Acute effect of haemodialysis on arterial stiffness: membrane bioincompatibility?

BACKGROUND: Repetitive endothelial damage from dialysis membrane incompatibility is a probable cause of accelerated atherosclerosis in haemodialysis patients. Consequently pulse wave velocity (PWV), a measure of arterial stiffness, was utilized as a surrogate marker of vascular dysfunction during dialysis with two commonly used synthetic dialysers. METHODS: PWV was monitored before, during and after haemodialysis using both polysulphone and polyamide membranes. PWV, an arterial stiffness measure, was calculated from the carotid to the femoral (C-F) and also to the radial (C-R) artery. In a further group, PWV was monitored while polysulphone and polyamide membranes were perfused with blood without dialysate. RESULTS: Mean aortic (C-F) PWV was lower during dialysis with the polyamide membrane, being 14 and 16% less following 75 and 135 min of dialysis (P<0.05) in 24 patients. Because intradialytic intravascular volume changes alter PWV, a subgroup analysis in 11 patients where dialysis fluid removal during both periods was minimal (<1 kg) was performed, and a persistent and significant increase in aortic PWV was detected with the polysulphone kidney being maximal (40%) at 75 min (P<0.01). This increase was negatively correlated with pre-dialysis PWV (P<0.01). In contrast, the polyamide dialyser did not change PWV. An increase in C-R PWV was also noted with the polysulphone membrane (P<0.05). In the nine patients where membranes were perfused with blood without dialysate, aortic PWV was again significantly increased by the polysulphone (P<0.01), but not the polyamide dialyser. CONCLUSIONS: Haemodialysis with polysulphone but not polyamide membranes acutely alters aortic 'stiffness', an effect postulated to be due to membrane bioincompatibility. However, factors including age, time on dialysis and underlying vascular disease, were also found to impact on these acute dialysis-induced changes to vascular function. Since these acute changes disappear post-dialysis, their long-term consequences are uncertain.