Predialysis systolic BP variability and outcomes in hemodialysis patients

Abstract

BP variability (BPV) is an important predictor of outcomes in the general population, but its association with clinical outcomes in hemodialysis patients is not clear. We identified 11,291 patients starting dialysis in 2003-2008 and followed them through December 31, 2008 (median=22 months). Predialysis systolic BPV was assessed over monthly intervals. Outcomes included factors associated with BPV, mortality (all-cause and cardiovascular), and first cardiovascular event (cardiovascular death or hospitalization). Patients' mean age was 62 years, 55% of patients were men, and 58% of patients were white. Modifiable factors associated with higher BPV included obesity, higher calcium-phosphate product levels, and lower hemoglobin concentration; factors associated with lower BPV included greater fluid removal, achievement of prescribed dry weight during dialysis, higher hemoglobin concentration, and antihypertensive regimens without β-blockers or renin-angiotensin system blocking agents. In total, 3200 deaths occurred, including 1592 cardiovascular deaths. After adjustment for demographics, comorbidities, and clinical factors, higher predialysis BPV was associated with increased risk of all-cause mortality (hazard ratio [HR], 1.18; 95% confidence interval [95% CI] per 1 SD increase in BPV, 1.13 to 1.22), cardiovascular mortality (HR, 1.18; 95% CI, 1.12 to 1.24), and first cardiovascular event (HR, 1.11; 95% CI, 1.07 to 1.15). Results were similar when BPV was categorized in tertiles and patients were stratified by baseline systolic BP. In summary, predialysis systolic BPV is an important, potentially modifiable risk factor for death and cardiovascular outcomes in incident hemodialysis patients. Studies of BP management in dialysis patients should focus on both absolute BP and BPV.

Figure 1.

Graphical display of the mid 95% of systolic BP values for a hypothetical individual with a given predialysis systolic BP. (A) An individual with systolic BP of 100 mmHg. (B) An individual with systolic BP of 140 mmHg. (C) An individual with systolic BP of 180 mmHg. In each panel, the midpoint represents the average BP, and the bars represent the variability of systolic BP at a given percentile of the BPV metric (5th, 25th, 75th, and 95th percentiles).

Figure 2.

Overview of cohort formation. Selection of the final cohort of 11,291 incident in-center hemodialysis patients from the initial cohort of all patients starting dialysis at Dialysis Clinic, Inc. (DCI) outpatient dialysis clinics from 2003 to 2008.