Dialysis encephalopathy and osteomalacic bone disease: a case-controlled study

Advances in dialysis encephalopathy research: a review

Dialysis encephalopathy (DE) is a progressive, fatal disease with a high mortality rate. Understanding the causes of this disease and the efforts to prevent and treat it would help improve the prognosis and quality of life of affected patients. This paper reviews the etiology, clinical features, methods of examining accessory features, diagnosis, treatment, and prevention of DE. We found that DE is likely to be related to aluminum poisoning. The clinical manifestations of DE include language disorders, mental and behavioral disorders, cognitive decline, and movement disorders. Electroencephalogram (EEG) findings mainly consist of an abundance of low waves, intermittent bilateral synchronous high-amplitude spikes, and ridge waves. Assessing the clinical features and obtaining an EEG are of great value in diagnosis, and DE is treated by both reducing aluminum intake and increasing aluminum excretion. Deferoxamine (DFO) is an effective treatment for DE.

Effects of sodium acetate on rat bone-nodule formation and mineralization in vitro

Sodium acetate reportedly promotes bone atrophy by inducing resorption and inhibiting osteoprogenitor-cell proliferation, but little is known about its effects on bone-matrix deposition and mineralization by a population containing osteoprogenitor cells. The objective here was to assess the effects of 1-20 mM sodium acetate on the proliferation and differentiation of these cells and their resultant bone-nodule formation and mineralization in an in vitro assay. Exposure to 10 mM sodium acetate had no effect on cellular proliferation but significantly increased the production and mineralization of bone nodules (p < 0.01), suggesting that it affected osteoprogenitor differentiation and subsequent metabolism. However, 10 mM acetate did not increase net bone mass. Dilutions of 1-5 and 20 mM inhibited cellular proliferation and resultant bone-nodule formation and mineralization, significantly reducing the percentage bone area as compared to controls (p < 0.001). These data suggest that 1-5 and 20 mM sodium acetate significantly inhibit bone deposition, whereas 10 mM has no effects, which could contribute to iatrogenic metabolic bone disease in patients receiving either renal dialysis or total parenteral nutrition.

Interaction of synthetic Alzheimer beta-protein-derived analogs with aqueous aluminum: a low-field 27Al NMR investigation

Synthetic peptides corresponding to the soluble Alzheimer beta-protein, i.e., beta 1-40 and beta 6-25, were utilized to investigate the association of aluminum using low-field 27Al nuclear magnetic resonance (NMR) spectroscopy and reversed-phase high-performance liquid chromatography (RP-HPLC). Addition of beta 1-40 or beta 6-25 to aqueous Al3+ gives rise to a 27Al NMR signal corresponding to the association of Al3+ with the peptides; this effect is not easily reversed by EDTA. Based on the relative intensity of the Al(3+)-peptide signal between pH 4 and 6, there are at least 4 Al3+ ions associated with each peptide molecule. Microheterogeneity is observed with RP-HPLC on incubating solutions of Al3+ with beta 1-40 and beta 6-25. The 27Al NMR spectra of chromatographically pure fractions of beta 1-40 and beta 6-25 indicate that the peptide-associated Al3+ is released below pH 3.5. We propose that soluble beta 1-40 provides an anchor for Al3+ to bind, eventually leading to an increased deposition of amyloid in the Alzheimer brain.

Plasma aluminum levels (unstimulated and stimulated): clinical and biochemical findings in 185 patients undergoing chronic hemodialysis for 4 to 95 months

Plasma aluminum levels (unstimulated and stimulated by deferoxamine infusion), along with signs and symptoms associated with aluminum overload, were evaluated in 185 patients (97 men, 88 women; mean age, 58 +/- 8 years) who had been undergoing dialysis for 4 to 95 months and who were still receiving treatment in 1985 at a free-standing dialysis facility which has always used water purified by reverse osmosis. Monthly water aluminum levels never exceeded 15 micrograms/L; therefore, the major source of aluminum in these patients was oral phosphate binders. Unstimulated plasma aluminum levels ranged from 7 to 392 micrograms/L, averaged 81.5 +/- 56.4, and did not correlate with the duration of dialysis (r = 0.07; P greater than 0.31) or frequency of symptoms. Stimulated plasma aluminum levels increased in a linear fashion (r = 0.57; P less than 0.0001) with time on dialysis; however, there was no statistical association between the stimulated aluminum levels and a variety of nonspecific musculoskeletal or CNS symptoms, evidence of hyperparathyroidism, hematocrit, or calcium or phosphorus levels. These findings suggest that total body aluminum, as reflected in deferoxamine-stimulated serum aluminum levels, increases as a function of time undergoing dialysis.

Sporadic aluminum osteomalacia: identification of patients at risk

Chronic dialysis patients at risk for aluminum osteomalacia in areas of low water-aluminum content are not well identified. We, therefore, studied retrospectively a cohort of 59 patients who underwent bone biopsy at two hospital-based dialysis centers in Montreal (water aluminum content less than 10 micrograms/L). Overall, 25% of patients biopsied had aluminum-related osteomalacia defined by aluminum staining of more than 30% of the trabecular surface and low levels of bone formation as measured by tetracycline labeling. Multiple linear regression analysis showed high predialysis serum creatinine (P less than .05) and the amount of aluminum prescribed per month (P less than .05) as the most important determinants of aluminum staining. We conclude that aluminum-related osteomalacia can be a frequent disease entity in areas of low water-aluminum content. Our findings also suggest predialysis serum creatinine and the amount of aluminum prescribed per month are risk factors for the development of aluminum-related osteomalacia. Though the relationship between serum creatinine and aluminum staining of trabecular bone is unclear, serum creatinine is probably a marker for adequacy of dialysis in these patients.

Aluminium toxicity in chronic renal insufficiency

Aluminium is a ubiquitous element in the environment and has been demonstrated to be toxic, especially in individuals with impaired renal function. Not much is known about the biochemistry of aluminium and the mechanisms of its toxic effects. Most of the interest in aluminium has been in the clinical setting of the haemodialysis unit. Here aluminium toxicity occurs due to contamination of dialysis solutions, and treatment of the patients with aluminium-containing phosphate binding gels. Aluminium has been shown to be the major contributor to the dialysis encephalopathy syndrome and an osteomalacic component of dialysis osteodystrophy. Other clinical disturbances associated with aluminium toxicity are a microcytic anaemia and metastatic extraskeletal calcification. Aluminium overload can be treated effectively by chelation therapy with desferrioxamine and haemodialysis. Aluminium is readily transferred from the dialysate to the patient's bloodstream during haemodialysis. Once transferred, the aluminium is tightly bound to non-dialysable plasma constituents. Very low concentrations of dialysate aluminium in the range of 10-15 micrograms/l are recommended to guard against toxic effects. Very few studies have been directed towards the separation of the various plasma species which bind aluminium. Gel filtration chromatography has been used to identify five major fractions, one of which is of low molecular weight and the others appear to be protein-aluminium complexes. Recommendations on aluminium monitoring have been published and provide 'safe' and toxic concentrations. Also, the frequency of monitoring has been addressed. Major problems exist with the analytical methods for measuring aluminium which result from inaccurate techniques and contamination difficulties. The most widely used analytical technique is electrothermal atomic absorption spectrometry which can provide reliable measurements in the hands of a careful analyst.

In vitro studies using ion exchange resins as potential phosphate binders for renal failure patients

The uptake of phosphate [expressed as phosphorus (P)] by the anion exchange resins, Dowex 1-X8, Dowex SBR, and Bio-Rex 5, aluminum hydroxide, and sucralfate tablets was evaluated. The maximum uptake capacities (in mg P per gram of "wet" resin or solid) were 56, 49, and 84 mg for Dowex SBR, Dowex 1-X8, and Bio-Rex 5 resins, respectively, and 164-168 mg for aluminum hydroxide and sucralfate. At a concentration of P considered to approximate that encountered in the stomach (0.3 mg/ml), Bio-Rex 5 resin, aluminum hydroxide, and sucralfate bound similar amounts of P. Physiologic concentrations of bicarbonate or chloride and simulated gastric or intestinal fluids caused small changes in P uptake by Bio-Rex 5 resin. The resins bound large quantities of taurocholic (TA) and glycocholic (GA) acids. However, when Bio-Rex 5 was converted to the taurocholate form, it bound the same amount of P as the original chloride-form resin, and the binding of TA was prevented.

Dialysis encephalopathy: a review

Dialysis encephalopathy (DE) is a distinct neuropsychiatric syndrome typically occurring in patients undergoing longterm hemodialysis. It is characterized by electroencephalographic abnormalities in association with disturbances of speech, cognition, movement, affect, or behavior. Previously thought to be relentlessly progressive, recent evidence linking the illness to aluminum overload has led to advances in prevention and treatment. Early diagnosis aids in the reversal or amelioration of the syndrome and can be of immense value to the patient, the family and involved health personnel. The general features of the syndrome, etiologic considerations, differential diagnosis and treatment are discussed. Three case studies are included to illustrate salient features of the syndrome.

Uremic encephalopathies: clinical, biochemical, and experimental features

Patients with renal failure may manifest a variety of neurologic disorders. Patients with chronic renal failure who have not yet received dialytic therapy may develop a symptom complex progressing from mild sensorial clouding to delirium and coma, with tremor, asterixis, multifocal myoclonus, and seizures. After the institution of adequate maintenance dialysis therapy, patients may continue to be afflicted with more subtle nervous dysfunction, including impaired mentation, generalized weakness, and peripheral neuropathy. These central nervous system disorders are referred to as uremic encephalopathy. The dialytic treatment of end-stage renal disease has itself been associated with the emergence of two distinct, new disorders of the central nervous system; dialysis dysequilibrium and dialysis dementia. The dialysis disequilibrium syndrome consists of headache, nausea, muscle cramps, obtundation, and seizures, and is a consequence of the initiation of dialysis therapy in some patients. Dialysis dementia is a progressive, generally fatal encephalopathy which affects patients on chronic hemodialysis. There are at least three different forms of dialysis encephalopathy: sporadic, epidemic; and that associated with renal disease in children. In addition to the foregoing neurologic diseases which are specifically related to uremia and/or dialysis, a number of other neurologic disorders occur with increased frequency in patients with end-stage renal disease on chronic hemodialysis. These include subdural hematoma, electrolyte disorders, vitamin deficiencies, drug intoxication, hypertensive encephalopathy, and acute trace element intoxication. Renal transplantation is associated with a variety of central nervous system infections, reticulum cell sarcoma, and central pontine myelinosis. The present manuscript will review the clinical, structural, and biochemical components of those neurologic disorders which are peculiar to the uremic state and its treatment with dialysis.