Investigating the Relationship between Cerebral Blood Flow and Cognitive Function in Hemodialysis Patients

Abstract

Background The immediate and longer-term effects of hemodialysis on cerebral circulation, cerebral structure, and cognitive function are poorly understood.Methods In a prospective observational cohort study of 97 adults (median age 59 years) receiving chronic hemodialysis, we used transcranial Doppler ultrasound to measure cerebral arterial mean flow velocity (MFV) throughout dialysis. Using a well validated neuropsychological protocol, we assessed cognitive function during and off dialysis and after 12 months of treatment. We also used brain magnetic resonance imaging (MRI) to assess atrophy, white matter hyperintensities (WMHs), and diffusion parameters, and tested correlations between MFV, cognitive scores, and changes on MRI.Results MFV declined significantly during dialysis, correlating with ultrafiltrate volumes. Percentage of decline in MFV correlated with intradialytic decline in cognitive function, including global function, executive function, and verbal fluency. At follow-up, 73 patients were available for repeat testing, 34 of whom underwent repeat MRI. In a subgroup of patients followed for 12 months of continued dialysis, percentage of decline in MFV correlated significantly with lower global and executive function and with progression of WMH burden (a marker of small vessel disease). Twelve of 15 patients who received renal transplants during follow-up had both early and follow-up off-dialysis assessments. After transplant, patients' memory (on a delayed recall test) improved significantly; increased fractional anisotropy of white matter (a measure of cerebral diffusion) in these patients correlated with improving executive function.Conclusions Patients undergoing hemodialysis experience transient decline in cerebral blood flow, correlating with intradialytic cognitive dysfunction. Progressive cerebrovascular disease occurred in those continuing dialysis, but not in transplanted patients. Cognitive function and cerebral diffusion improved after transplant.

Cerebral Ischemia and Cognitive Dysfunction in Patients on Dialysis

“…Higher tympanic temperature, ultrafiltration volume, ultrafiltration rate, and pH were significantly associated with a lower cerebral blood flow. A second study found similar results in a prospective, observational, cohort study of 97 adults, using transcranial Doppler ultrasound to measure cerebral arterial mean flow velocity throughout dialysis, with assessment of cognitive function during and off dialysis and after 12 months of treatment (2). Mean flow velocity declined significantly during dialysis, correlating with ultrafiltrate volumes and intradialytic decline in cognitive function, including verbal fluency and global and executive function.…”

Event- and time-based prospective memory in hemodialysis patients

“…An alternative explanation may be related to the fact that conventional hemodialysis can cause recurrent acute cerebral ischemia [27]. Mark et al showed that patients undergoing hemodialysis experience transient declines in cerebral blood flow, correlating with intradialytic cognitive dysfunction [34], which in turn may contribute to a chronic decline in PM function. Additionally, small-vessel cerebrovascular disease is the most common cause of vascular dementia [35].…”

Dialysis-Induced Cardiovascular and Multiorgan Morbidity

“…Recent studies using neuropsychological tests and sophisticated tools (transcranial doppler ultrasonography, cerebral MRI) have identified a link between the deleterious effects of hemodialysis on cognitive function and changes in cerebral arterial flow velocity. 106,107 In a prospective observational cohort study of 97 adults receiving hemodialysis, the degree of decline in flow velocity in the middle cerebral arteries correlated with the decline in cognitive function. 107 Further, transient cognitive impairment has a negative impact on the patients' experience, but also on their health literacy and ability to process medical information, possibly affecting their ability to adhere to their treatment regimen.…”

“…106,107 In a prospective observational cohort study of 97 adults receiving hemodialysis, the degree of decline in flow velocity in the middle cerebral arteries correlated with the decline in cognitive function. 107 Further, transient cognitive impairment has a negative impact on the patients' experience, but also on their health literacy and ability to process medical information, possibly affecting their ability to adhere to their treatment regimen. Moreover, repetitive hemodialysis-induced brain insults may result in ischemic brain and white matter damage (leukoaraiosis) as shown in a prospective cerebral MRI study.…”