A model of systolic blood pressure during the course of dialysis and clinical factors associated with various blood pressure behaviors

Background: Little is known about the behavior of systolic blood pressure (SBP) during hemodialysis.

Study design: Prospective observational cohort.

Setting & participants: 218 prevalent hemodialysis patients treated at 5 participating DaVita Dialysis units.

Predictors: Clinical variables that may plausibly influence the behavior of SBP during the course of hemodialysis sessions.

Outcomes: SBP at the onset of dialysis and its rate of change (slope) over the first 25% and latter 75% of the treatment interval.

Measurements: SBPs measured and recorded per clinical protocol during the first 30 days of study (median, 11 treatments/patient; SBP measured at 30-minute intervals).

Results: Intradialytic SBP behavior is well characterized by a 2-slope linear spline model, which describes SBP at time zero, a rapid decrease during the first 25% of the treatment (early), and a more gradual decrease thereafter (late). Higher ultrafiltration volume and rate each are associated with greater SBP at the start of dialysis and more rapid early and late SBP decreases. Use of a higher number of antihypertensives was associated with greater time zero SBP. Calcium acetate use is associated with high SBP at the start of hemodialysis and a more pronounced decrease during the early and late parts of treatment.

Limitations: Over-representation of blacks and patients with congestive heart failure; observational design; use of clinically measured blood pressures.

Conclusions: Intradialytic SBP can be characterized using 3 parameters: value at the start of dialysis and slopes during the first 25% and latter 75% of treatment. Practices related to fluid management, antihypertensive use, and metabolic bone disease control are associated with blood pressure behavior during dialysis. Further work is needed to confirm findings and measure associations between various aspects of intradialytic blood pressure behavior and clinical outcomes.