Association between Cerebral Blood Flow Changes during Hemodialysis Treatment and Cognitive Function Decline in Elderly Patients Undergoing Hemodialysis

Background: The etiology of cognitive impairment in hemodialysis patients is multifactorial and still not clear, among those, the relationship between cerebral blood flow and cognitive function is poorly understood. Our study was to investigate the association between changes in cerebral blood flow (CBF) during hemodialysis treatment and the decline of cognitive function in elderly patients undergoing hemodialysis. Methods: In this prospective observational cohort study of 121 elderly patients undergoing hemodialysis, we used transcranial Doppler ultrasound (TCD) to measure cerebral arterial mean flow velocity (MFV) as the index of CBF; assessed cognitive function at baseline and 12-month follow-up, and then explored associations between MFV and changes of cognitive scores. Results: TCD recordings demonstrated a significant decline in MFV throughout dialysis, which significantly associated with combined diabetes (β=3.889, 95% CI 1.373-6.405, P=0.003), lower serum albumin (β=- 0.456, 95% CI -0.877-0.036, P=0.034), higher ultrafiltration rate (β=11.099, 95% CI 6.402-15.797, P<0.001) and the decline in systolic blood pressure throughout dialysis (β=0.062, 95% CI 0.008-0.116, P=0.026). After 12 months of follow-up, test scores of cognitive functions decreased in 5 cognitive domains (P<0.05). The decreased MFV was significantly associated with worsening scores in global cognitive function (MOCA) (β=0.066, 95% CI 0.018-0.113, P=0.007); the test of memory function (Auditory Verbal Learning Test) (β=0.050, 95% CI 0.004-0.097, P=0.035) and executive function tests including Trail Making Tests B (TMT-B) (β=1.955, 95% CI 0.457-3.453, P=0.011), and a modified version of the Stroop Color-Word Test (SCWT) (β=1.955, 95% CI 0.457-3.453, P=0.011; β=0.298, 95% CI 0.112-0.484, P=0.002) were also associated with the reduced MFV. Conclusion: Conventional Hemodialysis may significantly reduce cerebral blood flow in elderly patients. Repetitive intradialytic decreases in CBF may be one of the underlying mechanisms for the deterioration of cognitive function in elderly hemodialysis patients.