Just Do It- Exercise before or during Hemodialysis

Cardiovascular disease (CVD) is the leading cause of death accounting for >50% of mortality in chronic maintenance hemodialysis (MHD) population.¹ Pathophysiology of CVD in MHD is multifactorial including factors such as chronic inflammation and oxidative stress contributing to atherosclerosis, bone and mineral disorders leading to vascular calcification and stiffening of arteries, hypervolemia exacerbating cardiac remodeling and hypertension, and hemodynamic instability during dialysis that leads to undue stress on the heart. Previous research that has focused on reducing CVD burden in MHD patients include dialysis dose, modality of dialysis, electrolytes control, statins, antihypertensives, aspirin, and exercise interventions.

Timing of exercise in MHD patients has been a growing area of interest. Interdialytic exercise occurs on nondialysis days. Predialytic exercise usually occurs on the day of dialysis, before treatment. Intradialytic exercise occurs during dialysis, typically during the first 1–2 hours, often using stationary cycling or resistant bands. Previous research has mostly focused on intradialytic exercise, with findings significant for improved physical functioning,² decreased myocardial stunning,^3,4 and improving ejection fraction⁵ as well as other cardiovascular outcomes.⁶ Although these results are promising, practical issues such as patient fatigue, maintaining safe hemodialysis access, and dialysis staff burden have limited widespread adoption of intradialytic exercise.

Comparisons of predialytic versus intradialytic exercise have not been well evaluated. The study by Josse et al.⁷ seeks to address that knowledge gap. They examined cardioprotection and the effect of timing of exercise in relation to hemodialysis: predialytic, intradialytic, and control in a randomized crossover trial of 25 patients with ESKD.

The rationale for their study is sound. In hemodialysis patients, intradialytic hypotension and acute subclinical myocardial ischemia can lead to wall motion abnormalities and left ventricular dysfunction, also known as myocardial stunning. Recurrent myocardial stunning can render patients potentially more susceptible to heart failure and sudden cardiac death. Myocardial stunning can be identified by the presence of regional wall motion abnormalities (RWMA).⁸ Rapid ultrafiltration leading to reduced intravascular volume, causing repeated ischemic insults during hemodialysis sessions, can lead to progressive cardiac damage. More frequent hemodialysis sessions, such as what is seen in home dialysis, have been associated with less RWMA than in conventional, thrice weekly hemodialysis.⁹ In addition, those patients who were more frequently dialyzed had lower ultrafiltration volumes and rates, as well as lower high sensitivity C-reactive protein, cardiac troponin T, and N-terminal prohormone brain natriuretic peptide. Intradialytic exercise may mitigate myocardial stunning by increasing cardiac output, stabilizing BP, and increasing oxygen delivery to tissues, including the heart, during hemodialysis. It has been unclear whether predialytic exercise could potentially reduce myocardial stunning.

Josse et al. included participants who were age 20–79 years and had been on MHD for >3 months. Participants were excluded if they had orthopedic limitations, ejection fraction <45%, severe heart/respiratory diseases, severe obesity, and poor echogenicity. All participants participated in all three exercise conditions in a randomized order. In the predialytic exercise condition, participants exercised for 30 minutes before the beginning of dialysis; in the intradialytic exercise condition, participants underwent dialysis for 30 minutes before exercising for 30 minutes. Echocardiogram was obtained twice during each session; immediately before dialysis and 30 minutes before dialysis ending. Hemodynamic data and BP were obtained immediately before dialysis and every 30 minutes throughout the session. Whole blood viscosity, which is a measure of blood flow resistance, was obtained at native hematocrit and different sheer rates, with analyses being performed within 30 minutes of blood sampling. It has been shown that whole blood viscosity pathologically increases across all shear rates during hemodialysis.

The primary outcome was the within-patient difference in the number of RWMA in the predialytic exercise group compared with the intradialytic exercise group and the control group. The authors found that compared with controls, both predialytic exercise and intradialytic exercise resulted in similar reduction in RWMA.

A secondary outcome was within-patient difference in the number of intra-dialytic hypotension episodes per 100 hours of dialysis, which was less with both predialytic and intradialytic exercise compared with the control. Changes in global longitudinal strain, as assessed by echocardiography, were also attenuated with both predialytic and intradialytic exercise.

Interestingly, the authors found no significant associations between changes in RWMA and hemodynamics variables. In addition, the hemodynamic profiles of predialytic and intradialytic exercise were nearly identical during the 2 hours preceding RWMA assessment. These results are suggestive but not conclusive proof that the effects of exercise on reducing RWMA are independent of hemodynamic changes.

This study highlights the importance of the cardioprotective benefits of exercise in MHD patients irrespective of whether the exercise occurred predialysis or intradialysis. It also suggests that this benefit may not be due to transient hemodynamic alternations.

Although these results are very promising, there are some caveats to this study. First, reduction in RWMA is a surrogate end point, and it remains to be seen whether predialysis or intradialysis exercise would reduce the risk of heart failure or cardiovascular death. The interventions lasted only 1 week. Long-term adherence to exercise interventions is low, and it also remains to be seen whether the exercise and beneficial myocardial effects are sustained over long-term. Patients with heart failure and coronary artery disease were excluded; therefore, the benefit seen in the population who may need the intervention the most was not evaluated.

Overall, this study adds the novel finding that predialytic exercise is as cardioprotective as intradialytic exercise. This is important as intradialytic exercise has not been well adopted; being able to exercise predialysis, without the limitations seen in the dialysis units, and still achieving the same cardioprotective benefit can significantly affect hemodialysis patients' health.

Supplementary Material

cjasn-20-1177-s001.pdf ^{(1.4MB, pdf)}

Disclosures

Disclosure forms, as provided by each author, are available with the online version of the article at http://links.lww.com/CJN/C357.

Author Contributions

Conceptualization: Srinivasan Beddhu, Amara Sarwal.

Supervision: Srinivasan Beddhu.

Visualization: Srinivasan Beddhu.

Writing – original draft: Amara Sarwal.

Writing – review & editing: Srinivasan Beddhu, Amara Sarwal.

Funding

None.