Hyponatremia and mortality in patients undergoing maintenance hemodialysis: Systematic review and meta‐analysis

Introduction This systematic review and meta‐analysis examined the relationship between hyponatremia and worse outcomes in patients undergoing maintenance hemodialysis. Methods The MEDLINE, EMBASE, CENTRAL, and Web of Science databases were used to search for relevant articles. The target population was patients on maintenance hemodialysis (those undergoing hemodialysis for ≥60 days). The defined outcomes were death, cardiovascular disease, cognitive decline, and falls. Meta‐analysis was performed with a random‐effects model of pairwise comparisons of normonatremia and hyponatremia defined for each study, 1‐mmol/L increment of sodium analysis, and dose–response analysis using the sodium concentration defined for each study. This study was registered with PROSPERO (registration number CRD42018087667). Results Thirteen articles were included. The pairwise analysis revealed that the hazard ratio for all‐cause mortality was 1.45 (95% confidence interval, 1.31–1.61). The analysis of 1‐mmol/L increment of sodium included six studies with a hazard ratio for all‐cause mortality of 0.94 (95% confidence interval, 0.91–0.97) for each 1‐mmol/L increase in the serum sodium concentration. In the dose–response analysis, assuming a linear relationship, a sodium increment of 1 mmol/L revealed a hazard ratio for all‐cause mortality of 0.97 (95% confidence interval, 0.96–0.98). Other outcomes could not be integrated. Conclusions Hyponatremia is associated with all‐cause mortality in patients undergoing maintenance hemodialysis. Healthcare providers should pay special attention to even the slightest indication of hyponatremia.