Electrophysiological indices of CNS function in hemodialysis and CAPD

Better Preservation of Cognitive Faculty in Continuous Ambulatory Peritoneal Dialysis

We employed the so-called event-correlated potential (ECP) P300, a neurophysiological test which explores the circuits of attention and memory in the brain and is altered in subjects with a dismetabolic or degenerative encephalopathy, in order to evaluate the cognitive faculty in two groups of uremic patients [18 on continuous ambulatory peritoneal dialysis (CAPD), 15 on hemodialysis (HD)] comparable with respect to age and time on dialysis. The values of latency (msec) of P300 resulted in CAPD patients 356±26 in CZ (central zero electrodes) and 357.5±25 in PZ (parietal zero electrodes), not significantly different from the values in normal controls (341±14.5 in CZ and 340± 15.6 in PZ) and in HD patients postdialysis (354±24.4 in CZ and 354±25.6 in PZ). On the contrary, the predialytic values of HD patients (384±25.6 CZ and 385±25.5 in PZ) were significantly different from the postdialytic values and from the values of CAPD patients and controls (p<0.01). These results support the conclusion that HD Is able to restore a normal cognitive faculty only transiently in the postdialytic phase, while CAPD maintains this important function steadily close to the normal range, thus being clearly better than HD.

Latency and amplitude changes in cognitive event related potentials due to hemodialysis

Chronic kidney disease impacts the cognitive abilities of patients, and yet few works have analyzed functional electroencephalographic changes on event-related potentials before and after an hemodialysis session. This work shows that, as a consequence of hemodialysis, cognitive potential waveforms suffer changes, occurring with reduced latency $( \sim 50$ ms) and with larger amplitude $( \sim 0.128\mathrm {a}$.u.) after the treatment session. While only a limited sample of five patients is reported herein, the observed changes immediately after hemodialysis could be a sign of central nervous system alterations that are not clinically evaluated. Signs like these could entail an early indicator of possible evolution into some neuropathology.

Consequences of CKD on Functioning

Chronic kidney disease (CKD) is highly prevalent in the United States and throughout the world,(1) with approximately 13% of adults affected.(2) In addition, according to recent estimates, almost half of patients with CKD stages 3 to 5 are 70 years of age and older.(2) In the United States, the number of prevalent end-stage renal disease cases continues to increase in patients older than age 65. In light of the demographic characteristics of patients with CKD and ESRD, there has been considerable focus on associations between CKD and cardiovascular outcomes.(3) Until recently, less attention had been paid to other consequences of CKD in general and among older individuals with CKD in particular, but there is now solid evidence linking CKD with impairments of physical function, cognitive function, and emotional function and quality of life. This review summarizes available literature on these topics, focusing specifically on physical functioning and frailty, cognitive function, emotional health, including depression and anxiety, and health-related quality of life.

Cerebral blood flow changes in hemodialysis and peritoneal dialysis patients: an arterial-spin labeling MR imaging

We used arterial-spin labeling (ASL) MR imaging, a non-invasive technique to evaluate cerebral blood flow (CBF) changes in patients with end-stage renal disease (ESRD) undergoing peritoneal dialysis (PD) and hemodialysis (HD), and nondialysis ESRD patients compared with healthy cohort. Ninety seven ESRD patients including 32 PD patients (20 male, 12 female; mean age 33 ± 8 years), 33 HD patients (22 male, 11 female; mean age 33 ± 8 years) and 32 nondialysis patients (20 male, 12 female; mean age 35 ± 7 years) and 31 age- and gender-matched healthy controls (20 male, 11 female; mean age 32 ± 8 years) were included in this study. All subjects underwent ASL MR imaging, neuropsychologic tests, and ESRD patients underwent laboratory testing. CBF values were compared among PD, HD, nondialysis patients and control groups. Correlation analysis and multiple regression analysis were performed to investigate the association between CBF values and hemoglobin, neuropsychologic test results, serum creatinine, urea levels, disease duration, and dialysis duration. Elevated CBFs of whole brain region, gray matter, and white matter were found in all ESRD patient groups compared with healthy controls (all P < 0.001). However, compared with non-dialysis ESRD patients, both PD and HD patients had widespread regional CBF decline mainly in bilateral frontal and anterior cingulate cortices. There were no differences for CBF between PD and HD patient groups. Negative correlations were observed between mean CBFs of whole brain region, gray matter, and white matter and the hemoglobin level in all ESRD patients. Multiple linear regression showed elevated CBF of multiple brain areas correlated with some neuropsychological tests in ESRD patients (all P < 0.001, AlphaSim corrected), but the association was not present or shrank after adjusting hemoglobin level. This study found that mean CBF was predominantly increased in patients with ESRD, which correlated with their hemoglobin level and neurocognitive disorders. There were no differences of CBF change and cognitive function between PD and HD ESRD patients with long-term treatment. The degree of anemia may be a predominant risk factor for cognitive impairment in these ESRD patients.

Prevalence and patterns of hearing loss among chronic kidney disease patients undergoing haemodialysis

BACKGROUND

The prevalence, degree, and patterns of hearing loss associated with chronic kidney disease (CKD) reported by various studies differ significantly. The effects of haemodialysis and duration of disease on hearing loss remain unclear.

AIMS

The aim of this study was to determine the prevalence and degree of hearing loss in CKD patients on haemodialysis.

METHODS

This study included 120 CKD patients on haemodialysis. Information regarding age, gender, duration of disease, subjective hearing loss, exposure to ototoxic drugs, comorbidities like diabetes, hypertension, and hypothyroidism, renal functions, electrolytes and number of haemodialysis sessions received were obtained. An equal number of age and sex matched controls were used to determine prevalence of hearing loss in CKD patients after subjecting both groups to pure tone audiometry. We compared CKD patients with and without hearing loss for association of hearing loss with disease duration, number of haemodialysis, and blood parameters.

RESULTS

Hearing loss was present in 41.7 per cent of CKD patients, significantly higher than controls (p=0.001), and was mild in the majority of patients. Impairment was noted across high and low frequencies of audiometric testing. Median duration of disease was the same (18 months) among CKD patients with and without hearing loss (p=0.62). CKD patients with hearing loss received 72 haemodialysis compared to 122 sessions by those without hearing loss (p=0.04).

CONCLUSION

Mild sensorineural hearing loss is common in CKD. Hearing loss has no specific pattern as it prevails at high and low frequencies. Hearing loss may be inversely associated with the number of haemodialysis sessions but not with duration of disease.

Effect of Hemodialysis on Cognitive Function in ESRD Patients

BACKGROUND

Uremia is associated with impairment of different cognitive functions. However the pathogenesis of this cognitive dysfunction is unknown.

OBJECTIVE

In this study, long-latency event related potentials (ERPs) were used to assess changes in cortical function due to hemodialysis treatment.

METHODS

In this cross-sectional study, we measured event related potentials in 15 end stage renal disease (ESRD) patients maintained on hemodialysis, two hours before and two hours after they underwent hemodialysis and compared their data with a strictly age and sex matched healthy control group. The P3 was elicited by using standard auditory "odd-ball" paradigm and the data obtained was statistically analyzed (Wilcoxon signed ranks, Mann Whitney).

RESULTS

Before hemodialysis, the patients' P3 latency (347.73 +/- 39.47 ms) was significantly increased as compared with that of healthy control group (308.4 +/- 13.73 ms) (p = 0.001). After hemodialysis, P3 latency of the patients showed a significant decrease (347.73 +/- 39.47 ms to 325.20 +/- 37.15 ms, p = 0.001). P3 latency after dialysis was not significantly different from controls. No significant correlation was noted between various biochemical parameters (hemoglobin, blood urea, creatinine, uric acid and calcium) and P3 latency or amplitude.

CONCLUSIONS

Removal of uremic toxins by hemodialysis leads to an improvement in cognitive processing.

Effects of hemodialysis on profound memory deficits in renal insufficiency due to multiple myeloma: a case study

Multiple myeloma, a rare cancer for individuals less than 65 years of age, and its pathophysiological effects have a profound impact on neurocognitive function. Specific transient deficits in patients with renal failure secondary to multiple myeloma have been noted to improve with hemodialysis. We present a complex case of an individual with multiple myeloma, renal insufficiency, treated seizure disorder, and schizophrenia, paranoid type, who experienced functional improvements in memory and visuospatial function with short- and long-term administration of hemodialysis. Within weeks of treatment, memory impairments resolved. With continued hemodialysis, some areas of neurocognitive function were in the superior range, indicating an overall improvement of more than three standard deviations. Implications and recommendations for clinicians treating individuals with similar challenges are offered.

Improvements in cognition in patients converting from thrice weekly hemodialysis to nocturnal hemodialysis: a longitudinal pilot study

Cognitive impairment has been documented in uremia with partial improvement after dialysis. Nocturnal daily hemodialysis (NHD) is a novel dialysis modality with multiple benefits. Previous reports have shown marked improvements in quality of life, cardiac function, resolution of peripheral vascular disease, and reversal of central sleep apnea. We hypothesized that patients maintained on NHD would have better cognitive functioning than those receiving conventional therapy. Using a longitudinal study design, patients were tested at baseline and again after >or=6 months NHD. At each of the two time points, a battery of 10 neuropsychological tests were used to evaluate three domains of cognitive functioning--attention and working memory skills, psychomotor efficiency and processing speed, and learning efficiency. Clinical subjective symptoms for cognitive functioning and depression were measured using the Patients Assessment of Own Functioning inventory and the Beck Depression Index. Twelve patients (six males, six females) were recruited. Patients were aged 39.6+/-3.3 years at the time of first testing. Thirty-three percent were diabetic, with a mean Charlson comorbidity score of 3.5+/-2.0. Depression (defined as >16 on the Beck Depression Index score) was not seen in any patient. Over the 6-month period, a 22% reduction in cognitive symptoms (P=0.01), 7% improvement in psychomotor efficiency and processing speed (P=0.02), and 32% improvement in attention and working memory (P=0.04) was seen. Learning efficiency scores were unchanged. NHD may be associated with improved general cognitive efficiency as measured by psychomotor efficiency and attention and working memory.

Positive correlations between cerebral choline and renal dysfunction in chronic renal failure

INTRODUCTION

Cerebral metabolism in chronic renal failure (CRF) patients has not been fully evaluated. This study examined cerebral metabolites in CRF, using proton magnetic resonance spectroscopy (MRS).

METHODS

Subjects comprised 19 CRF patients and 21 healthy volunteers. Spectra were acquired from voxels of interest positioned in the parietal gray and white matter, and concentrations of the following cerebral metabolites were measured: N-acetyl group (NA), creatine + phosphocreatine (Cr), choline-containing compounds (Cho), myo-inositol and glutamate + glutamine. Among the 19 CRF patients, 9 who were started on hemodialysis (HD) underwent careful follow-up. Proton MRS was performed before and about 2 weeks after starting HD. In six patients in whom follow-up was possible, a third MRS was performed after about 18 months.

RESULTS

The NA/Cr ratio was not significantly changed in CRF. However, elevations in the Cho/Cr ratio were found in both gray and white matter compared with controls. To the best of our knowledge, this is the first report of positive correlations between the Cho/Cr ratio in both regions and serum osmotic pressure. Compared with baseline data, no significant changes in cerebral metabolite ratios were found about 2 weeks after starting HD. About 18 months after starting HD, however, the elevated Cho/Cr ratio was significantly reduced in the gray matter and tended to be reduced in the white matter.

CONCLUSIONS

Cho appear to play an important role in the regulation of cerebral metabolism to compensate for alterations in serum osmotic pressure in CRF, and HD may correct this abnormal cerebral metabolism.

Cognitive function in dialysis patients

There are few detailed studies of cognitive function in dialysis patients. However, appreciating the prevalence and risk factors for cognitive impairment is important because cognitive impairment may decrease an individual's quality of life, increase resource utilization, and result in suboptimal medical care because of difficulty following caregiver recommendations. Cognitive impairment also is likely to become more of a problem as the dialysis population ages. In this review, we argue that cerebrovascular disease is an important cause of cognitive impairment in dialysis patients and discuss risk factors specific for vascular disease, as well as other factors that may influence cognitive function. We describe the structural brain abnormalities frequently seen in dialysis patients and the specific neurocognitive changes noted in prior studies. We explore potential measures to reduce cognitive impairment in this population. We conclude that additional research is needed in this area.

Influence of end-stage renal failure and hemodialysis on event-related potentials

Chronic renal failure frequently causes uremic encephalopathy with impairment of different cognitive functions, but the pathophysiology of uremic encephalopathy is still unknown. We measured visually evoked event-related potentials (ERPs) in 33 neurologically asymptomatic patients before and after they underwent hemodialysis and compared their data with those of a strictly age-matched healthy control group. Before hemodialysis, the patients' P3 latency was significantly increased and P3 amplitude was significantly decreased as compared with that of the healthy control group. After hemodialysis, P3 latency of the patients showed a significant decrease (457+/-56 before and 438+/-54 ms after hemodialysis) and the P3 latency habituation during the ERP measurement was also significantly decreased. Patients with higher levels of blood urea nitrogen (BUN), creatinine, and uric acid performed better in ERP measurement than did patients with lower levels. Hemoglobin did not influence ERP latencies and amplitudes. Our data suggest that impaired cognitive processing can be disclosed by ERP even in neurologically asymptomatic chronic renal disease. Removal of uremic toxins by hemodialysis leads to an improvement in cognitive processing.

Dialysis and transplantation affect cerebral abnormalities of end-stage renal disease

Localized short echo time proton magnetic resonance spectroscopy was performed to determine whether chronic and end-stage renal failure, hemodialysis, continuous ambulatory peritoneal dialysis, or renal transplantation result in alterations of cerebral water and metabolites in humans. Hemodialysis patients show an increased cerebral concentration of myo-inositol (+ 14%; P < .05). Increased metabolite ratios are found for myo-inositol/creatine (+14%; P <.01) and choline containing compounds choline/creatine (+10%; P < .01) and are more marked in gray than in white matter. N-acetylaspartate and total creatine concentrations are unaffected. Compared to hemodialysis, continuous ambulatory peritoneal dialysis patients show a larger increase in choline and less elevated myo-inositol. Acutely, hemodialysis significantly decreases the cerebrospinal fluid content of the examined brain regions, but metabolite changes are small compared to the persistent alterations in patients receiving hemodialysis or continuous ambulatory peritoneal dialysis. Undialyzed patients with chronic renal failure do not differ from patients on hemodialysis, but cerebral metabolite changes are completely reversed by transplantation. Cerebral metabolic effects of end-stage renal disease differ from Alzheimer's disease, which is associated with markedly reduced N-acetylaspartate, increased myo-inositol, and normal choline concentrations. The small but significant cerebral metabolic disorders associated with renal failure and dialysis may be a consequence of osmotic dysregulation.

Sensorineural hearing loss in patients reaching chronic renal failure in childhood

The incidence of sensorineural hearing loss (SNHL) was investigated in 68 patients who reached chronic renal failure (CRF) in childhood with the aim of identifying possible risk factors. Tests were carried out by means of pure-tone and impedance audiometry. SNHL was found in 29% of patients on conservative treatment, 28% of patients on hemodialysis, and 47% after renal transplantation. Differences among groups were not significant. A significant correlation was found with the administration of ototoxic drugs (aminoglycosides and furosemide). We hypothesize that SNHL may be reduced in patients with CRF or on renal replacement therapy by strictly monitoring ototoxic therapy.

Assessment of the learner: physiological readiness

Patients with end-stage renal disease (ESRD) who undergo dialytic therapy or who receive a kidney transplant are expected to learn a great deal of information about their disease and treatment. As this population encompasses a vast number of persons of varying age, education, and life skills, the ability to learn new information may be a challenge for both the patient and staff. The uremic state and its effect on cognitive function influences the patient's physiological readiness and ability to learn. Recent research, testing methods, and understanding of other effects of renal failure on cognitive function have provided more information about the patient's physiological readiness/ability to learn. Health care professionals can incorporate these new findings into their teaching programs and strategies to assure successful patient learning and outcomes.

Evoked potentials in children with chronic renal failure, treated conservatively or by continuous ambulatory peritoneal dialysis

Children with chronic renal failure (CRF) show developmental, intellectual and motor disturbances. It is questionable if an early start of renal replacement therapy may prevent or delay these disturbances. We studied the neurological and intellectual development of children < 5 years suffering from CRF (creatinine clearance < 20% of normal) prospectively, over a period of 3 years. As part of the neurological study, brainstem auditory evoked potentials (BAEP) and somatosensory evoked potentials (SSEP) were recorded. Measurements were performed in a group of 22 children every 6 months. In 18 of these children CRF was present from birth. Sufficient data were available for analysis in 19 (BAEP) and 22 (SSEP), respectively. A delay of peak I of BAEP gave indications for peripheral conduction disturbances, possibly due to cochlear dysfunction. Brainstem conduction was normal. There were no differences between the children treated conservatively (n = 9) and those treated with continuous ambulatory peritoneal dialysis (CAPD) (n = 10). In children < 2.5 years SSEP showed a delayed thalamocortical conduction, which was not observed in older children. This might indicate a delayed myelination in young children with CRF. No differences were found between the children treated conservatively (n = 10) and those treated with CAPD (n = 12).

Renal replacement therapies in the elderly: Part 1. Hemodialysis and chronic peritoneal dialysis

Recent demographic data from the United States and Europe demonstrate that the dialysis population is growing progressively older. In the United States the median age at onset of end-stage renal disease (ESRD) had reached 61 years in 1990, and the fraction of ESRD patients older than 65 years will approach 60% by the year 2000. The primary treatment of geriatric ESRD is center hemodialysis (82% of elderly patients). Chronic peritoneal dialysis in this age group is limited in the United States to less than 10%. Only 2.7% of elderly patients have a functioning transplant. Despite their complex medical and psychosocial conditions, survival and rehabilitation are acceptable in the elderly dialysis patient and these patients tend to be more complaint. Five-year dialysis patient survival rates in the United States are 19% and 10%, respectively, for the 65 to 74 and 75 to 84 age groups compared with 32% and 19%, respectively, for the same age groups in Europe. Five-year survival, particularly in the elderly, is even higher in Japan. Several factors favor the delivery of low doses of hemodialysis in the elderly and discontinuing dialysis is more common in the elderly. Continuous ambulatory peritoneal dialysis is a satisfactory alternative treatment modality for geriatric ESRD. Most studies confirm that survival of elderly patients on continuous ambulatory peritoneal dialysis and hemodialysis is similar. The 1991 United States Renal Data System report showing higher mortality among diabetic continuous ambulatory peritoneal dialysis patients than among hemodialysis patients may reflect selection of such patients, who may have more co-morbid conditions. In special cases, continuous cyclic peritoneal dialysis can be an alternative treatment for elderly ESRD patients.

Effects of rHuEPO on Q-EEG and event-related potentials in chronic renal failure

Quantitative electroencephalography is a powerful tool to evaluate brain function, and preliminary data have shown its usefulness in the evaluation of patients with chronic renal failure (CRF). In this study, baseline values of different quantitative EEG variables, as well as data from the P300 component of the visual event-related potential, in 43 patients with chronic renal failure, were compared with those of a group of healthy subjects and with the results obtained after 3, 6, 9 and 12 months of treatment of these patients with rHuEPO. Baseline total power was much lower in patients with CRF than in healthy subjects, and the distribution of power among the frequency bands was also abnormal. rHuEPO promptly normalized total power and progressively improved power distribution, although full normality was not achieved. Mean dominant frequencies in brain areas were abnormal in patients with CRF, and progressive improvement was seen along the study. The latency of P300, which was increased before treatment, decreased in all subjects, but normal values were not reached. The same applies to the hypomanic and psychopathic scores of psychological tests. Altogether, brain dysfunction of CRF seems to substantially improve by treatment of the anemia with rHuEPO.

rHuEPO treatment improves brain and cognitive function of anemic dialysis patients

Twenty-four patients with chronic renal failure, stabilized on hemodialysis, were treated with recombinant human erythropoietin. Before treatment, all patients were anemic (mean Hct = 23.7%). Hematocrits reached normal levels (36.5%) after three months of treatment. Brain event-related potentials and neuropsychological tests were used to assess changes in brain and cognitive functions associated with the correction of anemia. Assessments were done prior to and after three and twelve months of rHuEPO treatment. The P3 component of the event-related potential increased in amplitude significantly with treatment, while its latency was unaffected. Of the four neuropsychological tests administered, scores on two improved significantly with treatment, and the other two approached significance. Taken together, these findings suggest that the correction of anemia to hematocrits near normal in uremic patients by rHuEPO treatment improves brain and cognitive function by raising levels of sustained attention, thus increasing speed and efficiency of scanning and perceptual-motor functions and enhancing learning and memory. These findings also suggest that anemia, either directly or indirectly, may impair brain function.

Cognitive function, mood and P3 latency: effects of the amelioration of anemia in dialysis patients

Attention difficulties and psychomotor slowing associated with depressed mood affect the ability of individuals to perform on most neuropsychological tests. It has been suggested that latency of the P3 (P300) component of the event-related EEG potential is an index of neurocognitive status which is not affected by mood. Dialysis patients, who experience diminished dysphoric mood with the reversal of anemia when treated with recombinant human erythropoietin (rHuEPO), were tested for neurocognitive performance, mood and latency of P3. Prior to rHuEPO treatment mood was dysphoric, and neurocognitive testing showed mild deficits, but P3 latency was normal. After treatment, mood improved and neurocognitive test performance was normal. P3 amplitude increased over frontal areas, while P3 latency remained unchanged. Thus, in the case of dysphoric mood, P3 latency may provide a more accurate index of cognitive capacity (as opposed to level of functioning) than neurocognitive test measures.

Improvement of brain function in hemodialysis patients treated with erythropoietin

To evaluate the effects of recombinant human erythropoietin (rHuEPO) on brain function, 15 chronic hemodialysis patients were studied by event-related P300, stimulus-related evoked potentials, and trailmaking before (hematocrit 22.7%) and after rHuEPO (hematocrit 30.6%). P300 peak latency elicited by a tone discrimination paradigm improved (391 before vs. 366 ms after; Cz = vertex; P less than 0.01) confirming beneficial effects on cerebral cognitive processing. P300 amplitude (13.6 vs. 15.8 microV; P = 0.06) and trailmaking tended to improve (55 vs. 43 s). P300 measures were influenced by low hemoglobin levels before rHuEPO (P less than 0.01), suggesting that severe anemia may contribute to uremic brain dysfunction. Furthermore, decrease of stimulus-related auditory brainstem I-V interpeak latency (4.28 before vs. 4.17 ms after; P less than 0.05) and increase of somatosensory N20/P25 amplitude (4.8 vs. 7.0 microV; P less than 0.05) pointed to improvement of sensory pathways by mechanisms unrelated to cognition. Brain dysfunction in chronic hemodialysis patients may, beside other factors, in part be caused by severe anemia and can be improved by rHuEPO treatment.

Recombinant human erythropoietin treatment may improve quality of life and cognitive function in chronic hemodialysis patients

Medical, psychological, and social adaptation (quality of life) as well as cognitive function were studied in 15 chronic stable hemodialysis patients before the onset of treatment with recombinant human erythropoietin (r-HuEPO), 1 month after stabilization of normal hematocrit levels, and 10 to 15 months after treatment onset. After r-HuEPO treatment, subjects had significantly higher hematocrits, markedly improved energy levels, and marginally improved global health. r-HuEPO treatment was also associated with progressively decreased levels of subject mood disturbance and dialysis-related stresses. Subjects had no increased participation in paid employment and only minimally increased participation in social and leisure activities at posttreatment data points. There was no significant improvement in cognitive function after treatment. r-HuEPO treatment appears to be associated with higher energy levels, significant psychological benefits, and minimal improvements in social adaptation. The effects on cognitive function merit further study.

Relationship of dialysis modality and other factors to cognitive function in chronic dialysis patients

To determine if dialysis modality may be an independent factor in the level of cognitive function in chronic dialysis patients, cognitive function was studied in 17 pairs of continuous ambulatory peritoneal dialysis (CAPD) and center hemodialysis (CHD) subjects matched for sex, age, diabetic status, and interval since dialysis onset. Data on current metabolic, medical, psychological, and vocational function status were obtained. Neuropsychological (NP) measures included the Number Cancellation Protocol (NCP), Trailmaking test forms A and B (TMT A, TMT B), Symbol Digit Modalities (SDM), and the Rey Auditory Verbal Learning Test (RAVLT). The CAPD subject group had consistently more efficient cognitive function than the CHD subject group. Regardless of modality, the groups of subjects under age 51 and those who were vocationally active had significantly better NP performance. No cognitive function differences were found in groups categorized by sex or duration of dialysis. Creatinine levels were more highly correlated with NP scores than were BUN levels, with higher creatinine levels associated with better cognitive function. Serum calcium, CO2, total protein, albumin, and SGOT levels also were correlated with NP scores. CAPD may be more effective than HD in reversing uremic encephalopathy by mechanisms mostly unrelated to serum creatinine and BUN levels. Longitudinal studies will be needed to determine if dialysis modality is an independent factor in the degree of reversal of uremic encephalopathy.