Cardiovascular and metabolic responses to submaximal exercise in hemodialysis patients

Exercise and chronic kidney disease: potential mechanisms underlying the physiological benefits

Increasing evidence indicates that exercise has beneficial effects on chronic inflammation, cardiorespiratory function, muscle and bone strength and metabolic markers in adults with chronic kidney disease (CKD), kidney failure or kidney transplants. However, the mechanisms that underlie these benefits have received little attention, and the available clinical evidence is mainly from small, short-duration (<12 weeks) exercise intervention studies. The available data, mainly from patients with CKD or on dialysis, suggest that exercise-mediated shifts towards a less inflammatory immune cell profile, enhanced activity of the NRF2 pathway and reduced monocyte infiltration into adipose tissue may underlie improvements in inflammatory biomarkers. Exercise-mediated increases in nitric oxide release and bioavailability, reduced angiotensin II accumulation in the heart, left ventricular remodelling and reductions in myocardial fibrosis may contribute to improvements in left ventricular hypertrophy. Exercise stimulates an anabolic response in skeletal muscle in CKD, but increases in mitochondrial mass and satellite cell activation seem to be impaired in this population. Exercise-mediated activation of the canonical wnt pathway may lead to bone formation and improvements in the levels of the bone-derived hormones klotho and fibroblast growth factor 23 (FGF23). Longer duration studies with larger sample sizes are needed to confirm these mechanisms in CKD, kidney failure and kidney transplant populations and provide evidence for targeted exercise interventions.

Cardiopulmonary exercise testing to observe subclinical abnormalities in cardiopulmonary function in patients undergoing peritoneal dialysis

BACKGROUND

Decreased cardiorespiratory fitness (CRF) related to cardiopulmonary function increases the risk of cardiovascular disease in patients with end-stage kidney disease. Thus, early detection of the cause of impaired cardiopulmonary function in patients undergoing peritoneal dialysis (PD) is of important clinical significance.

METHODS

In this cross-sectional study, Symptom-restricted cardiopulmonary exercise testing (CPET) was performed in 30 patients undergoing PD and in 23 age- and sex-matched healthy control subjects.A fixed workload was added every minute until fatigue, and breath-by-breath respiratory gas was analyzed with an automated gas analyzer at 10-second intervals.

RESULTS

The peak oxygen uptake ( 16.39±0.83 vs 25.77±1.33 ml/kg/min p<0.001) and the oxygen uptake at the anerobic threshold of patients undergoing PD (9.61±0.34 vs 14.55± 0.64 ml/kg/min; p<0.001) were lower than in healthy control subjects, and both of these parameters correlated with body mass index and left atrial dimension. A steeper minute ventilation / carbon dioxide production slope (27.20±0.68 vs 24.29±0.69；p<0.01) and a lower end-tidal carbon dioxide partial pressure (37.93±0.54 vs 41.27±0.83mmHg；p<0.05) were observed in patients undergoing PD. The oxygen pulse and oxygen uptake efficiency slope was smaller in patients undergoing PD. The Maximum heart rate (126.07±4.01 vs 149.96±5.29 bpm；p<0.01) and 1-minute heart rate recovery (13.93±1.52 vs 24.39±1.61bpm；p<0.01) were also lower in patients undergoing PD.

CONCLUSION

Subclinical cardiopulmonary dysfunction may exist in patients with PD, and a reduction in CRF in patients undergoing PD is affected by both central and peripheral functions. CPET has potential value in revealing the mechanism of impaired CRF and in discovering subclinical abnormalities in cardiopulmonary function. This article is protected by copyright. All rights reserved.

A Useful Blood Flow Restriction Training Risk Stratification for Exercise and Rehabilitation

Blood flow restriction training (BFRT) is a modality with growing interest in the last decade and has been recognized as a critical tool in rehabilitation medicine, athletic and clinical populations. Besides its potential for positive benefits, BFRT has the capability to induce adverse responses. BFRT may evoke increased blood pressure, abnormal cardiovascular responses and impact vascular health. Furthermore, some important concerns with the use of BFRT exists for individuals with established cardiovascular disease (e.g., hypertension, diabetes mellitus, and chronic kidney disease patients). In addition, considering the potential risks of thrombosis promoted by BFRT in medically compromised populations, BFRT use warrants caution for patients that already display impaired blood coagulability, loss of antithrombotic mechanisms in the vessel wall, and stasis caused by immobility (e.g., COVID-19 patients, diabetes mellitus, hypertension, chronic kidney disease, cardiovascular disease, orthopedic post-surgery, anabolic steroid and ergogenic substance users, rheumatoid arthritis, and pregnant/postpartum women). To avoid untoward outcomes and ensure that BFRT is properly used, efficacy endpoints such as a questionnaire for risk stratification involving a review of the patient’s medical history, signs, and symptoms indicative of underlying pathology is strongly advised. Here we present a model for BFRT pre-participation screening to theoretically reduce risk by excluding people with comorbidities or medically complex histories that could unnecessarily heighten intra- and/or post-exercise occurrence of adverse events. We propose this risk stratification tool as a framework to allow clinicians to use their knowledge, skills and expertise to assess and manage any risks related to the delivery of an appropriate BFRT exercise program. The questionnaires for risk stratification are adapted to guide clinicians for the referral, assessment, and suggestion of other modalities/approaches if/when necessary. Finally, the risk stratification might serve as a guideline for clinical protocols and future randomized controlled trial studies.

Ventilatory and chronotropic incompetence during incremental and constant load exercise in end-stage renal disease: a comparative physiology study

Maximal O₂ uptake is impaired in end-stage renal disease (ESRD), reducing quality of life and longevity. While determinants of maximal exercise intolerance are well defined, little is known of limitation during submaximal constant load exercise. By comparing individuals with ESRD and healthy controls, the aim of this exploratory study was to characterize mechanisms of exercise intolerance in participants with ESRD by assessing cardiopulmonary physiology at rest and during exercise. Resting spirometry and echocardiography were performed in 20 dialysis-dependent participants with ESRD (age: 59 ± 12 yr, 14 men and 6 women) and 20 healthy age- and sex-matched controls. Exercise tolerance was assessed with ventilatory gas exchange and central hemodynamics during a maximal cardiopulmonary exercise test and 30 min of submaximal constant load exercise. Left ventricular mass (292 ± 102 vs. 185 ± 83 g, P = 0.01) and filling pressure (E/e': 6.48 ± 3.57 vs. 12.09 ± 6.50 m/s, P = 0.02) were higher in participants with ESRD; forced vital capacity (3.44 ± 1 vs. 4.29 ± 0.95 L/min, P = 0.03) and peak O₂ uptake (13.3 ± 2.7 vs. 24.6 ± 7.3 mL·kg^-1·min^-1, P < 0.001) were lower. During constant load exercise, the relative increase in the arterial-venous O₂ difference (13 ± 18% vs. 74 ± 18%) and heart rate (32 ± 18 vs. 75 ± 29%) were less in participants with ESRD despite exercise being performed at a higher percentage of maximum minute ventilation (48 ± 3% vs. 39 ± 3%) and heart rate (82 ± 2 vs. 64 ± 2%). Ventilatory and chronotropic incompetence contribute to exercise intolerance in individuals with ESRD. Both are potential targets for medical and lifestyle interventions.

Hemodynamic and perceptual responses to blood flow-restricted exercise among patients undergoing dialysis

End-stage kidney disease is associated with reduced exercise capacity, muscle atrophy, and impaired muscle function. While these may be improved with exercise, single modalities of exercise do not traditionally elicit improvements across all required physiological domains. Blood flow-restricted exercise may improve all of these physiological domains with low intensities traditionally considered insufficient for these adaptions. Investigation of this technique appeals, but is yet to be evaluated, in patients undergoing dialysis. With the use of a progressive crossover design, 10 satellite patients undergoing hemodialysis underwent three exercise conditions over 2 wk: two bouts (10 min) of unrestricted cycling during two consecutive hemodialysis sessions (condition 1), two bouts of cycling with blood flow restriction while off hemodialysis on 2 separate days (condition 2), and two bouts of cycling with blood flow restriction during two hemodialysis sessions (condition 3). Outcomes included hemodynamic responses (heart rate and blood pressure) throughout all sessions, participant-perceived exertion and discomfort on a Borg scale, and evaluation of ultrafiltration rates and dialysis adequacy (Kt/V) obtained post hoc. Hemodynamic responses were consistent regardless of condition. Significant increases in heart rate, systolic blood pressure, and mean arterial blood pressure (P < 0.05) were observed postexercise followed by a reduction in blood pressures during the 60-min recovery (12, 5, and 11 mmHg for systolic, diastolic, and mean arterial pressures, respectively). Blood pressures returned to predialysis ranges following the recovery period. Blood flow restriction did not affect ultrafiltration achieved or Kt/V. Hemodynamic safety and tolerability of blood flow restriction during aerobic exercise on hemodialysis is comparable to standard aerobic exercise.

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.

Virtual touch IQ elastography in evaluation of Achilles tendon in patients with chronic renal failure

PURPOSE

To evaluate the sonoelastographic changes in the Achilles tendon in patients with chronic renal failure (CRF) using virtual touch imaging quantification (VTIQ) elastography.

METHODS

Twenty-six patients undergoing three hemodialysis sessions per week and 26 subjects admitted to our institution between January 2016 and April 2016 were included in this prospective study. The characteristics and body mass index of the patients were noted. Ultrasonography was performed parallel to the long axis of the bilateral Achilles tendons during relaxation of the legs using the Siemens Acuson S3000™ ultrasound device (Siemens HealthCare, Erlangen, Germany). Tendon thickness was reviewed, and tissue stiffness was quantitatively assessed using VTIQ elastography. Independent samples t test and Mann-Whitney U test were used for statistical analyses.

RESULTS

The median values of shear wave velocities of the Achilles tendon in patients with CRF were 7.19 m/s (4.23-9.77 m/s) on the right and 6.98 m/s (4.00-9.82 m/s) on the left, while they were 5.11 m/s (4.09-8.82 m/s) on the right and 5.36 m/s (4.05-8.80 m/s) on the left in controls. The stiffness of the Achilles tendons in patients with CRF was found to be higher than that in controls (right: P < 0.001, left: P = 0.004). There was no statistically significant difference in tendon thickness between the CRF and control groups (P > 0.05).

CONCLUSION

The thickness and stiffness of tendon can be effectively evaluated with sonoelastography. The thickness of the Achilles tendon did not significantly differ between the patients with CRF and healthy subjects. However, the stiffness of the Achilles tendon measured with VTIQ elastography was demonstrated to be increased in the patients with CRF.

Hemodynamic Instability during Dialysis: The Potential Role of Intradialytic Exercise

Acute haemodynamic instability is a natural consequence of disordered cardiovascular physiology during haemodialysis (HD). Prevalence of intradialytic hypotension (IDH) can be as high as 20–30%, contributing to subclinical, transient myocardial ischemia. In the long term, this results in progressive, maladaptive cardiac remodeling and impairment of left ventricular function. This is thought to be a major contributor to increased cardiovascular mortality in end stage renal disease (ESRD). Medical strategies to acutely attenuate haemodynamic instability during HD are suboptimal. Whilst a programme of intradialytic exercise training appears to facilitate numerous chronic adaptations, little is known of the acute physiological response to this type of exercise. In particular, the potential for intradialytic exercise to acutely stabilise cardiovascular hemodynamics, thus preventing IDH and myocardial ischemia, has not been explored. This narrative review aims to summarise the characteristics and causes of acute haemodynamic instability during HD, with an overview of current medical therapies to treat IDH. Moreover, we discuss the acute physiological response to intradialytic exercise with a view to determining the potential for this nonmedical intervention to stabilise cardiovascular haemodynamics during HD, improve coronary perfusion, and reduce cardiovascular morbidity and mortality in ESRD.

Heart Rate Variability, Mortality, and Exercise in Patients with End-Stage Renal Disease

Context

Cardiac autonomic function has been associated with mortality in patients with end-stage renal disease. It is unknown whether end-stage renal disease patients who have succumbed to sudden cardiac death can be better identified by a newer test of heart rate variability that uses spectral analysis, rather than laboratory evoked measures.

Objective

This series of studies sought to characterize cardiac autonomic function in patients awaiting kidney transplantation, identify factors associated with heart rate variability, identify tests which distinguish patients at-risk for death, and compare evoked measures with 24-hour heart rate variability measures.

Patients

Data were collected on 184 nondiabetics, 60 type 1 diabetics, and 34 type 2 diabetics with end-stage renal disease, all of whom had been referred for kidney transplantation.

Main Outcome Measures

The 278 patients and 67 healthy control subjects underwent evoked tests (changes in heart rate with deep breathing and Valsalva maneuver) and 24-hour heart rate variability Holter monitoring (time and frequency domains). Five patients had sudden cardiac deaths during the study.

Results

Data showed that end-stage renal disease patients, particularly diabetics, had compromised autonomic function. The standard deviation of all R-to-R intervals for the electrocardiogram recording (<50 minutes in 60% of the deceased patients), a 24-hour heart rate variability time domain measure, holds the promise of identifying patients at increased risk for death. Exercise was identified as a factor associated with better autonomic function. Examining relationships between 24-hour heart rate variability and characteristics of patients who succumb to death could make quantification of the mortality risk for individual pretransplant end-stage renal disease patients possible, much as it has in other populations. The data from this study may also make it possible to design interventions, such as exercise, aimed at reducing mortality risk.

Clinical usefulness of response profiles to rapidly incremental cardiopulmonary exercise testing

The advent of microprocessed "metabolic carts" and rapidly incremental protocols greatly expanded the clinical applications of cardiopulmonary exercise testing (CPET). The response normalcy to CPET is more commonly appreciated at discrete time points, for example, at the estimated lactate threshold and at peak exercise. Analysis of the response profiles of cardiopulmonary responses at submaximal exercise and recovery, however, might show abnormal physiologic functioning which would not be otherwise unraveled. Although this approach has long been advocated as a key element of the investigational strategy, it remains largely neglected in practice. The purpose of this paper, therefore, is to highlight the usefulness of selected submaximal metabolic, ventilatory, and cardiovascular variables in different clinical scenarios and patient populations. Special care is taken to physiologically justify their use to answer pertinent clinical questions and to the technical aspects that should be observed to improve responses' reproducibility and reliability. The most recent evidence in favor of (and against) these variables for diagnosis, impairment evaluation, and prognosis in systemic diseases is also critically discussed.

Exercise training for adults with chronic kidney disease

BACKGROUND

Chronic kidney disease (CKD) is a worldwide public health problem. In the National Kidney Foundation Disease Outcomes Quality Initiative guidelines it is stressed that lifestyle issues such as physical activity should be seen as cornerstones of the therapy. The physical fitness in adults with CKD is so reduced that it impinges on ability and capacity to perform activities in everyday life and occupational tasks. An increasing number of studies have been published regarding health effects of various regular exercise programmes in adults with CKD and in renal transplant patients.

OBJECTIVES

We aimed to: 1) assess the effects of regular exercise in adults with CKD and kidney transplant patients; and 2) determine how the exercise programme should be designed (e.g. type, duration, intensity, frequency of exercise) to be able to affect physical fitness and functioning, level of physical activity, cardiovascular dimensions, nutrition, lipids, glucose metabolism, systemic inflammation, muscle morphology and morphometrics, dropout rates, compliance, adverse events and mortality.

SEARCH STRATEGY

We searched the Cochrane Renal Group's specialised register, CENTRAL, MEDLINE, EMBASE, CINAHL, Web of Science, Biosis, Pedro, Amed, AgeLine, PsycINFO and KoreaMed. We also handsearched reference lists of review articles and included studies, conference proceeding's abstracts. There were no language restrictions.Date of last search: May 2010.

SELECTION CRITERIA

We included any randomised controlled trial (RCT) enrolling adults with CKD or kidney transplant recipients undergoing any type of physical exercise intervention undertaken for eight weeks or more. Studies using less than eight weeks exercise, those only recommending an increase in physical activity, and studies in which co-interventions are not applied or given to both groups were excluded.

DATA COLLECTION AND ANALYSIS

Data extraction and assessment of study and data quality were performed independently by the two authors. Continuous outcome data are presented as standardised mean difference (SMD) or mean difference (MD) with 95% confidence intervals (CI).

MAIN RESULTS

Forty-five studies, randomising 1863 participants were included in this review. Thirty two studies presented data that could be meta-analysed. Types of exercise training included cardiovascular training, mixed cardiovascular and resistance training, resistance-only training and yoga. Some studies used supervised exercise interventions and others used unsupervised interventions. Exercise intensity was classed as 'high' or 'low', duration of individual exercise sessions ranged from 20 minutes/session to 110 minutes/session, and study duration was from two to 18 months. Seventeen per cent of studies were classed as having an overall low risk of bias, 33% as moderate, and 49% as having a high risk of bias.The results shows that regular exercise significantly improved: 1) physical fitness (aerobic capacity, 24 studies, 847 participants: SMD -0.56, 95% CI -0.70 to -0.42; walking capacity, 7 studies, 191 participants: SMD -0.36, 95% CI-0.65 to -0.06); 2) cardiovascular dimensions (resting diastolic blood pressure, 11 studies, 419 participants: MD 2.32 mm Hg, 95% CI 0.59 to 4.05; resting systolic blood pressure, 9 studies, 347 participants: MD 6.08 mm Hg, 95% CI 2.15 to 10.12; heart rate, 11 studies, 229 participants: MD 6 bpm, 95% CI 10 to 2); 3) some nutritional parameters (albumin, 3 studies, 111 participants: MD -2.28 g/L, 95% CI -4.25 to -0.32; pre-albumin, 3 studies, 111 participants: MD - 44.02 mg/L, 95% CI -71.52 to -16.53; energy intake, 4 studies, 97 participants: SMD -0.47, 95% CI -0.88 to -0.05); and 4) health-related quality of life. Results also showed how exercise should be designed in order to optimise the effect. Other outcomes had insufficient evidence.

AUTHORS' CONCLUSIONS

There is evidence for significant beneficial effects of regular exercise on physical fitness, walking capacity, cardiovascular dimensions (e.g. blood pressure and heart rate), health-related quality of life and some nutritional parameters in adults with CKD. Other outcomes had insufficient evidence due to the lack of data from RCTs. The design of the exercise intervention causes difference in effect size and should be considered when prescribing exercise with the aim of affecting a certain outcome. Future RCTs should focus more on the effects of resistance training interventions or mixed cardiovascular- and resistance training as these exercise types have not been studied as much as cardiovascular exercise.

Effects of modality change and transplant on peak oxygen uptake in patients with kidney failure

BACKGROUND

Exercise capacity as measured by peak oxygen uptake (Vo₂(peak)) is low in hemodialysis patients. The present study assesses determinants of VO₂(peak) in patients with chronic kidney failure who either changed kidney replacement modality to frequent hemodialysis therapy or received a kidney transplant.

STUDY DESIGN

Cohort study with assessment at baseline and 6 months after modality change.

SETTING & PARTICIPANTS

Participants included nondiabetic individuals receiving conventional hemodialysis who: (1) remained on conventional hemodialysis therapy (n = 13), (2) changed to short daily hemodialysis therapy (n = 10), or (3) received a transplant (n = 5) and (4) individuals who underwent a pre-emptive transplant (n = 15). Additionally, 34 healthy controls were assessed at baseline only.

PREDICTOR

Modality change.

MEASUREMENT & OUTCOMES

Exercise capacity, assessed using the physiologic components of the Fick equation (Vo₂ = cardiac output × a-vo₂(dif), where a-vo₂(dif) is arterial to venous oxygen difference) was determined using measurement of Vo₂(peak) and cardiac output during symptom-limited exercise testing. Analysis of covariance was used to compare differences in changes in Vo₂(peak), cardiac output, heart rate, stroke volume, and a-vo₂(dif) at peak exercise between participants who remained on hemodialysis therapy and those who underwent transplant.

RESULTS

Transplant was the only modality change associated with a significant change in Vo₂(peak), occurring as a result of increased peak cardiac output and reflecting increased heart rate without a change in peak a-vo₂(dif) despite increased hemoglobin levels. There were no differences in participants who changed to daily hemodialysis therapy compared with those who remained on conventional hemodialysis therapy.

LIMITATIONS

Small nonrandomized study.

CONCLUSIONS

Vo₂(peak) increases significantly after kidney transplant, but not with daily hemodialysis; this improvement reflects increased peak cardiac output through increased peak heart rate. Despite statistical significance, the increase in Vo₂(peak) was not clinically significant, suggesting the need for interventions such as exercise training to increase Vo₂(peak) in all patients regardless of treatment modality.

Determinants of exercise capacity in CKD patients treated with hemodialysis

There are many ways to measure physical functioning. Oxygen uptake at peak exercise is considered to be the most objective or 'gold-standard' measure and is determined by the integrated functioning of multiple physiological systems. Renal failure can affect the functioning of several of these systems which results in low levels of peak oxygen uptake. This review examines the determinants of oxygen uptake as defined by the Fick Equation, and presents data from studies that have reported these physiological measures. It becomes clear that there are many factors that may limit peak oxygen uptake in these patients and any one mechanism may be difficult to identify.

Factors limiting physical working capacity in predialytic uraemic patients

The exercise capacity of 20 predialytic uraemic patients (mean age 43 +/- 12 years) was studied prospectively. Nine of these patients were examined twice in a longitudinal study. The maximal working capacity, measured by standardized exercise test on a bicycle ergometer, averaged 74 +/- 19% of the expected normal. Normal exercise ECG were registered in 16 out of 20 patients. Total hemoglobin/kg body weight (THb) was 67 +/- 16% of the expected normal and serum parathyroid hormone concentration (PTH) was 39 +/- 39 micrograms/l (normal range 0.5-1.5). Partial correlation showed a correlation between exercise capacity and PTH (p less than 0.05). In the longitudinal study the decrease in steady state exercise capacity was correlated to the decrease in THb (p less than 0.05), but not to the increase in PTH. In conclusion, patients with predialytic uraemia have a reduced maximal working capacity, due to several possible factors one of which is a reduced THb. Ischaemic heart disease seems to be of minor importance.

Exercise pressor reflex in humans with end-stage renal disease

Previous work has suggested that end-stage renal disease (ESRD) patients may have an exaggerated sympathetic nervous system (SNS) response during exercise. We hypothesized that ESRD patients have an exaggerated blood pressure (BP) response during moderate static handgrip exercise (SHG 30%) and that the exaggerated BP response is mediated by SNS overactivation, characterized by augmented mechanoreceptor activation and blunted metaboreceptor control, as has been described in other chronic diseases. We measured hemodynamics and muscle sympathetic nerve activity (MSNA) in 13 ESRD and 16 controls during: 1) passive hand movement (PHM; mechanoreceptor isolation); 2) low-level rhythmic handgrip exercise (RHG 20%; central command and mechanoreceptor activation); 3) SHG 30%, followed by posthandgrip circulatory arrest (PHGCA; metaboreceptor activation); and 4) cold pressor test (CPT; nonexercise stimulus). ESRD patients had exaggerated increases in systolic BP during SHG 30%; however, the absolute and relative increase in MSNA was not augmented, excluding SNS overactivation as the cause of the exaggerated BP response. Increase in MSNA was not exaggerated during RHG 20% and PHM, demonstrating that mechanoreceptor activation is not heightened in ESRD. During PHGCA, MSNA remained elevated in controls but decreased rapidly to baseline levels in ESRD, indicative of markedly blunted metaboreceptor control of MSNA. MSNA response to CPT was virtually identical in ESRD and controls, excluding a generalized sympathetic hyporeactivity in ESRD. In conclusion, ESRD patients have an exaggerated increase in SBP during SHG 30% that is not mediated by overactivation of the SNS directed to muscle. SBP responses were also exaggerated during mechanoreceptor activation and metaboreceptor activation, but without concomitant augmentation in MSNA responses. Metaboreceptor control of MSNA was blunted in ESRD, but the overall ability to mount a SNS response was not impaired. Other mechanisms besides SNS overactivation, such as impaired vasodilatation, should be explored to explain the exaggerated exercise pressor reflex in ESRD.

Physical activity patterns in chronic hemodialysis patients: comparison of dialysis and nondialysis days

OBJECTIVE

To determine physical activity patterns in chronic hemodialysis patients with a specific emphasis on the difference between dialysis and nondialysis days. Design A cross-sectional single-center study.

SETTING

Vanderbilt University Outpatient Dialysis Unit.

PATIENTS

Twenty current chronic hemodialysis patients: 10 male, 10 female; 15 black, 5 white; mean age, 50.1 +/- 9.9 years; height, 164.5 +/- 10.9 cm; weight, 82.5 +/- 15.4 kg; length on dialysis, 57.3 +/- 45.3 months.

METHODS

Minute-by-minute physical activity was assessed over a 7-day period using a triaxial accelerometer, which consists of raw numbers or counts calculated by the 3 axes of the accelerometer (PA counts). PA counts were extrapolated on a daily and hourly basis. Physical functioning tests included: sit-to-stand, 6-minute walk, and 1-repetition maximal leg press exercise. Laboratory values for serum concentrations of albumin, prealbumin, C-reactive protein, and cholesterol were also collected.

MAIN OUTCOME MEASURE

PA counts.

RESULTS

Total PA counts were significantly lower on dialysis days when compared with nondialysis days (128,279 +/- 74,009 versus 168,744 +/- 95,168, respectively, P = .025). The average PA counts during the 4-hour dialysis time period were significantly lower on dialysis days when compared with nondialysis days (3,086 +/- 3,749 versus 11,070 +/- 7,695, respectively, P = .001). At postdialysis hours 1 and 2, PA counts on dialysis days were significantly higher than on nondialysis days (11,410 +/- 5,340 versus 9,082 +/- 6,646, P = .008, and 14,048 +/- 9,728 versus 8,662 +/- 6,433, P = .016, respectively). By postdialysis hour 4, PA counts on dialysis days had significantly decreased when compared with nondialysis days (6,068 +/- 6,268 versus 10,512 +/- 7,420 PA counts, P = .01, respectively). From postdialysis hours 5 to 20, there was no significant difference in PA counts between dialysis and nondialysis days.

CONCLUSION

This study shows that physical activity is lower on dialysis days when compared with nondialysis days, and this decrease is caused by the lack of activity during the 4-hour hemodialysis procedure. New behavior modification strategies involving physical activity, both during hemodialysis and on nondialysis days, must be examined in this patient population.

Similarities in skeletal muscle strength and exercise capacity between renal transplant and hemodialysis patients

Exercise intolerance is common in hemodialysis (HD) and renal transplant (RTx) patients. Aim of the study was to assess to what extent exercise capacity and skeletal muscle strength of RTx patients differ from HD patients and healthy controls and to elucidate potential determinants of exercise capacity in RTx patients. Exercise capacity, muscle strength, lean body mass (LBM) and physical activity level (PAL) were measured by cycle-ergometry, isokinetic dynamometry, DEXA and Baecke Questionnaire, respectively, in 35 RTx, 16 HD and 21 controls. VO2peak and muscle strength of the RTx patients were significantly lower compared to controls (p<0.01), but not different compared to HD patients. In RTx patients, strength (p<0.001), PAL (p=0.001) and age (p=0.045) were significant predictors of VO2peak. Muscle strength was related to LBM (p=0.001) and age (p=0.001), whereas gender (p<0.001) and renal function (p=0.01) turned out to be significant predictors of LBM. No effects of corticosteroids were observed. Exercise capacity and muscle strength seem equally reduced in RTx and HD patients compared to controls. In RTx patients, muscle strength and PAL are highly related to exercise capacity. Renal function appears to be a significant predictor of LBM, and through the LBM, of muscle strength and exercise capacity.

Physical functioning in end-stage renal disease patients: Update 2005

Physical functioning in patients with end-stage renal disease treated with dialysis is low, whether measured using objective laboratory measures, physical performance testing, or self-reported measures. Peak oxygen uptake (VO2peak), self-reported functioning measures, and physical activity levels are independent predictors of mortality in these patients. Cardiovascular exercise training studies result in improvements in VO2peak, physical performance tests, and self-reported functioning. Resistance exercise training improves muscle strength. Exercise training may have positive benefits on other factors that are important clinical issues in dialysis patients, including cardiovascular risk profile, oxidative stress, and inflammation. Endothelial function, a surrogate marker of atherosclerosis, has been shown to improve with exercise training in dialysis patients. Although there have been numerous recent studies on benefits of exercise, few dialysis clinics or nephrologists provide encouragement or programs as a part of their routine care of their patients. There are many national guidelines that include exercise or increasing physical activity as a part of the treatment of many conditions that are relevant in dialysis patients, including hypertension, hyperlipidemia, and high cardiovascular disease risk. The nephrology community continues to state concern for outcomes; however, a simple, low-tech intervention that has many benefits to their patients (i.e., encouragement, recommendations, and opportunity for increasing physical activity) has not been adopted as part of the standard care. Adoption of routine counseling and encouragement for physical activity has the potential to improve outcomes, improve physical functioning, and optimize quality of life and overall health of dialysis patients.

Exercise capacity and muscle structure in kidney recipient and twin donor

Exercise capacity and muscle function are known to be abnormal in patients with renal disease. We present a case study in which we studied a kidney transplant recipient who received a kidney from his identical twin. Testing included maximal exercise testing with measurement of oxygen uptake (VO2max), isokinetic muscle function testing, body composition analysis using dual energy X-ray absorptiometry (DEXA) imaging and quality of life using The Medical Outcomes Short Form (SF-36) questionnaire. Muscle biopsies were also analysed for fibre composition and size and ultrastructure. We found that the twin recipient had lower values for VO2max, muscle strength, muscle mass and quality of life scales (physical domains) compared with the twin donor. Muscle fibre composition was identical in the twins, however, muscle fibres size was reduced in the twin donor in Type I, and Type IIA fibre types. The twin recipient also showed lower fibre density (volume percentage) and greater intrafibrillar space than the donor. The twins were both sedentary, thus we conclude that the low exercise capacity and abnormalities observed in the recipient are characteristics of renal failure, and not the result of physical deconditioning, nor was it related to prednisone therapy, which may negatively affect muscle function.

Muscle atrophy in patients receiving hemodialysis: effects on muscle strength, muscle quality, and physical function

BACKGROUND

Dialysis patients are less active and have reduced functional capacity compared to individuals with normal renal function. Muscle atrophy and weakness may contribute to these problems. This investigation was undertaken to quantify the extent of atrophy in the lower extremity muscles, to determine whether defects in muscle specific strength (force per unit mass) or central nervous system (CNS) activation are present, and to assess the relationship between muscle size and physical performance in a group of patients on hemodialysis.

METHODS

Thirty-eight dialysis subjects (aged 55 +/- 15 years) and nineteen healthy sedentary controls (aged 55 +/- 13 years) were enrolled. Magnetic resonance imaging of the lower leg was used to determine the total cross-sectional area (CSA) and the area of contractile and non-contractile tissue of the ankle dorsiflexor muscles. Isometric dorsiflexor strength was measured during a maximal voluntary contraction with and without superimposed tetanic stimulation (N = 22 for dialysis subjects, N = 12 for controls). Physical activity was measured by accelerometry, and gait speed was recorded as a measure of physical performance.

RESULTS

Dialysis subjects were weaker, less active, and walked more slowly than controls. Total muscle compartment CSA was not significantly different between dialysis subjects and controls, but the contractile CSA was smaller in the dialysis patients even after adjustment for age, gender, and physical activity. Central activation and specific strength were normal. Gait speed was correlated with contractile CSA.

CONCLUSIONS

Significant atrophy and increased non-contractile tissue are present in the muscle of patients on hemodialysis. The relationship between contractile area and strength is intact in this population. Muscle atrophy is associated with poor physical performance. Thus, interventions to increase physical activity or otherwise address atrophy may improve performance and quality of life.

Assessing the efficacy of exercise training in patients with chronic disease

PURPOSE

The purpose of this study was to evaluate the meaningfulness of exercise training responses in patients with end stage renal disease (ESRD).

METHODS

Eighteen ESRD patients [(mean +/- SD); 54.3 +/- 17.1 yr] completed a training regime progressing to accumulate 40 min of stationary cycling, three times per week for 6 months. .VO(2peak) determined via incremental cycle ergometer protocol, and .VO(2) kinetics determined from a transition from unloaded pedalling to an exercise intensity corresponding to 90% of VT, were assessed at baseline and at 3 and 6 months of training.

RESULTS

Repeated measures analysis of variance revealed significant changes (P < 0.05) on the time factor for .VO(2peak), VO(2)-V(T), and .VO(2) kinetics. Post hoc analysis revealed that .VO(2peak) and .VO(2) kinetics significantly (P < 0.05) improved at 3 months of training with no further improvements thereafter. Analysis of individual subject response data revealed that after 3 months of training, 61% of the patients improved .VO(2peak) by greater than the standard error of measurement (SEM = 0.07 L.min(-1)). At 6 months of training, approximately 89% of the patients improved by more than the SEM .VO(2) kinetics improved by more than the SEM (12.3 s) at 3 months of training in approximately 55% of the patients, with no increase in the number of patients exhibiting faster time constants after 6 months of training.

CONCLUSION

Although conventional statistical analyses indicate that exercise training favorably alters .VO(2peak) and oxygen uptake kinetics of patients with ESRD, it is apparent that considerable interindividual variability exists in the response to training. Consideration of the SEM data underscores the heterogeneity of adaptive response in this patient group and may be valuable in assessing the efficacy of therapeutic exercise rehabilitation.

Effects of regular exercise on anxiety, depression, and quality of life in maintenance hemodialysis patients

BACKGROUND

Psychological problems such as depression and anxiety are common in hemodialysis patients. In several studies, exercise programs were effective in relieving depression or anxiety in these patients, although not all agree.

PURPOSE

In this study, we evaluated the effects of an exercise program on exercise capacity, anxiety, depression and quality of life in maintenance hemodialysis patients.

METHODS

Twenty hemodialysis patients were enrolled in the study. Six patients were later excluded; two due to anemia, one due to nausea with vomiting during exercise, one due to a neurologic problem, and the other two due to noncompliance. Thus, fourteen patients, 3 men and 11 women, aged 42 +/- 10 years, completed the study. The exercise program composed of bicycle ergometer, treadmill or upper limb ergometer, 60 min per session, 3 times per week, for 12 weeks. At the beginning and the end of the exercise program, the exercise capacity was determined by measuring the maximal oxygen consumption and exercise duration. In addition, psychological tests for the assessment of depression, anxiety and quality of life were performed.

RESULTS

Maximal oxygen consumption was increased from 26.3 +/- 4.6 mL/kg/min to 29.8 +/- 4.9 mL/kg/min (p = 0.013). Exercise duration was 483 +/- 138 s at the start. At the end of the exercise program it was increased to 607 +/-119s (p = 0.002). The score of anxiety was significantly improved from 47.9 +/- 5.9 to 42.8 +/- 6.3 after exercise (p = 0.004). Though it did not reach statistical significance there was a trend of improvement in depression (from 44.8 +/- 8.4 to 39.7 +/- 6.4, p = 0.073). The score of quality of life also showed a significant improvement (from 124.5 +/- 16.5 to 133.6 +/- 19.3, p = 0.031).

CONCLUSION

The results of this study indicate that an appropriate application of exercise program would improve the psychological status in long-term maintenance hemodialysis patients.

Clinical and demographic predictors of exercise capacity in end-stage renal disease

Patients on maintenance hemodialysis therapy for end-stage renal disease have reduced exercise tolerance. Multiple processes related to uremia and hemodialysis have been implicated in the pathophysiology of this impairment. However, limited data are available to identify the separate and combined effects of clinical factors on the degree of impairment for individuals within this population. For this purpose, data from 193 patients who had undergone exercise testing for two clinical trials were retrospectively analyzed. Univariate and multiple linear regression analyses were used to identify demographic and clinical correlates of peak exercise oxygen uptake (VO2). Peak VO2 averaged 18.5 +/- 6.4 mL/min/kg. On univariate analysis, peak VO2 correlated positively with male sex and hemoglobin, serum albumin, and serum creatinine concentrations and correlated negatively with dialytic age and diagnosis of diabetes or chronic heart failure. In a multiple linear regression model, sex, hemoglobin concentration, age, and diagnosis of diabetes each remained statistically significant. Together, factors included in the model accounted for 41% of the variability in peak VO2 (P = 0.0001). Among factors not correlating significantly with peak VO2 were resting blood pressure, serum carnitine level, and urea clearance assessed by Kt/V. Findings show the range of exercise impairment among clinically stable ambulatory hemodialysis patients, which may be sufficient to interfere with normal daily activities for many of these patients. Although this impairment may be broadly attributable to physiological consequences of uremia, the degree of impairment for individual patients is predicted by demographic factors, coexistent disease, and factors potentially modified by medical therapeutics.

Heart rate variability, mortality, and exercise in patients with end-stage renal disease

CONTEXT

Cardiac autonomic function has been associated with mortality in patients with end-stage renal disease. It is unknown whether end-stage renal disease patients who have succumbed to sudden cardiac death can be better identified by a newer test of heart rate variability that uses spectral analysis, rather than laboratory evoked measures.

OBJECTIVE

This series of studies sought to characterize cardiac autonomic function in patients awaiting kidney transplantation, identify factors associated with heart rate variability, identify tests which distinguish patients at-risk for death, and compare evoked measures with 24-hour heart rate variability measures.

PATIENTS

Data were collected on 184 nondiabetics, 60 type 1 diabetics, and 34 type 2 diabetics with end-stage renal disease, all of whom had been referred for kidney transplantation.

MAIN OUTCOME MEASURES

The 278 patients and 67 healthy control subjects underwent evoked tests (changes in heart rate with deep breathing and Valsalva maneuver) and 24-hour heart rate variability Holter monitoring (time and frequency domains). Five patients had sudden cardiac deaths during the study.

RESULTS

Data showed that end-stage renal disease patients, particularly diabetics, had compromised autonomic function. The standard deviation of all R-to-R intervals for the electrocardiogram recording (< 50 minutes in 60% of the deceased patients), a 24-hour heart rate variability time domain measure, holds the promise of identifying patients at increased risk for death. Exercise was identified as a factor associated with better autonomic function. Examining relationships between 24-hour heart rate variability and characteristics of patients who succumb to death could make quantification of the mortality risk for individual pretransplant end-stage renal disease patients possible, much as it has in other populations. The data from this study may also make it possible to design interventions, such as exercise, aimed at reducing mortality risk.

Cardiac effects of exercise rehabilitation in hemodialysis patients

Exercise training has well documented beneficial effects in a variety of cardiac disorders. End stage renal disease patients present many cardiovascular complications and suffer from impaired exercise capacity. No study to date has adequately examined the cardiac responses to exercise training in renal patients on hemodialysis (HD). To determine the effects of an exercise rehabilitation program on the left ventricular function at rest and during submaximal effort, 38 end-stage renal disease patients on maintenance HD were randomised into three groups. Sixteen of them (group A--mean age 46.4+/-13.9 years), without clinical features of heart failure, participated in a 6-month supervised exercise renal rehabilitation program consisting of three weekly sessions of aerobic training, 10 (group B--mean age 51.4+/-12.5 years) followed a moderate exercise program at home, and the other 12 (group C--mean age 50.2+/-7.9 years) were not trained and remained as controls. The level of anemia and the HD prescription remained constant during the study. Fifteen sex- and age-matched sedentary individuals (group D--mean age 46.9+/-6.4 years) were the healthy controls. All subjects at the start and end of the program underwent physical examination, laboratory tests, treadmill exercise testing, M-mode and 2-D echocardiograms performed at rest and at peak of supine bicycle exercise. Left ventricular volumes (EDV, ESV) and mass (LVM) were measured and ejection fraction (EF), stroke volume index (SVI) and cardiac output index (COI) were calculated by standard formulae. The maximal oxygen consumption increased by 43% (P<0.001) and the exercise time by 33% (P<0.001) after training in group A, by 17% (P<0.001) and 14% (P<0.01), respectively, in B, and both remained unchanged in group C. Training in group A was also associated with an increase in LVIDd (from 52.1+/-6.4 to 54.0+/-6.1 mm, P<0.001) and LVM (226+/-67 to 240+/-84 g, P<0.05) at rest with no change noted in groups B and C. Following a 6-month exercise training in group A an increase was also found in the resting EF by 5% (P<0.01) and SVI by 14% (P<0.001). There was no change found in groups B and C. Supine bicycle exercise after training in group A was associated with an improvement in EF by 14% compared to the pre-training change (P<0.001), SVI by 14% (P<0.001) and COI by 73% (P<0.001). These changes from rest to submaximal exercise were less pronounced in group B following training at home. The untrained patients demonstrated no changes in LV systolic function over the 6-month period. These results demonstrate that intense exercise training improves LV systolic function at rest in HD patients; both intense and moderate physical training leads to enhanced cardiac performance during supine submaximal exercise.

The role of exercise in rehabilitation for patients with end-stage renal disease

End-stage renal disease (ESRD) is a major health problem in the United States. Many patients with ESRD experience a decline in physical functioning as a result of the disease process and its associated sequelae. Cardiovascular changes, anemia, and skeletal muscle weakness contribute significantly to this decreased capacity, leading, in many instances, to a primarily sedentary lifestyle. Studies conducted on the effectiveness of exercise training for patients with ESRD reveal numerous physiological and psychological benefits, particularly when training is continued for several months. However, the number of structured exercise programs available as part of a rehabilitation program for ESRD patients is limited. This article provides an overview of the role of exercise for patients with renal disease, and a case study illustrates how nurses, in collaboration with the interdisciplinary team, can be effective in preventing continued deconditioning and in maintaining a more positive outlook in patients with ESRD.

Effects of the correction of renal anaemia by erythropoietin on physiological changes during exercise

The effects of treating the anaemia of end-stage renal failure with erythropoietin were studied in nine dialysis patients. The increase in haemoglobin concentration (by 59% from 7.0 +/- 1.2 to 11.1 +/- 1.1 g dl-1) was associated with increases in exercise duration (by 41%) and maximum oxygen consumption (by 34%). Treatment reduced resting heart rate but did not significantly alter heart rate at maximum exercise, nor resting or exercise blood pressure. Resting arterial potassium concentrations were slightly increased after treatment, but they increased similarly in relation to minute ventilation during exercise. Lactic acidaemia developed during exercise at both levels of haemoglobin, and was accompanied by similar reductions in arterial pH and bicarbonate levels but constant PaO2 and PaCO2. Ventilation was coupled to the metabolic rate of carbon dioxide production, ventilatory dead-space and arterial PCO2 before and after treatment of anaemia, the ventilatory requirement for carbon dioxide elimination being unchanged. Treatment of anaemia did not alter resting arterial lactate concentration; the concentration of lactate at maximum exercise was increased slightly following treatment but this increase did not reach statistical significance. The rate of increase in arterial lactate concentration as a function of oxygen consumption, assessed both with respect to the 'lactate threshold' and 'lactate slope index', was significantly delayed by treatment. Treatment of anaemia also delayed the 'anaerobic threshold', and there was good correlation between lactate and anaerobic thresholds. Treatment of renal anaemia by erythropoietin thus results in improved tissue oxygen supply during exercise, reflected by delay in the onset of lactic acidaemia.

Improvement in exercise capacity after correction of anemia in patients with end-stage renal failure

Changes in exercise tolerance occurring after correction of anemia with recombinant human erythropoietin in a group of patients with end-stage renal failure were evaluated. Ten patients, aged 29 +/- 11 years, on chronic hemodialysis treatment, with no associated diseases, were evaluated by cardiopulmonary bicycle exercise testing and M-mode, 2-dimensional and pulsed doppler echocardiography before and after anemia correction. After 1 and 3 months of therapy, hemoglobin plasma levels increased from 5.9 +/- 1.2 to 7.7 +/- 1.3 and 9.9 +/- 1.4 g/dl, with a concomitant increase in peak oxygen consumption (VO2) from 21.4 +/- 4.3 to 24.4 +/- 4.3 and 26.6 +/- 4.6 ml/kg/min and of VO2 at the ventilatory threshold from 15.0 +/- 3.7 to 17.3 +/- 3.7 and 16.8 +/- 3.4 ml/kg/min. After 3 months of therapy, systolic blood pressure significantly decreased both at peak exercise (159 +/- 35 to 134 +/- 22 mm Hg) and ventilatory threshold (140 +/- 27 to 123 +/- 19 mm Hg), whereas cardiac index at rest decreased from 3.3 +/- 0.7 to 2.8 +/- 0.5 liters/min/m2 and heart rate from 77 +/- 12 to 70 +/- 10 beats/min. However, no significant relation was found between hemoglobin plasma levels and peak VO2, whereas a significant relation was found between hemoglobin concentration and cardiac index at rest.

Factors affecting adherence of end-stage renal disease patients to an exercise programme

Recently it has been shown that regular exercise is both physiologically and psychologically beneficial to patients with end-stage renal disease (ESRD). However, ESRD patients traditionally have a high non-adherence level to their self-care and medical regimens. To date, their adherence to exercise programmes has not been studied. Background information about employment, medical history, previous exercise habits and locus of control was obtained from 40 volunteer ESRD patients who started exercise at home. Twenty-eight participants maintained the exercise programme, consisting of aerobic activity lasting an average of 25 min, four times per week, for 12 weeks. The adherent patients were found to have encouraging support groups (75 versus 25%), to be between 41 and 60 years of age (64 versus 33%), to have been on dialysis for between 2 and 5 years, and to have loci of control (feeling of control over life events) classed as 'internal' (68 versus 25%). Factors such as sex, race, employment status and depression were found to have little influence on adherence. The major finding of this study was that patients adherent to exercise could be distinguished by unique psychological and psychosocial factors, and that adherence in this population was higher (70 compared with 50%) than some estimates for the general population.

Spiroergometric performance of children and adolescents with chronic renal failure

Maximal physical performance (Wmax), maximal oxygen consumption (VO2max), maximal carbon dioxide production (VCO2max) and blood lactate (L) levels were measured in 34 paediatric patients with chronic renal failure (CRF) and 25 controls by spiroergometric testing on a bicycle ergometer. No patient was treated with erythropoietin. The workload was increased step-wise by 0.5 W/3 min up to a Wmax determined from the attainment of VO2max. In patients on conservative treatment (CT), on haemodialysis (HD) and after transplantation (TP) median Wmax per kilogram body weight was reduced to 76%, 73% and 73% of controls (C), respectively. In CT and HD patients VO2max and VCO2max were decreased to an even higher extent. The ventilatory anaerobic threshold, calculated from the levelling off of the respiratory equivalent (VE/VO2) during increasing workload, was only slightly higher in patients than in C when related to Wmax (NS). The physiological rise in L during exercise was blunted in CRF; 72% of patients on CT or HD did not exceed the expected threshold L level of 4 mmol/l; after TP the L changes normalized. The findings indicate that most children and adolescents with CRF are able to attain maximal physical performance but both the aerobic and the anaerobic capacity are often reduced. Preliminary findings indicate that treatment of renal anaemia with erythropoietin is able to considerably improve Wmax and VO2max in paediatric HD patients.

Factors influencing physical working capacity in renal transplant patients

Clyne N, Jogestrand T, Lins L-E & Pehrsson SK. Division of Nephrology and Cardiology, Department of Medicine and Department of Clinical Physiology, Karolinska Hospital, Stockholm, Sweden. We have examined uraemic patients' exercise capacity, and the factors influencing this capacity, before and after successful renal transplantation. Eleven uraemic patients (mean age 41 +/- 10 years) with an average glomerular filtration rate (GFR) of 5 +/- 4 ml/min x 1.73 before and 45 +/- 19 ml/min x 1.73 after transplantation participated in the study. The maximal exercise capacity, measured by standardized exercise test on a bicycle ergometer, averaged 106 +/- 25 W before and 126 +/- 35 W (p less than 0.05) after transplantation. The patients interrupted the tests prior to and after transplantation because of general fatigue, leg tiredness or both. No patient experienced angina pectoris. All, but one, had a normal ECG reaction during exercise. Total haemoglobin (THb) was 55 +/- 8% of the expected normal before and 84 +/- 19% after transplantation (p less than 0.01). The increase in working capacity was linearly correlated to the increase in THb (r = 0.84, p less than 0.01), but not to the improvement in GFR nor to the decrease in parathyroid hormone. In conclusion, successful renal transplantation improves working capacity. The results indicate that an increased THb is a major determinant for this increase in working capacity.

Metabolic response to exercise in dialysis patients

The metabolic and hormonal response to acute moderate intensity (40% of VO2 max) bicycle exercise was examined in eight uremic subjects maintained on chronic dialysis and in 12 age- and weight-matched controls before and after the administration of low dose, selective (metoprolol) and nonselective (propranolol), beta adrenergic antagonists. The fasting plasma glucose concentration and basal rates of hepatic glucose production (HGP) and tissue glucose disappearance (Rd) were similar in control and uremic subjects. In both groups HGP and Rd increased in parallel during exercise, and the plasma glucose concentration remained constant at the fasting level. However, the increments in Rd (2.27 +/- 0.27 vs. 0.87 +/- 0.31 mg/kg.min, P less than 0.01) and HGP (2.47 +/- 0.22 vs. 0.92 +/- 0.19 mg/kg.min, P less than 0.01) were 2.5-3 fold greater in the control compared to uremic subjects. Although the VO2max was decreased by 50% (39 +/- 2 vs. 20 +/- 2 ml/min.kg; P less than 0.01), the correlation between Rd and VO2max was weak (r = 0.33, P less than 0.10), suggesting that factors other than diminished physical fitness contribute to diminished tissue uptake of glucose in the dialyzed uremic patients. Following the cessation of exercise, HGP and Rd promptly returned toward basal levels in both uremic and control subjects. The glucose homeostatic response to exercise was not significantly altered by either propranolol or metoprolol. In the postabsorptive state fasting levels of insulin, glucagon, epinephrine, and norepinephrine all were significantly increased in the uremic group (P less than 0.01 to 0.05). During exercise in the healthy young controls the plasma insulin concentration declined and plasma epinephrine and norepinephrine levels rose three- to fourfold. In contrast, in uremics plasma insulin failed to fall (P less than 0.05) and the increase in circulating epinephrine and norepinephrine levels was markedly impaired (P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Acid-base and electrolyte changes following maximal and submaximal exercise in hemodialysis patients

Maximal treadmill exercise was conducted in nine hemodialysis patients and in 15 unconditioned healthy subjects. Exercise capacity in the dialysis patients, as measured by duration of exercise, maximal oxygen consumption (VO2 max), and workload achieved (METS) was approximately 50% of that of the nonuremic volunteers. Four of the dialysis patients were studied on both dialysis (predialysis) and nondialysis days and also at 60% of VO2 max for 30 minutes on a nondialysis day. In these individuals, serum electrolytes, acid-base, and biochemical parameters were analyzed preexercise and at regular intervals following cessation of treadmill exercise. Transient metabolic acidosis and mild hyperkalemia developed after maximal exercise but not after prolonged submaximal exercise. Patients were slightly more acidotic and hyperkalemic on a dialysis day compared to a nondialysis day. Cardiopulmonary performance was similar on both days. These changes in serum electrolytes and acid-base parameters provide documentation of the extent of biochemical changes that develop following exercise in dialysis patients.

Exercise tolerance changes following renal transplantation

Maximal exercise capacity was measured in 20 nondiabetic patients with end-stage renal disease before and soon after successful renal transplantation. Maximal oxygen consumption increased significantly in all patients posttransplant. Increases in maximal heart rate and heart rates at 70% of maximal levels were also observed. The changes in maximal oxygen consumption were not significantly correlated with changes in hematocrit. The removal of uremia may result in improved functioning of one or more of the systems involved in oxygen transport and utilization that determine exercise capacity.

Arterial hypotension in chronic hemodialyzed patients

We studied in 32 patients on maintenance hemodialysis (duration of treatment 6 to 133 months) whether duration of dialysis treatment affects blood pressure, plasma noradrenaline levels and alpha 2-adrenoceptor density (assessed in platelet membranes by 3H-yohimbine binding). Plasma noradrenaline levels were a significant inverse correlation to platelet alpha 2-adrenoceptor density. In addition, mean arterial blood-pressure, plasma noradrenaline levels and platelet alpha 2-adrenoceptor density were significantly related to the duration of treatment: with increasing duration of treatment plasma noradrenaline levels increased, whereas mean arterial blood-pressure and platelet alpha 2-adrenoceptor density decreased. Furthermore, changes in mean arterial blood-pressure were inversely related to plasma noradrenaline levels and positively to platelet alpha 2-adrenoceptor density. Platelet alpha 2-adrenoceptor changes were accompanied by similar alterations in (vascular) alpha 1-adrenoceptor responsiveness (assessed by blood pressure responses to i.v. injections of phenylephrine); in hypotensive hemodialysis patients, who had high, plasma noradrenaline levels and low, platelet alpha 2-adrenoceptor density, the dose of phenylephrine necessary to increase systolic blood pressure by 20 mm Hg was nearly twice as high as in normotensive dialysis patients and healthy controls. In autonomic tests, Valsalva-ratio was lower in hypotensive than in normotensive dialysis patients and healthy controls, whereas no differences were found in blood pressure and heart rate responses during sustained hand-grip exercise as well as in beat-to-beat variation during deep breathing.(ABSTRACT TRUNCATED AT 250 WORDS)

Graded exercise testing and training after renal transplantation: a preliminary study

Aerobic exercise training has been used as part of the treatment for a variety of chronic disorders, most notably cardiovascular disease. In order to determine the feasibility and utility of regular exercise after renal transplantation, the responses of 10 patients to graded exercise testing were compared before training (T1), immediately after a program of supervised exercise training (T2), and a mean of 2.2 years after completion of the supervised program (T3). Supervised exercise sessions began a mean of 17 days postoperatively and continued for a mean of 5.5 weeks. Patients were encouraged to continue regular unsupervised exercise thereafter. All patients easily tolerated the supervised exercise sessions, which consisted of treadmill walking and cycle ergometry. Exercise capacity improved 90% between T1 and T2 and an additional 12% between T2 and T3. On the average, patients achieved a normal exercise capacity by 8 weeks after transplantation. Of the 10 patients, 7 had continued regular exercise training at T3. The observed increase in aerobic exercise capacity was probably related to improved renal function, an increased hemoglobin concentration, and the surgical healing process as well as the exercise training. We conclude that supervised exercise training for selected patients after renal transplantation is feasible and worthwhile.

Exercise in end-stage renal disease

Available studies indicate that exercise tolerance in renal patients is low. Although significant improvements in maximal oxygen consumption have been reported following exercise training in these patients, there may be physiologic limitations to the attainable levels of aerobic capacity due to the multisystemic nature of the disease. Long-term exercise training may result in other medical benefits. Compliance to regular exercise in hemodialysis patients remains a problem, however, exercise training during the dialysis treatment may prove beneficial in terms of compliance and supervision.

Exercise capacity in chronic renal failure patients managed by continuous ambulatory peritoneal dialysis

Exercise capacity is documented to be poor in patients with end stage renal failure undergoing regular hemodialysis, but there is little information about exercise capacity in patients on continuous ambulatory peritoneal dialysis (CAPD). We studied a group of 18 patients undergoing CAPD, with a variety of cardiorespiratory disorders, using a progressive load treadmill exercise test. The influence of intraperitoneal fluid on work capacity was also assessed. The mean maximum oxygen uptake (VO2max) of the CAPD patients was reduced considerably (14.6 ml kg-1 min-1) compared with matched control subjects (33.6 ml kg-1 min-1). This corresponded to the difficulty experienced by these patients in carrying out daily activities. There was no significant change in VO2max or in maximum heart rate with the peritoneal cavity full. We conclude that physical fitness is poor in CAPD patients and that the infusion of dialysis fluid into the peritoneal cavity does not affect physical work capacity further.