Increased risk of cardiac death with cumulative exposure to fluid overload and dialysate sodium ≤ 138 mmol/L in hemodialysis patients

Background Fluid overload (FO) is an established risk factor for mortality in hemodialysis patients, who face higher cardiovascular mortality risk than the general population. Despite the known impact of FO on cardiovascular outcomes, the effects of cumulative FO exposure, dialysate sodium ≤ 138 mmol/L, and specific cardiac deaths remain unclear. This study aimed to assess these relationships in a large cohort of hemodialysis patients. Methods This historical cohort study included 68 196 hemodialysis patients from the NephroCare network with data from 2010 to 2019. Eligible patients had valid bioimpedance, plasma and dialysate sodium measurements within 90 days of starting hemodialysis. FO was defined as > 7% relative fluid overload, as assessed by bioimpedance spectroscopy. Cause-specific Cox proportional hazards models were used to evaluate the impact of these exposures on different cardiac endpoints, including death from heart failure, sudden cardiac death, and fatal myocardial infarction. Results In 68 196 patients, a total of 2 123 957 patient-months were analyzed. Compared to patients with no prior exposure (zero month cumulative past exposure time), increasing cumulative exposure to fluid overload (measured in months) significantly increased the risk of death from heart failure (HR peaking at 4.4, 95%CI: 3.4- 5.6), sudden cardiac death (HR peaking at 4.0, 95%CI: 3.1- 5.2), and fatal myocardial infarction (HR peaking at 3.3, 95%CI: 2.5–4.4). Cumulative exposure (in month) to Dialysate sodium ≤ 138 mmol/L was associated with an elevated risk of death from heart failure (HR peaking at 6.0, 95%CI: 1.9–18.3) and a moderate increase in sudden cardiac death (HR peaking at 2.7, 95%CI: 1.3–5.6). The risk of all-cause mortality was consistently higher in patients exposed to fluid overload (HR peaking at 3.4, 95%CI: 3.1–3.8) and those exposed to dialysate sodium ≤ 138 mmol/L (HR peaking at 2.0, 95%CI: 1.3–3.1). Conclusion Cumulative FO and dialysate sodium ≤ 138 mmol/L significantly increase cardiac death risk in hemodialysis patients, particularly from heart failure. Stringent fluid management and careful consideration of dialysate sodium prescription is crucial to reduce cardiovascular mortality.