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Uremia has been associated with a number of neuro-behavioral deficits. In this study, long-latency event-related potentials (ERP's) and the Symbol Digit Modalities Test (SDMT) were used to assess changes in cortical function due to dialysis treatment. Ten chronic renal failure patients, maintained on hemodialysis, were tested. ERP and SDMT measures were taken immediately before and after dialysis. As a control for any practice effects or neurocognitive changes not associated with hemodialysis, the patients were also assessed with the same procedures on a day off dialysis. Significant increases in N2 and P3 amplitude were demonstrated following the dialysis treatment suggesting that a routine hemodialysis treatment increases the intensity of neural activation. Speed of cortical function, as indexed by ERP component latency and the SDMT, was not affected in any consistent manner by dialysis. However, changes during dialysis in the latency of late ERP components were correlated with changes in subject's serum electrolyte levels, indicating that the speed of cortical function is related to blood electrolyte levels. Differences between subjects in the pre-dialysis latency of the P3 component of the ERP was correlated with pre-dialysis levels of calcium and uric acid, as well as with performance on the SDMT.

The submaximum effort tourniquet technique (SETT) is becoming more widely used as part of the clinical assessment of chronic pain patients despite little information about the scaling of this technique. Ratio scaling procedures resulted in a linear function, presumed to underlie clinical application of the SETT, for only 11% of the subjects. Therefore, current clinical use of the tourniquet ratio score should be questioned. Normals also obtained significantly more negatively accelerated power functions than pain patients with no difference in tolerances. Differences in these growth curves are discussed with reference to the concept of pain endurance. Continued needs for standardized pain evaluation techniques suggest that this type of psychophysical scaling procedure may improve the precision of some clinical pain assessments.