Neurologic disorders in renal failure

Movement Disorders and Renal Diseases

Movement disorders often emerge from the interplay of complex pathophysiological processes involving the kidneys and the nervous system. Tremor, myoclonus, ataxia, chorea, and parkinsonism can occur in the context of renal dysfunction (azotemia and electrolyte abnormalities) or they can be part of complications of its management (dialysis and renal transplantation). On the other hand, myoglobinuria from rhabdomyolysis in status dystonicus and certain drugs used in the management of movement disorders can cause nephrotoxicity. Distinct from these well-recognized associations, it is important to appreciate that there are several inherited and acquired disorders in which movement abnormalities do not occur as a consequence of renal dysfunction or vice versa but are manifestations of common pathophysiological processes affecting the nervous system and the kidneys. These disorders are the emphasis of this review. Increasing awareness of these conditions among neurologists may help them to identify renal involvement earlier, take timely intervention by anticipating complications and focus on therapies targeting common mechanisms in addition to symptomatic management of movement disorders. Recognition of renal impairment in a patient with complex neurological presentation may narrow down the differentials and aid in reaching a definite diagnosis.

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.

Neuropsychological Studies of CAPD: Preliminary Findings

A neuropsychological study of CAPD was initiated to assess potential neurotoxic complications. Results are presented for the first year of treatment. A significant improvement in psychometric performance over this time indicated that there was a substantive decline in the relative degree of neurotoxic impairment among the patients as a group. Individually, 70% of patients found to be cognitively impaired before CAPD reach normal psychometric levels by the end of the first year. A reduction in dialysis from eight to six liters/day in a limited number of highly stable patients did not increase their levels of neurotoxic impairment. Correlations between psychometric scores and biochemical indices could not be established either before or after CAPD.

Chronic dialysis in patients with end-stage renal disease: Relevance to kidney xenotransplantation

Renal allotransplantation clearly offers better survival and quality of life for end-stage renal disease (ESRD) patients than chronic dialysis. The median waiting time for a deceased donor kidney in a suitable ESRD patient is 3.9 years. The initial candidates for pig kidney xenotransplantation will be those with ESRD unlikely to receive an allograft within a reasonable period of time. It is thus reasonable to ascertain whether clinical trials of xenotransplantation might likewise offer superior outcomes. Chronic dialysis in patients with ESRD is associated with poor quality of life, significant morbidity, and relatively high mortality, with only 56% surviving 3 years and 42% at 5 years. However, a significant number of these patients, because of comorbidities, frailty, etc, would not be considered for renal allotransplantation and likely not for xenotransplantation. As genetically engineered pig kidneys have satisfactorily supported life in immunosuppressed nonhuman primates for many months or even more than a year, consideration in carefully selected patients could be given to pig kidney xenotransplantation. We suggest that, in order to give a patient the best possible outcome, the pig kidney could be transplanted pre-emptively (before dialysis is initiated). If it fails at any stage, the patient would then begin chronic dialysis and continue to await an allograft. The present (limited) evidence is that failure of a pig graft would not be detrimental to a subsequent allograft.

Hypertensive Encephalopathy in Cats with Reduced Renal Function

The clinical, hemodynamic, and pathologic features of hypertensive encephalopathy in two cats with reduced renal mass are described. The cats developed a progressive syndrome of lethargy, ataxia, blindness, stupor, and seizures following an abrupt increase in blood pressure associated with a surgical reduction in renal mass. The cats had severe gross brain edema, evidenced by cerebellar changes of caudal coning and cranial displacement over the corpora quadrigemina and cerebral changes of widening and flattening of the gyri. Histologically, interstitial edema was most pronounced in the cerebral white matter. Hypertensive vascular lesions were present as hyaline arteriolosclerosis in one cat and hyperplastic arteriolosclerosis in the other. Rare foci of parenchymal microhemorrhages and necrosis were also observed. Systemic hypertension (especially severe or rapidly developing) accompanied by neurologic signs and the pathologic findings of diffuse brain edema with cerebral arteriolosclerosis are consistent with an etiologic diagnosis of hypertensive encephalopathy.

Solving the conundrum of Job: a probable biblical description of chronic renal failure with neurological symptoms

The disease described in the Bible's Book of Job is controversial and had been of interest of theologists, psychiatrists, and dermatologists for many years. We describe several signs and symptoms compatible with chronic renal failure with neurological alterations.

Haemodynamic effects of prenalterol in patients on dialysis

Haemodialysis hypotension occurs with particular frequency in bilateral nephrectomised patients. This reflects the importance of the renin-angiotensin-aldosterone system for maintaining normal blood pressure. Failure of vascular access (due to clotting and thrombosis of shunts) and ischaemic necrosis of transplanted kidneys in hypotensive patients prompted us to treat them orally with a new beta 1-adrenergic agent (prenalterol). Blood pressure was normalised in 4 out of 5 patients. Because of delayed renal elimination of the drug, daily dosage must be reduced to prevent symptoms of adrenergic stimulation. A study of the pharmacokinetics of prenalterol in uraemia is in preparation.

Neurologic manifestations of renal disease

Mortality and morbidity from kidney disease and the spectrum of renal-associated neurologic disease have changed markedly since the introduction of renal dialysis and with the advent of renal transplantation. This article includes historical studies of the neurologic complications of acute uremia, now fairly uncommon, and recent literature regarding neurologic side effects associated with dialysis and renal transplantation.

Diagnostic predictors of complications and survival after renal transplantation in cats

OBJECTIVE

To identify preoperative diagnostic results that predict postoperative complications and survival in feline renal-transplant recipients.

STUDY DESIGN

Retrospective clinical study.

ANIMALS

Sixty-one feline renal allograft recipients.

METHODS

Medical records for 61 consecutive cats that underwent renal allograft transplantation between January 1, 1996, and December 1, 1999, were reviewed. Age, diagnosis, body weight, body condition score, preoperative medical treatment, systolic blood pressure, packed cell volume, biochemical parameters at admission and at the time of surgery, postoperative complications, and postoperative survival were recorded. Associations of preoperative data with the occurrence of postoperative complications were determined using logistic regression. Postoperative survival was graphed using a Kaplan-Meier cumulative-survival plot. Associations of covariates with postoperative survival were analyzed using Cox proportional hazards analysis.

RESULTS

Two parameters were significantly associated with occurrence of postoperative central nervous system (CNS) disorders: blood urea nitrogen concentration (odds ratio = 1.083; 95% CI = 1.018 to 1.148) and serum creatinine concentration (odds ratio = 1.8; 95% CI = 1.413 to 2.187) at the time of surgery. Postoperative survival 6 months after transplantation was 59%, though 3-year survival remained at 42%. Of all covariates investigated, only recipient age (relative hazard = 1.183; 95% CI = 1.039 to 1.334) was significantly associated with survival.

CONCLUSION AND CLINICAL RELEVANCE

Standard measures of preoperative renal dysfunction do not predict postoperative survival in cats after renal transplantation, although an increase in the degree of preoperative azotemia is associated with an increased risk of CNS disorders after surgery. Increased recipient age is associated with decreased survival after renal transplantation.

Central nervous system disorders after renal transplantation in cats

OBJECTIVE

This study describes the incidence and severity of postoperative central nervous system (pCNS) disorders in feline renal transplant recipients.

STUDY DESIGN

A retrospective study based on the medical records of cats that received renal allografts from 1987 to 1996.

ANIMALS OR SAMPLE POPULATION

Fifty-seven client-owned cats received renal allografts for the treatment of renal failure.

METHODS

The frequency, duration, severity, and treatment of episodes of pCNS disorders were recorded from the medical records.

RESULTS

Twelve (21%) of 57 cats had pCNS disorders 1 hour to 5 days after the surgical procedure. Seven cats survived; four had single or multiple seizure episodes, and two had seizure episodes or disorientation followed by a period of coma. One cat became temporarily ataxic and blind after restraint for venipuncture. Five cats died; all had episodes of disorientation or seizures, or both, that progressed to a nonrecoverable comatose state, respiratory arrest or cardiac arrest, or both. There were no significant differences between the two groups in preoperative serum creatinine, blood urea nitrogen, or cholesterol levels, and intraoperative blood pressure measurements. There were no significant differences in the postoperative serum glucose levels, electrolytes levels, or osmolality between the two groups. The cats with pCNS disorders had a mean preoperative trough cyclosporine A (CyA) whole blood level of 429 ng/mL; cats without pCNS disorders had a significantly (P = .0116) higher mean preoperative trough CyA whole blood level of 736 ng/mL.

CONCLUSION

Central nervous system disorders are a common and often fatal complication of renal transplantation in cats.

CLINICAL RELEVANCE

Recognition of pCNS disorders, and possible causes, will help develop hypotheses to investigate the problem.

Evaluation of surgical scrub methods for large animal surgeons

OBJECTIVE

The objective of this study was to determine the effectiveness of a 5-minute surgical scrub using either a one-brush or a two-brush technique in clean and dirty surgical procedures, and to compare the efficacy of povidone iodine with chlorhexidine as surgical scrub solutions.

STUDY DESIGN

Prospective clinical trial.

METHODS

Nine veterinarians scrubbed their hands on eight separate occasions using either povidone iodine or chlorhexidine gluconate. A 5-minute scrub and either a one-brush or two-brush technique used in both clean and dirty operations were evaluated by taking glove juice samples before scrubbing, immediately after scrubbing, and 30, 60, 90, and 120 minutes after scrubbing. Glove juice samples were cultured and the colonies were counted. Percent reductions of bacterial forming units were calculated for all eight scrub procedures.

RESULTS

All scrub procedures provided an adequate percent reduction in colony forming units (CFU) during the 2-hour sampling period. The number of CFU immediately after scrubbing were significantly lower than prescrub. At 120 minutes, there were significantly fewer CFUs than presecrub, but there were more than immediately after scrubbing. No significant difference in reduction in CFUs were detected between one-brush and two-brush techniques. Both chlorhexidine and povidone iodine scrub solutions adequately reduced bacterial colony counts for 120 minutes after scrubbing regardless of the amount of contamination before skin preparation.

CONCLUSIONS

Bacterial counts after a hand scrub procedure using a one-brush technique were not significantly different than after a procedure that used a two-brush technique. Povidone iodine and chlorhexidine are equally effectively in decreasing bacterial numbers on the skin, given a variety of contamination levels present before the scrub procedure.

CLINICAL RELEVANCE

Surgeons may use either chlorhexidine or povidone iodine for antiseptic preparation of their hands before surgery. A two-brush technique is not necessary.

Function and metabolism of brain synaptosomes in chronic renal failure

Patients with advanced renal failure have derangements in the function of their nervous system. The available clinical and experimental data indicate that the state of the secondary hyperparathyroidism of renal failure plays a major role in the genesis of the nervous system dysfunction. The excess parathyroid hormone (PTH) mediates its deleterious effect by causing an elevation in cytosolic calcium of brain cells. This report reviews the evidence leading to the conclusion that PTH is a major uremic toxin.

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.

The spectrum of epilepsy in sickle cell anemia

In a study population of 152 patients seen at Thomas Jefferson University Hospital's sickle cell center between 1981 and 1992, 21 patients with seizures were identified. Clinical charts, electroencephalograms and neuroradiological studies were reviewed retrospectively. Seventeen patients with epilepsy were identified. Eleven had generalized tonic-clonic, 2 had partial, and 4 had poorly characterized seizures. CT/MRI evaluation was focally abnormal in 6 patients, 4 of whom had cortical lesions. Atrophy was noted in 3 patients, while imaging studies were normal in 6 patients. The EEGs demonstrated focal epileptiform discharges in 9 patients, generalized slowing in 5 patients, and was normal in 3 patients. Four patients had generalized seizures only with meperidine administration, all of whom had nonfocal EEG and radiological studies. We concluded that (1) epilepsy is more common in sickle cell patients than in the general population; (2) the majority of our epileptic sickle cell patients have nonfocal CT or MRI studies but demonstrate focal EEG abnormalities; and (3) meperidine administration is associated with generalized seizures in sickle cell patients.

Post-traumatic transient cortical blindness

Five patients: three children, one adolescent, and one young adult, examined in an emergency room setting were diagnosed with post-traumatic transient cortical blindness. This syndrome is characterized by transient visual loss, normal pupillary response and normal funduscopic examination following minor head trauma. In each case, vision returned to normal within minutes to hours following injury, leaving no neurological sequelae. Headache, confusion, irritability, anxiety, nausea and vomiting were the most common related symptoms. While the mechanism responsible for the transient blindness is unknown, most authors propose an abnormal vascular response to trauma with resultant transient hypoxia and cerebral dysfunction. The similarity between the symptoms accompanying this syndrome and those seen during a classic migraine attack has led many investigators to suggest a common underlying pathophysiology. The purpose of this report is to highlight the salient clinical features and diagnostic approaches to this syndrome, thereby providing ophthalmologists and emergency room physicians a heightened awareness of this entity and the means to detect it.

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.

Increased cerebral blood flow in anemic patients on long-term hemodialytic treatment

CBF was measured in 15 patients on chronic hemodialytic treatment. CBF was measured with xenon-133 inhalation using single photon emission tomography. In addition, computerized tomography (CT) and a neurological examination were done prior to hemodialysis. Mean CBF was 66.2 +/- 17.3 (SD) ml 100 g-1 min-1, which was significantly higher (t-test, p less than 0.05) than for an age-matched control group (54.7 +/- 10.2 ml 100 g-1 min-1). However, the hematocrit for the patients was considerably lower, 0.30 +/- 0.07, as compared to 0.43 +/- 0.03 in the controls. A significant negative correlation was observed between CBF and the hematocrit (y = -1.79x + 120.7, r = -0.71, p less than 0.01). Calculating CBF from this equation in the dialyzed patients using a hematocrit of 0.43 yielded a mean CBF value of 43.7 ml 100 g-1 min-1, i.e., 20% below the expected. Two patients showed a focal CBF decrease. CT showed central or cortical atrophy in five patients, and two had small hypodense lesions. The neurological examination revealed slight to moderate dementia in seven cases. Although mean CBF was found to be increased by 21% as compared to the control group, an even higher CBF level would have been expected to outweigh the decreased oxygen carrying capacity of the blood. The findings suggest a lowered metabolic demand of the brain tissue, probably due to subtle brain damage.

The function of large and small nerve fibers in renal failure

Previous clinical and neurophysiological studies of uremic neuropathy have focused almost exclusively on the function of large sensory and motor axons. The sensations of heat and cold depend on the function of unmyelinated afferents and small myelinated afferents, respectively, and these sensations can be quantified using a standardized psychophysical technique. Thermal thresholds were measured in 20 patients with end-stage renal failure to determine the extent of small afferent fiber involvement and to compare this with the clinical and electrophysiological evidence of large fiber involvement. Whereas abnormalities of standard nerve conduction studies were found in 16 patients, abnormal thermal thresholds were found in only 6 patients. In the nerve conduction studies, the amplitudes of nerve potentials were reduced more than their conduction velocities, consistent with an axonopathy. This study found little evidence of significant dysfunction of small afferent fibers in end-stage renal failure and, when such changes occurred, they did not correlate with the clinical evidence of polyneuropathy. The functional sparing of axons of small diameter is consistent with the relative sparing of these axons in pathological studies.

Effect of treatment of anaemia with erythropoietin on neuromuscular function in patients on long term haemodialysis

To study the effect of treatment of anaemia with recombinant human erythropoietin (r-HUEPO) on neuromuscular function in patients undergoing haemodialysis for chronic renal failure, six patients were given r-HUEPO in an initial dose of 50 u/kg three times a week and their haemoglobin concentration was measured. The dose was increased by 25 u/kg every four weeks if the response was not satisfactory. In five patients anaemia had been corrected within 12 weeks of initiation of treatment. Neuromuscular function was evaluated before treatment, half way through, and after correction of anaemia by clinical examination and neurophysiological studies including motor nerve conduction velocity, distal latency, electromyography and test for neuromuscular fatigue. After correction of anaemia there was a significant increase in motor nerve conduction velocity, a decrease in the duration of motor unit action potential, and a lessening of neuromuscular fatigue. We conclude that treatment of anaemia with r-HUEPO in patients with chronic renal failure undergoing haemodialysis may improve neuromuscular function.

Cortical blindness in children: a study of etiology and prognosis

Thirty-four children (20 boys, 14 girls) with congenital and acquired cortical blindness were analyzed for visual outcome in relation to etiology, visual evoked potentials, electroencephalography, and cranial computed tomography. All 7 children with congenital cortical blindness remained blind on subsequent examination. Of the 27 children with acquired blindness, 16 (59%) had poor visual outcome. Poor visual outcome occurred in those with cardiac arrest, hypoxia, status epilepticus, intracranial hemorrhage, cerebral thrombosis, and head trauma. Good visual outcome occurred in children with hypotensive episodes after cardiac surgery. Of the 12 children with recovery of vision, the interval from acute loss of vision to partial or total recovery was 2 weeks to 5 months. Seven children had complete recovery of vision with no residual visual field defect. The majority of children (87%) had focal or multifocal spike-and-waves and slow sharp-wave discharges on electroencephalography. None had photic recruitment response or occipital spike-and-wave discharges. Flash visual evoked potential studies performed during acute episodes of cortical blindness documented 11 with absent response, 10 with bilateral increases in latency, and 6 with normal responses. There was no correlation between normal visual evoked potentials and a good visual outcome. Only 2 of 6 children with normal responses had normal vision. Abnormal or absent responses are more predictive of a poor recovery of vision because only 3 of 21 (14%) had normal vision on subsequent examination. Abnormal electroencephalographic findings with focal or multifocal spike-and-wave discharges or cerebral atrophy on cranial computed tomography are also poor prognostic signs.

Somatosensory evoked potentials in acute renal failure: effect of parathyroidectomy

Effects of acute renal failure (ARF) on somatosensory evoked potentials (SEP) were studied in rats. Cervical and cortical SEPs were measured both before and after bilateral ureteral ligation. A significant augmentation of amplitudes and an increase in latencies of the cortical SEP were observed in ARF. The peripheral nerve conduction velocities were unchanged. Serum parathyroid hormone (PTH) levels in uremic rats were significantly elevated after the bilateral ureteral ligation. In previously parathyroidectomized rats, the bilateral ureteral ligation had no effects on amplitudes of SEP or serum PTH levels.

Neurologic complications in chronic renal failure: a retrospective study

We have retrospectively examined 324 patients with chronic renal failure and evaluated the probable underlying causes of neurologic complications, laboratory data and therapeutic interventions. The common neurologic problems in our patients were alterations in consciousness (40.7%) and convulsions (35.1%). When BUN concentration was above 135 mg/dl and creatinine clearance was below 8 m/min/1.73 m2, alteration of consciousness was observed and when BUN concentration was 200 mg/dl and creatinine clearance was below 7 m/min/1.73 m2, abnormal convulsives appeared. Changes in deep tendon reflexes and pathologic reflexes were associated with hypertension. All of the patients with cortical atrophy using computerized cranial tomography aluminum hydroxide at least for 18 months, and six of them had hemodialysis. Fourteen patients who underwent dialysis developed convulsions and were thought to have disequilibrium syndrome. These findings are consistent with the suggestion that the metabolic and biochemical derangements associated with CRF may be particularly detrimental to the still developing CNS of the child.

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.

MMPI differences for renal, psychiatric, and general medical patients

Renal failure has both medical and psychological implications. Indeed, various psychiatric problems related to end-stage renal disease have been reported in the literature; however, the focus has been on anxiety and depression. While previous research has dealt with the comparisons of patients with renal failure, few studies have investigated the comparison of renal patients with psychiatric and general medical patients. The present study compared renal patients (N = 24) with a group of depressed psychiatric patients (N = 24) and a group of general medical patients (N = 24) on the MMPI. The results suggested that the renal group presented a psychological profile that more closely resembled that of the depressed psychiatric group than that of patients with other chronic medical conditions.

Association between renal function and cognition in childhood chronic renal failure

Forty-five children with renal failure who were either being medically managed, receiving dialysis (hemodialysis or continuous ambulatory peritoneal dialysis) therapy or who had received successful kidney transplants were longitudinally examined on multiple neuropsychological measures. A variety of medical parameters was also obtained at each time of testing. The neuropsychological variables were correlated with the medical variables using the repeated measures regression analysis method. There were associations between levels of renal function, short-term memory and list learning. Other neuropsychological variables did not in general correlate with the medical parameters consistently for all ages at the time of initial testing. Verbal performance decreased with increasing duration of renal failure in 6- to 11-year-olds and immediate recall decreased with increasing percentile rank of systolic blood pressure in 16- to 18-year-olds.

Convulsions in children undergoing renal transplantation

We reviewed the records of 154 children who received 207 renal transplants for end-stage renal disease from 1965 to 1987, and discovered that 48 (31%) had had convulsive seizures, some before transplant surgery, others only after transplant, and some during both before and after transplantation. The majority of children had minimal long-term problems, and 60% of the children had only a single convulsion. In six of the patients, convulsions were a manifestation of more serious underlying conditions that produced significant morbidity. Seizures of differing clinical type occurred, with hypertension being the most significant etiologic factor. In children with renal failure, there are minimal symptoms heralding the hypertensive encephalopathy. Rapid resolution without recurrence of seizures after control of hypertension is a major sign that hypertension was the cause and that the long-term prognosis is good.

Upper extremity entrapment neuropathy and tourniquet use in patients undergoing hemodialysis

Patients with end-stage renal disease, undergoing hemodialysis, have been shown to have an increased prevalence of carpal tunnel syndrome. From mid-1981 through 1986, 21 patients undergoing hemodialysis were operated on for 33 cases of clinically diagnosed entrapment of the median and/or ulnar nerves, including 14 extremities with functioning vascular access. All patients report improvement in symptoms and function in the affected extremity. Preoperative tourniquet use did not have a permanent adverse effect on any access site. Electrophysiologic studies were not reliable predictors of clinically resolvable nerve entrapment.

Optic neuropathy in uremia

We examined three patients who developed optic neuropathies while undergoing chronic hemodialysis. One patient developed severe bilateral deterioration of vision, but recovered totally four weeks after discontinuing deferoxamine chelation therapy. Another patient had bilateral visual loss associated with chronic papilledema of idiopathic increased intracranial pressure. A third showed atypically severe consecutive anterior ischemic optic neuropathy. The latter two patients showed little improvement with high-dose intravenous methylprednisolone therapy combined with more vigorous hemodialysis. These cases, in addition to those previously described, underscore the heterogeneity of optic nerve disease in patients with uremia.

Kinetics of drug action in disease states. XXXIII: Disparate effects of pentylenetetrazol in rats as a function of renal disease model and pharmacologic endpoint

The purpose of this investigation was to determine if the pharmacodynamics of the central nervous system stimulant pentylenetetrazol (PTZ) are altered in renal dysfunction. Female rats subjected to bilateral ureteral ligation (with sham-operated controls) or injected with uranyl nitrate (with saline injected controls) were infused intravenously with PTZ until the onset of either a minimal (myoclonic jerk) or maximal (tonic hindlimb extension) seizure. Neither chemically nor surgically induced renal dysfunction caused a change in the concentrations of PTZ in CSF, serum, or brain at onset of minimal seizures. When PTZ was infused to onset of maximal seizures, the rats with chemically induced renal dysfunction required higher concentrations, whereas the ureter-ligated rats convulsed at lower concentrations of PTZ than did the corresponding control animals. Thus, the effects of experimental renal dysfunction on the convulsant action of PTZ are dependent on both the disease model and the endpoint used for the pharmacodynamic measurement. Apparently, renal dysfunction did not affect the PTZ-induced seizure threshold, but inhibited the spread of seizures. The increased sensitivity of ureter-ligated rats may be due to their pronounced retention of water, since water loading is known to increase seizure susceptibility.

Uptake of amino acids by brain microvessels isolated from rats with experimental chronic renal failure

The neurological disorders seen in patients with chronic renal failure and liver cirrhosis are analogous. Previous in vivo studies have shown that the impaired blood-brain amino acid transport seen in rats with chronic renal failure is similar to that of rats with portocaval anastomosis. To elucidate whether a comparable underlying pathogenic mechanism plays a role in both pathological conditions, blood and brain amino acid levels together with amino acid transport by isolated brain microvessels have been studied in rats with chronic renal failure and in sham-operated rats. Brain microvessels isolated from rats with experimental chronic renal failure showed that the uptake of labeled large neutral amino acid, i.e., leucine or phenylalanine, but not of lysine or alpha-methylaminoisobutyric acid, was significantly increased with respect to sham-operated rats; conversely, the uptake of glutamic acid in rats with chronic renal failure was significantly lower compared with values in controls. Kinetic analysis indicated that this was mainly due to increased exchange transport activity (Vmax) of the L-system, rather than to changes in the affinity (Km) of the carrier system for the relative substrate. These data, together with the significant rise of brain glutamine levels and an increased brain-to-plasma ratio of the sum of large neutral amino acids, are analogous to what was previously observed in rats with portocaval anastomosis.(ABSTRACT TRUNCATED AT 250 WORDS)

[Electroencephalogram before and after hemodialysis, peritoneal dialysis and renal transplantation: study of correlations between background activity and plasma biochemistry]

We report disorganization of background activity in the EEG of 49 patients with chronic renal failure. An electroencephalographic and biochemical study was performed in 20 patients before and after dialysis sessions. We did the same study before and after peritoneal dialysis in 14 patients. We analysed the EEG compared to biochemical blood abnormalities before and after renal transplantation in 15 patients. We observed worsening of the EEG after hemodialysis and peritoneal dialysis and improvement after renal transplantation, suggesting that in our patients the abnormalities in EEG caused by chronic renal failure were reversible. From our results, we found it difficult to establish correlations between the EEG and the biochemical blood abnormalities. However, there is statistical correlation between hypernatremia, improvement of metabolic acidosis, increase of the ratio of zinc to copper and worsening of the background activity in EEG.

Tryptophan distribution and metabolism in experimental chronic renal insufficiency

Several aspects of tryptophan distribution and metabolism in chronic renal insufficiency (CRI) were investigated in a rat model prepared by partial nephrectomy. Partially nephrectomized (pNx) rats with a moderate degree of CRI demonstrated a 40% decrease in plasma total tryptophan concentration between 5 and 11 weeks after the acute reduction of renal functional mass. This decrease was accompanied by hypoalbuminemia, polyuria, albuminuria, and tryptophanuria. After 5 weeks of sustained plasma total tryptophan deficiency (from Week 6 to Week 11), the plasma free tryptophan concentration, the plasma concentrations of large neutral amino acids, and the tryptophan levels in red cells, liver, and kidney of the pNx rats were similar to those of the controls. However, evidence for abnormal brain tryptophan metabolism in pNx rats after 11 weeks of CRI included 16% reductions of tryptophan levels in the midbrain and pons and 65% increases in the serotonin contents of the hypothalamus and medulla. Monoamine oxidase activities in hypothalamus and cerebellum of pNx rats were the same as those of the controls. These studies indicate that tryptophanuria is an important factor in the development of the plasma tryptophan deficiency in the pNx model. In addition, the results support the hypothesis that regional abnormalities in tryptophan metabolism contribute to the neurological and neuroendocrine dysfunction of CRI.

Some parameters of haem synthesis in dialysed and non-dialysed uraemic patients

Some parameters of haem synthesis were estimated in 60 uraemic patients (30 non-dialysed, 30 dialysed) and in 30 matched controls. Serum delta-aminolaevulinic acid and erythrocyte coproporphyrin and protoprophyrin were found significantly higher in the non-dialysed uraemics than in the controls. Erythrocyte delta-aminolaevulinic acid dehydrase (ALA-D) activity was 498 +/- 174 mumol/h.l in the non-dialysed patients, 321 +/- 146 in the dialysed (just before haemodialysis) and 833 +/- 281 in the healthy controls, the differences between these groups all being statistically significant (p less than 0.001). After haemodialysis the enzymic activity in the dialysed group increased significantly (380 +/- 167, p less than 0.001), but remained lower than normal (p less than 0.001). A similar pattern - although with less statistical significance of the differences between groups - was observed concerning erythrocyte uroporphyrinogen I synthase activity. Incubation of normal erythrocytes with uraemic plasma resulted in a considerable decrease of their ALA-D activity (from 830 +/- 263 to 616 +/- 126) while incubation of uraemic erythrocytes with normal plasma increased their ALA-D (from 384 +/- 139 to 494 +/- 77). Addition of zinc in the haemolysate caused a similar induction of ALA-D in both controls and uraemics. The zinc-induced uraemic ALA-D practically reached normal levels. The mechanism of enzymic depression and the possible role of elevated delta-aminolaevulinic acid concentrations (to which depressed ALA-D activity considerably contributes) in the pathogenesis of the neurologic manifestations of uraemia, are discussed.

Alzheimer's disease in a patient on long-term hemodialysis: a case report

This case report describes a progressive dementia in a 49-year-old black male on long-term hemodialysis. The initial presentation simulated depression. The dementia persisted after an unsuccessful cadaver homograft transplant. The character of the dementia was nonspecific but typical features of dialysis dementia were lacking. Autopsy revealed a ruptured cerebral aneurysm, polycystic kidneys, moderately severe atherosclerosis, miliary tuberculosis, and neurofibrillary degeneration of the hippocampus. The significance of a possible relationship between end-stage renal disease (ESRD), hemodialysis, and Alzheimer's disease in this case is discussed.

Urea-induced myoclonus: medullary glycine antagonism as mechanism of action

Stimulus sensitive myoclonus is a prominent symptom of uremia in both man and animals. Intravenous injection of urea into cats had been previously reported to produce spike and sharp wave electrical discharges in the medullary reticular formation which correlated with the myoclonic movements. In the present investigations, intraperitoneal injections of 2 g/kg urea every 15 minutes for 4 injections produced myoclonus in rats accompanied by brain urea concentrations of 6.8 X 10(-2)M, which is sevenfold higher than normal. 10(-2) and 10(-1) M urea significantly reduced 3H-strychnine binding to rat medulla membranes by 30% and 43% respectively. Urea inhibition of 3H-strychnine binding was reversible and binding kinetics revealed that 10(-1)M urea decreased Bmax by 65% with no effect on the affinity. Brain glycine levels did not change after urea injections and urea had no effect on synaptosomal uptake of 3H-glycine. Urea did not alter 3H-GABA, 3H-glutamate and 3H-QNB receptor binding but decreased 3H-diazepam receptor binding in the medulla. Mannitol also reduced 3H-diazepam binding but had no effect on 3H-strychnine binding. Stereotaxic injection of the glycine receptor antagonist, strychnine, into the rat medullary reticular formation produced myoclonus, whereas Ro 15-1788, a benzodiazepine antagonist, had no effect. Urea may produce myoclonus by blockade of glycine receptors in the medullary reticular formation.

Experimental uremic neuropathy. Part 1. Decreased nerve conduction velocity in rats

Acute and chronic renal failure were induced in adult male albino rats by conventional surgical methods. The glomerular filtration rate of rats with chronic uremia was reduced to approximately 15% of normal. Despite this drastic degree of renal failure, the motor nerve conduction velocity (MCV) increased from 47.5 +/- 6.4 m/s, preoperatively, to 55.6 +/- 4.0 m/s after 4 weeks. In rats with acute uremia, MCV decreased from 51.4 +/- 3.0 m/s to 45.2 +/- 2.7 m/s after 48 h. The conduction velocity, measured in vitro of excised sciatic nerves was 55.2 +/- 4.4 m/s in acute uremia and 64.7 +/- 4.7 m/s in a control group. There was no difference in the refractory period between these groups. It is concluded that this decrease in the nerve conduction velocity was not caused by changes in the composition of the extracellular fluid but rather by changes in the nodal membrane function.

Hemodialysis of doxepin and desmethyldoxepin in uremic patients

The disposition of doxepin and its active metabolite desmethyldoxepin was investigated in five uremic patients undergoing hemodialysis. The hemodialysis system yielded a mean extraction efficiency of 7.6% for doxepin and 13.9% for desmethyldoxepin. Mean dialysis clearances were 10.8 and 18.1 ml/min for doxepin and desmethyldoxepin, respectively. The drug and metabolite recovery constituted a very small fraction of the body store, i.e., less than 1%. Hemodialysis did not significantly alter the plasma half-life of doxepin, 14.6 +/- 4.3 h, or of desmethyldoxepin, 25.4 +/- 5.5 h. The nondialyzability of both compounds could be attributed to the compounds' protein binding and volume of distribution. The dialysis experiments show that modification of the usual dosage regimen is not necessary during hemodialysis or on dialysis days. The dialysis parameters confirm that hemodialysis is not likely to be of value in the management of acute doxepin poisoning.

Lack of effect of prenalterol on dialysis-associated hypotension

Prenalterol, a cardio selective beta adrenergic receptor antagonist was given perorally in doses from 20-150 mg/day in three patients with dialysis associated hypotension. No effect on blood pressure was seen over several months during this treatment.

Changes in short-latency somatosensory evoked potentials during hemodialysis in chronic renal failure

Short-latency SEPs were monitored in eight patients undergoing hemodialysis for end-stage renal disease. The peak latencies of EP,N13, and N20 were significantly delayed compared with those of the control group. Because the interpeak latency of N13 - N20 (central conduction time) was not significantly prolonged, there could be no possible subclinical involvement of the ascending sensory fibers in the brainstem. The dialysis did alter the peak latencies of EP,N20, and interpeak latencies of EP-N13 and EP-N20; these changes, however, were not highly significant. The evoked potential changes did not correlate with the routine biochemical data. Monitoring short-latency SEP may lead to early recognition of pathologic involvement of the peripheral nervous system.

Computer methods, uremic encephalopathy, and adequacy of dialysis

It has been recognized for over 30 years that increased renal dysfunction results in increased slow wave activity in the EEG generally prior to the clinical appearance of disabling, dialysis-responsive encephalopathic symptoms of clinical uremia. This paper describes computerized methods that have been used to quantify this slow wave activity and the results of studies that have employed such computerized techniques. Practical information is furnished to guide those who wish to use these methods in their own research and practice. A survey of the limitations and pitfalls inherent in the various techniques is given. A prospectus outlines possible future directions in the field.