Cerebral blood flow pulsatility and cerebral artery stiffness acutely decrease during hemodialysis

Abstract

End-stage kidney disease (ESKD) is associated with increased arterial stiffness and cognitive impairment. Cognitive decline is accelerated in ESKD patients on hemodialysis and may result from repeatedly inappropriate cerebral blood flow (CBF). The aim of this study was to examine the acute effect of hemodialysis on pulsatile components of CBF and their relation to acute changes in arterial stiffness. In eight participants (age: 63 ± 18 years, men: 5), CBF was estimated using middle cerebral artery blood velocity (MCAv) assessed with transcranial Doppler ultrasound before, during, and after a single hemodialysis session. Brachial and central blood pressure, along with estimated aortic stiffness (eAoPWV) were measured using an oscillometric device. Arterial stiffness from heart to MCA was measured as the pulse arrival time (PAT) between electrocardiogram (ECG) and transcranial Doppler ultrasound waveforms (cerebral PAT). During hemodialysis, there was a significant reduction in mean MCAv (-3.2 cm/s, p < 0.001), and systolic MCAv (-13.0 cm/s, p < 0.001). While baseline eAoPWV (9.25 ± 0.80 m/s) did not significantly change during hemodialysis, cerebral PAT increased significantly (+0.027 , p < 0.001) and was associated with reduced pulsatile components of MCAv. This study shows that hemodialysis acutely reduces stiffness of arteries perfusing the brain along with pulsatile components of blood velocity.

Keywords: arterial stiffness; cerebral pulsatility index; end-stage kidney disease; hemodialysis; middle cerebral artery mean blood velocity; pulse wave velocity.

FIGURE 1

Study flowchart: This flowchart outlines the recruitment process for this pilot study.

FIGURE 2

Study protocol: Time into hemodialysis is shown as a horizontal arrow. Intra‐HD indicates the averaged data obtained at each hour during hemodialysis. Vertical arrows represent timing of measurements. Thin dark vertical arrows indicate timing of continuous monitoring over 5 min periods. AVF, arteriovenous fistula; BP, Blood pressure; ECG, electrocardiogram; MCAv, middle cerebral artery blood velocity.

FIGURE 3

Visual representation of cerebral and finger pulse arrival time assessment. The left panel of the figure provides a visual representation of the arterial tree adapted from Obeid et al. (2017) Physiol Meas. Circles indicate location of measurements, that is, the middle cerebral artery, digital arteries, and heart. On the right panel, sample data taken at each location are represented along an x‐axis (time in seconds). Dotted vertical lines indicate the time differences between the peak of the ECG R wave and the foot of the middle cerebral artery waveform (upper third of right panel) and finger pulse waveform (lower third of right panel).

FIGURE 4

Cerebral blood velocities, pulsatility, and stiffness during hemodialysis. Each panel presents the evolution of a cerebral or systemic hemodynamic variable during hemodialysis. Time into hemodialysis is presented on the x‐axis. Data obtained Pre‐HD were collected just before dialysis initiation. Data points presented as Intra‐HD are averaged from measurements taken at 1, 2, and 3 h into hemodialysis. Data marked as Post‐HD was collected within 15 min after hemodialysis. Diast MCAv, diastolic middle cerebral artery velocity; eAoPWV, estimated aortic pulse wave velocity; cerebral PAT, pulse arrival time between the peak of the ECG R wave and the foot of the transcranial Doppler ultrasound waveform; Mean MCAv, mean middle cerebral artery velocity; P‐MCAv, pulsed middle cerebral artery velocity; Syst MCAv, systolic middle cerebral artery velocity. p‐values indicate the level of statistical significance of the change relative to the Pre‐HD baseline and is obtained from generalized estimating equation models.