Blood Pressure Before Initiation of Maintenance Dialysis and Subsequent Mortality

Abstract

Background: Mortality is extremely high immediately after the transition to dialysis therapy, but the association of blood pressure (BP) before dialysis therapy initiation with mortality after dialysis therapy initiation remains unknown.

Study design: Observational study.

Setting & participants: 17,729 US veterans transitioning to dialysis therapy in October 2007 to September 2011, with a median follow-up of 2.0 years.

Predictor: Systolic (SBP) and diastolic BP (DBP) averaged over the last 1-year predialysis transition period as 6 (<120 to ≥160mmHg in 10-mmHg increments) and 5 (<60 to ≥90mmHg in 10-mmHg increments) categories, respectively, and as continuous measures.

Outcomes & measurements: Postdialysis all-cause mortality, assessed over different follow-up periods (ie, <3, 3-<6, 6-<12, and ≥12 months after dialysis therapy initiation) using Cox regressions adjusted for demographics, comorbid conditions, medications, cardiovascular medication adherence, body mass index, estimated glomerular filtration rate, and type of vascular access.

Results: Mean predialysis SBP and DBP were 141.2±16.1 (SD) and 73.7±10.6mmHg, respectively. There was a reverse J-shaped association of SBP with all-cause mortality, with significantly higher mortality seen with SBP<140mmHg. Mortality risks associated with lower SBP were greatest in the first 3 months after dialysis therapy initiation, with multivariable-adjusted HRs of 2.40 (95% CI, 1.96-2.93), 1.99 (95% CI, 1.66-2.40), 1.35 (95% CI, 1.13-1.62), 0.98 (95% CI, 0.78-1.22), and 0.76 (95% CI, 0.57-1.00) for SBP <120, 120 to <130, 130 to <140, 150 to <160, and ≥160 (vs 140-<150) mmHg, respectively. No consistent association was observed between predialysis DBP and postdialysis mortality.

Limitations: Results cannot be inferred to show causality and may not be generalizable to women or the general US population.

Conclusions: Lower predialysis SBP is associated with higher all-cause mortality in the immediate postdialysis period. Predialysis DBP showed no consistent association with postdialysis mortality. Further studies are needed to clarify ideal predialysis SBP levels among incident dialysis patients as a potential means to improve the excessively high early dialysis mortality.

Keywords: Blood pressure (BP); chronic kidney disease (CKD); dialysis; dialysis initiation; diastolic BP (DBP); end-stage renal disease (ESRD); incident ESRD; mortality; reverse epidemiology; risk factor paradox; systolic BP (SBP); transition; transition of care.

Figure 1. Association of pre-dialysis SBP with all-cause mortality in the first 3 months after dialysis initiation

Solid and dashed lines represent hazard ratio and 95% CI, respectively. A hazard reference ratio of 1 (solid horizontal line) and a histogram of observed SBP values are overlaid. The x-axis shows SBP levels, trimmed at 0.5% and 99.5%. Model is adjusted for age, sex, race/ethnicity, marital status, comorbidities (cardiovascular disease, congestive heart failure, peripheral vascular disease, lung disease, diabetes mellitus, liver disease, and Charlson comorbidity index), BMI averaged over the one-year pre-dialysis period, eGFR slope, last eGFR before dialysis initiation, medications (ACEIs/ARBs, β-blockers, calcium channel blockers, vasodilators, diuretics, statins, and ESAs), cardiovascular medication adherence, and type of vascular access (arteriovenous fistula, arteriovenous graft, or catheter). Abbreviations: ACEI, angiotensin-converting enzyme inhibitor; ARB, angiotensin receptor blocker; BMI, body mass index; eGFR, estimated glomerular filtration rate; ESA, erythropoietin stimulating agent; SBP, systolic blood pressure

Figure 2. Adjusted hazard ratios (95% CIs) of all-cause mortality in the first 3 months after dialysis initiation associated with pre-dialysis SBP categories in selected subgroups

Model is adjusted for age, sex, race/ethnicity, marital status, comorbidities (cardiovascular disease, congestive heart failure, peripheral vascular disease, lung disease, diabetes mellitus, liver disease, and Charlson comorbidity index), BMI averaged over the one-year pre-dialysis period, eGFR slope, last eGFR before dialysis initiation, medications (ACEIs/ARBs, β-blockers, calcium channel blockers, vasodilators, diuretics, statins, and ESAs), cardiovascular medication adherence, and type of vascular access (arteriovenous fistula, arteriovenous graft, or catheter). Abbreviations: ACEI, angiotensin-converting enzyme inhibitor; ARB, angiotensin receptor blocker; BMI, body mass index; CHF, congestive heart failure; CVD, cardiovascular disease; DM, diabetes mellitus; eGFR, estimated glomerular filtration rate; ESA, erythropoietin stimulating agent; SBP, systolic blood pressure

Figure 3. Association of pre-dialysis DBP with all-cause mortality in the first 3 months after dialysis initiation

Solid and dashed lines represent hazard ratio and 95% CI, respectively. A hazard reference ratio of 1 (solid horizontal line) and a histogram of observed DBP values are overlaid. The x-axis shows DBP levels, trimmed at 0.5% and 99.5%. Model is adjusted for age, sex, race/ethnicity, marital status, comorbidities (cardiovascular disease, congestive heart failure, peripheral vascular disease, lung disease, diabetes mellitus, liver disease, and Charlson comorbidity index), SBP and BMI averaged over the one-year pre-dialysis period, eGFR slope, last eGFR before dialysis initiation, medications (ACEIs/ARBs, β-blockers, calcium channel blockers, vasodilators, diuretics, statins, and ESAs), cardiovascular medication adherence, and type of vascular access (arteriovenous fistula, arteriovenous graft, or catheter). Abbreviations: ACEI, angiotensin-converting enzyme inhibitor; ARB, angiotensin receptor blocker; BMI, body mass index; DBP, diastolic blood pressure; eGFR, estimated glomerular filtration rate; ESA, erythropoietin stimulating agent; SBP, systolic blood pressure