Comparison of Ambulatory Blood Pressure Patterns in Patients With Intradialytic Hypertension and Hemodialysis Controls.

Background/aims: Intradialytic hypertension (IH) patients have higher mortality risk than other hemodialysis patients and have been shown to have higher ambulatory blood pressure (BP). We hypothesized that interdialytic BP patterns would differ in IH patients and hypertensive hemodialysis controls.

Methods: We consecutively screened hemodialysis patients at our university-affiliated units. Based on pre and post-HD BP measurements during the prior 2 week period, we identified IH patients and demographically matched hemodialysis controls. We measured ambulatory interdialytic BP, flow-mediated vasodilation, and intradialytic endothelin-1 (ET-1). Using linear mixed-models, we compared BP slopes during the following intervals: 1-24 hours post-dialysis, 25-44 hours post-dialysis, and 1-44 hours post-dialysis.

Results: There were 25 case subjects with IH and 24 controls. Systolic BP during hours 1-44, 1-24, and 25-44 were 143.1 (16.5), 138.0 (21.2), and 150.8 (22.3) mmHg in controls. For IH subjects, they were 155.4 (14.2), 152.7 (22.8), and 156.5 (20.8) mmHg (p=0.008, 0.02, 0.4). In controls, the slopes were +0.6, +0.6, and +0.4 mmHg/hr. In IH subjects, they were +0.1, -0.3, and +0.3 mmHg/hr. The IH 1-24 hour slope differed from the IH 25-44 hour slope (p=0.001) and the control 1-24 hour slope (p=0.002). The change in ET-1 from pre to post dialysis was 0.5 (1.5) pg/mL in controls and 1.0 (2.3) pg/mL in IH patients (p=0.4). In a univariate model, there was an association with screening BP and BP slope (p=0.002 for controls and p=0.1 for IH patients).

Conclusions: Interdialytic BP patterns differ in IH patients and hemodialysis controls. The elevated post dialysis blood pressure persists for many hours in IH patients contributing to the overall increased BP burden.