Association of intradialytic blood pressure variability with increased all-cause and cardiovascular mortality in patients treated with long-term hemodialysis

Background: Blood pressure is known to fluctuate widely during hemodialysis; however, little is known about the association between intradialytic blood pressure variability and outcomes. Study Design: Retrospective observational cohort. Setting & Participants: A random sample of 6,393 adult, thrice-weekly, in-center, maintenance hemodialysis patients dialyzing at 1,026 dialysis units within a single large dialysis organization. Predictor: Intradialytic systolic blood pressure (SBP) variability. This was calculated using a mixed linear effects model. Peridialytic SBP phenomena were defined as starting SBP (regression intercept), systematic change in SBP over the course of dialysis (2 regression slopes), and random intradialytic SBP variability (absolute regression residual). Outcomes: All-cause and cardiovascular mortality. Measurements: SBPs (n = 631,922) measured during hemodialysis treatments (n = 78,961) during the first 30 days in the study. Outcome data were obtained from the dialysis unit electronic medical record and were considered beginning on day 31. Results: High (ie, greater than the median) versus low SBP variability was associated with greater risk of all-cause mortality (adjusted HR, 1.26; 95% CI, 1.08-1.47). The association between high SBP variability and cardiovascular mortality was even more potent (adjusted HR, 1.32; 95% CI, 1.01-1.72). A dose-response trend was observed across quartiles of SBP variability for both all-cause (P = 0.001) and cardiovascular (P = 0.04) mortality. Limitations: Inclusion of patients from a single large dialysis organization, over-representation of African Americans and patients with diabetes and heart failure, and lack of standardized SBP measurements. Conclusions: Greater intradialytic SBP variability is associated independently with increased all-cause and cardiovascular mortality. Further prospective studies are needed to confirm findings and identify means of reducing SBP variability to facilitate randomized study.