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Dialysis adequacy is an independent predictor of high mortality rates in hemodialysis patients. Intradialytic exercise is a potential strategy to increase uremic solute removal by increasing blood flow to low perfusion tissue beds. The purpose of this review is to establish the efficacy of intradialytic exercise for hemodialysis adequacy. Additionally, this review aims to provide practical information to aid health care professionals implement intradialytic exercise for dialysis adequacy. Database and hand searches identified 15 published interventional studies that implemented intradialytic exercise for dialysis adequacy as a primary outcome measure in adult maintenance hemodialysis patients. Data pertaining to dialytic solute clearance of urea, creatinine, beta 2 microglobulin, phosphate, and potassium were extracted. Mean differences, normalized to percentages, and effect sizes were calculated and reported. The current data pertaining to the use of intradialytic exercise for improving dialysis adequacy in terms of Kt/V urea or small molecule uremic toxin clearance are equivocal. Limited data showed that intradialytic exercise has no effect middle molecule toxin (beta 2 - microglobulin) clearance. Intradialytic exercise favored increased phosphate removal showing medium to large effects for reduced serum concentrations, reduced rebound and increased clearance. In summary, supervised light to moderate intradialytic aerobic cycling appears to be beneficial for increasing phosphate removal and may be an adjunct therapy for patients failing to meet clinical phosphate targets. Further work is required to establish the effect of intradialytic exercise on Kt/V urea and other middle molecule and protein bound solutes. Research aimed at establishing the most effective exercise prescription for improved solute clearance is warranted., (© 2019 Wiley Periodicals, Inc.)

Endothelial dysfunction and arterial stiffness are nontraditional risk factors of chronic kidney disease (CKD)-related cardiovascular disease (CVD) that could be targeted with exercise. This study investigated the effect of moderate to vigorous aerobic exercise on vascular function in nondialysis CKD. In this randomized, controlled trial, 36 nondialysis patients with CKD (means ± SE, age: 58 ± 2 yr, estimated glomerular filtration rate: 44 ± 2 ml·min -1 ·1.73 m -2 ) were allocated to an exercise training (EXT) or control (CON) arm. The EXT group performed 3 × 45 min of supervised exercise per week at 60-85% heart rate reserve for 12 wk, whereas the CON group received routine care. Outcomes were assessed at 0 and 12 wk. The primary outcome, microvascular function, was assessed via cutaneous vasodilation during local heating measured by laser-Doppler flowmetry coupled with microdialysis. Participants were instrumented with two microdialysis fibers for the delivery of 1 ) Ringer solution and 2 ) the superoxide scavenger tempol. Conduit artery function was assessed via brachial artery flow-mediated dilation. Aortic pressure waveforms and pulse wave velocity were acquired with tonometry and oscillometry. Microvascular function improved after EXT ( week 0 vs . week 12 , EXT: 87 ± 2% vs. 91 ± 2% and CON: 86 ± 2% vs. 84 ± 3%, P = 0.03). At baseline, pharmacological delivery of tempol improved microvascular function (Ringer solution vs. tempol: 86 ± 1% vs. 90 ± 1%, P = 0.02) but was no longer effective after EXT (91 ± 2% vs. 87 ± 1%, P = 0.2), suggesting that an improved redox balance plays a role in EXT-related improvements. Brachial artery flow-mediated dilation was maintained after EXT (EXT: 2.6 ± 0.4% vs. 3.8 ± 0.8% and CON: 3.5 ± 0.6% vs. 2.3 ± 0.4%, P = 0.02). Central arterial hemodynamics and arterial stiffness were unchanged after EXT. Aerobic exercise improved microvascular function and maintained conduit artery function and should be considered as an adjunct therapy to reduce CVD risk in CKD.

Background/aims: According to mathematical modeling, intradialytic exercise of sufficient intensity and duration implemented in the second half of dialysis should be as efficacious as increasing dialysis time for dialysis adequacy. This assumption has not been tested in vivo., Methods: In this controlled trial, 11 hemodialysis (HD) patients (mean (SD) age 56 (13) years) were recruited. Each patient completed three trial arms in a randomized order: routine care (CONT), increased HD time of 30 min (TIME), and intradialytic exercise (EXER), 60 min of cycling at 90% of the lactate threshold in the last 90 min of HD. The primary outcome was eKt/Vurea. Secondary outcomes included reduction and rebound ratios of urea, creatinine, phosphate and β2-microglobulin. Outcomes were calculated from blood sampling collected pre-, post- and 30 min post-HD and confirmed with dialysate sampling., Results: Exercise was not as efficacious as increased HD time for eKt/Vurea (EXER vs. CONT, mean change (95% CI): 0.03 (-0.05 to 0.12); TIME vs. CONT: 0.15 (0.05-0.26)). Exercise was less efficacious at improving reduction ratios of urea and creatinine. However, exercise was more efficacious than increased dialysis time for phosphate reduction ratio (EXER vs. CONT: 8.6% (0.5-16.7); TIME vs. CONT: 5.0% (-1.0 to 11.1))., Conclusion: This study utilized a rigorously controlled in vivo design to test mathematical models and assumptions regarding dialysis adequacy. Intradialytic exercise towards the end of HD cannot replace the prescription of increased HD time for dialysis adequacy, but may be an adjunctive therapy for serum phosphate control., (© 2013 S. Karger AG, Basel.)