Effect of haemodialysis on visual-evoked potential parameters

Different papers have emphasized the presence of visual-evoked potential (VEP) abnormalities in metabolic disorders. The aim of this study was to perform pattern VEP (PVEP) recordings in patients with chronic renal failure just before and 24 h after dialysis to test the effect of this procedure on visual pathway generated parameters. Twenty-four haemodialysis patients (M/F:14/10; mean age: 48.8 +/- 14.1 years) were examined. None of them were complaining from visual difficulties or from visual loss. The recording sessions were performed just before and 24 h after dialysis. The control group consisted from 27 healthy subjects matched for age and sex. Eight (33%) patients demonstrated abnormal P100 latency prolongation in at least one tested eye (six patients in one tested eye, two in both eyes) in the recording session just prior to dialytic treatment. In the post-treatment session, it was found that the abnormal P100 latencies that were present in six patients (75%) before dialysis had returned to normal, while in the remaining two (25%), the latency abnormality persisted. No correlation was found between VEP parameters and dialysis duration, serum blood urea nitrogen (BUN), creatinine, parathyroid hormone and haematocrit levels. However, a positive correlation in the intradialytic percentage variation of bodyweight with P100 latencies was found. Visual evoked potential is a reliable, simple and non-invasive technique that can be used for the investigation and follow up of subclinical involvement of visual pathways in patients with chronic renal failure. Detected abnormalities in some uraemic patients are reversible by using dialysis.