The time of onset of intradialytic hypotension during a hemodialysis session associates with clinical parameters and mortality

Abstract

Intradialytic hypotension (IDH) is a common complication of hemodialysis, but there is no data about the time of onset during treatment. Here we describe the incidence of IDH throughout hemodialysis and associations of time of hypotension with clinical parameters and survival by analyzing data from 21 dialysis clinics in the United States to include 785682 treatments from 4348 patients. IDH was defined as a systolic blood pressure of 90 mmHg or under while IDH incidence was calculated in 30-minute intervals throughout the hemodialysis session. Associations of time of IDH with clinical and treatment parameters were explored using logistic regression and with survival using Cox-regression. Sensitivity analysis considered further IDH definitions. IDH occurred in 12% of sessions at a median time interval of 120-149 minutes. There was no notable change in IDH incidence across hemodialysis intervals (range: 2.6-3.2 episodes per 100 session-intervals). Relative blood volume and ultrafiltration volume did not notably associate with IDH in the first 90 minutes but did thereafter. Associations between central venous but not arterial oxygen saturation and IDH were present throughout hemodialysis. Patients prone to IDH early as compared to late in a session had worse survival. Sensitivity analyses suggested IDH definition affects time of onset but other analyses were comparable. Thus, our study highlights the incidence of IDH during the early part of hemodialysis which, when compared to later episodes, associates with clinical parameters and mortality.

Keywords: blood volume; hemodialysis; intradialytic hypotension; oximetry; survival.

Graphical abstract

Figure 1

Hemodialysis sessions-intervals used to define incidence of intradialytic hypotension across a treatment session. All sessions routinely had automated blood pressure (BP) measured every 30 minutes, whereas BP measured on indication could occur at any point in each session interval.

Figure 2

Patient flow diagram. CLM, Crit-Line monitor; IDH, intradialytic hypotension.

Figure 3

Intradialytic hypotension (IDH) episodes per 100 sessions-intervals at risk, with time into hemodialysis (HD) session using IDH definitions of decline in systolic blood pressure (SBP) >30 mm Hg and nadir SBP <90 mm Hg; fluids administered; nadir SBP <90 mm Hg; and decline in SBP >30 mm Hg.

Figure 4

Intradialytic relative blood volume (RBV), ultrafiltration volume (UFV), arterial oxygen saturation (SaO₂), central venous oxygen saturation (ScvO₂), and estimated upper-body blood flow (eUBBF). Each data point represents an average value at the start of every session-interval, stratified by whether intradialytic hypotension (IDH) occurred in the subsequent 30 minutes or not, with error bars representing 95% confidence intervals. Comparisons of each variable at all time points showed statistically significant differences (P < 0.05).

Figure 5

Kaplan-Meier curves for patients who tended to have intradialytic hypotension (IDH) in the first half of a session compared with those who tended to have IDH in the second half of a session. Data presented for all-cause and cardiovascular mortality, with accompanying 95% confidence intervals.