 2020. Their blood sodium, glucose, albumin, alkaline phosphatase, and other laboratory results were measured before dialysis every 1-3 months, and the time-averaged values including time-averaged serum sodium (TASNa) were calculated. Bioimpedance analysis (BIA) was also measured every 1-3 months, and the indexes including overhydration (OH), extracellular water, intracellular water (ICW), and lean tissue index (LTI) were recorded. The patients were then divided into two groups based on the TASNa, hyponatremia (TASNa≤135mmol/L) and normonatremia (135＜ TASNa ＜145 mmol /L). The differences between the two groups were compared by independent sample t-test or chi square test, and the risk factors for pre-dialysis chronic hyponatremia were analyzed by binary logistic regression.  Results  The prevalence of hyponatremia based on TASNa was 23.7%, and the prevalence of hyponatremia adjusted by blood glucose was 9.9%. Compared with the normonatremia group, the hyponatremia group had a higher proportion of diabetes (c2=27.134, P＜0.001), and higher levels of clinic systolic blood pressure (t=2.175, P=0.031), blood glucose  (t=6.408, P＜0.001) and OH         (t=2.930,  P=0.004) in the hyponatremia group, while serum creatinine (t=-4.008, P＜0.001), blood urea nitrogen(t=-2.169, P=0.032), chloride (t=-7.898, P＜0.001), prealbumin (t=-3.692, P＜0.001), albumin (t=-2.170,   P=0.032), phosphorus (t=-2.476, P=0.014), uric acid (t=-2.168, P=0.032), effective plasma osmolality (t=        -3.737, P=0.001), ICW (t=-2.113, P=0.038) and LTI (t=-3.180, P=0.002) were lower in the hyponatremia group. Binary logistic regression showed that hyperglycemia (OR=1.409, 95% CI: 1.245～1.593, P＜0.001), elevated serum alkaline phosphatase (OR=1.010, 95% CI: 1.001～1.019, P=0.034) and decreased LTI (OR=0.809, 95% CI: 0.659-0.993, P=0.042) were the risk factors for pre-dialysis chronic hyponatremia in MHD patients.  Conclusion  pre-dialysis chronic hyponatremia is common in MHD patients. Hyperglycemia, elevated serum alkaline phosphatase and malnutrition are the risk factors for pre-dialysis chronic hyponatremia.

Key words: Maintenance hemodialysis, Chronic hyponatremia, Risk factor, Bioimpedance analysis