Intradialytic hypertension and the association with interdialytic ambulatory blood pressure

Abstract

Background and objectives: Increasing BP during maintenance hemodialysis or intradialytic hypertension is associated with increased morbidity and mortality. In hemodialysis patients, ambulatory BP measurements predict adverse cardiovascular outcomes better than in-center measurements. We hypothesized that patients with intradialytic hypertension have higher interdialytic ambulatory systolic BP than those without intradialytic hypertension.

Design, setting, participants, & measurements: We performed a case-control study in adult hemodialysis patients. Cases consisted of subjects with intradialytic-hypertension (systolic BP increase ≥10 mmHg from pre- to posthemodialysis in at least four of six treatments), and controls were subjects with ≥10 mmHg decreases from pre- to posthemodialysis in at least four of six treatments. The primary outcome was mean interdialytic 44-hour systolic ambulatory BP.

Results: Fifty subjects with a mean age of 54.5 years were enrolled (25 per group) among whom 80% were men, 86% diabetic, 62% Hispanic, and 38% African American. The mean prehemodialysis systolic BP for the intradialytic-hypertension and control groups were 144.0 and 155.5 mmHg, respectively. Mean posthemodialysis systolic BP was 159.0 and 128.1 mmHg, for the intradialytic-hypertension and control groups, respectively. The mean systolic ambulatory BP was 155.4 and 142.4 mmHg for the intradialytic-hypertension and control groups, respectively (P = 0.005). Both daytime and nocturnal systolic BP were higher among those with intradialytic hypertension as compared with controls. There was no difference in interdialytic weight gain between groups.

Conclusions: Time-integrated BP burden as measured by 44-hour ambulatory BP is higher in hemodialysis patients with intradialytic hypertension than those without intradialytic hypertension.

Figure 1.

Hemodialysis unit 2-week time averaged systolic BP measurements for control and intradialytic hypertension subjects. The 2-week average prehemodialysis and posthemodialysis systolic BP for each subject in the control and intradialytic hypertension group (n = 25 for each group). For the control group, the mean systolic BP was 155.5 mmHg prehemodialysis and 128.1 mmHg posthemodialysis. For the intradialytic hypertension group, the mean systolic BP was 144.0 mmHg prehemodialysis and 159.0 mmHg posthemodialysis. HD, hemodialysis.

Figure 2.

44-hour ambulatory blood pressure measurements in control and intradialytic-hypertension subjects. Shown is a box and whisker plot of the mean 44-hour systolic ambulatory BP measurements for the control and intradialytic-hypertension groups. The plot demonstrates the maximum value, third quartile, median, first quartile, and minimum value. The mean systolic BP was 142.4 mmHg for the control group and 155.4 mmHg for the intradialytic-hypertension group.

Figure 3.

Average systolic BP measured during each hour after hemodialysis in intradialytic-hypertension and control subjects. For each hour during the entire interdialytic time period, the average ambulatory systolic BP (measured every 30 minutes during the daytime and every hour at night) is shown for the intradialytic-hypertension and control groups. From the first hour after dialysis until approximately the 24^th hour, systolic BP is higher in the intradialytic-hypertension group than controls. BP decreases during the initial 24 hours after hemodialysis in the intradialytic-hypertension group and then increases until shortly before the next treatment. BP generally increases during the entire interdialytic time period in the control group until shortly before the next treatment. For the final hour, the 2-week average pre-HD systolic BP is added for each group.

Figure 4.

Average systolic BP per postdialysis time period in subjects with intradialytic-hypertension and controls. The entire 44-hour interdialytic time period is separated into five periods reflecting the different daytime and nocturnal periods. Average systolic BP for each group during each time period is shown. During the first nocturnal time period, BP decreases in intradialytic-hypertension subjects and increases in controls. During the second nocturnal time period, BP increases in both groups.