Factors Associated With Intradialytic Systolic Blood Pressure Variability

Background: Although blood pressure lability during hemodialysis has long been recognized, little is known about factors that promote nonsystematic intradialytic blood pressure variability. Study Design: Prospective observational cohort. Setting & Participants: Random cluster sample of 218 prevalent hemodialysis patients treated at 5 participating DaVita Dialysis units. Predictors: Clinical variables that may plausibly influence intradialytic systolic blood pressure (SBP) variability. Outcomes: SBP variability as described by: (1) the deviation of SBP from its anticipated course (primary metric) and (2) the absolute value of the difference between successive SBP measurements (secondary metric). Measurements: SBPs measured and recorded (n = 19,170) per clinical protocol during hemodialysis treatments (n = 2,422; median 11 per patient) occurring in the first 30 days of study. Predictors were assessed through standardized interview, examination, and medical record abstraction. Results: Results were similar when SBP variability was considered in terms of the primary and secondary metrics. Older age and longer dialysis vintage were associated with increased SBP variability, whereas other patient characteristics were not. Greater fluid removal during hemodialysis (whether considered as volume or rate either absolute or relative to total-body water) was associated with greater SBP variability independently of its effects on net pre- to posttreatment SBP reduction. Neither number nor dialyzability of antihypertensive medications nor individual classes of agents showed an association with SBP variability. Limitations: Over-representation of African Americans and patients with congestive heart failure; observational design; use of clinically measured blood pressures; absence of medication adherence confirmation. Conclusions: Increased intradialytic SBP variability is associated with greater dialytic fluid removal and rate, as well as demographic characteristics, such as older age and dialysis vintage. Further work is needed to confirm these findings and measure associations between SBP variability and clinical outcomes. Am J Kidney Dis. 59(3): 409-418. (C) 2012 by the National Kidney Foundation, Inc.