Uremic Pruritus, Cytokines and Polymethylmethacrylate Artificial Kidney

Background: Uremic pruritus is one of the common complications in long-term dialysis patients. In general, many factors including xerosis, elevated serum calcium, phosphate, calcium-phosphate product, hyperparathyroidism and inadequate dialysis may contribute to it. Recently, researchers reported that immuno-hypothesis with high serum level of cytokines could be the cause of uremic pruritus. Polymethylmethacrylate (PMMA) artificial kidney (AK) has been reported to adsorb more serum cytokines than other high flux artificial kidneys.

Methods: In July 2006, 30 patients with severe uremic pruritus from 300 chronic hemodialysis patients in a single center entered this prospective study. Their dialyzers were changed to PMMA AK for 4 weeks. The severity of pruritus was evaluated every week using the results of a questionnaire (pruritus score). Laboratory assays including pre-dialysis serum blood urea nitrogen, creatinine, β2-microgblubulin (β2M), calcium, phosphate, intact parathyroid hormone (iPTH), total CO2, ferritin, hematocrit, high sensitivity C-reactive protein (hsCRP), IL-1, IL-2, IL-6, IL-18, TNF-α, KT/V and β2M clearance were measured before and at the end of 4 weeks of PMMA AK use.

Expected Results:To prove the PMMA membrane could improve the uremic pruritus and to reveal the effect of PMMA membrane on serum level of possible factors contributing to uremic pruritus.

Inclusion Criteria:

• Patients with chronic pruritus (>3 months) were screened using traditional visual analogue scale (VAS) and then scored using a pruritus questionnaire (pruritus scoring system).
• Other inclusion criteria were that patients enrolled should be dialysed for 4 hours, three times a week, with KT/V >1.2, serum albumin> 3.0 mg/dl, hematocrit > 24%, ferritin < 900 ng/ml, phosphate <7 mg/dl, corrected calcium <11 mg/dl, calcium-phosphate product < 70, intact parathyroid hormone (iPTH) <600 pg/ml, and normal serum level of alanine aminotransferase and bilirubin in past 3 months.

Exclusion Criteria:

• Pruritus unrelated to renal failure
• Evidence of malignancy
• Liver cirrhosis diagnosed by echogram or admission within 3 months of the start of the study.