Attention and information processing in end stage renal disease and effect of hemodialysis: a bedside study.

The neurobehavioral syndrome of uremia in chronic kidney disease affects the functioning of the central nervous system. Cognitive impairment is one of the most important manifestations of this dysfunction. The process of hemodialysis is known to bring about conflicting changes in the cognitive status of patients. In the present study an assessment of cognitive status of patients with end stage renal disease was done in comparison to controls before and after a session of hemodialysis using simple bedside paper-pencil tests. Thirty patients of end stage renal disease on maintenance dialysis for at least one month with MMSE score >24 were assessed one hour before and one hour after hemodialysis using Digit Symbol Substitution Test, One Letter and Three Letter Cancellations tasks. Their results were compared to age and sex matched healthy controls. The patients with end stage renal disease had significantly lower performance in cognitive tests in comparison to controls. The performance improved 1 hour after hemodialysis in comparison to pre-dialysis values. However, the values after dialysis were significantly lower than in controls, thereby indicating that though the cognitive functions improved after hemodialysis, they did not reach the control levels. There was also a significant change in the biochemical parameters after dialysis. We conclude that patients with end stage renal disease suffered from cognitive impairment which improved on hemodialysis due to removal of metabolic waste products.