The effects of dialysis on brain water and EEG in stable chronic uremia

Interventions for preventing haemodialysis dysequilibrium syndrome

BACKGROUND

Dialysis dysequilibrium syndrome (DDS) refers to neurological symptoms usually seen during or after new initiation or following reinitiation of haemodialysis (HD) after missing multiple sessions. DDS is associated with death and morbidity. We studied interventions aimed at preventing DDS.

OBJECTIVES

To evaluate the benefits and harms of different types of interventions for preventing DDS.

SEARCH METHODS

We contacted the information specialist and searched the Cochrane Kidney and Transplant Register of Studies up to 8 May 2024 using search terms relevant to this review. Studies in the Register were identified through searches of CENTRAL, MEDLINE, and EMBASE, conference proceedings, the International Clinical Trials Registry Platform (ICTRP) Search Portal, and ClinicalTrials.gov.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) that compared any intervention against standard care, including individuals initiated on HD, regardless of age.

DATA COLLECTION AND ANALYSIS

Two authors independently determined study eligibility, assessed quality and extracted data. Data were collected on methods, interventions, participants, and outcomes (DDS incidence, severe DDS, death, adverse events). Risk ratios (RR) and confidence intervals (CI) were calculated. Study quality was assessed using the Cochrane Risk of Bias 2 (ROB2) tool. Confidence in the evidence was assessed using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach.

MAIN RESULTS

We included two RCTs, enrolling 32 adult participants. Interventions included were slow dialysis, sodium modelling, standard sodium dialysate, and high sodium dialysate. The risk of bias was of some concern to high risk of bias in both studies. Slow dialysis compared to sodium modelling (1 study, 15 participants) may result in little to no difference in DDS, severe DDS, and death (low certainty evidence) and has uncertain effects on adverse events (RR 1.33, 95% CI 0.15 to 11.64; very low certainty evidence). Standard sodium dialysate compared to high sodium dialysate (1 study, 17 participants) has uncertain effects on the incidence of DDS (RR 0.07, 95% CI 0.00 to 1.12), severe DDS (RR 0.47, 95% CI 0.02 to 10.32), and adverse events (RR 0.29, 95% CI 0.08 to 1.02) (very low certainty evidence).

AUTHORS' CONCLUSIONS

In HD patients, sodium modelling, compared to slow dialysis, may result in little to no difference in DDS and death (low certainty evidence) and has uncertain effects on adverse events (very low certainty evidence). The evidence is very uncertain for the effect of high-sodium dialysate and standard sodium dialysate on DDS, death and adverse events (very low certainty evidence).

Fatigue in Patients Receiving Maintenance Hemodialysis: A Review

Fatigue surrounding hemodialysis treatments is a common and often debilitating symptom that impacts patients' quality of life. Intradialytic fatigue develops or worsens immediately before hemodialysis and persists through the dialysis treatment. Little is known about associated risk factors or pathophysiology, although it may relate to a classic conditioning response. Postdialysis fatigue (PDF) develops or worsens after hemodialysis and may persist for hours. There is no consensus on how to measure PDF. Estimates for the prevalence of PDF range from 20%-86%, likely due to variation in methods of ascertainment and participant characteristics. Several hypotheses seek to explain the pathophysiology of PDF, including inflammation, hypothalamic-pituitary-adrenal axis dysregulation, and osmotic and fluid shifts, but none is currently supported by compelling or consistent data. PDF is associated with several clinical factors, including cardiovascular and hemodynamic effects of the dialysis procedure, laboratory abnormalities, depression, and physical inactivity. Clinical trials have reported hypothesis-generating data about the utility of cold dialysate, frequent dialysis, clearance of large middle molecules, treatment of depression, and exercise as potential treatments. Existing studies are often limited by sample size, lack of a control group, observational design, or short intervention duration. Robust studies are needed to establish the pathophysiology and management of this important symptom.

Dialysis disequilibrium syndrome (DDS) in pediatric patients on dialysis: systematic review and clinical practice recommendations

BACKGROUND AND OBJECTIVES

Dialysis disequilibrium syndrome (DDS) is a rare neurological complication, most commonly affecting patients undergoing new initiation of hemodialysis (HD), but can also be seen in patients receiving chronic dialysis who miss regular treatments, patients having acute kidney injury (AKI), and in those treated with continuous kidney replacement therapy (CKRT) or peritoneal dialysis (PD). Although the pathogenesis is not well understood, DDS is likely a result of multiple physiological abnormalities. In this systematic review, we provide a synopsis of the data available on DDS that allow for a clear picture of its pathogenesis, preventive measures, and focus on effective management strategies.

METHODS

We conducted a literature search on PubMed/Medline and Embase from January 1960 to January 2021. Studies were included if the patient developed DDS irrespective of age and gender. A summary table was used to summarize the data from individual studies and included study type, population group, age group, sample size, patient characteristics, blood and dialysate flow rate, and overall outcome. A descriptive analysis calculating the frequency of population size, symptoms, and various treatments was performed using R software version 3.1.0.

RESULTS

A total of 49 studies (321 samples) were identified and analyzed. Out of the included 49 studies, a total of 48 studies reported the presence of DSS among patients (1 study reported based on number of dialysis and therefore was not considered for analysis). Among these 48 studies, 74.3% (226/304) patients were reported to have DSS. The most common symptoms were nausea (25.2%), headache (24.8%), vomiting (23.9%), muscle cramps (18.1%), affected level of consciousness (8.8%), confusion (4.4%), and seizure (4.9%) among the 226 DDS patients. Furthermore, 12 studies decided to switch from HD to alternative dialysis modalities including continuous venovenous hemofiltration/hemodiafiltration (CVVH/CVVHDF) or PD which reported no DDS symptoms.

CONCLUSION

Early recognition and timely prevention are crucial for DDS patients. We have provided comprehensive clinical practice points for pediatric, adolescent, and young adult populations. However, it is essential to recognize that DDS was reported more frequently in the early dialysis era, as there was a lack of advanced dialysis technology and limited resources.

EEG spectral changes induced by hemodialysis

OBJECTIVE

To investigate the EEG spectral changes induced during hemodialysis in patients with chronic kidney disease (CKD), and to identify the risk factors associated with changes in the Central Nervous System (CNS) during hemodialysis. Paradoxical neurological deterioration at the end of hemodialysis sessions, known as dialysis disequilibrium syndrome (DDS) has been described, but previous studies on EEG spectral changes during hemodialysis were controversial.

METHODS

We performed quantitative EEG spectral analysis in 56 consecutive patients who underwent hemodialysis. We compared EEG at the start and at the end of the hemodialysis, and we correlated the spectral changes with the biochemical and clinical characteristics of the patients, using multivariate analysis.

RESULTS

At the end of hemodialysis sessions, we found a significant increase in total EEG power, relative power in delta frequency band and the ratio of delta-theta/alpha-beta power. EEG spectral changes were associated with younger age, recent start of hemodialysis therapy, level of uremia and lower level of glycaemia.

CONCLUSIONS

Quantitative EEG spectral analysis showed that hemodialysis induced slowing of the EEG background activity. These changes were associated with risk factors of DDS.

SIGNIFICANCE

EEG spectral changes are potential biomarkers for monitoring CNS function during hemodialysis.

Haemodiafiltration, haemofiltration and haemodialysis for end-stage kidney disease

BACKGROUND

Convective dialysis modalities (haemofiltration (HF), haemodiafiltration (HDF), and acetate-free biofiltration (AFB)) removed excess body fluid across the dialysis membrane with positive pressure and accumulated middle- and larger-size accumulated solutes more efficiently than haemodialysis (HD). This increased larger solute removal combined with use of ultra-pure dialysis fluid in convective dialysis is hypothesised to reduce the frequency and severity of symptoms during dialysis as well as improve clinical outcomes. Convective dialysis therapies (HDF and HF) are associated with lower mortality compared to diffusive therapy (HD) in observational studies. This is an update of a review first published in 2006.

OBJECTIVES

To compare convective (HF, HDF, or AFB) with diffusive (HD) dialysis modalities on clinical outcomes (mortality, major cardiovascular events, hospitalisation and treatment-related adverse events) in men and women with end-stage kidney disease (ESKD).

SEARCH METHODS

We searched the Cochrane Renal Group's Specialised Register (to 18 February 2015) through contact with a Trials' Search Co-ordinator using search terms relevant to this review.

SELECTION CRITERIA

We included randomised controlled trials comparing convective therapy (HF, HDF, AFB) with another convective therapy or diffusive therapy (HD) for treatment of ESKD.

DATA COLLECTION AND ANALYSIS

Two independent authors identified studies, extracted data and assessed study risk of bias. We summarised treatment effects using the random effects model. We reported results as a risk ratio (RR) for dichotomous outcomes and mean difference (MD) for continuous data together with 95% confidence intervals (CI). We assessed for heterogeneity using the Chi(2) test and explored the amount of variation in treatment estimates beyond that expected by chance using the I(2) statistic.

MAIN RESULTS

Twenty studies comprising 667 participants were included in the 2006 review. In that review, there was insufficient evidence of treatment effects on major clinical outcomes to draw clinically meaningful conclusions. Searching to February 2015 identified 40 eligible studies comprising 3483 participants overall. In total, 35 studies (4039 participants) compared HF, HDF or AFB with HD, three studies (54 participants) compared AFB with HDF, and three studies (129 participants) compared HDF with HF.Risks of bias in all studies were generally high resulting in low confidence in estimated treatment effects. Convective dialysis had no significant effect on all-cause mortality (11 studies, 3396 participants: RR 0.87, 95% CI 0.72 to 1.05; I(2) = 34%), but significantly reduced cardiovascular mortality (6 studies, 2889 participants: RR 0.75, 95% CI 0.61 to 0.92; I(2) = 0%). One study reported no significant effect on rates of nonfatal cardiovascular events (714 participants: RR 1.14, 95% CI 0.86 to 1.50) and two studies showed no significant difference in hospitalisation (2 studies, 1688 participants: RR 1.23, 95% CI 0.93 to 1.63; I(2) = 0%). One study reported rates of hypotension during dialysis were significantly reduced with convective therapy (906 participants: RR 0.72, 95% CI 0.66 to 0.80). Adverse events were not systematically evaluated in most studies and data for health-related quality of life were sparse. Convective therapies significantly reduced predialysis levels of B2 microglobulin (12 studies, 1813 participants: MD -5.55 mg/dL, 95% CI -9.11 to -1.98; I(2) = 94%) and increased dialysis dose (Kt/V urea) (14 studies, 2022 participants: MD 0.07, 95% CI -0.00 to 0.14; I(2) = 90%) compared to diffusive therapy, but results across studies were very heterogeneous. Sensitivity analyses limited to studies comparing HDF with HD showed very similar results. Directly comparative data for differing types of convective dialysis were insufficient to draw conclusions.Studies had important risks of bias leading to low confidence in the summary estimates and were generally limited to patients who had adequate dialysis vascular access.

AUTHORS' CONCLUSIONS

Convective dialysis may reduce cardiovascular but not all-cause mortality and effects on nonfatal cardiovascular events and hospitalisation are inconclusive. However, any treatment benefits of convective dialysis on all patient outcomes including cardiovascular death are unreliable due to limitations in study methods and reporting. Future studies which assess treatment effects of convection dose on patient outcomes including mortality and cardiovascular events would be informative.

Analytic Review: Neurological Complications of Transplantation

Recipients of solid organ or hematopoietic cell transplants are at risk of life-threatening neurological disorders including encephalopathy, seizures, infections and tumors of the central nervous system, stroke, central pontine myelinolysis, and neuromuscular disorders—often requiring admission to, or occurring in, the intensive care unit (ICU). Many of these complications are linked directly or indirectly to immunosuppressive therapy. However, neurological disorders may also result from graft versus host disease, or be an expression of the underlying disease which prompted transplantation, as well as injury induced during radiation, chemotherapy, surgery, and ICU stay. In rare cases, neuroinfectious pathogens may be transmitted with the transplanted tissue or organ. Diagnosis may be a challenge because clinical symptoms and findings on neuroimaging lack specificity, and a biological specimen or tissue diagnosis is often needed for definitive diagnosis. Management is centered on preventing further neurological injury, etiology-targeted therapy, and balancing the benefits and toxicities of specific immunosuppressive agents.

Dialysis disequilibrium syndrome: a narrative review

Dialysis Disequilibrium Syndrome (DDS) is characterized by neurological symptoms caused by rapid removal of urea during hemodialysis. It develops primarily from an osmotic gradient that develops between the brain and the plasma as a result of rapid hemodialysis. This results in brain edema that manifests as neurological symptoms such as headache, nausea, vomiting, muscle cramps, tremors, disturbed consciousness, and convulsions. In severe cases, patients can die from advanced cerebral edema. Recent advancements in cell biology implicate the role of urea disequilibrium (with a smaller contribution from organic osmolytes) as the pathophysiological mechanism responsible for this syndrome. In this review, we discuss the pathogenesis, clinical features and prevention of DDS.

Identification of factors responsible for postdialysis fatigue

Ultrafiltration, diffusion, osmotic shifts, blood-membrane interactions, and psychological factors have all been implicated in the pathogenesis of postdialysis fatigue (PDF). To identify responsible factors, we performed a prospective, randomized, crossover analysis of fatigue scores (scale, 0 to 4) in 12 maintenance hemodialysis subjects with PDF. Fatigue scores were evaluated on nondialysis days (baseline) and after the following procedures on midweek treatment days: standard dialysis using either a 135- to 140-mEq/L sodium bath (routine hemodialysis) or a 150- to 155-mEq/L sodium bath (hypernatric hemodialysis); isolated ultrafiltration; isolated diffusion; and sham procedures with (isolated membrane) or without (recirculation) exposure to a dialysis membrane. Maximal fatigue scores are expressed as mean and 95% confidence intervals (CIs). The highest scores were recorded by patients who had just undergone routine hemodialysis (mean score, 2. 6; 95% CI, 1.7 to 3.4), isolated ultrafiltration (mean score, 2.1; 95% CI, 1.3 to 2.9), and isolated diffusion (mean score, 2.4; 95% CI, 1.5 to 3.2). There were no significant differences in fatigue scores between baseline periods and isolated membrane and recirculation procedures (mean score, 1.3; 95% CI, 0.4 to 2.2). Fatigue scores after hypernatric hemodialysis occupied an intermediate position (mean score, 1.7; 95% CI, 0.8 to 2.6). These results suggest that rapid hydraulic and molecular flux have a greater role in the pathogenesis of PDF than psychological stress and blood-membrane interactions. Use of a high-sodium bath may ameliorate PDF. We conclude that appropriate adjustments in both ultrafiltration and sodium profiling remain the most important means for controlling PDF in patients on short-duration hemodialysis.

Hemodialysis increases apparent diffusion coefficient of brain water in nephrectomized rats measured by isotropic diffusion-weighted magnetic resonance imaging

The nature of brain edema in dialysis disequilibrium syndrome (DDS) was investigated by diffusion-weighted magnetic resonance imaging (DWI). DWI was performed on normal or bilaterally nephrectomized rats before, and immediately after, hemodialysis. Hemodialysis was performed with a custom-made dialyzer (surface area 150 cm2) against a bicarbonate-buffered bath for 90 min with or without 70 mM urea. Hemodialysis with non-urea bath decreased plasma urea by 21 mM, and plasma osmolality by 22 mosmol/kg H2O, and increased brain water content by 8.0% (all < 0.05), while hemodialysis with urea bath did not affect plasma urea, osmolality, or brain water content. Three sets of axial DWI images of the brain were obtained at different gradient weighing factors with an in-plane resolution of 0.39 mm2. The apparent diffusion coefficient (Dapp) of the brain water was not affected by bilateral nephrectomy, or by hemodialysis in normal rats. In nephrectomized rats, brain Dapp was significantly increased after dialysis with non-urea bath (1.15 +/- 0.08 vs 0.89 +/- 0.07 x 10(-9)m2/sec, P < 0.01). No significant changes of brain water Dapp could be observed after dialysis with urea bath. The increased Dapp associated with DDS indicates that brain extracellular water increases and/or intracellular water decreases after hemodialysis. Our results strongly suggest that the brain edema induced by hemodialysis in uremic rats is due to interstitial edema rather than cytotoxic edema. Furthermore, our results support a primary role for the "reverse urea effect" in the pathogenesis of brain edema in DDS.DWI may be a useful diagnostic tool for DDS in patients with end-stage renal disease.

Cerebral function analyzing monitor and visual evoked potentials as a noninvasive method of detecting cerebral dysfunction in patients with acute hepatic and renal failure treated with intermittent machine hemofiltration

We monitored the effect of 7 intermittent machine hemofiltration treatments in 4 patients with fulminant hepatic failure who had progressed to grade IV coma and developed acute oliguric renal failure. Prior to treatment the processed EEG showed excess slow wave activity, and the latency of the later visual evoked potentials (N2 and P2) was delayed. Following treatment there was a further increase in both EEG slow wave activity and latency of the N1, N2, and P2 potentials. Intracranial pressure increased from a median of 8 mm Hg (2-12, range) to 14 (8-28) following treatment, p < 0.05. There was a correlation between intracranial pressure and all of the later visual evoked potentials, for N3 r = 0.71, for P1 r = 0.39, and P2 r = 0.74, all p < 0.05. Although there appeared to be a good correlation between intracranial pressure and the noninvasive electrophysiological recordings, there were major changes in intracranial pressure, cerebral perfusion pressure, and cerebrospinal fluid pH during the first hour of treatment, during which time there were no discernable changes in EEG or evoked potentials. In this study, non-invasive neurophysiological methods were not found to be reliable as invasive methods in assessing acute, minute-by-minute changes in cerebral metabolism but these methods may have a role in the longer term in assessing patient prognosis.

Morbidity and mortality due to cerebral edema complicating the treatment of severe leptospiral infection

Although neurological signs and symptoms are well described in leptospiral infections, cerebral edema has not been reported previously. We have encountered two patients with severe leptospiral infection, associated with multisystem involvement, who developed cerebral edema. Both patients were in acute oligoanuric renal failure, one being treated by acetate hemodialysis and the other by hemofiltration. Grand mal seizures developed in both patients, followed by respiratory, then cardiac arrest, as a consequence of dialytic therapy. Only one patient could be resuscitated and he was left with a hemiparesis. Cerebral edema may develop in patients with severe leptospiral infections consequent to treatments used in the management of renal failure.

Intraocular pressures during high-flux hemodialysis

The intraocular pressures of 16 patients with end stage renal failure treated with high-flux dialysis were measured before and during a high-flux dialysis treatment. The patients were selected so as not to have glaucoma or history of glaucoma. Intraocular pressures did not change significantly in any patients during or following a high-flux hemodialysis treatment. These data suggest that high-flux hemodialysis does not result in increases in intraocular pressure nor does it precipitate acute glaucoma in well-dialyzed patients undergoing intermittent in-center hemodialysis.