Cardiovascular response to submaximal stationary cycling during hemodialysis

Exercise intolerance is a problem in renal failure. Stationary cycle training during hemodialysis treatment is recommended as safe, effective, and practical, but requires compensations for both exercise and acute changes in uremia. Eight patients pedalled for 5 minutes, at 60% of VO2peak, at 0, 1, 2, and 3 hours of a hemodialysis treatment. Fluid removed, blood pressure, cardiac output, heart rate, O2 uptake, hematocrit, and arterial O2 content were measured. Mean arterial blood pressure, systemic vascular resistance, stroke volume, (a-v)O2 difference, and mixed-venous O2 content were calculated. Fluid removed was 1,356 mL/hr (P < 0.002 for each hour), but with no significant cardiovascular effects during the first 2 hours. At 3 hours, decreasing cardiac output, stroke volume, and mean arterial pressure all reached significance at rest (P < 0.05), and five of eight patients could not exercise. We conclude that the cardiovascular exercise response is superimposed on hemodynamic effects of dialysis and is adequately stable during the first 2 hours of treatment. After 2 hours, cardiovascular decompensation may preclude exercise.     

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.     

The functional, metabolic, and anabolic responses to exercise training in renal transplant and hemodialysis patients

BACKGROUND: Exercise intolerance is common in hemodialysis (HD) and renal transplant (RTx) patients and is related to muscle weakness. Its pathogenesis may vary between these groups leading to a different response to exercise. The aim of the study was to compare intrinsic muscular parameters between HD and RTx patients and controls, and to assess the response to exercise training on exercise capacity and muscular structure and function in these groups. METHODS: Quadriceps function (isokinetic dynamometry), body composition (dual-energy x-ray absorptiometry), and vastus lateralis muscle biopsies were analyzed before and after a 12-week lasting training-program in 35 RTx patients, 16 HD patients, and 21 healthy controls. RESULTS: At baseline, myosin heavy chain (MyHC) isoform composition and enzyme activities were not different between the groups. VO2peak and muscle strength improved significantly and comparably over the training-period in RTx, HD patients and controls (p(time)<0.05). The proportion of MyHC type I isoforms decreased (p(time)<0.001) and type IIa MyHC isoforms increased (p(time)<0.05). The 3-hydroxyacyl-CoA-dehydrogenase activity increased (p(time)=0.052). Intrinsic muscular changes were not significantly different between groups. In the HD group, changes in lean body mass were significantly related to changes in muscle insulin-like growth factor (IGF)-II and IGF binding protein-3. CONCLUSIONS: Abnormalities in metabolic enzyme activities or muscle fiber redistribution do not appear to be involved in muscle dysfunction in RTx and HD patients. Exercise training has comparable beneficial effects on functional and intrinsic muscular parameters in RTx patients, HD patients, and controls. In HD patients, the anabolic response to exercise training is related to changes in the muscle IGF system.     

Cardiovascular adaptations associated with exercise in patients on hemodialysis

Patients on hemodialysis are physically inactive. Less than 50% of hemodialysis patients undertake exercise once a week and such patients have increased mortality compared to patients who undertake regular exercise. The reasons for physical inactivity and reduced functional capacity are complex and inter‐related, with skeletal muscle catabolism, chronic inflammation, anemia, malnutrition, uremia, the burden of co‐morbid diseases, and “enforced” sedentary time during hemodialysis all contributing. Many of these factors drive cardiovascular disease (CVD) processes in this cohort of patients and in the general population, exercise interventions have been shown to modify many of these risk factors. Whilst there is increasing evidence about the beneficial effects of exercise interventions on quality of life, functional capacity, aerobic fitness, and muscular strength, there are few compelling data on the effects of such programs on cardiovascular outcome measures. The reasons for this are manifold and include: limitations in study size; inconsistencies in study design; the heterogeneous nature of exercise interventions; assessment of nonstandardized outcome measures and; a lack of understanding of what changes in certain traditional measures of CVD (such as blood pressure or lipid profile) mean for patients on hemodialysis. This review summarizes the current evidence base for the effects of exercise on traditional and nontraditional cardiovascular risk factors and the effects of exercise interventions on cardiovascular structure and function, including a review of study limitations and future research priorities.     

Cardiovascular responses to velocity-specific isokinetic exercise

This paper was part of a doctoral dissertation for the degree of Doctorate of Education at Teachers College, Columbia University and was presented at the Sports Physical Therapy Section Team Concept Meeting, December 1990, Orlando, FL. The purpose of this study was to measure cardiovascular responses to velocity-specific isokinetic exercise. Ten experienced recreational weight trainers, aged 20 to 40 years, took part in a repeated measures design consisting of three separate treatments (30 degrees /sec, 120 degrees /sec, and 300 degrees /sec performed maximally for one minute by the right knee flexors and extensors on an isokinetic dynamometer). Systolic blood pressure (SBP), diastolic blood pressure (DBP), heart rate (HR), and rate pressure product (RPP) were measured at rest and during peak response. There were no significant differences between the three treatments in increasing SBP and DBP, although peak SBP for all three treatments was above 188 mm Hg, clinically significant. The 300 degrees /sec treatment was significantly different (P < 0.05) than the 30 degrees /sec treatment on increasing HR and RPP. The data suggest that the magnitude of HR and RPP responses are strongly dependent on the velocity of movement utilized during maximal isokinetic exercise. J Orthop Sports Phys Ther 1991;13(1):28-32.     

Cardiovascular and metabolic responses to severe head injury

The cardiovascular and metabolic responses to severe head injury were studied in the acute phase after severe head injury with the object of determining if a common response was present and, if so, its significance in the management of the patients' intracranial and systemic physiological states. The cardiovascular response to head injury was studied by measurement of cardiac output, pulmonary capillary wedge pressure, arterial blood pressure, arterial and mixed venous blood gases and arterial and mixed venous epinephrine and norepinephrine serially in 15 patients during the first three days after injury. A hyperdynamic state was found characterized by increased cardiac output and cardiac work, moderate hypertension, tachycardia, decreased or normal systemic and pulmonary vascular resistance, increased pulmonary shunting and increased oxygen delivery and utilisation. Arterial E and NE levels correlated well with the cardiac output, cardiac work, blood pressure, heart rate, oxygen delivery, and oxygen utilization but not with vascular resistance or pulmonary shunt. The magnitude of the hyperdynamic state did not correlate with intracranial pressure, Glasgow Coma Score, or findings on CT scan.The metabolic response to head injury was studied by measurement of resting metabolic expenditure (RME) in 14 comatose head-injured patients in the first nine days after injury. During this period patients were fed with a continuous parenteral infusion of a formula containing 2 Kcal/cc and 10 mg nitrogen/liter. Indirect calorimetry was carried out for 102 patient-days. The mean resting metabolic expenditure (RME) for nonsedated, nonparalysed patients was 138 ± 37% of that expected for a non-injured resting person of equivalent age, sex, and body surface area. Nitrogen excretion was measured for 109 patient-days. The mean excretion was 20.2 ± 6.4 mg/day. The mean protein caloric contribution was 23.9 ± 6.7% and was greater than 25% for six patients, compared to normal values of 10–15%. Despite hyperalimentation, positive nitrogen balance for any 3-day period was achieved in only seven patients, and required replacement of 161% to 240% of RME with the parenterally administered formula. Head-injured patients had a metabolic response similar to that reported for patients with burns of 20–40% of the body surface.     

Melatonin ingestion before intradialytic exercise improves immune responses in hemodialysis patients

International Urology and Nephrology - The present study aimed to investigate the effects of melatonin (MEL) intake on systemic inflammation and immune responses during intradialytic exercise....     

Association of physiologic responses to metabolic changes in exhaustive physical exercise

The purpose of this work was to identify changes in some hematic variables in recreational athletes of middle level competition exposed to exhaustive physical exercise, as well as the association among physiologic changes, personal characteristics, and physical level produced by marathon running. Ten healthy males participated (20-55 years of age). Blood cell count, blood chemistry, lipids, and enzymes were determined. Exercise produced hemoconcentration by reduction in plasma volume (8%; p<0.05). There was significant increment in leukocytes (149%) by neutrophilia (64%) and decrease in lymphocytes (74%). Fibrinogen increased 10.7% (p<0.05). Lipids (CT, C-HDL) did not modify, except C-LDL, which increased significantly (71%), attributing this response to stress of the marathon. Triglyceride decreased 47%. Enzymes increased significantly, particularly CK. Age and physical activity were related with physiologic and metabolic variables, as demonstrated by multivariate analysis. These data contributed to new knowledge in physiologic responses of our ethnic race when exposed to exhaustive exercise such as a marathon. To these results new approaches of risk and different schedules of intervention programs could be generated for better and effective practice of physical exercise in our population.     

Addressing myths about exercise in hemodialysis patients

Despite decades of research, there are few published guidelines related to the safety and efficacy of exercise training in hemodialysis patients. This has led to disparate recommendations regarding the type, intensity, and timing for exercise, especially for patients with multiple comorbidities. Many common recommendations are not supported by research data, so their justification is uncertain. These recommendations include exercising in the first hour of dialysis; not exercising if hypertensive, cramping, or volume overloaded; avoiding heavy weights on vascular access limb; clinicians managing an exercise program; intradialytic exercise or interdialytic exercise is better; and strength training during dialysis is impractical. The purpose of this review is to describe the evidence that supports or refutes these beliefs. In summary, these beliefs or myths have generally led to an overly conservative approach to exercise that serves as a barrier to increasing physical activity levels in an overly sedentary population that could benefit from moving more.     

Cardiovascular and musculoskeletal response to supervised exercise in patients with intermittent claudication

ObjectiveIntermittent claudication occurs in 20% of the population older than 70 years, and treatment includes a supervised exercise program (SEP). Whereas there is evidence demonstrating walking improvements after an SEP, there are conflicting data on the physiologic changes behind this. This study aimed to explore and to identify the potential cardiovascular and musculoskeletal changes with exercise.MethodsThis was a single-center study at a vascular unit in England. Following written informed consent, 109 patients were recruited for an SEP, three times per week for 12 weeks. Outcome measures included walking distances, quality of life, cardiorespiratory fitness, flow-mediated dilation, and muscle strength and endurance. For normal data, paired sample t-tests were performed to compare baseline data to all time points for significance. For nonparametric data, Wilcoxon signed rank tests were performed. Significance was set at P < .05. The association between functional improvement (ie, walking distance at 3 months after the SEP) and metabolic response and patients' characteristics was determined by multivariable regressions.ResultsMaximum walking distance significantly improved from baseline by 117% at 1 week, 143% at 4 weeks, and 143% at 12 weeks after exercise. Claudication distance also significantly improved from baseline by 222% at week 1, 393% at week 4, and 452% at week 12. Quality of life significantly improved at all time points in seven of nine domains of the 36-Item Short Form Health Survey and two of five domains of the Vascular Quality of Life questionnaire. Markers of cardiorespiratory fitness significantly improved at all time points. Flow-mediated dilation demonstrated a 50% improvement, but this was not statistically significant. Muscle strength and muscle endurance significantly improved at all time points. Multivariate regression demonstrated that the ventilatory anaerobic threshold and the physical component summary score for quality of life predicted improvements in 12-week walking distance.ConclusionsThis study identified that the ventilatory anaerobic threshold and physical component summary scores from quality of life were the best predictors of improvement in an SEP. Future studies should prioritize these outcomes and assess whether different SEPs have similar effects. Cardiorespiratory fitness was also a predictor of outcome and should be prioritized in future studies alongside traditional measures.     

Effect of intradialytic exercise in maintenance hemodialysis patients

Objective To assess the impact of 24-week intradialytic exercise on the nutritional status, muscle strength and cardiorespiratory endurance of maintenance hemodialysis (MHD) patients. Methods Forty nine clinically stable MHD patients from Beijing Bo'ai Hospital were enrolled into the study, among forty three patients [65.1% men, (60.2±10.6) years] completed the trial. For 24 consecutive weeks, all patients performed one or two sets of cycle intradialytic exercise program during the first 2 h of their three dialysis sessions per week, 20 min for each set. The parameters included body mass index (BMI), albumin (Alb), total cholesterol (TC), cross-sectional area of triceps brachii, triceps skinfold and grip strength. Nineteen patients performed the symptom-limited treadmill exercise test (modified Bruce protocol) to measure peak oxygen uptake (VO2peak), metabolic equivalents (METs), vital capacity and stress-test duration. Their the knee extensor muscle strength was also meadured with the isokinetic test. Results After 24 weeks of exercise, there were increased Alb level (42.1 g/L vs 41.3 g/L, P=0.016), improved grip strength (25.5 kg vs 23.9 kg, P=0.012), and increased stress-test duration (14.5 min vs 13.2 min, P=0.005) in MHD patients. Conclusion The intradialytic exercise partially improves the nutritional status, muscle strength and cardiorespiratory endurance of MHD patients.     

Psychological effects of exercise training in hemodialysis patients

To assess the psychological effects of exercise training in hemodialysis patients 4 dialysis patients, matched by age, sex, and medical history with 4 controls, received psychological testing before and after a 6-month period of exercise training. The trained patients had a 28% improvement in graded exercise treadmill stress test duration and a 13% improvement in aerobic capacity. This was associated with a significant reduction in anxiety and depression (p less than 0.06), but no measurable change in these moods occurred in the control groups. These results suggest that exercise training may improve psychological functioning in dialysis patients.     

Cardiac adaptations following exercise training in hemodialysis patients

Patients with chronic renal failure (CRF) on hemodialysis (HD) are at increased risk of cardiovascular disease. This is due, mainly, to a higher prevalence of established arteriosclerotic risk factors, including diabetes mellitus, hypertension, dyslipidemia, physical inactivity, as well as to unique CRF-related risk factors. Accordingly, cardiorespiratory insufficiency, left ventricle dysfunction, atherosclerosis and cardiac sympathetic overestimation may often antedate, and hence contribute to exercise intolerance and to increased morbidity and mortality. In HD patients the application of exercise training programs is effective in improving cardiorespiratory capacity, as demonstrated mainly by the increasing of VO2peak. Moreover, better left ventricular systolic function at rest, as well as at effort following training was suggested. Indeed, the increase of cardiac vagal outflow and the decrease of sympathetic over-activity at rest are significantly beneficial results of exercise training in HD patients. However, whether these outcomes reduce the incidence of cardiac morbidity and mortality rate remains to be determined.     

Forearm hemodynamics and responses to exercise in middle-aged adult-onset diabetic patients

Much of the difficulty in assessing the progress of diabetic angiopathy and effects of experimental modes of therapy arises from the lack of quick, simple, inexpensive, and noninvasive tests to perform on the circulatory system of human subjects. We report here on values obtained by the use of mercury-in-rubber strain gauge plethysmography on 15 middle-aged, adult-onset diabetics who had minimal clinical evidence of microangiopathy. Standard tests are described for assessing forearm vascular function at rest, during tonic exercise of the fingers, and after interrupted repetitive exercise of the fingers. When matched against a similar aged nondiabetic group, the diabetics had slightly higher forearm vascular resistance at each level of exercise, a marked reduction (approximately 50 per cent) in capillary filtration coefficient, which is believed to be related to vascular filtering surface area, and a slight reduction in venous capacitance at all levels of exercise. The method of mercury-in-rubber strain gauge venous occlusion plethysmography provides the clinician with a sensitive and inexpensive tool with which to follow the evolution of angiopathy in diabetic patients.     

Cardiovascular and neuromuscular responses to high-dose pancuronium-metocurine in pediatric burned and reconstructive patients

The efficacy of the combined use of pancuronium and metocurine (Pm-MTC) in high doses to produce rapid-onset muscle paralysis was evaluated in 15 patients with acute burns and 18 recovered burned patients scheduled for reconstructive surgery. Two and three times the previously determined ED95 of the combination for each group was used. (ED95 for Pm-MTC combination is 0.032/0.129 mg/kg for acute burns and 0.013/0.051 mg/kg for reconstructive patients.) Doubling ED95 produced 95% paralysis in 3.1 +/- 0.9 min in acutely burned children and in 4.3 +/- 0.7 min in reconstructive children (mean +/- SEM). These onset times were not significantly different from each other. Tripling the ED95 of the combination in burned children reduced the onset time to 1.3 +/- 0.14 min, but this was not significantly different from 2 X ED95 onset time in burned patients. The administration of 3 X ED95 to the reconstructive group, however, resulted in a significantly more rapid onset time of 1.8 +/- 0.4 min compared with 2 X ED95 in the same population. With 3 X ED95 the onset times between burn and reconstructive patients were not significantly different. Time for recovery of twitch to 25% of control twitch height (75% twitch depression) was significantly prolonged in burned patients compared with reconstructive patients for equipotent doses administered. Although the occasional patient showed prominent changes in heart rate and blood pressure, overall cardiovascular stability was impressive.(ABSTRACT TRUNCATED AT 250 WORDS)