This study addresses mechanisms of the clinical, encephalopathic uremic illness and its suppression by dialysis. Renoprival rats were treated with peritoneal dialysis (8 exchanges per day, 30 min dwell), or untreated (attrition group), and their EEG's were automatically sampled overnight and subjected to power spectrum analysis as an index of encephalopathy. As in man the background rhythm of the quantified EEG (Q.EEG) in the attrition group slowed with time as extracellular fluid composition became increasingly abnormal; these changes were normalized by therapeutic dialysis (TD) using standard, commercial dialysate. However, Q.EEG slowing was only partially normalized by solute-specific dialysis using "mock uremic dialysate" (M-UD), prepared from laboratory chemicals to equal plasma concentrations in preterminal uremic rats of urea, creatinine, potassium, phosphorus, calcium, magnesium, bicarbonate, sodium, and chloride. When only phosphate was added to TD, the Q.EEG slowed to the same level achieved after M-UD. We conclude that uremic encephalopathy in this model is produced by an unknown neurotoxin and augmented by one or more of the M-UD solutes, phosphate being a likely candidate. To localize the encephalopathic effect, regional brain glucose uptake was estimated in 20 discrete brain areas. Significance of reduced uptake in three areas is discussed.
The heat-beam dolorimeter has previously been used to obtain cutaneous pain tolerance measures in normal volunteers and patients with chronic pain. In the present study, normal reference data were collected at two stimulus intensities for 24 volunteers, and the stimulus-effect relationship (decreasing tolerance latency with increasing stimulus intensity) was found significant (p less than 0.001) for all body sites tested. No overall sex differences were found; males behaved slightly more stoically than females, with differences significant only at the T3 site over the breasts. At the second evaluation at the higher stimulus intensity, females exhibited lower pain tolerance (greater pain sensitivity) at the right breast than males (p less than 0.05). No significant lateral asymmetry was found in cutaneous pain tolerance except at the dorsum of the hand: the right hand evinced elevated pain tolerance compared with the left hand in both right- and left-handed subjects. Eight radiculopathic pain patients with clinically involved left L5 nerve roots were evaluated and their responses were compared with the volunteer normal reference data. The radiculopathic group evinced elevated tolerance levels in both the radiculopathic dermatome and noninvolved sites compared with normal individuals (p less than 0.05).
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