Anatomic brain disease in hemodialysis patients: a cross-sectional study

Cerebrovascular Reactivity and Cerebral Ischemia During Chronic Hemodialysis

BACKGROUND

Cerebral hypo-perfusion during hemodialysis (HD) may contribute to cerebral ischemic lesions and atrophy in HD patients. Vascular disease and stiffness can impair cerebrovascular reactivity (CVR) in HD patients, placing them at higher risk for cerebral hypo-perfusion during the hemodynamic stress of HD. We evaluated the relationship between CVR and change in cerebral perfusion during HD.

METHODS

In a cohort of in-center HD patients, we used hypercapnia to induce a change in cerebral blood flow velocity measured with transcranial Doppler to assess CVR. We used continuous cerebral oximetry during HD to measure a change in cerebral oxygen saturation (ScO2), calculating overall decline and the largest drop as markers of cerebral perfusion. We used multiple linear regression to assess the relationship between CVR and the ScO2-associated endpoints.

FINDINGS

We measured CVR in 42 HD patients and of those, 41 had the ScO2 measurements completed. The mean age was 58.5 (11.0) years, and most were male (90.5%, N = 38) with diabetes (59.5%, N = 25) and hypertension (87.5%, N = 36). The average CVR was 2.7 (1.6)%/mmHg. The average overall decline in ScO2 during HD was 2.2 (2.5)% and the average largest drop in ScO2 was 5.9 (2.8)%. CVR was negatively associated with both the largest drop in ScO2 (β = -0.67 95% CI [-1.20, -0.15], p = 0.01) and the overall decline in ScO2 (β = -0.62 95% CI [-1.09, -0.15], p = 0.01). Vascular disease was a risk factor for lower CVR (β = -1.21, 95% CI [-2.16, -0.26] p = 0.01).

CONCLUSIONS

A lower CVR increases the risk for cerebral hypo-perfusion during HD. Impaired CVR may be an important part of the pathophysiology of ischemic brain injury and cognitive impairment in HD patients.

Cognitive impairment in chronic kidney disease: role of brain imaging, functional imaging, electroencephalography, cerebrospinal fluid biomarkers and sensors

Chronic kidney disease is associated with cognitive impairment although the underlying mechanisms are still not fully understood. Characterization and efficient monitoring of the cognitive impact of kidney disease and ensuing therapies are critical for the accurate clinical management of patients. A vast array of imaging modalities, biomarkers, and sensors have shown relevance for the assessment of cognitive impairment. Knowing the potential and limitations of these paraclinical techniques is a necessary condition to improve the understanding of this phenomenon and to design monitoring protocols and guidelines applicable to this clinical population. The goal of this review is to provide an overview of current imaging modalities and biomarker sources available to the community, for the benefit of the research and clinical community.

Research progress on the kidney-gut-brain axis in brain dysfunction in maintenance hemodialysis patients

Maintenance hemodialysis (MHD) has become the primary renal replacement therapy for patients with end-stage renal disease. The kidney-gut-brain axis represents a communication network connecting the kidney, intestine and brain. In MHD patients, factors such as uremic toxins, hemodynamic changes, vascular damage, inflammation, oxidative stress, and intestinal dysbiosis in MHD patients refers to a range of clinical syndromes, including brain injury, and is manifested by conditions such as white matter disease, brain atrophy, cerebrovascular disease, cognitive impairment, depression, anxiety, and other behavioral or consciousness abnormalities. Numerous studies have demonstrated the prevalence of these brain disorders in MHD patients. Understanding the mechanisms of brain disorders in MHD patients, particularly through the lens of kidney-gut-brain axis dysfunction, offers valuable insights for future research and the development of targeted therapies. This article reviews the brain dysfunction associated with MHD, the impact of the kidney-brain axis, intestinal barrier damage, gut microbiota dysbiosis caused by MHD, and the role of the gut-brain axis in brain dysfunction.

Effect of glymphatic system function on cognitive function in patients with chronic kidney disease

Objectives

Studies have recently shown an alteration of the structural connectivity and a dysfunctional glymphatic system in patients with chronic kidney disease (CKD). In this study, we aimed to investigate the effects of the structural connectivity and glymphatic system on the cognitive function of patients with CKD.

Methods

We prospectively enrolled patients with CKD and healthy controls. The CKD group was divided into two regarding their cognitive function. All patients received brain magnetic resonance imaging, including diffusion tensor imaging (DTI). We calculated the measures of structural connectivity and diffusion tensor image analysis along the perivascular space (DTI-ALPS) index, a neuroimaging marker of the glymphatic system function, and compared the indices between groups.

Results

The mean clustering coefficient, local efficiency, and small-worldness index in patients with CKD were lower than those in healthy controls (0.125 ± 0.056 vs. 0.167 ± 0.082, p = 0.008; 1.191 ± 0.183 vs. 1.525 ± 0.651, p = 0.002; 0.090 ± 0.043 vs. 0.143 ± 0.102, p = 0.003; respectively). The DTI-ALPS index was lower in patients with CKD than in healthy controls (1.436 vs. 1.632, p < 0.001). Additionally, the DTI-ALPS index differed significantly between CKD patients with and without cognitive impairment. Notably, this index was lower in patients with CKD and cognitive impairment than in patients without cognitive impairment (1.338 vs. 1.494, p = 0.031). However, there were no differences of the structural connectivity between CKD patients with and without cognitive impairment.

Conclusion

We found lower DTI-ALPS index in patients with CKD, which could be related with glymphatic system dysfunction. Moreover, those with cognitive impairment in the CKD group had a lower index than those without, indicating a link between the glymphatic system function and cognitive function.

Research Progress on Cognitive Frailty in Older Adults with Chronic Kidney Disease

BACKGROUND

As the medical challenges posed by the ageing population become increasingly severe, the proportion of older people among patients with chronic kidney disease (CKD) is increasing every year.

SUMMARY

The prevalence of frailty in patients with CKD is significantly higher than that in the general population, and older patients are also a high-risk group for frailty and cognitive impairment. Cognitive frailty, as an important subtype of frailty, is a syndrome characterised by cognitive dysfunction caused by physiological factors, excluding Alzheimer's disease and other types of dementia. It is characterised by the coexistence of physical frailty and cognitive impairment. Previous studies have mainly focused on cognitive impairment, and there is limited research on cognitive frailty, particularly in older patients with CKD.

KEY MESSAGES

This article provides a comprehensive review of the concept, epidemiology, screening methods, prevention, and treatment measures and possible pathogenesis of cognitive frailty in patients with CKD.

More rapid progression of brain atrophy in patients on peritoneal dialysis compared with hemodialysis: The VCOHP Study

We previously reported that brain atrophy was more severe and progressed more rapidly in patients with end-stage kidney disease on peritoneal dialysis (PD) than those with non-dialysis-dependent chronic kidney disease. However, it remains unknown whether there is a difference between patients on PD and hemodialysis (HD). In total, 73 PD and 34 HD patients who underwent brain magnetic resonance imaging (MRI) were recruited for a cross-sectional analysis. Among them, 42 PD and 25 HD patients who underwent a second brain MRI after 2 years were recruited for a longitudinal analysis. T1-weighted MRI images were analyzed. Total gray matter volume (GMV), total white matter volume, and cerebrospinal fluid volume were segmented, and each volume was quantified using statistical parametric mapping software. The ratio of GMV (GMR) was calculated by dividing GMV by intracranial volume, to adjust for variations in head size. We compared GMR between PD and HD patients in the cross-sectional analysis and the annual change in GMR (AC-GMR) in the longitudinal analysis. In the cross-sectional analysis, age- and sex-adjusted GMR was significantly lower in PD than HD patients [least square mean (LSM): 39.2% vs. 40.0%, P = 0.018]. AC-GMR was significantly greater in PD than HD patients and this difference remained significant even after adjustment for potential confounding factors (LSM: -0.68 vs. -0.28 percentage-points/year, P = 0.011). In conclusion, the present study demonstrated a more rapid progression of brain atrophy in PD patients compared with HD patients. We demonstrated that decline in GMR progressed significantly more rapidly in PD than HD patients independent of potential confounding factors. GMR gray matter volume ratio, HD hemodialysis, PD peritoneal dialysis.

Association between white matter hyperintensities and altered cerebral blood flow in maintenance hemodialysis patients: a longitudinal study

OBJECTIVES

To explore changes in cerebral blood flow (CBF) and white matter in hemodialysis patients.

METHODS

Thirty-three hemodialysis patients who underwent two brain MRI at an interval of three years and 33 age- and sex-matched healthy controls (HC) underwent structural and arterial spin-labeling MRI examinations. Intergroup differences in CBF in the gray matter, white matter, and whole matter, and regional white matter hyperintensities (WMH) were analyzed. Based on the changes in CBF between the baseline and follow-up groups, the hemodialysis patients were divided into two subgroups: an increased CBF group and a decreased CBF group. Differences in CBF and WMH between the subgroups and HC were analyzed.

RESULTS

Patients undergoing hemodialysis exhibited increased cerebral watershed (CW) WMH, deep WMH, and periventricular WMH (P < 0.01). The CBF of patients with decreased CBF was higher than that of HC at baseline (,P < 0.01) and lower than that of HC at follow-up (P < 0.01). Compared with the increased CBF group, obvious development of deep WMH was found in the decreased CBF group for the gray matter, white matter, and whole matter (P < 0.01).

CONCLUSIONS

WMH in hemodialysis patients were distributed in the deep white matter, periventricular white matter and CW, and progressed with the extension of hemodialysis duration. CBF in hemodialysis patients could manifest as both increased and decreased, and WMH in patients with decreased CBF developed severely with prolongation of hemodialysis duration.

ADVANCES IN KNOWLEDGE

These findings provide a basis for exploring neuropathological changes of hemodialysis patients.

Chronic Kidney Disease Interplay with Comorbidities and Carbohydrate Metabolism: A Review

Chronic kidney disease (CKD) poses a global health challenge, engendering various physiological and metabolic shifts that significantly impact health and escalate the susceptibility to severe illnesses. This comprehensive review delves into the intricate complexities of CKD, scrutinizing its influence on cellular growth homeostasis, hormonal equilibrium, wasting, malnutrition, and its interconnectedness with inflammation, oxidative stress, and cardiovascular diseases. Exploring the genetic, birth-related, and comorbidity factors associated with CKD, alongside considerations of metabolic disturbances, anemia, and malnutrition, the review elucidates how CKD orchestrates cellular growth control. A pivotal focus lies on the nexus between CKD and insulin resistance, where debates persist regarding its chronological relationship with impaired kidney function. The prevalence of insulin abnormalities in CKD is emphasized, contributing to glucose intolerance and raising questions about its role as a precursor or consequence. Moreover, the review sheds light on disruptions in the growth hormone and insulin-like growth factor axis in CKD, underscoring the heightened vulnerability to illness and mortality in cases of severe growth retardation. Wasting, a prevalent concern affecting up to 75% of end-stage renal disease (ESRD) patients, is analyzed, elucidating the manifestations of cachexia and its impact on appetite, energy expenditure, and protein reserves. Taste disturbances in CKD, affecting sour, umami, and salty tastes, are explored for their implications on food palatability and nutritional status. Independent of age and gender, these taste alterations have the potential to sway dietary choices, further complicating the management of CKD. The intricate interplay between CKD, inflammation, oxidative stress, and cardiovascular diseases is unraveled, emphasizing the profound repercussions on overall health. Additionally, the review extends its analysis to CKD's broader impact on cognitive function, emotional well-being, taste perception, and endothelial dysfunction. Concluding with an emphasis on dietary interventions as crucial components in CKD management, this comprehensive review navigates the multifaceted dimensions of CKD, providing a nuanced understanding essential for developing targeted therapeutic strategies.

Cerebrovascular Function is Altered in Hemodialysis Patients

Key Points

Hemodialysis patients have impaired cerebrovascular reactivity. Hemodialysis patients have cerebral structural deficits.

Background

Hemodialysis patients have declines in cerebral blood flow (CBF) and cerebral oxygenation during hemodialysis that may lead to ischemic brain injury. Cerebrovascular reactivity (CVR) may indicate which individuals are more susceptible to intradialytic hypoperfusion and ischemia. We hypothesized that hemodialysis patients would have decreased CVR and increased CBF relative to controls and deficits in CVR would be related to brain structural deficits.

Methods

We measured cortical thickness and white matter hyperintensity (WMH) volume from T1 and T2 fluid attenuation inversion recovery images, respectively; CVR from a breath hold blood oxygen level–dependent CVR functional magnetic resonance imaging (fMRI); and arterial transit time and CBF from arterial spin labeling. Cerebrovascular and structural deficits in gray matter and white matter (GM and WM) were tested by averaging across the tissue and with a pothole analysis. Finally, we correlated cortical thickness and WMH volume with GM and WM cerebrovascular variables to assess the relationship between brain structure and cerebrovascular health.

Results

In ten hemodialysis patients, cortical thickness was found to be decreased (P = 0.002), WMH volume increased (P = 0.004), and WM CBF increased (P = 0.02) relative to ten controls. Pothole analysis indicated a higher number of increased GM and WM CBF voxels (P = 0.03, P = 0.02) and a higher number of decreased GM and WM CVR voxels (P = 0.02, P = 0.01).

Conclusions

This pilot study demonstrates that hemodialysis patients have decreased CVR and increased CBF relative to controls, along with reduced brain integrity. Further investigation is required to fully understand whether these cerebrovascular deficits may lead to structural changes.

Intra-Cranial Arterial Calcifications in Hemodialysis Patients

Background and objectives: Vascular calcification is an integral part of atherosclerosis and has been reported to be an independent risk factor for cardiovascular diSsease. Intra Cranial Arterial Calcifications (ICAC) in maintenance hemodialysis (MHD) is highly prevalent. Materials and Methods: The aim of this retrospective study was to assess the predictors and outcomes of ICAC in MHD patients compared to a control group without kidney disease. A blinded neuroradiologist graded ICAC in brain imaging (computerized tomography) of MHD patients. Age- and sex-matched patients with normal kidney function served as the control group. Results: A total of 280 patients were included in the cohort; 140 of them were MHD patients with a mean ICAC score of 2.3 ± 0.2 versus a mean ICAC score of 1.4 ± 0.2 in the control group (p < 0.01). More than 90% of hemodialysis patients in our study had some degree of ICAC. Lower albumin and higher phosphorus and CRP levels were associated with increased ICACs. The multivariate analysis model for predictors of 1-year mortality demonstrated an increased odds ratio for mortality as the ICAC score increased. Conclusions: ICAC is very prevalent among MHD patients and results not simply from passive deposition of calcium and phosphate but rather from complex and active processes involving inflammation and structural changes in blood vessels. ICAC independently predicted all-cause mortality and may help with risk stratification of this high-risk population.

Patterns of Cognitive Impairment in Hemodialysis Patients and Related Factors including Depression and Anxiety

INTRODUCTION

Hemodialysis patients are at higher risk of developing cognitive impairment, but the pattern of affected cognitive domains is still undetermined. Little is also known about the symptoms of depression and anxiety in hemodialysis patients.

METHODS

In this cross-sectional study, we included 74 consecutive adult patients undergoing hemodialysis. Cognitive functions were assessed using the Addenbrooke Cognitive Test III. In addition, all patients were screened for symptoms of depression and anxiety using the Hospital Anxiety and Depression Scale.

RESULTS

The mean age of hemodialysis patients was 65.69 ± 14 years. Among the patients, there were 27% and 31% of patients with mild cognitive impairment and suspected dementia, respectively. In the group of patients with suspected dementia, all cognitive functions had significantly lower values compared to these functions in incognitively unimpaired and mild cognitive impairment patients. The most impaired domain was verbal fluency, which reflects impairments in executive function. Depression and anxiety symptoms were observed in 28% and 22% of patients, respectively. Patients with anxiety symptoms had higher levels of endogenous creatinine, parathyroid hormone, and hemoglobin, as well as decreased creatinine clearance, being younger and less educated. No factors contributing to the occurrence of depressive symptoms were found.

CONCLUSION

Cognitive dysfunction is a significant problem in hemodialysis patients. Our study showed that the prevalence of cognitive impairment and depression and anxiety symptoms in hemodialysis patients was high. The domain of executive functions was most affected. Furthermore, creatinine, parathyroid hormone, hemoglobin levels, creatinine clearance, and education affected the anxiety scale score.

Dialysis adequacy and hemoglobin levels predict cerebral atrophy in maintenance-hemodialysis patients

The pathogenesis of cerebral atrophy (CA) is not clear. Previous studies show a high incidence of preterm CA in hemodialysis patients. This study aims to investigate the factors influencing CA and to derive a CA prediction nomogram in maintenance-hemodialysis patients. First, brain volumes of hemodialysis patients (≤55 years) were compared against age- and sex-matched healthy controls, and differences were revealed in bilateral insular cisterns width, maximum cerebral sulci width, Evans index, ventricular-brain ratio, frontal atrophy index, and temporal lobe ratio. Then, the patients were divided equally into "no or mild" or "severe" CA groups. Potential factors influencing CA were screened. Kt/V (urea removal index) and hemoglobin levels negatively correlated with CA degree, and were used to establish a nomogram within randomly assigned training and validation patient groups. The areas under the receiver operating characteristic curves (AUROC) for training and validation groups were 0.703 and 0.744, respectively. When potassium and calcium were added to the nomogram, the AUROC for training/validation group increased to 0.748/0.806. The nomogram had optimal AUROC for training (0.759) and validation (0.804) groups when albumin was also included. Hemodialysis patients showed reduced anterior brain volumes and the nomogram established herein may have predictive value for developing CA.

Alterations of amplitude of low-frequency fluctuations and fractional amplitude of low-frequency fluctuations in end-stage renal disease on maintenance dialysis: An activation likelihood estimation meta-analysis

BACKGROUND

Cognitive impairment (CI) is a common complication of end-stage renal disease (ESRD). Many resting-state functional magnetic resonance imaging (rs-fMRI) studies have identified abnormal spontaneous low-frequency brain activity in ESRD dialysis patients. However, these studies have reported inconsistent results. So far, no meta-analyses on this topic have been published. This meta-analysis aimed to identify the more consistently vulnerable brain regions in ESRD patients at rest and to reveal its possible neuropathophysiological mechanisms.

METHODS

We systematically searched PubMed, Cochrane Library, Web of Science, Medline, and EMBASE databases up to July 20, 2022 based on the amplitude of low-frequency fluctuation (ALFF) or fractional amplitude of low-frequency fluctuation (fALFF). Brain regions with abnormal spontaneous neural activity in ESRD compared to healthy controls (HCs) from previous studies were integrated and analyzed using an activation likelihood estimation (ALE) method. Jackknife sensitivity analysis was carried out to assess the reproducibility of the results.

RESULTS

In total, 11 studies (380 patients and 351 HCs) were included in the final analysis. According to the results of the meta-analysis, compared with HCs, ESRD patients had decreased ALFF/fALFF in the right precuneus, right cuneus, and left superior temporal gyrus (STG), while no brain regions with increased brain activity were identified. Jackknife sensitivity analysis showed that our results were highly reliable.

CONCLUSION

Compared to HCs, ESRD dialysis patients exhibit significant abnormalities in spontaneous neural activity associated with CI, occurring primarily in the default mode network, visual recognition network (VRN), and executive control network (ECN). This contributes to the understanding of its pathophysiological mechanisms.

SYSTEMATIC REVIEW REGISTRATION

[https://www.crd.york.ac.uk/prospero/], identifier [CRD42022348694].

Insights into Cognitive Brain Health in Chronic Kidney Disease

Cognitive impairment and Chronic Kidney Disease (CKD) are common in older adults. With advances in medicine, the average lifespan is expected to increase, further increasing the prevalence of both conditions. The mechanisms underlying cognitive impairment in CKD are unclear. While mild-moderately low estimated glomerular filtration rate (eGFR) may not be associated with cognitive impairment, severely decreased eGFR and albuminuria do. Patients on dialysis have a high prevalence of cognitive impairment. Cognitive function improves after kidney transplantation. However, some residual cognitive deficits persist after transplantation, indicating that restoring the kidney function alone may not be enough to restore cognitive function, and other etiological factors may play a role. Albuminuria, another marker of CKD is also associated with cognitive impairment. However, albuminuria is often undiagnosed. Improving early identification and management of patients with albuminuria may be a good population-based dementia prevention strategy. Other factors associated with cognitive impairment in CKD include anemia and other metabolic derangements commonly observed in CKD. In this article, we reviewed the prevalence of cognitive impairment in CKD, the potential mechanisms underlying cognitive impairment in CKD, andthecurrent evidence on the association between cognitive impairment and eGFR and albuminuria.

Could salt intake directly affect the cerebral microvasculature in hypertension?

OBJECTIVES

Excess dietary salt and chronic kidney disease (CKD) are acknowledged stroke risk factors. The development of small vessel disease, similarly affecting the cerebral and renal microvasculatures, may be an important mechanistic link underlying this interaction. Therefore, we aimed to evaluate if the dietary salt intake and markers of CKD (estimated glomerular filtration rate, albuminuria) relate to transcranial Doppler (TCD) markers of cerebral small vessel disease (CSVD) in hypertensive patients.

MATERIALS AND METHODS

Fifty-six hypertensive patients (57% with diabetes) underwent TCD monitoring in the middle (MCA) and posterior (PCA) cerebral arteries for evaluating neurovascular coupling (NVC), dynamic cerebral autoregulation (dCA), and vasoreactivity to carbon dioxide (VRCO₂). We investigated the relation between renal parameters and TCD studies using Pearson's correlation coefficient and linear regression analyses.

RESULTS

There were no associations between dCA, VRCO₂, NVC, and renal function tests. However, there was a negative association between the daily salt intake and the natural frequency during visual stimulation (r²=0.101, ß=-0.340, p=0.035), indicative of increased rigidity of the cerebral resistance vessels that react to cognitive activation.

CONCLUSIONS

In this cross-sectional study, we found an association between excess dietary salt consumption and CSVD in hypertensive patients. Future research is needed to evaluate whether the natural frequency could be an early, non-invasive, surrogate marker for microvascular dysfunction in hypertension.

Cognitive impairment and microvascular function in end-stage renal disease

OBJECTIVE

Hemodialysis patients show an approximately threefold higher prevalence of cognitive impairment compared to the age-matched general population. Impaired microcirculatory function is one of the assumed causes. Dynamic retinal vessel analysis is a quantitative method for measuring neurovascular coupling and microvascular endothelial function. We hypothesize that cognitive impairment is associated with altered microcirculation of retinal vessels.

METHODS

152 chronic hemodialysis patients underwent cognitive testing using the Montreal Cognitive Assessment. Retinal microcirculation was assessed by Dynamic Retinal Vessel Analysis, which carries out an examination recording retinal vessels' reaction to a flicker light stimulus under standardized conditions.

RESULTS

In unadjusted as well as in adjusted linear regression analyses a significant association between the visuospatial executive function domain score of the Montreal Cognitive Assessment and the maximum arteriolar dilation as response of retinal arterioles to the flicker light stimulation was obtained.

CONCLUSION

This is the first study determining retinal microvascular function as surrogate for cerebral microvascular function and cognition in hemodialysis patients. The relationship between impairment in executive function and reduced arteriolar reaction to flicker light stimulation supports the involvement of cerebral small vessel disease as contributing factor for the development of cognitive impairment in this patient population and might be a target for noninvasive disease monitoring and therapeutic intervention.

Gait disorders in CKD patients: muscle wasting or cognitive impairment? A cross-sectional pilot study to investigate gait signatures in Stage 1-5 CKD patients

BACKGROUND

Instrumental gait analysis in nephrology is widely neglected, although patients with chronic kidney disease (CKD) show brain changes due to cerebrovascular disease and metabolic disorders that can potentially influence gait quality. Our study assesses the association between CKD stages and gait parameters, to understand the prevalent status of brain related gait parameters (i.e. variability) and of performance related parameters (i.e. gait speed, stride length). We hypothesize that gait changes are detectable already in early stages of CKD.

METHODS

Forty-five participants distributed in 5 CKD severity groups underwent an instrumental gait analysis via a triaxial accelerometer affixed to the lower trunk under single- and dual-task conditions. In addition to spatio-temporal parameters, variability and dual-task cost of gait were extracted. A battery of clinical assessments was conducted with the aim of helping to better explain the findings of the gait analysis. A correlation analysis was made to investigate a linear relation between gait parameters and CKD severity.

RESULTS

Statistically significant correlations (Pearson correlation coefficient) with CKD severity were found for gait speed (p < 0.01, r = -0.55, 95% CI [-0.73;-0.30]), stride length ( p < 0.01, r = -0.40, 95% CI [-0.62;-0.12]), step length (p < 0.01, r = -0.41, 95% CI [-0.63;-0.13], coefficient of variance (CV) of step length (p = 0.01, r = 0.36, 95% CI [0.08;0.59]), gait regularity (p < 0.01, r = -0.38, 95% CI [-0.61;-0.10]), dual-task cost of gait speed (p < 0.01, r = 0.40, 95% CI [0.13;0.62]) and dual-task cost of stride time (p = 0.03, r = 0.32, 95% CI [0.03;0.57]). Adjustment for age and gender confirmed all results except for gait regularity. With increasing severity of renal failure, Handgrip strength, Time for the Expanded Timed Get Up and Go test, executive functions, haemoglobin, and haematocrit, worsen.

CONCLUSIONS

The correlation of CKD severity with spatio-temporal parameters (performance indices mainly relatable to peripheral functionality) and with variability of gait (related to central factors) supported by the results of the clinical assessments, suggests that gait disturbance in CKD patients is not only due to metabolic factors that lead to muscle wasting, but also to brain changes that affect motor control. This suggests that the treatment of renal disease should include cognitive aspects in addition to metabolic and functional factors.

Regional cerebral gray matter atrophy is associated with cognitive impairment in hemodialysis patients: a cross-sectional and longitudinal voxel-based morphological MRI study

This study aimed to explore gray matter volume (GMV) changes in patients undergoing hemodialysis and assess the clinical risk factors associated with GMV changes and the relationship between GMV changes and neuropsychologic test results. Eighty-eight hemodialysis patients and 76 healthy controls (HCs) were recruited in this study. Fifty patients underwent follow-up examinations (follow-up duration: 1.75 ± 0.55 years), including magnetic resonance imaging, blood biochemical, and neuropsychologic testing. Changes in GMV between the patients and HCs were assessed. Longitudinal GMV changes were also explored in the patients. The clinical risk factors associated with longitudinal GMV changes and the correlations between longitudinal GMV changes and neuropsychologic test results were analyzed in the patients. Patients undergoing hemodialysis had diffusely decreased GMV compared with HCs (with age, sex, and total intracranial volume [TIV] as covariates, P<0.001, voxel-wise threshold false discovery rate [FDR] corrected). Compared with patients at baseline, regional decreased GMV were found in patients at follow-up (with age and TIV as covariates, P<0.05, voxel-wise threshold FDR corrected). Increased serum urea concentrations, parathyroid hormone levels, and hemodialysis duration were independent risk factors for decreased GMV in patients undergoing hemodialysis (all P<0.05, FDR corrected). Patients undergoing hemodialysis had lower mini-mental state examination (MMSE) (27[26, 29]) and Montreal cognitive assessment (MoCA) (22[19.5, 24.0]) scores than those of the HCs (30[29, 30] and 28[26.9, 29]) (all P<0.05). The MMSE scores of the patients at follow-up (26[25, 28.5]) were lower than those of patients at baseline (28[25, 29.5]) (P=0.02). The decreased left caudate volumes were positively correlated with reduced MMSE scores in hemodialysis patients (r_s=0.437, P=0.033). Patients undergoing hemodialysis had noticeable GM atrophy over time, related to cognitive impairments.

Risk factors for intradialytic decline in cerebral perfusion and impaired cerebral autoregulation in adults on hemodialysis

INTRODUCTION

Hemodialysis (HD) patients have significant burden of cerebral ischemic pathology noted on brain imaging. These ischemic type lesions maybe due to cerebral hypoperfusion that may be occurring during blood pressure (BP) fluctuations commonly noted during HD sessions. We evaluated changes in cerebral perfusion and measured an index of cerebral autoregulation (CA index) during HD to identify potential risk factors for intradialytic decline in cerebral perfusion and impaired cerebral autoregulation.

METHODS

In this cross-sectional study, we included HD patients age 50 years or older receiving conventional in-center HD. We measured cerebral perfusion during HD, using cerebral oximetry, and calculated the correlation between cerebral perfusion and BP during HD as an index of CA. We measured the association between potential risk factors for intradialytic decline in cerebral perfusion and CA index.

FINDINGS

We included 32 participants and 118 HD sessions in our analysis. The mean ± SD decline in cerebral oxygen saturation during HD was 6.5% ± 2.9% with a relative decline from baseline values of 9.2% ± 4.4%. Greater drop in systolic BP (SBP) during HD was associated with decline in cerebral oxygen saturation, p = 0.02. Impaired CA index was noted in 37.3% of HD sessions. Having diabetes and >20 mmHg drop in SBP during HD were associated with increased (worse) CA index with an increase of 0.24 95%CI [0.06, 0.41] for diabetes and increase of 0.43 95%CI [0.27, 0.56] for a >20 mmHg drop in SBP during HD.

DISCUSSION

Cerebral perfusion can decline during HD and is associated with changes in systemic BP. This may be due to impaired cerebral autoregulation in HD patients. Risk factors for worse CA index include diabetes and >20 mmHg drop in SBP during HD. This study highlights the risk of intradialytic decline in cerebral perfusion and impaired cerebral autoregulation in HD patients.

Changes of Brain Functional Connectivity in End-Stage Renal Disease Patients Receiving Peritoneal Dialysis Without Cognitive Decline

Background: Functional connectivity detected by resting-state functional MRI (R-fMRI) helps to discover the subtle changes in brain activities. Patients with end-stage renal disease (ESRD) on hemodialysis (HD) have impaired brain networks. However, the functional changes of brain networks in patients with ESRD undergoing peritoneal dialysis (PD) have not been fully delineated, especially among those with preserved cognitive function. Therefore, it is worth knowing about the brain functional connectivity in patients with PD by using R-fMRI.

Methods: This case-control study prospectively enrolled 19 patients with ESRD receiving PD and 24 age- and sex- matched controls. All participants without a history of cognitive decline received mini-mental status examination (MMSE) and brain 3-T R-fMRI. Comprehensive R-fMRI analyses included graph analysis for connectivity and seed-based correlation networks. Independent t-tests were used for comparing the graph parameters and connectivity networks between patients with PD and controls.

Results: All subjects were cognitively intact (MMSE > 24). Whole-brain connectivity by graph analysis revealed significant differences between the two groups with decreased global efficiency (E_glob, p < 0.05), increased betweenness centrality (BC) (p < 0.01), and increased characteristic path length (L, p < 0.01) in patients with PD. The functional connections of the default-mode network (DMN), sensorimotor network (SMN), salience network (SN), and hippocampal network (HN) were impaired in patients with PD. Meanwhile, in DMN and SN, elevated connectivity was observed in certain brain regions of patients with PD.

Conclusion: Patients with ESRD receiving PD had specific disruptions in functional connectivity. In graph analysis, E_glob, BC, and L showed significant connectivity changes compared to the controls. DMN and SN had the most prominent alterations among the observed networks, with both decreased and increased connectivity regions. Our study confirmed that significant changes in cerebral connections existed in cognitively intact patients with PD.

Preserved Cerebral Oxygenation with Worsening Global Myocardial Strain during Pediatric Chronic Hemodialysis

BACKGROUND

Cerebral and myocardial hypoperfusion occur during hemodialysis in adults. Pediatric patients receiving chronic hemodialysis have fewer cardiovascular risk factors, yet cardiovascular morbidity remains prominent.

METHODS

We conducted a prospective observational study of pediatric patients receiving chronic hemodialysis to investigate whether intermittent hemodialysis is associated with adverse end organ effects in the heart or with cerebral oxygenation (regional tissue oxyhemoglobin saturation [rSO2]). We assessed intradialytic cardiovascular function and rSO2 using noninvasive echocardiography to determine myocardial strain and continuous noninvasive near-infrared spectroscopy for rSO2. We measured changes in blood volume and measured central venous oxygen saturation (mCVO2) pre-, mid-, and post-hemodialysis.

RESULTS

The study included 15 patients (median age, 12 years; median hemodialysis vintage, 13.2 [9-24] months). Patients were asymptomatic. The rSO2 did not change during hemodialysis, whereas mCVO2 decreased significantly, from 73% to 64.8%. Global longitudinal strain of the myocardium worsened significantly by mid-hemodialysis and persisted post-hemodialysis. The ejection fraction remained normal. Lower systolic BP and faster blood volume change were associated with worsening myocardial strain; only blood volume change was significant in multivariate analysis (β-coefficient, -0.3; 95% confidence interval [CI], -0.38 to -0.21; P<0.001). Blood volume change was also associated with a significant decrease in mCVO2 (β-coefficient, 0.42; 95% CI, 0.07 to 0.76; P=0.001). Access, age, hemodialysis vintage, and ultrafiltration volume were not associated with worsening strain.

CONCLUSIONS

Unchanged rSO2 suggested that cerebral oxygenation was maintained during hemodialysis. However, despite maintained ejection fraction, intradialytic myocardial strain worsened in pediatric hemodialysis and was associated with blood volume change. The effect of hemodialysis on individual organ perfusion in pediatric versus adult patients receiving hemodialysis might differ.

Assessment of cerebral oxygenation response to hemodialysis using near-infrared spectroscopy (NIRS): Challenges and solutions

To date, the clinical use of functional near-infrared spectroscopy (NIRS) to detect cerebral ischemia has been largely limited to surgical settings, where motion artifacts are minimal. In this study, we present novel techniques to address the challenges of using NIRS to monitor ambulatory patients with kidney disease during approximately eight hours of hemodialysis (HD) treatment. People with end-stage kidney disease who require HD are at higher risk for cognitive impairment and dementia than age-matched controls. Recent studies have suggested that HD-related declines in cerebral blood flow might explain some of the adverse outcomes of HD treatment. However, there are currently no established paradigms for monitoring cerebral perfusion in real-time during HD treatment. In this study, we used NIRS to assess cerebral hemodynamic responses among 95 prevalent HD patients during two consecutive HD treatments. We observed substantial signal attenuation in our predominantly Black patient cohort that required probe modifications. We also observed consistent motion artifacts that we addressed by developing a novel NIRS methodology, called the HD cerebral oxygen demand algorithm (HD-CODA), to identify episodes when cerebral oxygen demand might be outpacing supply during HD treatment. We then examined the association between a summary measure of time spent in cerebral deoxygenation, derived using the HD-CODA, and hemodynamic and treatment-related variables. We found that this summary measure was associated with intradialytic mean arterial pressure, heart rate, and volume removal. Future studies should use the HD-CODA to implement studies of real-time NIRS monitoring for incident dialysis patients, over longer time frames, and in other dialysis modalities.

Chronic Kidney Disease Associated with Worsening White Matter Disease and Ventricular Enlargement

BACKGROUND

Chronic kidney disease (CKD), a growing public health issue in the elderly, is associated with increased risk of cognitive impairment.

OBJECTIVE

To investigate the mechanisms through which CKD impacts brain health using longitudinal imaging.

METHODS

We identified 97 participants (74 CKD and 23 non-CKD) from the BRINK (BRain IN Kidney Disease), a longitudinal study of CKD with two MRI scans (baseline and 3-year follow-up). We measured the associations between baseline and change in kidney disease biomarkers of estimated glomerular filtration rate (eGFR) and urinary albumin to creatinine ratio (UACR), considered a measure of microvascular inflammation, and imaging outcomes of cortical thickness and ventricular volume from structural MRI, white matter hyperintensities (WMH) volume from FLAIR images, and fractional anisotropy of the corpus callosum (FACC).

RESULTS

There were white matter-specific changes as observed by increased WMH volume and decreased FACC in CKD participants, as well as ventricular volume increase in both CKD and non-CKD groups reflective of aging-related changes. Decline in eGFR was associated with decrease in the FACC, suggesting that subtle early white matter changes due to kidney disease can be captured using DTI. An increase in UACR was associated with increase in ventricular volume.

CONCLUSION

Our results support the role of eGFR as a measure of kidney microvascular disease which is associated with concurrent white matter damage in CKD. Future work is needed to investigate the possible link between endothelial microvascular inflammation (as measured by an increased UACR) and ventricular volume increase.

Abnormal brain activity patterns during spatial working memory task in patients with end-stage renal disease on maintenance hemodialysis: a fMRI study

Hemodialysis (HD) is associated with cognitive impairment in patients with end-stage renal disease (ESRD). However, the neural mechanism of spatial working memory (SWM) impairment in HD-ESRD patients remains unclear. We investigated the abnormal alterations in SWM-associated brain activity patterns in HD-ESRD patients using blood oxygen level-dependent functional magnetic resonance imaging (BOLD-fMRI) technique during n-back tasks. Twenty-two HD-ESRD patients and 22 well-matched controls underwent an fMRI scan while undergoing a three-load n-back tasks with different difficulty levels. Cognitive and mental states were assessed using a battery of neuropsychologic tests. The HD-ESRD patients exhibited worse memory abilities than controls. Compared with the control group, the HD-ESRD patient group showed lower accuracy and longer response time under the n-back tasks, especially in the 2-back task. The patterns of brain activation changed under different working memory loads in the HD-ESRD patients, showing decreased activity in the right medial frontal gyrus and inferior frontal gyrus under 0-back and 1-back task, while more decreased activation in the bilateral frontal cortex, parietal lobule, anterior/posterior cingulate cortex and insula cortex under 2-back task. With the increase of task difficulty, the activation degree of the frontal and parietal cortex decreased. More importantly, we found that lower activation in frontal cortex and parietal lobule was associated with worse cognitive function in the HD-ESRD patients. These results demonstrate that the abnormal brain activity patterns of frontal cortex and parietal lobule may reflect the neural mediation of SWM impairment.

Signatures of Gait Movement Variability in CKD Patients Scheduled for Hemodialysis Indicate Pathological Performance Before and After Hemodialysis: A Prospective, Observational Study

Background: The frailty status of hemodialysis patients is well-known, but the role of the therapy in the frailty process is not yet clear. Nowadays gait analysis in nephrology is neglected, although gait performance is known to be related to frailty and kidney function. We hypothesized that gait quality and physical activity level is already affected before, and does not change because of the start of hemodialysis.

Methods: Fourteen patients (72.3 ± 5.7 years old) in a pre-dialysis program underwent an instrumental gait analysis and their physical activity was monitored for a week. This protocol was repeated 3, 6, 12, and 24 months after the first hemodialysis session.

Results: At baseline, our sample showed a conservative gait with pathologic gait variability, high dual-task cost, and a sedentary lifestyle. No statistically significant change was found in any parameter in the analyzed period, but there was a tendency toward an improvement of gait quality and physical activity in the first year of treatment, and a decline in the second year.

Conclusion: Elderly patients in the pre-dialysis stage show a conservative gait, however variability was in a pathological range and did not change post-hemodialysis. This hints toward changes in the central nervous system due to the kidney disease. This finding suggests the importance of gait analysis in the early stages of renal disease in the diagnosis of changes in the nervous system due to kidney failure that affect gait. Early detection of these changes would potentially allow a prevention program tailored to this population to be developed.

Increased Premature Cerebral Small Vessel Diseases in Dialysis Patients: A Retrospective Cross-Sectional Study

BACKGROUND

Growing data indicate a higher prevalence of cerebrovascular diseases in patients with ESRD. Cerebral small-vessel disease (CSVD) is an important risk factor of stroke and dementia. A comprehensive assessment of CSVD in a dialysis population is needed.

METHODS

In this retrospective cross-sectional study, we enrolled 179 dialysis patients and 351 controls matched by sex and age with normal serum creatinine. The presence and locations of 3 main features of CSVD in dialysis patients, including lacunes, cerebral microbleeds (CMBs), and white matter hyperintensities (WMHs), were evaluated with brain magnetic resonance imaging and compared with controls. Univariate and multivariate analyses were performed to identify risk factors.

RESULTS

Compared with controls, the prevalence of CSVD was significantly increased in dialysis patients (odds ratio [OR] 2.66, 95% confidence interval [CI] 1.26-5.62). Among them, risks of CMBs and WMHs were increased in dialysis (OR 4.01, 95% CI 1.78-9.42; 3.91, 95% CI 1.67-9.15), except for lacunes. The age of subjects with CSVD detected was significantly younger in the dialysis group (p = 0.002). Unlike controls, basal ganglia were most affected by lacunes and CMBs in dialysis patients. In dialysis patients, multivariate analysis further revealed that aging, smoking, and hyperlipidemia were significantly associated with CSVD, while dialysis modality was not significant.

CONCLUSION

We demonstrated a higher prevalence and early-onset tendency of CSVD in dialysis patients, especially for CMBs and WMHs. Dialysis patients showed different patterns and associated factors for CSVD.

A Narrative Review of Management Strategies for Common Symptoms in Advanced CKD

Patients with advanced chronic kidney disease (CKD) experience multiple bothersome symptoms, undermining their quality of life (QOL). With growing attention to the importance of symptom management in advanced CKD, the evidence regarding symptoms is increasing. In this review, we briefly summarize the current evidence of effective pharmacologic and nonpharmacologic interventions to improve symptoms and QOL in patients with advanced CKD, including those on dialysis. We focused on symptoms that are commonly experienced by patients, such as pain, fatigue, sleep disturbances, itching, nausea and vomiting, cognitive impairment, and anxiety and depression. We noted that research in symptom science focused on improving symptom management in CKD is still very limited. In addition to the lack of clinical practice guidelines to address those common symptoms, the major gaps in the current literature include the evidence regarding mechanistic pathways to inform the development of effective symptom management for CKD populations, the evidence to confirm effective pharmacologic interventions in other populations for CKD populations, and research on how to incorporate effective symptom management approaches into clinical care. Although improving mortality remains as an important area in the kidney community, there is an urgent need to focus on improving symptom management to improve QOL in advanced CKD.

Diastolic blood pressure is associated with brain atrophy in hemodialysis patients: A single center case-control study

Brain atrophy (BA) is often found in neuroimaging of hemodialysis patients, representing parenchymal cerebral damage. Likely contributing factors to BA are age, chronic hypertension, diabetes mellitus and other cardiovascular risk factors of atherosclerosis that are also common among hemodialysis patients. BA may also occur due to focal ischemia and hypoperfusion during hemodialysis. However, data on optimal blood pressure (BP) in these patients are limited. The goal of this study was to determine whether the prevalence and severity of BA would be higher among hemodialysis patients with lower BP. A blinded neuroradiologist graded BA of all hemodialysis patients who underwent brain non-contrast computerized tomography (CT) from 2015 to 2017 in our institution. Age- and sex-matched patients with normal kidney function who underwent brain CT during the same period and technique served as the control group. A total of 280 patients were included in this retrospective study, with average BP of 140/70 mmHg among hemodialysis patients and 142/75 mmHg in the control group. BA was more common in dialysis patients and its severity increased with age and traditional cardiovascular risk factors. We observed a significant negative correlation between diastolic BP (DBP) at dialysis initiation and BA. Average DBP decreased with increasing severity of BA. These findings were observed in both hemodialysis and non-CKD patients. BA was associated with lower DBP, which may induce cerebral hypoperfusion and ischemia. This finding should discourage over-treatment of hypertension among hemodialysis patients.

Cognitive impairment, endothelial biomarkers and mortality in maintenance haemodialysis patients: a prospective cohort study

BACKGROUND

Haemodialysis (HD) patients have a high prevalence of cardiovascular disease risk factors as well as cognitive impairment. The objective of the present study was to evaluate the interrelationship between cognitive impairment, endothelium-related biomarkers and cardiovascular/non-cardiovascular mortality.

METHODS

A total of 216 outpatients were recruited from three centres in a dialysis network in Brazil between June 2016 and June 2019. Sociodemographic and clinical data were obtained by applying a patient questionnaire, reviewing medical records data and conducting patient interviews. Cognitive function was assessed using the Cambridge Cognitive Examination. Plasma endothelium-related biomarkers [syndecan-1, intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion protein-1 (VCAM-1) and angiopoietin-2 (AGPT2)] were measured. Patients were followed for 30 months. Cox proportional hazards regression models were used to assess the associations of the cognitive function scores and each endothelium-related biomarker with cardiovascular/non-cardiovascular mortality.

RESULTS

Cognitive function was associated with cardiovascular mortality {each standard deviation [SD] better cognitive score was associated with a 69% lower risk for cardiovascular mortality [hazard ratio (HR) 0.31 [95% confidence interval (CI) 0.17-0.58]} but not with non-cardiovascular mortality. Moreover, cognitive function was also correlated with all endothelial-related biomarkers, except VCAM-1. ICAM-1, AGPT2 and syndecan-1 were also associated with cardiovascular mortality. The association between cognitive function and cardiovascular mortality remained significant with no HR value attenuation [fully adjusted HR 0.32 (95% CI 0.16-0.59)] after individually including each endothelial-related biomarker in the Cox model.

CONCLUSIONS

In conclusion, cognitive impairment was associated with several endothelium-related biomarkers. Moreover, cognitive impairment was associated with cardiovascular mortality but not with non-cardiovascular mortality, and the association between cognitive impairment and cardiovascular mortality in HD patients was not explained by any of the endothelial-related biomarkers.

Normalization of Cerebral Blood Flow, Neurochemicals, and White Matter Integrity after Kidney Transplantation

BACKGROUND

CKD is associated with abnormalities in cerebral blood flow, cerebral neurochemical concentrations, and white matter integrity. Each of these is associated with adverse clinical consequences in the non-CKD population, which may explain the high prevalence of dementia and stroke in ESKD. Because cognition improves after kidney transplantation, comparing these brain abnormalities before and after kidney transplantation may identify potential reversibility in ESKD-associated brain abnormalities.

METHODS

In this study of patients with ESKD and age-matched healthy controls, we used arterial spin labeling to assess the effects of kidney transplantation on cerebral blood flow and magnetic resonance spectroscopic imaging to measure cerebral neurochemical concentrations (N-acetylaspartate, choline, glutamate, glutamine, myo-inositol, and total creatine). We also assessed white matter integrity measured by fractional anisotropy (FA) and mean diffusivity (MD) with diffusion tensor imaging. We used a linear mixed model analysis to compare longitudinal, repeated brain magnetic resonance imaging measurements before, 3 months after, and 12 months after transplantation and compared these findings with those of healthy controls.

RESULTS

Study participants included 29 patients with ESKD and 19 controls; 22 patients completed post-transplant magnetic resonance imaging. Cerebral blood flow, which was higher in patients pretransplant compared with controls (P=0.003), decreased post-transplant (P<0.001) to values in controls. Concentrations of neurochemicals choline and myo-inositol that were higher pretransplant compared with controls (P=0.001 and P<0.001, respectively) also normalized post-transplant (P<0.001 and P<0.001, respectively). FA increased (P=0.001) and MD decreased (P<0.001) post-transplant.

CONCLUSIONS

Certain brain abnormalities in CKD are reversible and normalize with kidney transplantation. Further studies are needed to understand the mechanisms underlying these brain abnormalities and to explore interventions to mitigate them even in patients who cannot be transplanted.

CLINICAL TRIAL REGISTRY NAME AND REGISTRATION NUMBER

Cognitive Impairment and Imaging Correlates in End Stage Renal Disease, NCT01883349.

Intradialytic hypotension and relationship with cognitive function and brain morphometry

Background

The haemodynamic stress brought about by dialysis could justify the loss of structural and functional integrity of the central nervous system (CNS). The main objective of this study was to analyse the relationship between intradialytic hypotension (IDH) and cognitive function and brain morphometry.

Methods

The cross-sectional KIDBRAIN study (Cohort Study of Morphological Changes of the Brain by MRI in Chronic Kidney Disease Patients) included 68 prevalent patients with no history of neurological disorders (cerebrovascular disease and cognitive impairment) undergoing haemodialysis (HD). We analysed 18 non-consecutive dialysis sessions (first three of each month over a 6-month period) and various definitions of IDH were recorded. Global cognitive function (GCF) was assessed using the Mini-Mental State Examination (MMSE) and parameters of structural integrity of the CNS were obtained using volume morphometry magnetic resonance imaging analysis [grey matter (GM), white matter (WM) and hippocampus).

Results

A greater number of sessions with IDH were associated with less volume of WM (r = −0.359,P = 0.003) and hippocampus (r = −0.395, P = 0.001) independent of cardiovascular risk factors according to multivariable linear regression models (β = −0.198, P = 0.046 for WM; β = −0.253, P = 0.017 for hippocampus). The GCF by the MMSE was 27.3 ± 7.3.1 and was associated with WM volume (β = 0.403, P = 0.001) independent of GM and hippocampus volume. Symptomatic IDH was associated with GCF (r = −0.420, P < 0.001) in adjusted analysis (β = −0.339, P = 0.008).

Conclusions

Even when asymptomatic, IDH is associated with a lower WM and hippocampus volume and reduced GCF in patients undergoing HD, thus suggesting greater vulnerability of the brain to the haemodynamic stress that may be generated by a dialysis session.

Interventions to Preserve Cognitive Functioning Among Older Kidney Transplant Recipients

PURPOSE OF REVIEW

To summarize the research on effective interventions for preserving cognitive function and prevent cognitive decline in patients with end-stage kidney disease (ESKD) who are undergoing dialysis and/or kidney transplantation (KT).

RECENT FINDINGS

Among ESKD patients undergoing hemodialysis, exercise training has been administered through home-based and intradialytic interventions. Additionally, one pilot study identified intradialytic cognitive training, electronic brain games, as an intervention to preserve cognitive function among patients undergoing hemodialysis. Fewer studies have investigated interventions to preserver cognitive function among KT recipients. To date, the only randomized controlled trial in this population identified B-vitamin supplements as an intervention to preserve cognitive function. The evidence from these trials support a short-term benefit of cognitive and exercise training as well as B-vitamin supplementation among patients with ESKD. Future studies should: 1) replicate these findings, 2) identify interventions specific to KT candidates, and 3) investigate the synergistic impact of both cognitive and exercise training.

SUMMARY

Cognitive prehabilitation, with cognitive and/or exercise training, may be novel interventions for KT candidates that not only reduces delirium risk and long-term post-KT cognitive decline but also prevents dementia.

Changes in Cerebral Volume and White Matter Integrity in Adults on Hemodialysis and Relationship to Cognitive Function

INTRODUCTION

Patients on hemodialysis (HD) have a significant burden of cognitive impairment. Characterizing the cerebral structural changes in HD patients compared to healthy controls and evaluating the relationship of cerebral structural integrity with cognitive performance in HD patients can help clarify the pathophysiology of the cognitive impairment in HD patients.

METHODS

In this cross-sectional study, in-center HD patients ≥50 years of age underwent brain structural and diffusion MRIs and cognitive assessment using the NIH Toolbox cognition battery. The cerebral imaging measures of the HD participants were compared to imaging from age-matched controls. Gray matter volume, white matter volume, and white matter integrity determined by diffusion tensor imaging parameters (including fractional anisotropy [FA]) were measured in both cohorts to determine differences in the cerebral structure between HD participants and healthy controls. The association between cognitive performance on the NIH Toolbox cognition battery and cerebral structural integrity was evaluated using multiple linear regression models.

RESULTS

We compared imaging measures form 23 HD participants and 15 age-matched controls. The HD participants had decreased gray matter volumes (526.8 vs. 589.5 cm3, p < 0.01) and worsened white matter integrity overall (FA values of 0.2864 vs. 0.3441, p < 0.01) within major white matter tracts compared to healthy controls. Decreases in white matter integrity in the left superior longitudinal fasciculus was associated with lower executive function scores (r2 = 0.24, p = 0.02) and inferior longitudinal fasciculus with lower memory scores (r = 0.25 and p = 0.03 for left and r2 = 0.21 and p = 0.03 for right).

CONCLUSIONS

HD patients have a pattern of decreased white matter integrity and gray matter atrophy compared to controls. Decreases in white matter integrity were associated with decreased cognitive performance in the HD population.

Cerebral blood flow regulation in end-stage kidney disease

Patients with chronic kidney disease (CKD) and end-stage kidney disease (ESKD) experience an increased risk of cerebrovascular disease and cognitive dysfunction. Hemodialysis (HD), a major modality of renal replacement therapy in ESKD, can cause rapid changes in blood pressure, osmolality, and acid-base balance that collectively present a unique stress to the cerebral vasculature. This review presents an update regarding cerebral blood flow (CBF) regulation in CKD and ESKD and how the maintenance of cerebral oxygenation may be compromised during HD. Patients with ESKD exhibit decreased cerebral oxygen delivery due to anemia, despite cerebral hyperperfusion at rest. Cerebral oxygenation further declines during HD due to reductions in CBF, and this may induce cerebral ischemia or "stunning." Intradialytic reductions in CBF are driven by decreases in cerebral perfusion pressure that may be partially opposed by bicarbonate shifts during dialysis. Intradialytic reductions in CBF have been related to several variables that are routinely measured in clinical practice including ultrafiltration rate and blood pressure. However, the role of compensatory cerebrovascular regulatory mechanisms during HD remains relatively unexplored. In particular, cerebral autoregulation can oppose reductions in CBF driven by reductions in systemic blood pressure, while cerebrovascular reactivity to CO₂ may attenuate intradialytic reductions in CBF through promoting cerebral vasodilation. However, whether these mechanisms are effective in ESKD and during HD remain relatively unexplored. Important areas for future work include investigating potential alterations in cerebrovascular regulation in CKD and ESKD and how key regulatory mechanisms are engaged and integrated during HD to modulate intradialytic declines in CBF.

Cognitive Function in Kidney Transplantation

Purpose of the review

Cognitive impairment is common in kidney transplant recipients and affects quality of life, graft survival, morbidity, and mortality. In this review article we discuss the epidemiology, diagnosis, pathophysiology and future directions for cognitive impairment in kidney transplantation. We describe the potential role of pre-transplant cognition, immunosuppression and peri-transplant factors in post -transplant cognitive impairment.

Recent Findings

A majority of patients with kidney transplant have cognitive impairment. Cognitive impairment affects both pre-transplant evaluation and post-transplant outcomes. Failure to identify patients with cognitive impairment can withhold appropriate care and timely intervention.

Summary

Cognitive impairment is common in kidney transplant and affects outcomes. Studies addressing modifiable risk factors and possible interventions to slow cognitive decline in patients with kidney disease are needed.

Immediate Abnormal Intrinsic Brain Activity Patterns in Patients with End-stage Renal Disease During a Single Dialysis Session : Resting-state Functional MRI Study

PURPOSE

To investigate cerebral amplitude of low-frequency fluctuations (ALFF) changes during a single hemodialysis (HD) in end-stage renal disease (ESRD) patients who need maintenance HD.

MATERIALS AND METHODS

A total of 24 patients and 27 healthy subjects were included. The patients underwent neuropsychological tests and took twice resting-state fMRI (rs-fMRI) (before and after HD). Healthy group had one rs-fMRI. The zALFF based on rs-fMRI was calculated. Paired t and independent t test was applied to compare zALFF among groups. The associations between zALFF and duration of HD, ultrafiltration volume, and neuropsychological tests was calculated by partial correlation.

RESULTS

Compared to healthy group, patients before HD showed significant worse performances on digit symbol test (DST) and serial dotting test (SDT). Patients after HD performed DST better than before HD. The patients after HD showed higher zALFF in left putamen than before HD. Multiple regions of both HD groups showed significant lower zALFF than healthy group. The zALFF of left putamen of patients after HD was significant negative correlated with the ultrafiltration volume (R = -0.679). The zALFF in patients before HD exhibited significantly positive or negative correlations with DST and SDT in multiple regions. The zALFF of patients after HD significantly negative correlated with DST in right temporal, positive and negative correlated with ultrafiltration volume in right frontal, left putamen respectively.

CONCLUSION

ESRD patients showed changed spontaneous brain activity and cognitive impairments. After a single HD session, patients performed better in neuropsychological test, and spontaneous brain activity changed in left putamen. Ultrafiltration volume might be associated with activity of left putamen.

Brain function and metabolism in patients with long-term tacrolimus therapy after kidney transplantation in comparison to patients after liver transplantation

Background

About 50% of the patients 5–7 years after kidney transplantation show impairment of memory, attention and executive function. Tacrolimus frequently induces neurological complications in the first few weeks after transplantation. Furthermore, tacrolimus treatment is associated with impaired cognitive function in the long-term in patients after liver transplantation. We hypothesize that long-term tacrolimus therapy is associated with cognitive dysfunction and alterations of brain structure and metabolism in patients after kidney transplantation.

Methods

Twenty-one patients 10 years after kidney transplantation underwent cognitive testing, magnetic resonance imaging and whole brain 31-phosphor magnetic resonance spectroscopy for the assessment of brain function, structure and energy metabolism. Using a cross-sectional study design the results were compared to those of patients 1 (n = 11) and 5 years (n = 10) after kidney transplantation, and healthy controls (n = 17). To further analyze the share of transplantation, tacrolimus therapy and kidney dysfunction on the results patients after liver transplantation (n = 9) were selected as a patient control group.

Results

Patients 1 and 10 years after kidney transplantation (p = 0.02) similar to patients 10 years after liver transplantation (p<0.01) showed significantly worse cognitive function than healthy controls. In contrast to patients after liver transplantation patients after kidney transplantation showed significantly reduced adenosine triphosphate levels in the brain compared to healthy controls (p≤0.01). Patients 1 and 5 years after kidney transplantation had significantly increased periventricular hyperintensities compared to healthy controls (p<0.05).

Conclusions

Our data indicate that cognitive impairment in the long-term after liver and kidney transplantation cannot exclusively be explained by CNI neurotoxicity.

Evaluation of Screening Tests for Cognitive Impairment in Patients Receiving Maintenance Hemodialysis

BACKGROUND

Neurocognitive testing shows that cognitive impairment is common among patients receiving maintenance hemodialysis. Identification of a well performing screening test for cognitive impairment might allow for broader assessment in dialysis facilities and thus optimal delivery of education and medical management.

METHODS

From 2015 to 2018, in a cohort of 150 patients on hemodialysis, we performed a set of comprehensive neurocognitive tests that included the cognitive domains of memory, attention, and executive function to classify whether participants had normal cognitive function versus mild, moderate, or severe cognitive impairment. Using area-under-the-curve (AUC) analysis, we then examined the predictive ability of the Mini Mental State Examination, the Modified Mini Mental State Examination, the Montreal Cognitive Assessment, the Trail Making Test Part B, the Mini-Cog test, and the Digit Symbol Substitution Test, determining each test's performance for identifying severe cognitive impairment.

RESULTS

Mean age was 64 years; 61% were men, 39% were black, and 94% had at least a high-school education. Of the 150 participants, 21% had normal cognitive function, 17% had mild cognitive impairment, 33% had moderate impairment, and 29% had severe impairment. The Montreal Cognitive Assessment had the highest overall predictive ability for severe cognitive impairment (AUC, 0.81); a score of ≤21 had a sensitivity of 86% and specificity of 55% for severe impairment, with a negative predictive value of 91%. The Trails B and Digit Symbol tests also performed reasonably well (AUCs, 0.73 and 0.78, respectively). The other tests had lower predictive performances.

CONCLUSIONS

The Montreal Cognitive Assessment, a widely available and brief cognitive screening tool, showed high sensitivity and moderate specificity in detecting severe cognitive impairment in patients on maintenance hemodialysis.

Quality of life and cognitive and functional performance of octogenarians and nonagenarians undergoing hemodialysis

OBJECTIVE

To evaluate the quality of life, cognitive and functional capacity of older adult patients undergoing hemodialysis who are 80 years of age or older and compare them to older adults without chronic kidney disease (CKD) treated at a geriatrics outpatient clinic.

METHOD

First, 103 older adult patients undergoing hemodialysis and 103 older adults without CKD matched by gender and age were evaluated. Cognitive aspects as evaluated by the mini mental state examination, the Boston Naming Test and verbal fluency were analyzed; comorbidities according to the Charlson's comorbidity index; social support through the Medical Outcomes Study scale; functional ability through the chair sit-to-stand and gait speed tests, as well as the basic activities of daily living (BADL) and instrumental activities of daily living (IADL) and quality of life according to the Kidney Disease Quality of Life Short Form (KDQOL SF-36) questionnaires.

RESULTS

The hemodialysis group had a higher rate of comorbidities (7.8 ± 2.4 vs. 5.8 ± 2.3, p < 0.001). In the multiple logistic regression analysis, the group undergoing hemodialysis presented a ninefold greater chance of dependence for IADL than controls, a 4.3 and 3.2 times greater chances for inadequacy on the gait speed and chair sit-to-stand tests, respectively, as well as a 4.4-fold higher risk of cognitive decline on the verbal fluency test.

CONCLUSION

Long-lived patients undergoing hemodialysis presented worse quality of life and functional and cognitive performance compared to long-term patients attended at the outpatient clinic, indicating that preventive and protective measures should be considered and implemented.

Intradialytic Cerebral Hypoperfusion as Mechanism for Cognitive Impairment in Patients on Hemodialysis

The high frequency of cognitive impairment in individuals on hemodialysis is well characterized. In-center hemodialysis patients are disproportionately affected by cognitive impairment compared with other dialysis populations, identifying hemodialysis itself as a possible factor. The pathophysiology of cognitive impairment has multiple components, but vascular-mediated cerebral injury appears to contribute based on studies demonstrating increased cerebral ischemic lesions and atrophy in brain imaging of patients on hemodialysis. Patients on hemodialysis may be at increased risk for cerebral ischemic injury disease due to vasculopathy associated with ESKD and from their comorbid diseases, such as hypertension and diabetes. This review focuses on the intradialytic cerebral hypoperfusion that can occur during routine hemodialysis due to the circulatory stress of hemodialysis. This includes a review of current methods used to monitor intradialytic cerebral perfusion and the structural and functional cognitive outcomes that have been associated with changes in intradialytic cerebral perfusion. Monitoring of intradialytic cerebral perfusion may become clinically relevant as nephrologists try to avoid the cognitive complications seen with hemodialysis. Identifying the appropriate methods to assess risk for cerebral ischemic injury and the relationship of intradialytic cerebral hypoperfusion to cognitive outcomes will help inform the decision to use intradialytic cerebral perfusion monitoring in the clinical setting as part of a strategy to prevent cognitive decline.

Cognitive assessment in a predominantly Hispanic and Native American population in New Mexico and its association with kidney transplant wait-listing

The association between cognitive function and the likelihood of kidney transplant (KT) wait-listing, especially in minority populations, has not been clearly delineated. We performed a retrospective review of our pre-KT patients, who consist mainly of Hispanics and Native Americans, over a 16-month period. We collected data on baseline demographics and the Montreal Cognitive Assessment (MoCA) score, at the initial KT evaluation. We defined cognitive impairment as MoCA scores of <24. We constructed linear regression models to identify associations between baseline characteristics with MoCA scores and used Cox proportional hazards models to assess associations between MoCA score and KT wait-listing. During the study period, 154 patients completed the MoCA during their initial evaluation. Mean (standard deviation) MoCA scores were 23.9 (4.6), with 58 (38%) participants scoring <24. Advanced age, lower education and being on dialysis were associated with lower MoCA scores. For every one-point increase in MoCA, the likelihood of being wait-listed increased 1.10-fold (95% CI 1.01-1.19, P = .022). Being Native American and having kidney disease due to diabetes or hypertension were associated with longer time to wait-listing. Cognitive impairment was common in our pre-KT patients and was associated with a lower likelihood of KT wait-listing.

Cognitive Impairment in CKD: Pathophysiology, Management, and Prevention

Patients with chronic kidney disease (CKD) are at substantially higher risk for developing cognitive impairment compared with the general population, and both lower glomerular filtration rate and the presence of albuminuria are associated with the development of cognitive impairment and poorer cognitive function. Given the excess of vascular disease seen in individuals with CKD, cerebrovascular disease is likely the predominant pathology underlying these associations, though impaired clearance of uremic metabolites, depression, sleep disturbance, anemia, and polypharmacy may also contribute. Modification of vascular disease risk factors may be helpful in limiting decline, though definite data are lacking. Specific to CKD, targeting a low blood pressure and reduction in albuminuria with angiotensin-converting enzyme inhibitors or angiotensin receptor blockers may slow cognitive decline, albeit modestly. Initiation of dialysis can improve severe impairment associated with uremia but does not appear to affect more subtle chronic cognitive impairment. In contrast, kidney transplantation appears to lead to improved cognitive function in many transplant recipients, suggesting that dialysis methods do not provide the same cognitive benefits as having a functioning kidney. Management of patients with both CKD and cognitive impairment should include a comprehensive plan including more frequent follow-up visits; involvement of family in shared decision making; measures to improve compliance, such as written instruction and pill counts; and a focus on advance directives in conjunction with an emphasis on understanding an individual patient's life goals. Further research is needed on novel therapies, including innovative dialysis methods, that aim to limit the development of cognitive impairment, slow decline in those with prevalent impairment, and improve cognitive function.

Anticoagulation in Patients With Advanced Chronic Kidney Disease: Walking the Fine Line Between Benefit and Harm

Chronic kidney disease affects more than 3 million Canadians and is highly associated with cardiovascular diseases that require anticoagulation, such as atrial fibrillation and venous thromboembolism. Patients with chronic kidney disease are at a problematic crossroads; they are at high risk of thrombotic conditions requiring anticoagulation and bleeding complications due to anticoagulation. The limited high-quality clinical evidence to guide decision-making in this area further compounds the dilemma. In this review, we discuss the physiology and epidemiology of bleeding and thrombosis in patients with kidney disease. We specifically focus on patients with advanced kidney disease (estimated glomerular filtration rate ≤ 30 mL/min) or who are receiving dialysis and focus on the nephrologist perspective regarding these issues. We summarize the existing evidence for anticoagulation use in the prevention of stroke with atrial fibrillation and provide practical clinical recommendations for considering anticoagulation use in this population. Last, we examine specific scenarios such as the use of a glomerular filtration rate estimating equation and dosing, the use of existing prediction tools for stroke and hemorrhage risk, current patterns of anticoagulation use (including during the dialysis procedure), and vascular calcification with vitamin K antagonist use in patients with chronic kidney disease.

Exercise and cognitive function in patients with end-stage kidney disease

In this review we summarize the research pertaining to the role of exercise in preventing cognitive decline in patients with end-stage kidney disease (ESKD). Impairment in cognitive function, especially in executive function, is common in patients with ESKD, and may worsen with maintenance dialysis as a result of retention of uremic toxins, recurrent cerebral ischemia, and high burden of inactivity. Cognitive impairment may lead to long-term adverse consequences, including dementia and death. Home-based and intradialytic exercise training (ET) are among the nonpharmacologic interventions identified to preserve cognitive function in ESKD. Additionally, cognitive training (CT) is an effective approach recently identified in this population. While short-term benefits of ET and CT on cognitive function were consistently observed in patients undergoing dialysis, more studies are needed to replicate these findings in diverse populations including kidney transplant recipients with long-term follow-up to better understand the health and quality of life consequences of these promising interventions. ET as well as CT are feasible interventions that may preserve or even improve cognitive function for patients with ESKD. Whether these interventions translate to improvements in quality of life and long-term health outcomes, including dementia prevention and better survival, are yet to be determined.