Intradialytic Exercise and Patient Survival

The prevalence of chronic kidney disease (CKD) is increasing, leading to an exponential increase in the number of patients progressing to kidney failure requiring kidney replacement therapy (KRT) (hemodialysis, peritoneal dialysis or kidney transplantation). Worldwide, the most common treatment modality is hemodialysis, accounting for 69% of all KRT and 89% of all dialysis. Compared with individuals with normal kidney function, those receiving hemodialysis have higher rates of functional impairment, morbidity, hospitalization, and mortality.

According to Mohammad Ali Tabibi, PhD, and colleagues, adverse outcomes among individuals on hemodialysis are associated with low physical activity due to high rates of comorbidities, protein energy wasting, sarcopenia, decreased physical function, decreased aerobic capacity, enforced inactivity during weekly hemodialysis sessions, and postdialysis fatigue. The activity rates of patients receiving hemodialysis are between 20% to 50% that of healthy counterparts.

The researchers conducted a randomized, controlled trial in a hemodialysis center in Iran to examine the effect of intradialytic exercise on survival. The study also sought to assess the effect of intradialytic exercise on clinical outcomes associated with patient survival. Results were reported online in BMC Nephrology [doi.org/10.1186/s12882-023-03158-6].

The primary outcome measure was 1-year survival. Secondary outcome measures included changes in serum albumin, hemoglobin, hematocrit, red blood cell count, serum calcium, serum phosphorous, and parathyroid hormone over time. Also of interest were physical function and nutritional status.

Physical function was evaluated with the 6-minute walk test, performed according to the American Thoracic Society guidelines. The test weas performed on a 30-meter straight course. Participants were asked to walk as fast as possible for 6 minutes. Walking aids were allowed and recorded. Distance was measured at the end of the 6-minute period. Nutritional status was assessed by Geriatric Nutritional Risk Index.

Intervention adherence was defined as the number of sessions performed divided by the number of sessions offered, multiplied by 100. The adherence rate was 81%.

Prior to study initiation, educational and motivational posters were installed in the dialysis center to familiarize all patients with the benefits of exercise, particularly intradialytic exercise. Patients were then informed of the side effects of inactivity and a sedentary lifestyle. All eligible patients received a baseline assessment, including demographic characteristics, primary cause of kidney failure, and comorbidities. Comorbidities were quantified using the Charlson Comorbidity Index established for patients on dialysis, including the underlying cause of kidney failure plus 11 comorbidities (atherosclerotic heart disease, congestive heart failure, cerebrovascular accident/transient ischemic attack, peripheral vascular disease, dysrhythmia, and other cardiac diseases, chronic obstructive pulmonary disease, gastrointestinal bleeding, liver disease, cancer, and diabetes).

Patients were randomized 1:1 to either the intervention group or the control group. Those in the intervention group performed concurrent intradialytic exercise during the second hour of dialysis (60-minute exercise sessions three times a week) for 6 months. The intervention was a combination of aerobic and resistance exercises. Exercises were individualized to match participants’ level of physical fitness. Participants in the control group did not undertake any specific physical activity during dialysis. Follow-up for all participants was 12 months.

Of the 95 patients assessed for eligibility, 74 met eligibility criteria and were randomized. During the study period, two participants in the intervention group and four in the control group were excluded. Every patient who was lost to follow-up (for any reason except death) during follow-up was censored.

The intervention and control groups were balanced in baseline characteristics. In the intervention group, mean age was 62 years, 57% (n=27) were men, and mean dialysis history was 29 months. In the control group, mean age was 65 years, 62% (n=23) were men, and mean dialysis history was 26 months.

During the initial 6-month period when the exercise intervention was being performed, no one in the intervention group died and two participants in the control group died. During the 12-month follow-up period, two participants in the intervention group (6%) died: one due to cardiovascular disease and one due to unknown cause. In the control group, nine participants (27%) died during follow-up: three due to cardiovascular disease, two due to cerebrovascular disease, one due to infection, two due to other causes, and one due to unknown cause. The cumulative survival rate in the control group was significantly lower than that in the intervention group (log rank statistics=6.5, P=.01). Results of univariable Cox regression model analyses were similar.

In all secondary outcomes, there were significant between-group changes observed during the 6-month intervention period. Serum albumin, hemoglobin, red blood cell count, serum calcium, physical function, and nutritional status tended to increase in the intervention group, but remained relatively stable in the control group. Serum parathyroid hormone and phosphorous levels significantly decreased in the intervention group, but remained relatively stable in the control group.

During the study period, there were no treatment- or intervention-related serious adverse events. One patient in the intervention group had muscle cramp after two sessions of exercise and one patient had bleeding from fistula while doing the exercises.

In citing limitations to the study findings, the authors included the short duration (6 months) of the intradialytic exercise intervention as well as the short duration (12 months) of follow-up that resulted in the long-term effects of exercise on patient survival remaining uncertain. In addition, the small sample size resulted in an imprecise estimate of the effect of exercise on patient survival, and survival was timed from the end of the intervention, introducing immortal time bias. Finally, the secondary outcome measures assessing the effects of intradialytic exercise and patient survival were only examined during the first 6 months of the study.

“Intradialytic exercise performed for at least 60 minutes during thrice weekly dialysis sessions improves survival in adult patients receiving hemodialysis,” the researchers concluded. “Further large-scale studies are warranted.”

Takeaway Points

1. Researchers reported results of a study examining the effect of intradialytic exercise on survival in a population of adults receiving maintenance hemodialysis.
2. The primary outcome measure was survival rate at 12 months. Secondary outcomes included clinical outcomes associated with patient survival.
3. Survival in adults receiving maintenance hemodialysis was improved with intradialytic exercise for at least 60 minutes during thrice weekly dialysis sessions.

Source: BMC Nephrology