Are dialysis patients too frail to exercise?

Clinical manifestations of functional and morphological muscular abnormalities in dialysis patients are muscle weakness and low exercise capacity, possibly leading to a sedentary life style with low physical activity. Low cardiorespiratory fitness and muscle atrophy and weakness contribute to the development of frailty and affect patients' ability to physically navigate their environment. While many dialysis patients may appear too frail to participate in moderate-to-vigorous aerobic exercise training, those who can complete such programs appear to derive substantial benefit. Less vigorous aerobic exercise, resistance training, and alternative forms of exercise can also be beneficial. Most patients on dialysis are not too frail to perform resistance exercise of adequate intensity to achieve increases in muscle size and strength, therefore, frailty should not be considered a contraindication to exercise.

Anabolic and catabolic mechanisms in end-stage renal disease.

Muscle wasting is a prominent feature of end-stage renal disease and is associated with muscle weakness and poor physical functioning. Potential reasons for muscle wasting include advancing age, sedentary behavior, inflammation, poor nutritional intake, androgen deficiency, oxidative stress, metabolic acidosis, and insulin resistance. Each of these conditions can be associated with decreased protein synthesis, increased protein degradation, or both. The primary muscle protein synthesis pathway is the insulin insulin-like growth factor-1/phosphatidyl inositol-3 kinase/Akt pathway, which results in the phosphorylation of the mammalian target of rapamycin and subsequent increased protein synthesis. The major protein degradation pathway is the ubiquitin-proteasome system. This review discusses the ways in which end-stage renal disease tips the balance of protein turnover towards catabolism and the mechanisms by which various interventions may work to mitigate wasting or even cause anabolism.

Higher serum creatinine concentrations in black patients with chronic kidney disease: beyond nutritional status and body composition.

BACKGROUND AND OBJECTIVES: Serum creatinine concentrations tend to be higher in black than white individuals and people of other races or ethnicities. These differences have been assumed to be largely related to race-related differences in body composition, especially muscle mass. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: In a diverse population of hemodialysis patients, we compared mean serum creatinine concentrations in black versus nonblack patients, adjusting for case mix (age, gender, diabetes, and dialysis vintage), body size (height, weight), laboratory parameters of nutritional status (albumin, predialysis blood urea nitrogen, transferrin, phosphorus, glucose), dialysis dosage (urea reduction ratio), and parameters of bioelectrical impedance (resistance and reactance), proxies for body composition. RESULTS: Adjusted mean serum creatinine concentrations were significantly higher in black versus nonblack patients (11.7 versus 10.0 mg/dl; P < 0.0001). Black patients were roughly four-fold more likely to have a serum creatinine concentration >10 mg/dl and six-fold more likely to have a serum creatinine concentration >15 mg/dl. Higher serum creatinine concentrations were associated with a lower relative risk for death (0.93; 95% confidence interval 0.88 to 0.98 per mg/dl); the association was slightly more pronounced among nonblack patients. CONCLUSIONS: Serum creatinine concentrations are significantly higher in black compared with nonblack hemodialysis patients; these differences are not readily explained by differences in nutritional status or body composition.

Chronic kidney disease mineral bone disorder and health-related quality of life among incident end-stage renal-disease patients.

OBJECTIVE: Our objective was to determine the extent to which chronic kidney disease mineral bone disorder (CKD-MBD) is associated with health-related quality of life among incident dialysis patients. DESIGN: This study's design was a cross-sectional analysis. SETTING: This was part of the United States Renal Data System Dialysis Morbidity and Mortality Study (DMMS), Wave 2. PATIENTS: The patients comprised 2590 adult participants in DMMS Wave 2, for whom quality of life and laboratory data were available. METHODS: We stratified patients according to their serum concentrations of phosphorus, calcium, and parathyroid hormone (PTH), and compared health-related quality of life as a function of these indicators in analyses adjusted for demographic, clinical, and other laboratory variables. MAIN OUTCOME MEASURES: Main outcome measures included Physical Component Summary (PCS) and Mental Component Summary (MCS) scores, and the Symptom score of the Kidney Disease Quality of Life. RESULTS: Both high and low serum phosphorus concentrations were associated with lower PCS scores (-1.25 to -1.48 points compared with the reference category), as was low PTH (-1.49 points). Low serum phosphorus was associated with more severe symptoms of kidney disease (-3.88 points), but there were no associations between high phosphorus or either extreme of PTH and the Symptom score. Serum calcium concentration and the calcium x phosphorus product were unassociated with PCS or Symptom scores. There were no associations among phosphorus, calcium, or PTH and MCS. Analyses simultaneously controlling for serum phosphorus, calcium, and PTH showed similar results. CONCLUSION: High and low serum phosphorus and low PTH are associated with slightly poorer self-reported physical functioning. Clinical trials will be necessary to determine whether and to what extent improvement in health status may occur with the correction of selected disorders of mineral metabolism.

Factors associated with future amputation among patients undergoing hemodialysis: results from the Dialysis Morbidity and Mortality Study Waves 3 and 4.

BACKGROUND: Amputation is more common in hemodialysis patients than in the general population, but risk factors for amputation in this population have not been studied extensively. METHODS: We used the US Renal Data System Dialysis Morbidity and Mortality Study Waves 3 and 4 in combination with Medicare discharge data to identify factors associated with lower-extremity amputation (excluding toe amputations) in hemodialysis patients. We used stepwise multivariable logistic regression analysis to identify variables most strongly associated with amputation within 2 years of the study start date. RESULTS: Male sex, diabetes, previous diagnosis of peripheral vascular disease (PVD), mean systolic blood pressure, and elevated serum phosphorus level were associated with the outcome of amputation within 2 years of the study start date. Among patients without diabetes, a previous diagnosis of cardiac disease, longer time from initiation of dialysis therapy (vintage), and previous hospitalization for limb ischemia were associated with increased risk for future amputation. CONCLUSION: The importance of preventing amputation in this population cannot be overemphasized. The strength of the association of amputation with PVD makes a strong case for screening all dialysis patients for this disease. The association of amputation with serum phosphorus level reported here should be explored further because this may offer an avenue for future intervention to reduce amputation rates.