Intradialytic cerebral blood flow reduction occurs irrespective of vascular access type: a comparative study

BACKGROUND: Patients undergoing hemodialysis (HD) experience reductions in cerebral blood flow (CBF) during treatment. It remains unclear whether these changes are more pronounced in individuals with arteriovenous fistula (AVF). The study aimed to quantify and compare cerebral and cardiovascular hemodynamic changes during HD sessions in patients with AVF versus those with high-flow catheters (CVC). METHODS: In this cross-sectional study, 25 AVF patients were matched to 25 CVC patients by age, sex, and HD vintage. CBF was measured using transcranial doppler ultrasound at 15, 120, and 240 min during a routine HD session. Cardiac output (CO) was estimated pre- and post-dialysis. RESULTS: All CBF parameters declined significantly during HD: peak systolic velocity of the middle cerebral artery decreased by 18 cm/s (p < 0.001), end-diastolic velocity of the middle cerebral artery by 8 cm/s (p < 0.001), and mean flow velocity of the middle cerebral artery (MFVMCA) by 12 cm/s (p < 0.001). Conversely, pulsatility and resistance indices progressively increased (+ 0.3, and + 0.07, respectively; p < 0.001 for both). The main determinant of CBF reduction was CO decline. Both access group exhibited MFVMCA reductions, more pronounced in the AVF (-30.6% vs. -22.4%, p = 0.17). Cognitive impairment (MoCA < 26) was present in 72% of patients and inversely correlated with age (r=-0.51, p < 0.001). CONCLUSIONS: HD patients experience significant cerebral hemodynamic deterioration during treatment, irrespective of vascular access type, potentially contributing to the high prevalence of cognitive impairment.