| Abstract|| |
Memory and cognitive abnormalities such as decreased attention span, impulsiveness, and slow reaction are common among chronic hemodialysis patients. We studied the changes these parameters in 38 hemodialysis patients before and after hemodialysis sessions via Conner's continuous performance test. Mean age of the study patients was 38.0 ± 12.6 years. There was no significant difference before and after hemodialysis in the number of the successfully recognized matches, the number of the miss fires, and the mean of reaction time of matches. In addition, there was no significant effect of the duration of hemodialysis therapy on the number of successfully recognized matches, the number of missed matches, and the mean reaction time of matches. Educational level of patients did not significantly impact on the number of successfully recognized matches and the mean of reaction time of matches. However, this impact was significant on the number of miss fires during hemodialysis. (P = 0.04). We conclude from our results that hemodialysis did not significantly impact on the cognitive function. However, this hypothesis must be confirmed by other cognitive function tests on larger hemodialysis population.
Keywords: Hemodialysis, cognitive function, Conner′s continuous performance test, memory, renal disease, reaction time
|How to cite this article:|
Najafi M. Evaluation of Conner's Continuous Performance Test in Hemodialysis Patients. Saudi J Kidney Dis Transpl 2008;19:210-4
|How to cite this URL:|
Najafi M. Evaluation of Conner's Continuous Performance Test in Hemodialysis Patients. Saudi J Kidney Dis Transpl [serial online] 2008 [cited 2020 Jul 14];19:210-4. Available from: http://www.sjkdt.org/text.asp?2008/19/2/210/39032
| Introduction|| |
Hemodialysis patients are at high risk for cognitive impairment due to their older age and high prevalence of stroke and cardiovascular risk factors.  Memory and concentration abnormalities are common among chronic hemodialysis patients.  Ability to memorize is reduced with older age, however, it is directly proportional to the level of education.  Previous studies demonstrated that control of fluid overload in dialysis patients improved their cognitive function, which resulted in better levels of patients' self-care and compliance.  The incidence of cognitive abnormalities is variable among different studies. Fazekas et al believed that cerebral damage occurred more frequently in chronic hemodialysis patients, and brain degeneration with severe cognitive impairment was attributed to toxic-metabolic etiology.  However, Vasil'eva et al advocated that intellectual and memory functions remained unaffected in hemodialysis patients.  Recently, Altmann et al found that cognitive function deteriorated in hemodialysis patients. 
In this study, we evaluate the cognitive changes such as attention span, impulsiveness, and reaction time in our hemodialysis population using standardized measurement tools.
| Material and Methods|| |
Cognitive function of 45 Iranian hemodialysis patients at Hajar Hospital of Sharekord City, Iran, were evaluated before and after hemodialysis by Conners' Continuous Performance Test (CPT).  The test uses a computer program of visual sequence of symbols on cards selected by the patients. the cards have either symbols of diamonds or clubs, and numbered from 1 to 9. The card is displayed as simply a number next to the appropriate card symbol. The patient scores according to the sequence of matches of cards he identifies. The patient has to spot these matches, and respond by pressing the space bar button on keyboard when they see the second card. The reaction times are recorded for successful recognitions, and the number of miss fires and matches missed are counted. Once the trial is completed, the results are sent to a data file, the name of which is user specified .
The number of matches that occur in the sequence is determined from the program parameters, which can be changed if required. The program ensures that only the exact number of matches required can occur, and that there are no groups of three identical cards occur together. When the patient hits the space bar button on keyboard, a result will be recorded for the card that includes the reaction time to find the match and the total miss fire (if no match was not selected). The first hit is counted by the program, and all the extra hits are ignored until the next card appears. An acceptable response is made any time from the matching card appears to the point at which the next card appears . Patients must recall the target sign that was shown among several signs and press the key in hand.
The main variables in this study were the number of successfully recognized matches, the number of miss fires during trial, and the mean reaction time for the successfully recognized matches and miss fires.
The duration of each stimulus was 1 second, and the lag inter-val between stimuli was 1.5 seconds. The CPT was performed in 5 minutes for each patient after 3 minutes test presentation for orientation of patients. Other information such as demographic data, duration of hemodialysis, education levels, and jobs were obtained from designed questionnaire.
| Statistical analysis|| |
All data were entered in SPSS software and were analyzed by student's "t" test and chi square statistical tests. P values less than 0.05 were considered significant.
| Results|| |
Seven patients were excluded from the study due to non-compliance with the test, therefore, only data of 38 patients were available for analysis. The mean age of patients was 38.0 ± 12.6 years. The mean number of the successfully recognized matches was 37.6 ± 160 and the mean number of miss fires was 39.8±161.
There were no significant differences in the mean reaction time for the successfully recognized matches, the mean number of miss fires, and the mean reaction time for the successfully recognized matches for the tests performed before and after hemodialysis. In addition, there was no differences in these parameters with the duration of the dialysis therapy, [Table - 1].
The patients were divided into three groups according to their ages: less than 30 years, 30 - 50 and more than 50 years old. There were no differences between duration of hemodialysis and any of the above parameters, [Table - 2].
Educational level of the patients did not significantly impact on the mean number of the successfully recognized matches or the mean of reaction time. However, it had a significant impact on the mean of the miss fires (P= 0.04).
| Discussion|| |
In our study, the hemodialysis patients evaluated by Conners' Continuous Performance test (CPT) did not reveal significant differences in the cognitive function parameters before and after of hemodialysis.
Ratner et al advocated that despite significant daily changes in the serum levels of toxic substances retained in uremia, there was little or no evidence to suggest that well-dialyzed patients undergo daily fluctuations in their cognitive functioning.  On the other hand, Smith et al suggested that renal patients might have decreased cognitive functioning during the hemodialysis treatment.  The intelligence of hemodialysis patients remains unaffected and there is neither dementia related to dialysis, nor deterio ration of recent memory or attention span. Psychic adaptation to chronic hemodialpis proved unrelated to mental capacity. 
Renal patients may reveal decreased cognitive function during the hemodialysis treatment. The dialysis period, though a convenient and popular time for patient education, may not be the best time to teach patients. 
Murray et al advocated that severe cognitive impairment is common and undiagnosed in hemodialysis patients. They mentioned that further studies were required to determine whether dialysis exacerbates the cognitive impairment attributable to underlying disease. Furthermore, they recommended cognitive testing in hemodialysis patients before dialysis initiation and periodically thereafter. 
There are several approaches suggested in previously to improve the cognitive functions in the dialysis patients. Singh et al found that administration of recombinant human erythropoietin (EPO) in patients of anemia with chronic kidney disease resulted in a significant improvement in the electrophysiological markers of cognitive function.  Kurella et al believed that dementia is associated with adverse outcomes among ESRD patients, and that dialysis providers should consider instituting routine screening for cognitive impairment among elderly patients in order to identify those at risk for associated adverse outcomes.  Furthermore, short daily hemodialysis did not have clear effects on the cognitive function.  Finally, Tyrrell et al recommended regular assessments of the cognitive ability and quality of life in the dialysis patients. 
We conclude from our study that the cognitive function is stable in the chronic hemodialysis patients. Larger and long-term studies are warranted for this unresolved issue.
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Psychiatrist, Assistant Professor, Sharekord Medical University, Sharkord
[Table - 1], [Table - 2]