Background: Endothelial dysfunction is common in end-stage renal disease and may contribute to the development of both hypertension and atherosclerosis. Long-slow hemodialysis (HD) has been associated with superior blood pressure control and fewer cardiovascular complications. We hypothesized that long dialysis times would improve endothelial function compared with shorter dialysis times.
Method: Eight long-term hemodialysis patients, not on antihypertensive drugs and with no evidence of vascular disease, were studied in a three-way randomized crossover-controlled trial. Each received, for one week and in randomized sequence, four hours of HD (SD), eight hours of HD, and eight hours of HD using a smaller dialyzer and slower blood pump. The same post-dialysis target weights were used with each treatment. On the third day of each treatment endothelium-dependent (flow mediated) and independent glyceryl trinitrate (GTN) induced vasodilation were measured by forearm strain-gauge plethysmography, and von Willebrand (vW) antigen, plasma homocysteine (tHcy) and neurohormones were measured pre- and post-dialysis.
Results: Despite achieving target post-dialysis weights with all treatments, pre-dialysis weight tended higher on SD. Endothelial dependent vasodilation increased after all HD treatments but did not differ between them. Adrenomedullin, N-terminal brain natriuretic peptide and vW antigen increased similarly across all HD whereas atrial and C-type natriuretic peptide, and endothelin-1 decreased across dialysis and were higher with SD. Pre-dialysis plasma tHcy concentrations were 13% higher during SD treatment.
Conclusion: Hemodialysis improved endothelial-dependent vasodilation but the effect was similar with all three HD treatments. Improved endothelial function might result in part from altered local hormone production (endothelin-1 and adrenomedullin). These data suggest that increasing dialysis time is unlikely, in the short-term, to significantly improve endothelial function in patients with end-stage renal disease, but longer term studies are needed.