Association of mortality risk with various definitions of intradialytic hypotension

Abstract

Intradialytic hypotension is a serious and frequent complication of hemodialysis; however, there is no evidence-based consensus definition of intradialytic hypotension. As a result, coherent evaluation of the effects of intradialytic hypotension is difficult. We analyzed data from 1409 patients in the HEMO Study and 10,392 patients from a single large dialysis organization to investigate the associations of commonly used intradialytic hypotension definitions and mortality. Intradialytic hypotension definitions were selected a priori on the basis of literature review. For each definition, patients were characterized as having intradialytic hypotension if they met the corresponding definition in at least 30% of baseline exposure period treatments or characterized as control otherwise. Overall and within subgroups of patients with predialysis systolic BP<120 or 120-159 mmHg, an absolute nadir systolic BP<90 mmHg was most potently associated with mortality. Within the subgroup of patients with predialysis BP≥160 mmHg, nadir BP<100 mmHg was most potently associated with mortality. Intradialytic hypotension definitions that considered symptoms, interventions, and decreases in BP during dialysis were not associated with outcome, and when added to nadir BP, symptom and intervention criteria did not accentuate associations with mortality. Our results suggest that nadir-based definitions best capture the association between intradialytic hypotension and mortality.

Keywords: BP; epidemiology and outcomes; hemodialysis.

Figure 1.

Frequency of IDH was similar across both cohorts. Frequency of IDH was defined by the number of dialysis sessions with events meeting the specified IDH definition divided by the total number of dialysis treatments in the baseline period. Fall20, (pre-HD SBP−minimum intradialytic SBP) ≥20 mmHg; Fall20Nadir90: (pre-HD SBP−minimum intradialytic SBP) ≥20 mmHg and minimum intradialytic SBP<90 mmHg; Fall30, (pre-HD SBP−minimum intradialytic SBP) ≥30 mmHg; Fall30Nadir90, (pre-HD SBP−minimum intradialytic SBP) ≥30 mmHg and minimum intradialytic SBP<90 mmHg; HEMO, fall in SBP resulting in intervention of UF reduction, blood flow reduction, or saline administration; KDOQI, (pre-HD SBP − minimum intradialytic SBP) ≥20 mmHg and symptoms of cramping, headache, lightheadedness, vomiting, or chest pain during HD; Nadir90, minimum intradialytic SBP<90 mmHg; Nadir100, minimum intradialytic SBP<100 mmHg. ^aHEMO and KDOQI definitions of IDH could not be assessed in the LDO cohort because of the lack of symptom and intervention data in this cohort.

Figure 2.

Adjusted associations between IDH definitions and mortality in (A) the HEMO cohort and (B) the LDO cohort. Outcome for the HEMO cohort is 2-year mortality, and outcome for the LDO cohort is 1-year mortality. IDH was defined as ≥30% of the exposure period HD sessions meeting the specified definition. Multivariate logistic models for the HEMO cohort were adjusted for age (per 10 years), sex, race (black or nonblack), ICED (≤1, 2, or 3), smoking status (current smoker or nonsmoker), diabetes, heart failure, ischemic heart disease, cerebrovascular disease, peripheral vascular disease, vintage (≤0.9, 1–1.9, 2–3.9, or ≥4 years or missing), access (graft, fistula, or catheter), postdialysis weight (quartiles; kilograms), delivered treatment time (minutes), albumin (≤2.9, 3–3.9, or ≥4 g/dl or missing), hematocrit (percentage), UF volume (liters), predialysis SBP (≤129, 130–159, or ≥160 mmHg), residual renal function (≤200 or >200 ml/d), hospitalization during exposure period (yes or no), Kt/V group (high or low), flux group (high or low), center, and use of α-adrenergic blocker, renin-angiotensin system blocker, β-blocker, calcium channel blocker, nitrates, or other antihypertensives. Multivariate logistic models for the LDO cohort were adjusted for age (per 10 years), sex, race (black, nonblack, or missing), diabetes, heart failure, ischemic heart disease, cerebrovascular disease, peripheral vascular disease, vintage (≤0.9, 1–1.9, 2–3.9, or ≥4 years or missing), access (graft, fistula, or catheter), postdialysis weight (quartiles; kilograms), delivered treatment time (minutes), albumin (≤2.9, 3–3.9, or ≥4 g/dl or missing), hemoglobin (grams per deciliter), UF volume (liters), predialysis SBP (≤129, 130–159, or ≥160 mmHg), equilibrated Kt/V (<1.2, ≥1.2, or missing), missed sessions during exposure period (0, 1, 2, or ≥3), and use of α-adrenergic blocker, renin-angiotensin system blocker, β-blocker, calcium channel blocker, nitrates, or other antihypertensives.

Figure 3.

In the HEMO cohort, patients with more frequent episodes of IDH had incrementally greater mortality in both unadjusted and adjusted analyses. Analyses were adjusted for age (per 10 years), sex, race (black or nonblack), ICED (≤1, 2, or 3), smoking status (current smoker or nonsmoker), diabetes, heart failure, ischemic heart disease, cerebrovascular disease, peripheral vascular disease, vintage (≤0.9, 1–1.9, 2–3.9, or ≥4 years or missing), access (graft, fistula, or catheter), postdialysis weight (quartiles; kilograms), delivered treatment time (minutes), albumin (≤2.9, 3–3.9, or ≥4 g/dl or missing), hematocrit (percentage), UF volume (liters), predialysis SBP (≤129, 130–159, or ≥160 mmHg), residual renal function (≤200 or >200 ml/d), hospitalization during exposure period (yes or no), Kt/V group (high or low), flux group (high or low), center, and use of α-adrenergic blocker, renin-angiotensin system blocker, β-blocker, calcium channel blocker, nitrates, or other antihypertensives. Error bars indicate 95% CI.