Computerized recording of itch in patients on maintenance hemodialysis

Itch was assessed both continuously using a computerized method, Pain-Track, and retrospectively using visual analogue scales (VAS) by 28 patients undergoing maintenance hemodialysis and suffering from uremic pruritus. Measurements were performed during 7 consecutive days including three dialysis sessions. Pain-Track recordings showed that itch intensity was greater during dialysis than on days following dialysis (p less than 0.05). Possible explanations are that pruritogenic substances might be released during treatment or that removal of such substances during dialysis leads to amelioration of symptoms after treatment. Alternatively, lowering of the sensory threshold due to general discomfort in association with dialysis may exacerbate the itch intensity. There was no consistent difference between daytime and bedtime itch scores over the week, except on the second day without treatment, when bedtime itch ratings significantly exceeded those during the day (p less than 0.05), suggesting that factors other than inactivity are essential for this peak in itch intensity. Thus, after 2 days without treatment, when patients become increasingly metabolically deranged, they reported maximal itch, implying that the accumulation of pruritogenic substances is of major importance in the pathogenesis of uremic pruritus. There was a positive correlation between Pain-Track and VAS data, although significant fluctuations in itching could be detected only with Pain-Track.