Cerebral blood flow regulation in end-stage kidney disease

Transcutaneous auricular vagus nerve stimulation improves cognitive decline by alleviating intradialytic cerebral hypoxia in hemodialysis patients: A fNIRS pilot study

Cognitive impairment is common in hemodialysis patients, possibly due to inadequate cerebral blood flow during hemodialysis. No effective non-pharmacological interventions are available. This study investigates the impact of hemodialysis-induced cerebral hypoxia on cognitive decline in hemodialysis patients and the potential of transcutaneous auricular vagus nerve stimulation (taVNS) as a non-pharmacological intervention. A randomized controlled trial with 36 participants showed that cognitive performance and cerebral oxygenation in the dorsolateral prefrontal cortex (DLPFC) significantly declined in the sham group. In contrast, taVNS improved cognitive function by increasing cerebral oxygenation, with significant correlations to reaction times and MoCA scores. The study suggests that Hemodialysis-induced cerebral hypoxia may contribute to persistent cognitive decline in MHD patients. However, taVNS could be an effective intervention to prevent cognitive impairment in hemodialysis patients by alleviating cerebral hypoxia.

Treatment of chronic kidney disease in older populations

As the world population ages, an expected increase in the prevalence of chronic kidney disease (CKD) among older individuals will pose a considerable challenge for health care systems in terms of resource allocation for disease management. Treatment strategies for older patients with CKD should ideally align with those applied to the general population, focusing on minimizing cardiovascular events and reducing the risk of progression to kidney failure. Emerging therapies, such as SGLT-2 inhibitors and GLP-1 receptor agonists, hold promise for the effective management of CKD in older individuals. In addition, non-pharmacological interventions such as nutritional and exercise therapies have a crucial role. These interventions enhance the effects of pharmacotherapy and, importantly, contribute to the maintenance of cognitive function and overall quality of life. Various factors beyond age and cognitive function must be taken into account when considering kidney replacement therapy for patients with kidney failure. Importantly, all treatment options, including dialysis, transplantation and conservative management approaches, should be tailored to the individual through patient-centred decision-making. The dynamic integration of digital technologies into medical practice has the potential to transform the management of CKD in the aging population.

Prevention and resolution of headaches occurring during hemodialysis treatment by supplemental oxygen

A patient with end-stage renal disease experienced severe headaches exclusively during dialysis that were bilateral and throbbing with photophobia, weakness, and lightheadedness. The patient had no history of headaches, and dialysis was determined to be the cause of the severe headaches. More than 10 treatments were attempted without success. Headaches were successfully treated and prevented by addition of 100% oxygen (2 L via nasal cannula) for over 12 months without recurrence at time of publication. This case study indicates that oxygen therapy may be a valuable intervention for headaches during dialysis.

Blunted cerebral hemodynamic responses to incremental exercise in patients with end-stage renal disease

PURPOSE

The aims of this study were to compare cerebral hemodynamics and maximal oxygen uptake (VO2peak) in patients with end-stage renal disease (ESRD) vs. age-matched healthy controls during maximal exercise.

METHODS

Twelve patients with ESRD and twelve healthy adults (CTR group) performed exhaustive incremental exercise test. Throughout the exercise test, near-infrared spectroscopy allowed the investigation of changes in oxyhemoglobin (∆O2Hb), deoxyhemoglobin (∆HHb), and total hemoglobin (∆THb) in the prefrontal cortex.

RESULTS

Compared to CTR, VO2peak was significantly lower in ESRD group (P < 0.05). Increase in ∆THb (i.e., cerebral blood volume) was significantly blunted in ESRD (P < 0.05). ESRD patients also had impaired changes in cerebral ∆HHb and ∆O2Hb during high intensity of exercise (P < 0.05). Finally, no significant correlation was observed between VO2peak and changes in cerebral hemodynamics parameters in both groups (All P > 0.05).

CONCLUSION

Maximal exercise highlights subtle disorders of both hemodynamics and neuronal oxygenation in the prefrontal cortex in patients with ESRD. This may contribute to both impaired cognitive function and reduced exercise tolerance throughout the progression of the disease.

Assessing Cognition in CKD Using the National Institutes of Health Toolbox

Key Points

Participants with CKD had detectable cognitive deficits in fluid cognition, dexterity, and total cognition. Sex differences in cognition exist in people with CKD.

Background

CKD is largely an age-related clinical disorder with accelerated cognitive and cardiovascular aging. Cognitive impairment is a well-documented occurrence in midlife and older adults with CKD and affects multiple domains. We examined cognition function and potential sex differences in cognition in adults with CKD.

Methods

We included 105 individuals (49.5% women) with CKD stage 3b–4 (eGFR, 15–44 ml/min) from the Bicarbonate Administration in CKD Trial (NCT02915601 ). We measured cognitive function using the National Institutes of Health Toolbox Cognition Battery, which assesses cognitive and motor measures, such as executive function, attention, memory, and dexterity. All study measures were collected and analyzed at the study baseline.

Results

The mean (SD) age and eGFR were 61±12 years and 34.9±9.8 ml/min per 1.73 m2. Overall, when compared with the National Institutes of Health Toolbox reference population, participants scored, on average, below the 50th percentile across all cognitive domain tests and the dexterity test. Total cognition scores were also below the 50th percentile. Participants with stage 4 CKD had significantly lower fluid cognition scores compared with those with CKD stage 3b (β -estimate −5.4 [95% confidence interval, −9.8 to −0.9]; P = 0.03). Female participants with CKD performed significantly better on the episodic memory tests and dexterity tests (dominant and nondominant pegboard tests) and had higher crystallized cognition scores, on average, compared with male participants.

Conclusions

Participants with CKD had detectable cognitive deficits in fluid cognition, dexterity, and total cognition. In addition, sex differences in cognitive measures were found among people with CKD.

Bilateral nephrectomy impairs cardiovascular function and cerebral perfusion in a rat model of acute hemodilutional anemia

Anemia and renal failure are independent risk factors for perioperative stroke, prompting us to assess the combined impact of acute hemodilutional anemia and bilateral nephrectomy (2Nx) on microvascular brain Po2 (PBro2) in a rat model. Changes in PBro2 (phosphorescence quenching) and cardiac output (CO, echocardiography) were measured in different groups of anesthetized Sprague-Dawley rats (1.5% isoflurane, n = 5-8/group) randomized to Sham 2Nx or 2Nx and subsequently exposed to acute hemodilutional anemia (50% estimated blood volume exchange with 6% hydroxyethyl starch) or time-based controls (no hemodilution). Outcomes were assessed by ANOVA with significance assigned at P < 0.05. At baseline, 2Nx rats demonstrated reduced CO (49.9 ± 9.4 vs. 66.3 ± 19.3 mL/min; P = 0.014) and PBro2 (21.1 ± 2.9 vs. 32.4 ± 3.1 mmHg; P < 0.001) relative to Sham 2Nx rats. Following hemodilution, 2Nx rats demonstrated a further decrease in PBro2 (15.0 ± 6.3 mmHg, P = 0.022). Hemodiluted 2Nx rats did not demonstrate a comparable increase in CO after hemodilution compared with Sham 2Nx (74.8 ± 22.4 vs. 108.9 ± 18.8 mL/min, P = 0.003) that likely contributed to the observed reduction in PBro2. This impaired CO response was associated with reduced fractional shortening (33 ± 9 vs. 51 ± 5%) and increased left ventricular end-systolic volume (156 ± 51 vs. 72 ± 15 µL, P < 0.001) suggestive of systolic dysfunction. By contrast, hemodiluted Sham 2Nx animals demonstrated a robust increase in CO and preserved PBro2. These data support the hypothesis that the kidney plays a central role in maintaining cerebral perfusion and initiating the adaptive increase in CO required to optimize PBro2 during acute anemia.NEW & NOTEWORTHY This study has demonstrated that bilateral nephrectomy acutely impaired cardiac output (CO) and microvascular brain Po2 (PBro2), at baseline. Following acute hemodilution, nephrectomy prevented the adaptive increase in CO associated with acute hemodilution leading to a further reduction in PBro2, accentuating the degree of cerebral tissue hypoxia. These data support a role for the kidney in maintaining PBro2 and initiating the increase in CO that optimized brain perfusion during acute anemia.

Longitudinal changes in diffusion tensor imaging in hemodialysis patients

INTRODUCTION

Hemodialysis patients have increased white matter and gray matter pathology in the brain relative to controls based on MRI. Diffusion tensor imaging is useful in detecting differences between hemodialysis and controls but has not identified the expected longitudinal decline in hemodialysis patients. In this study we implemented specialized post-processing techniques to reduce noise to detect longitudinal changes in diffusion tensor imaging parameters and evaluated for any association with changes in cognition.

METHODS

We collected anatomical and diffusion MRIs as well as cognitive testing from in-center hemodialysis patients at baseline and 1 year later. Gray matter thickness, white matter volume, and white matter diffusion tensor imaging parameters were measured to identify longitudinal changes. We analyzed the diffusion tensor imaging parameters by averaging the whole white matter and using a pothole analysis. Eighteen hemodialysis patients were included in the longitudinal analysis and 15 controls were used for the pothole analysis. We used the NIH Toolbox Cognition Battery to assess cognitive performance over the same time frame.

FINDINGS

Over the course of a year on hemodialysis, we found a decrease in white matter fractional anisotropy across the entire white matter (p < 0.01), and an increase in the number of white matter fractional anisotropy voxels below pothole threshold (p = 0.03). We did not find any relationship between changes in whole brain structural parameters and cognitive performance.

DISCUSSION

By employing noise reducing techniques, we were able to detect longitudinal changes in diffusion tensor imaging parameters in hemodialysis patients. The fractional anisotropy declines over the year indicate significant decreases in white matter health. However, we did not find that declines in fractional anisotropy was associated with declines in cognitive performance.

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.

Macroscale neurovascular coupling and functional integration in end-stage renal disease patients with cognitive impairment: A multimodal MRI study

End-stage renal disease (ESRD) is associated with vascular and neuronal dysfunction, causing neurovascular coupling (NVC) dysfunction, but how NVC dysfunction acts on the mechanism of cognitive impairment in ESRD patients from local to remote is still poorly understood. We recruited 48 ESRD patients and 35 demographically matched healthy controls to scan resting-state functional MRI and arterial spin labeling, then investigated the four types of NVC between amplitude of low-frequency fluctuation (ALFF), fractional ALFF, regional homogeneity, degree centrality, and cerebral blood perfusion (CBF), and associated functional networks. Our results indicated that ESRD patients showed NVC dysfunction in global gray matter and multiple brain regions due to the mismatch between CBF and neural activity, and associated disrupted functional connectivity (FC) within sensorimotor network (SMN), visual network (VN), default mode network (DMN), salience network (SN), and disrupted FC between them with limbic network (LN), while increased FC between SMN and DMN. Anemia may affect the NVC of middle occipital gyrus and precuneus, and increased pulse pressure may result in disrupted FC with SMN. The NVC dysfunction of the right precuneus, middle frontal gyrus, and parahippocampal gyrus and the FC between the right angular gyrus and the right anterior cingulate gyrus may reflect cognitive impairment in ESRD patients. Our study confirmed that ESRD patients may exist NVC dysfunction and disrupted functional integration in SMN, VN, DMN, SN and LN, serving as one of the mechanisms of cognitive impairment. Anemia and increased pulse pressure may be related risk factors.

Predictors and Outcomes of Acute Brain Injury in Patients on Venoarterial Extracorporeal Membrane Oxygenation after Cardiopulmonary Resuscitation

Background

Venoarterial (V-A) extracorporeal membrane oxygenation (ECMO) after cardiac arrest often predisposes patients to acute brain injury (ABI), which affects survival and neurological performance. The investigation of the predictors of ABI will be beneficial for further management.

Objectives

To explore the predictors and outcomes of ABI and intracerebral hemorrhage (ICH) in patients experiencing cardiac arrest and cardiopulmonary resuscitation (CPR) with V-A ECMO support.

Methods

We retrospectively analyzed 150 patients who successfully weaned from V-A ECMO support after pre-ECMO CPR at our institution from January 2009 to December 2021. Short-term and long-term outcomes were evaluated. Characteristics before and during ECMO were analyzed for determining the predictors of ABI and ICH.

Results

Of the 150 patients, 66 (44.0%) had ABI. ABI was associated with higher in-hospital mortality (62.1% vs. 21.4%, p < 0.0001) and poorer long-term survival after discharge (p = 0.002). Patients who survived to discharge with ABI had significantly more severe neurological deficits at discharge (84.0% vs. 42.4%, p < 0.0001) and improved little at one year after discharge (33.3% vs. 11.4%, p = 0.027). We found that CPR duration [odds ratio (OR) = 1.04, p = 0.003] was the independent risk factor for ABI, whereas lower platelet counts was the independent risk factor for ICH (OR = 0.96, p = 0.019).

Conclusions

After CPR, development of ABI during V-A ECMO support impacted survival and further neurological outcome. Longer CPR duration before ECMO set up significantly increases the occurrence of ABI. Besides, severe thrombocytopenia during ECMO support increases the possibility of ICH.

Outcome of endovascular thrombectomy in patients with end-stage renal disease undergoing dialysis

BACKGROUND

Patients with end-stage renal disease (ESRD) are often excluded from clinical trials of endovascular thrombectomy (EVT). This study investigated the outcome in these patients.

METHODS

From September 2014 to July 2021, all patients undergoing EVT for anterior circulation stroke in two stroke centers in Taiwan were included. They were divided into no renal dysfunction (non-RD, estimated glomerular filtration rate (eGFR) ≥60 mL/min/1.73 m2), RD (eGFR <60 mL/min/1.73 m2 but no dialysis), and ESRD undergoing dialysis (ESRD-dialysis). The clinical features and outcomes were compared.

RESULTS

Of 482 patients included, there were 20 ESRD-dialysis, 110 RD, and 352 non-RD patients. The Alberta Stroke Program Early CT Score (ASPECTS), National Institutes of Health Stroke Scale (NIHSS), use of intravenous thrombolysis, EVT-related time metrics, and successful recanalization rates were comparable among the three groups. However, the ESRD-dialysis patients had more symptomatic intracerebral hemorrhage (ICH, 15% vs 3.6% vs 3.7%), more contrast-induced encephalopathy (15% vs 1.8% vs 0.9%), and a higher mortality at 90 days (35% vs 18% vs 11%) than the other groups. Multivariable analysis revealed that ESRD-dialysis was associated with a less favorable outcome (OR 0.21, 95% CI 0.04 to 0.77) and more severe disability or mortality (modified Rankin Scale 5 or 6; OR 13.1, 95% CI 3.93 to 48.1) at 90 days. In the ESRD-dialysis group, the patients with premorbid functional dependence had a significantly higher mortality than those without (75% vs 8.3%; P=0.004).

CONCLUSION

ESRD-dialysis patients were associated with symptomatic ICH and less favorable outcome at 90 days. Patients with premorbid functional dependency had an excessively high mortality.

Kidney disease and stroke: epidemiology and potential mechanisms of susceptibility

Patients with chronic kidney disease (CKD) have an increased risk of both ischaemic and haemorrhagic stroke compared with the general population. Both acute and chronic kidney impairment are independently associated with poor outcome after the onset of a stroke, after adjustment for confounders. End-stage kidney disease (ESKD) is associated with a 7- and 9-fold increased incidence of both ischaemic and haemorrhagic strokes, respectively, poorer neurological outcome and a 3-fold higher mortality. Acute kidney injury (AKI) occurs in 12% of patients with stroke and is associated with a 4-fold increased mortality and unfavourable functional outcome. CKD patients seem to have less access to revascularisation techniques like thrombolysis and thrombectomy despite their poorer prognosis. Even if CKD patients could benefit from these specific treatments in acute ischaemic stroke, their prognosis remains poor. After thrombolysis, CKD is associated with a 40% increased risk of intracerebral haemorrhage (ICH), a 20% increase in mortality and poorer functional neurological outcomes. After thrombectomy, CKD is not associated with ICH but is still associated with increased mortality, and AKI with unfavourable outcome and mortality. The beneficial impact of gliflozins on the prevention of stroke is still uncertain. Non-traditional risk factors of stroke, like uraemic toxins, can lead to chronic cerebrovascular disease predisposing to stroke in CKD, notably through an increase in the blood-brain barrier permeability and impaired coagulation and thrombosis mechanisms. Preclinical and clinical studies are needed to specifically assess the impact of these non-traditional risk factors on stroke incidence and outcomes, aiming to optimize and identify potential therapeutic targets.

Renal and Electrolyte Disorders and the Nervous System

OBJECTIVE

Neurologic complications are a major contributor to death and disability in patients with renal disease. Oxidative stress, endothelial dysfunction, accelerated arteriosclerosis, and uremic inflammatory milieu affect both the central and peripheral nervous systems. This article reviews the unique contributions of renal impairment to neurologic disorders and their common clinical manifestations as the prevalence of renal disease increases in a globally aging population.

LATEST DEVELOPMENT

Advances in the understanding of the pathophysiologic interplay between the kidneys and brain, also referred to as the kidney-brain axis, have led to more widespread recognition of associated changes in neurovascular dynamics, central nervous system acidification, and uremia-associated endothelial dysfunction and inflammation in the central and peripheral nervous systems. Acute kidney injury increases mortality in acute brain injury to nearly 5 times that seen in matched controls. Renal impairment and its associated increased risks of intracerebral hemorrhage and accelerated cognitive decline are developing fields. Dialysis-associated neurovascular injury is increasingly recognized in both continuous and intermittent forms of renal replacement therapy, and treatment strategies for its prevention are evolving.

ESSENTIAL POINTS

This article summarizes the effects of renal impairment on the central and peripheral nervous systems with special considerations in acute kidney injury, patients requiring dialysis, and conditions that affect both the renal and nervous systems.

Association between susceptibility value and cerebral blood flow in the bilateral putamen in patients undergoing hemodialysis

Hemodialysis (HD) is the most regularly applied replacement therapy for end-stage renal disease, but it may result in brain injuries. The correlation between cerebral blood flow (CBF) alteration and iron deposition has not been investigated in patients undergoing HD. Ferritin level may be a dominant factor in CBF and iron deposition change. We hypothesize that ferritin level might be the key mediator between iron deposition and CBF alteration. The correlation in the putamen was estimated between the susceptibility values and CBF in patients undergoing HD. Compared with healthy controls, patients showed more altered global susceptibility values and CBF. The susceptibility value was negatively correlated with CBF in the putamen in patients. Moreover, the susceptibility value was negatively correlated with ferritin level and positively correlated with serum iron level in the putamen of patients. CBF was positively correlated with ferritin level and negatively correlated with serum iron level in the putamen of patients. These findings indicate that iron dyshomeostasis and vascular damage might exist in the putamen in patients. The results revealed that iron dyshomeostasis and vascular damage in the putamen may be potential neural mechanisms for neurodegenerative processes in patients undergoing HD.

Cerebral blood flow pulsatility and cerebral artery stiffness acutely decrease during hemodialysis

End-stage kidney disease (ESKD) is associated with increased arterial stiffness and cognitive impairment. Cognitive decline is accelerated in ESKD patients on hemodialysis and may result from repeatedly inappropriate cerebral blood flow (CBF). The aim of this study was to examine the acute effect of hemodialysis on pulsatile components of CBF and their relation to acute changes in arterial stiffness. In eight participants (age: 63 ± 18 years, men: 5), CBF was estimated using middle cerebral artery blood velocity (MCAv) assessed with transcranial Doppler ultrasound before, during, and after a single hemodialysis session. Brachial and central blood pressure, along with estimated aortic stiffness (eAoPWV) were measured using an oscillometric device. Arterial stiffness from heart to MCA was measured as the pulse arrival time (PAT) between electrocardiogram (ECG) and transcranial Doppler ultrasound waveforms (cerebral PAT). During hemodialysis, there was a significant reduction in mean MCAv (-3.2 cm/s, p < 0.001), and systolic MCAv (-13.0 cm/s, p < 0.001). While baseline eAoPWV (9.25 ± 0.80 m/s) did not significantly change during hemodialysis, cerebral PAT increased significantly (+0.027 , p < 0.001) and was associated with reduced pulsatile components of MCAv. This study shows that hemodialysis acutely reduces stiffness of arteries perfusing the brain along with pulsatile components of blood velocity.

Altered Cerebral Blood Flow in the Progression of Chronic Kidney Disease

Background: In chronic kidney disease (CKD), cognitive impairment is a definite complication. However, the mechanisms of how CKD leads to cognitive impairment are not clearly known. Methods: Cerebral blood flow (CBF) information was collected from 37 patients with CKD (18 in stage 3; 19 in stage 4) and 31 healthy controls (HCs). For CKD patients, we also obtained laboratory results as well as neuropsychological tests. We conducted brain perfusion imaging studies using arterial spin labeling and calculated the relationship between regional CBF changes and various clinical indicators and neuropsychological tests. We also generated receiver operator characteristic (ROC) curves to explore whether CBF value changes in certain brain regions can be used to identify CKD. Results: Compared with HCs, CBF decreased in the right insula and increased in the left hippocampus in the CKD4 group; through partial correlation analysis, we found that CBF in the right insula was negatively correlated with the number connection test A (NCT-A) (r = −0.544, p = 0.024); CBF in the left hippocampus was positively correlated with blood urea nitrogen (r = 0.649, p = 0.005) and negatively correlated with serum calcium level (r = −0.646, p = 0.005). By comparing the ROC curve area, it demonstrated that altered CBF values in the right insula (AUC = 0.861, p < 0.01) and left hippocampus (AUC = 0.862, p < 0.01) have a good ability to identify CKD. Conclusions: Our study found that CBF alterations in the left hippocampus and the right insula brain of adult patients with stage 4 CKD were correlated with disease severity or laboratory indicators. These findings provide further insight into the relationship between altered cerebral perfusion and cognitive impairment in patients with non-end-stage CKD as well as, additional information the underlying neuropathophysiological mechanisms.

Cerebral O2 and CO2 transport in isovolumic haemodilution: Compensation of cerebral delivery of O2 and maintenance of cerebrovascular reactivity to CO2

This study investigated the influence of acute reductions in arterial O₂ content (CaO₂) via isovolumic haemodilution on global cerebral blood flow (gCBF) and cerebrovascular CO₂ reactivity (CVR) in 11 healthy males (age; 28 ± 7 years: body mass index; 23 ± 2 kg/m²). Radial artery and internal jugular vein catheters provided measurement of blood pressure and gases, quantification of cerebral metabolism, cerebral CO₂ washout, and trans-cerebral nitrite exchange (ozone based chemiluminescence). Prior to and following haemodilution, the partial pressure of arterial CO₂ (PaCO₂) was elevated with dynamic end-tidal forcing while gCBF was measured with duplex ultrasound. CVR was determined as the slope of the gCBF response and PaCO₂. Replacement of ∼20% of blood volume with an equal volume of 5% human serum albumin (Alburex® 5%) reduced haemoglobin (13.8 ± 0.8 vs. 11.3 ± 0.6 g/dL; P < 0.001) and CaO₂ (18.9 ± 1.0 vs 15.0 ± 0.8 mL/dL P < 0.001), elevated gCBF (+18 ± 11%; P = 0.002), preserved cerebral oxygen delivery (P = 0.49), and elevated CO₂ washout (+11%; P = 0.01). The net cerebral uptake of nitrite (11.6 ± 14.0 nmol/min; P = 0.027) at baseline was abolished following haemodilution (-3.6 ± 17.9 nmol/min; P = 0.54), perhaps underpinning the conservation of CVR (61.7 ± 19.0 vs. 69.0 ± 19.2 mL/min/mmHg; P = 0.23). These findings demonstrate that the cerebrovascular responses to acute anaemia in healthy humans are sufficient to support the maintenance of CVR.

Dynamic cerebral autoregulation is intact in chronic kidney disease

Chronic Kidney Disease (CKD) patients experience an elevated risk for cerebrovascular disease. One factor that may contribute to this heightened risk is an impairment in dynamic cerebral autoregulation, the mechanism by which cerebral vessels modulate cerebral blood flow during fluctuations in arterial pressure. We hypothesized that dynamic cerebral autoregulation would be impaired in CKD. To test this hypothesis, we compared dynamic cerebral autoregulation between CKD patients stages III-IV and matched controls (CON) without CKD. Fifteen patients with CKD and 20 CON participants performed 2, 5-minute bouts of repeated sit-to-stand maneuvers at 0.05 Hz and 0.10 Hz while mean arterial pressure (MAP, via finger photoplethysmography) and middle cerebral artery blood velocity (MCAv, via transcranial Doppler ultrasound) were measured continuously. Cerebral autoregulation was characterized by performing a transfer function analysis (TFA) on the MAP-MCAv relationship to derive coherence, phase, gain, and normalized gain (nGain). We observed no group differences in any of the TFA metrics during the repeated sit-to-stand maneuvers. During the 0.05 Hz maneuver, Coherence: CKD = 0.83 ± 0.13, CON = 0.85 ± 0.12, Phase (radians): CKD = 1.39 ± 0.41, CON = 1.25 ± 0.30, Gain (cm/s/mmHg): CKD = 0.69 ± 0.20, CON = 0.71 ± 0.22, nGain (%/mmHg): CKD = 1.26 ± 0.35, CON = 1.20 ± 0.28, p ≥ 0.24. During the 0.10 Hz maneuver (N = 6 CKD and N = 12 CON), Coherence: CKD = 0.61 ± 0.10, CON = 0.67 ± 0.11, Phase (radians): CKD = 1.43 ± 0.26, CON = 1.30 ± 0.23, Gain (cm/s/mmHg): CKD = 0.75 ± 0.15, CON = 0.84 ± 0.26, nGain (%/mmHg): CKD = 1.50 ± 0.28, CON = 1.29 ± 0.24, p ≥ 0.12. Contrary to our hypothesis, dynamic cerebral autoregulation remains intact in CKD stages III-IV. These findings suggest that other mechanisms likely contribute to the increased cerebrovascular disease burden experienced by this population. Future work should determine if other cerebrovascular regulatory mechanisms are impaired and related to cerebrovascular disease risk in CKD.

Association of Chronic Kidney Disease With Risk of Intracerebral Hemorrhage

Importance

The evidence linking chronic kidney disease (CKD) to spontaneous intracerebral hemorrhage (ICH) is inconclusive owing to possible confounding by comorbidities that frequently coexist in patients with these 2 diseases.

Objective

To determine whether there is an association between CKD and ICH risk.

Design, Setting, and Participants

A 3-stage study that combined observational and genetic analyses was conducted. First, the association between CKD and ICH risk was tested in the Ethnic/Racial Variations of Intracerebral Hemorrhage (ERICH) study, a multicenter case-control study in the US. All participants with available data on CKD from ERICH were included. Second, this analysis was replicated in the UK Biobank (UKB), an ongoing population study in the UK. All participants in the UKB were included in this study. Third, mendelian randomization analyses were implemented in the UKB using 27 CKD-related genetic variants to test for genetic associations. ERICH was conducted from August 1, 2010, to August 1, 2017, and observed participants for 1 year. The UKB enrolled participants between 2006 and 2010 and will continue to observe them for 30 years. Data analysis was performed from November 11, 2019, to May 10, 2022.

Exposures

CKD stages 1 to 5.

Main Outcomes and Measures

The outcome of interest was ICH, ascertained in ERICH via expert review of neuroimages and in the UKB via a combination of self-reported data and International Statistical Classification of Diseases, Tenth Revision, codes.

Results

In the ERICH study, a total of 2914 participants with ICH and 2954 controls who had available data on CKD were evaluated (mean [SD] age, 61.6 [14.0] years; 2433 female participants [41.5%]; 3435 male participants [58.5%]); CKD was found to be independently associated with higher risk of ICH (odds ratio [OR], 1.95; 95% CI, 1.35-2.89; P < .001). This association was not modified by race and ethnicity. Replication in the UKB with 1341 participants with ICH and 501 195 controls (mean [SD] age, 56.5 [8.1] years; 273 402 female participants [54.4%]; 229 134 male participants [45.6%]) confirmed this association (OR, 1.28; 95% CI, 1.01-1.62; P = .04). Mendelian randomization analyses indicated that genetically determined CKD was associated with ICH risk (OR, 1.56; 95% CI, 1.13-2.16; P = .007).

Conclusions and Relevance

In this 3-stage study that combined observational and genetic analyses among study participants enrolled in 2 large observational studies with different characteristics and study designs, CKD was consistently associated with higher risk of ICH. Mendelian randomization analyses suggest that this association was causal. Further studies are needed to identify the specific biological pathways that mediate this association.

The Relationship between Cerebrovascular Reactivity and Cerebral Oxygenation during Hemodialysis

BACKGROUND

Patients with kidney failure treated with hemodialysis (HD) may be at risk for cerebral hypoperfusion due to HD-induced BP decline in the setting of impaired cerebral autoregulation. Cerebrovascular reactivity (CVR), the cerebrovascular response to vasoactive stimuli, may be a useful indicator of cerebral autoregulation in the HD population and identify those at risk for cerebral hypoperfusion. We hypothesize that CVR combined with intradialytic BP changes will be associated with declines in cerebral oxygenation saturation (ScO2) during HD.

METHODS

Participants completed the MRI scans on a non-HD day and cerebral oximetry during HD. We measured CVR with resting-state fMRI (rs-fMRI) without a gas challenge and ScO2 saturation with near-infrared spectroscopy. Regression analysis was used to examine the relationship between intradialytic cerebral oxygen desaturation, intradialytic BP, and CVR in different gray matter regions.

RESULTS

Twenty-six patients on HD had complete data for analysis. Sixteen patients were men, 18 had diabetes, and 20 had hypertension. Mean±SD age was 65.3±7.2 years, and mean±SD duration on HD was 11.5±9.4 months. CVR in the anterior cingulate gyrus (ACG; P=0.03, r2 =0.19) and insular cortex (IC; P=0.03, r2 =0.19) regions negatively correlated with decline in intradialytic ScO2. Model prediction of intradialytic ScO2 improved when including intradialytic BP change and ultrafiltration rate to the ACG rsCVR (P<0.01, r2 =0.48) and IC rsCVR (P=0.02, r2 =0.35) models, respectively.

CONCLUSIONS

We found significant relationships between regional rsCVR measured in the brain and decline in intradialytic ScO2. Our results warrant further exploration of using CVR in determining a patient's risk of cerebral ischemic injury during HD.

K-Means Clustering Algorithm–Based Functional Magnetic Resonance for Evaluation of Regular Hemodialysis on Brain Function of Patients with End-Stage Renal Disease

This research was to evaluate the effects of regular hemodialysis (HD) on the brain function of patients with end-stage renal disease (ESRD). Resting-state functional magnetic resonance imaging (rs-fMRI) based on improved k-means clustering algorithm (k-means) was proposed to scan the brains of 30 regular dialysis patients with end-stage renal disease (ESRD) (experimental group) and 30 normal volunteers (control group). The proposed algorithm was compared with the traditional k-means algorithm and mean shift algorithm and applied to the magnetic resonance scan of patients with ESRD on long-term regular HD. The results showed that the neuropsychological cognitive function (NSCF) evaluation result of the test group was much better than that of the control group, and the difference was statistically obvious (P < 0.05). The results of blood biochemistry, Digit Symbol Substitution Test (DSST), and Montreal Cognitive Assessment Scale (MoCA) in the test group showed no statistical difference compared with those in the control group. The running time of the improved k-means algorithm was dramatically shorter than that of traditional k-means algorithm, showing statistical difference (P < 0.05). Comparison among the improved and traditional k-means algorithm and mean shift algorithm suggested that the improved k-means algorithm showed a lower error rate for image segmentation, and the differences were statistically remarkable (P < 0.05). In conclusion, the improved k-means algorithm showed better time efficiency and the lowest error rate in processing rs-fMRI images than the traditional k-means algorithm and mean shift algorithm, and the effects of regular HD on the brains of patients with ESRD were evaluated effectively.

Cerebral venous congestion exacerbates cerebral microhemorrhages in mice

Cerebral microhemorrhages (CMHs; microbleeds), which are small focal intracerebral hemorrhages, importantly contribute to the pathogenesis of cognitive decline and dementia in older adults. Although recently it has been increasingly recognized that the venous side of the cerebral circulation likely plays a fundamental role in the pathogenesis of a wide spectrum of cerebrovascular and brain disorders, its role in the pathogenesis of CMHs has never been studied. The present study was designed to experimentally test the hypothesis that venous congestion can exacerbate the genesis of CMHs. Increased cerebral venous pressure was induced by internal and external jugular vein ligation (JVL) in C57BL/6 mice in which systemic hypertension was induced by treatment with angiotensin II plus L-NAME. Histological analysis (diaminobenzidine staining) showed that mice with JVL developed multiple CMHs. CMHs in mice with JVL were often localized adjacent to veins and venules and their morphology was consistent with venous origin of the bleeds. In brains of mice with JVL, a higher total count of CMHs was observed compared to control mice. CMHs were distributed widely in the brain of mice with JVL, including the cortical gray matter, brain stem, the basal ganglia, subcortical white matter, cerebellum, and the hippocampi. In mice with JVL, there were more CMHs predominantly in cerebral cortex, brain stem, and cerebellum than in control mice. CMH burden, defined as total CMH volume, also significantly increased in mice with JVL. Thus, cerebral venous congestion can exacerbate CMHs. These observations have relevance to the pathogenesis of cognitive impairment associated with right heart failure as well as elevated cerebral venous pressure due to jugular venous reflux in older adults.

Long-term hemodialysis may affect enlarged perivascular spaces in maintenance hemodialysis patients: evidence from a pilot MRI study

BACKGROUND

Hemodialysis (HD) causes various nervous system abnormalities. Alterations in white matter (WM) microstructure after long-term HD have been reported in a few previous studies; however, no studies have been performed to investigate enlarged perivascular spaces (PVS) in WM regions. We measured cerebral blood flow (CBF) and white matter volume (WMV) in HD patients to assess enlarged PVS severity in the WM across the whole brain and suggest possible explanations for this.

METHODS

Fifty-one HD patients and 51 age-, sex-, and education-matched healthy controls (HCs) were recruited. The number of enlarged PVS in the centrum semiovale (CS), cerebral watershed (CW), and basal ganglia (BG) regions were assessed by T2-weighted MRI. CBF was estimated by arterial spin labeling (ASL), which is a non-invasive perfusion imaging technique. WMV was assessed by the computational anatomy toolbox (CAT12), which is a statistical analysis package. Differences in descriptive variables (two-tailed t-tests, χ² tests, Mann-Whitney U tests, and Friedman M tests), an intra-class correlation between radiologists, the relationship between enlarged PVS number and HD duration, normalized CBF and WMV (multiple regression), and group differences in CBF and WMV {voxel-wise t-tests with age and sex as covariates [cluster size >50 voxels, false discovery rate (FDR) corrected, P<0.05]} were assessed.

RESULTS

HD patients displayed a more significant number of CS-PVS and CW-PVS in WM regions compared with the HCs, but there was no significant difference in the number of BG-PVS. The number of CS-PVS and CW-PVS were positively associated with HD duration. The number of CW-PVS was positively associated with CBF changes and WMV alteration in HD patients. Meanwhile, significant differences in the blood pressure (BP) readings pre-HD, intra-HD, and post-HD were observed in HD patients. Compared with the HCs, the HD patients showed higher CBF in the CS, CW, and BG regions (P<0.05). Hence, decreased WMV in the CS, CW, and BG regions were shown in the HD patients compared with the HCs (P<0.05).

CONCLUSIONS

Enlarged CS-PVS and CW-PVS on MRI might be a feature of long-term HD patients. Enlarged CW-PVS number is associated with higher CBF in the CW region and lower WMV in the CW region in HD patients.

Chronic kidney disease as a risk factor for acute stroke

One of the most relevant issues of nephrology, neurology, and cardiology is the management and treatment of patients with chronic kidney disease and stroke. Patients with chronic kidney disease have a risk of both thrombotic complications and bleeding, and they have a high risk of both ischemic and hemorrhagic stroke. Chronic kidney disease significantly worsens the outcome of stroke by limiting the treatment due to reduced drug clearance and side effects. Hemodialysis which causes drastic hemodynamic and biochemical changes leads to the "stress" of the cerebral vascular system, increasing the risk of stroke; kidney transplantation reduces the risk of stroke due to functional recovery. Chronic kidney disease and stroke have significant socio-economic consequences. Patients with end-stage chronic kidney disease, as a rule, are not included in clinical trials; and stroke treatment tactics have not been developed for them. This review examines the interaction between kidneys and brain, the pathophysiology and epidemiology of stroke in all stages of chronic kidney disease, after kidney transplantation and discusses the management and treatment of chronic kidney disease patients with stroke.

The investigation of the factors responsible for the high prevalence of brain lesions in chronic kidney disease will allow developing new treatment methods.

Acidosis, cognitive dysfunction and motor impairments in patients with kidney disease

Metabolic acidosis, defined as a plasma or serum bicarbonate concentration <22 mmol/L, is a frequent consequence of chronic kidney disease (CKD) and occurs in ~10–30% of patients with advanced stages of CKD. Likewise, in patients with a kidney transplant, prevalence rates of metabolic acidosis range from 20% to 50%. CKD has recently been associated with cognitive dysfunction, including mild cognitive impairment with memory and attention deficits, reduced executive functions and morphological damage detectable with imaging. Also, impaired motor functions and loss of muscle strength are often found in patients with advanced CKD, which in part may be attributed to altered central nervous system (CNS) functions. While the exact mechanisms of how CKD may cause cognitive dysfunction and reduced motor functions are still debated, recent data point towards the possibility that acidosis is one modifiable contributor to cognitive dysfunction. This review summarizes recent evidence for an association between acidosis and cognitive dysfunction in patients with CKD and discusses potential mechanisms by which acidosis may impact CNS functions. The review also identifies important open questions to be answered to improve prevention and therapy of cognitive dysfunction in the setting of metabolic acidosis in patients with CKD.

Longitudinal change in microRNA-130a expression and its correlation with the risk of developing major adverse cardiovascular and cerebral events in patients undergoing continuous ambulatory peritoneal dialysis

BACKGROUND

MicroRNA-130a (miR-130a) regulates angio-cellular dysregulation, atherosclerosis, and cardiocerebral injuries, serving as a biomarker for major adverse cardiovascular and cerebral events (MACCE) in several chronic diseases. However, its clinical application in patients with end-stage renal disease (ESRD) undergoing continuous ambulatory peritoneal dialysis (CAPD), who are at a high risk of developing MACCE, has not been reported. Therefore, this study aimed to explore this aspect.

METHODS

miR-130a expression in peripheral blood mononuclear cells obtained from 50 healthy controls (HCs) at recruitment and 257 ESRD patients undergoing CAPD at month (M)0, M12, M24, and M36 was determined by reverse transcription-quantitative polymerase chain reaction. ESRD patients undergoing CAPD were followed up until MACCE occurred or M36. Then, MACCE were recorded, and MACCE-free survival was calculated.

RESULTS

miR-130a expression was significantly lower in ESRD patients undergoing CAPD than in HCs (p < 0.001). In addition, miR-130a expression significantly decreased from M0 to M36 in ESRD patients undergoing CAPD (p < 0.001). Moreover, miR-130a expression at M0, M12, and M24 was significantly lower in patients with MACCE than in those without MACCE (all p < 0.05). Furthermore, high miR-130a expression at M0, M12, and M36 was significantly correlated with prolonged MACCE-free survival in ESRD patients undergoing CAPD (all p < 0.05), and high miR-130a expression at M0 was an independent factor for improved MACCE-free survival (p = 0.015; hazard ratio (HR) (95% confidential interval): 0.456 (0.243-0.857)).

CONCLUSION

miR-130a expression decreases continuously with disease progression in patients with ESRD undergoing CAPD. Additionally, this expression is negatively correlated with MACCE risk in these patients.

Central and peripheral arterial diseases in chronic kidney disease: conclusions from a Kidney Disease: Improving Global Outcomes (KDIGO) Controversies Conference

Chronic kidney disease (CKD) affects about 10% of all populations worldwide, with about 2 million people requiring dialysis. Although patients with CKD are at high risk of cardiovascular disease and events, they are often underrepresented or excluded in clinical trials, leading to important knowledge gaps about how to treat these patients. KDIGO (Kidney Disease: Improving Global Outcomes) convened the fourth clinical Controversies Conference on the heart, kidney and vasculature in Dublin, Ireland, in February 2020, entitled Central and Peripheral Arterial Diseases in Chronic Kidney Disease. A global panel of multidisciplinary experts from the fields of nephrology, cardiology, neurology, surgery, radiology, vascular biology, epidemiology, and health economics attended. The objective was to identify key issues related to the optimal detection, management, and treatment of cerebrovascular diseases, central aortic disease, renovascular disease, and peripheral artery disease in the setting of CKD. This report outlines the common pathophysiology of these vascular processes in the setting of CKD, describes best practices for their diagnosis and management, summarizes areas of uncertainty, addresses ongoing controversial issues, and proposes a research agenda to address key gaps in knowledge that, when addressed, could improve patient care and outcomes.

Hemodialysis Patients Have Impaired Cerebrovascular Reactivity to CO2 Compared to Chronic Kidney Disease Patients and Healthy Controls: A Pilot Study

Introduction

Recurrent hemodialysis (HD)–induced ischemia has emerged as a mechanism responsible for cognitive impairment in HD patients. Impairment of cerebrovascular function in HD patients may render the brain vulnerable to HD-induced ischemic injury. Cerebrovascular reactivity to CO₂ (CVR) is a noninvasive marker of cerebrovascular function. Whether CVR is impaired in HD patients is unknown. In this study, we compared CVR between healthy participants, HD patients, and chronic kidney disease (CKD) patients not yet requiring dialysis.

Methods

This was a single-center prospective observational study carried out at Kidney Clinical Research Unit in London, Canada. We used carefully controlled hypercapnia to interrogate brain vasomotor control. Transcranial Doppler was combined with 10–mm Hg step changes in CO₂ from baseline to hypercapnia (intervention) and back to baseline (recovery) to assess CVR in 8 HD, 10 CKD, and 17 heathy participants.

Results

HD patients had lower CVR than CKD or healthy participants during both intervention and recovery (P < 0.0001). There were no differences in CVR between healthy and CKD participants during either intervention (P = 0.88) or recovery (P = 0.99). The impaired CVR in HD patients was independent of CO₂-induced changes in blood pressure, heart rate, cardiac output, or dialysis vintage. In the CKD group, CVR was not associated with the estimated glomerular filtration rate.

Conclusions

Our study shows that HD patients have impaired CVR relative to CKD and healthy participants. This renders HD patients vulnerable to ischemic injury during circulatory stress of dialysis and may contribute to the pathogenesis of cognitive impairment.

The Utility of Cerebrovascular Reactivity MRI in Brain Rehabilitation: A Mechanistic Perspective

Cerebrovascular control and its integration with other physiological systems play a key role in the effective maintenance of homeostasis in brain functioning. Maintenance, restoration, and promotion of such a balance are one of the paramount goals of brain rehabilitation and intervention programs. Cerebrovascular reactivity (CVR), an index of cerebrovascular reserve, plays an important role in chemo-regulation of cerebral blood flow. Improved vascular reactivity and cerebral blood flow are important factors in brain rehabilitation to facilitate desired cognitive and functional outcomes. It is widely accepted that CVR is impaired in aging, hypertension, and cerebrovascular diseases and possibly in neurodegenerative syndromes. However, a multitude of physiological factors influence CVR, and thus a comprehensive understanding of underlying mechanisms are needed. We are currently underinformed on which rehabilitation method will improve CVR, and how this information can inform on a patient's prognosis and diagnosis. Implementation of targeted rehabilitation regimes would be the first step to elucidate whether such regimes can modulate CVR and in the process may assist in improving our understanding for the underlying vascular pathophysiology. As such, the high spatial resolution along with whole brain coverage offered by MRI has opened the door to exciting recent developments in CVR MRI. Yet, several challenges currently preclude its potential as an effective diagnostic and prognostic tool in treatment planning and guidance. Understanding these knowledge gaps will ultimately facilitate a deeper understanding for cerebrovascular physiology and its role in brain function and rehabilitation. Based on the lessons learned from our group's past and ongoing neurorehabilitation studies, we present a systematic review of physiological mechanisms that lead to impaired CVR in aging and disease, and how CVR imaging and its further development in the context of brain rehabilitation can add value to the clinical settings.