Noninvasive Cerebrovascular Autoregulation Monitoring in Hemodialysis Patients: A Pilot Study
Background and objective: The hemodialysis (HD) is one of the main treatment options at end-stage renal disease (ESRD) used to remove uremic toxins from the body. Although HD procedures are individualized, they frequently lead to the removal of large quantities of fluid and electrolytes. This might provoke different impairments in the body. Previous studies have proven that chronic kidney diseases cause dysfunction of the central and peripheral nervous system. However, the pathophysiological mechanisms are not clear yet.
The aim of our study was to employ the method of noninvasive cerebrovascular autoregulation (CA) monitoring for dialysis patients during HD, to assess CA dynamics and to explore the association between changes of the level of uremic toxins, electrolytes and CA during an HD session.
Materials and methods: Noninvasive CA monitoring of 15 HD patients was performed during an HD session. Pre-dialysis and post-dialysis blood samples were taken and levels of uremic toxins and electrolytes were analyzed. The CA status was estimated by calculating the pressure reactivity index (vPRx) as the moving correlation coefficient between slow waves of noninvasively measured arterial blood pressure and noninvasively measured slow fluctuations of intracranial blood volume. The associations between the duration of the longest CA impairment (LCAI) and changes of the level of uremic toxins and electrolytes during an HD session were analyzed. Results: There were 9 male (60%) and 6 female (40%) HD patients in the study. The mean age was 58 ± 10.9 years, and the mean HD vintage was 31 ± 24 months. There was a negative correlation between the duration of LCAI during an HD session and duration on HD treatment in
months (r = −0.526, P = 0.044), post-dialysis potassium (r = −0.652, P = 0.006) and calcium (r = −0.610, P = 0.016) levels in the blood. The post-dialysis bicarbonate level in the blood and the duration of an LCAI event during an HD session correlated directly (r = 0.586, P = 0.027). There were no significant associations between the duration of LCAI and blood flow, dialysate flow, fluid ultrafiltration rate during HD, post-dialysis urea, creatinine, sodium, and magnesium levels in the blood.
Conclusions: The longer duration of CA impairment events has been associated with a shorter duration time on HD treatment in months, lower post-dialysis potassium and calcium levels in the blood and a higher bicarbonate level. These preliminary results allows us to formulate the hypothesis that HD procedures can cause excessive changes of the electrolyte level and these changes are associated with the appearance of CA impairment events during an HD procedure. Impaired CA was detected more often due to the electrolyte changes during an HD procedure in patients having less HD vintage.