Postdialysis fatigue: lack of effect of a biocompatible membrane

Tumor necrosis factor-alpha (TNF-alpha) has been shown to have somnogenic properties. Plasma levels of this cytokine have been found to increase significantly during dialysis with a bioincompatible (cuprophane) membrane in patients with postdialysis fatigue (PDF). We conducted a crossover study with random assignment to ascertain whether a biocompatible membrane might attenuate the increase of TNF-alpha and severity of PDF. Sixteen patients on maintenance hemodialysis underwent dialysis with either cuprophane (n = 8) or polymethylmethacrylate (PMMA; n = 8) membranes for 1 week and then switched to the opposite membrane during the second week. Predialysis and postdialysis measurements of plasma TNF-alpha levels were performed during the first and last dialysis treatments of each week. A fatigue score was determined from the sum of duration of fatigue and sleep within 6 hours of the completion of dialysis. TNF-alpha levels increased by an average of 18.3% during dialysis with cuprophane membranes but only 2.4% with PMMA membranes (P = 0.04). Despite this, fatigue scores remained unaltered (approximately 4 of 6). Hence, the biocompatible membrane, PMMA, failed to alleviate PDF. This suggests that dialytic stimulation of TNF-alpha plays no substantial role in the pathogenesis of PDF.