Factors associated with peak oxygen uptake in hemodialysis patients awaiting renal transplantation

Relationships between frailty and exercise capacity in patients undergoing hemodialysis: A cross-sectional study

AIM

Hemodialysis (HD) patients have a high prevalence of frailty. The association between frailty and exercise capacity in HD patients has not been established. This study aimed to clarify the relationships between frailty and exercise capacity in HD patients.

METHODS

This two-center cross-sectional study included HD patients who performed cardiopulmonary exercise testing. Participants were divided by frailty phenotype into robust, pre-frail, and frail using the revised Japanese version of the Cardiovascular Health Study criteria. Peak oxygen uptake (peakVO2 ) measured by cardiopulmonary exercise testing was compared with each frailty phenotype. The association between peakVO2 and frailty phenotype was analyzed using multivariate linear regression analysis adjusted for age, sex, body mass index diabetes mellitus, cardiovascular disease, cancer, history of fracture, hemoglobin, left ventricle ejection fraction, and percentage of heart rate reserve.

RESULTS

The study included 136 patients (median age, 71.0 years; female, 23.5%), with 15.4%, 44.9%, and 39.7% with frailty phenotypes robust, pre-frail, and frail, respectively. PeakVO2 decreased with deterioration of the frailty phenotype (robust, median 15.1 [13.7-18.3] mL/min/kg; pre-frail, median 12.2 [10.5-14.4] mL/min/kg; frail, median 10.6 [9.2-12.5] mL/min/kg, P < 0.05). PeakVO2 decline was significantly associated with frail (B = -2.19, P = 0.004). Modeling individual frailty components showed a significant association between peakVO2 , usual gait speed (B = 2.38, P = 0.04), and low physical activity (B = -1.44, P = 0.004).

CONCLUSION

Frailty in HD patients was associated with a decline in exercise capacity. HD patients with frailty need to improve exercise capacity, gait speed, and physical activity. Geriatr Gerontol Int 2023; 23: 795-802.

Cardiopulmonary exercise testing in patients with end-stage kidney disease: principles, methodology and clinical applications of the optimal tool for exercise tolerance evaluation

Chronic kidney disease (CKD), especially end-stage kidney disease (ESKD), is associated with an increased risk for cardiovascular events and all-cause mortality. Exercise intolerance as well as reduced cardiovascular reserve is extremely common in patients with CKD. Cardiopulmonary exercise testing (CPET) is a non-invasive, dynamic technique that provides an integrative evaluation of cardiovascular, pulmonary, neuropsychological and metabolic function during maximal or submaximal exercise, allowing the evaluation of functional reserves of these systems. This assessment is based on the principle that system failure typically occurs when the system is under stress and thus CPET is currently considered to be the gold standard for identifying exercise limitation and differentiating its causes. It has been widely used in several medical fields for risk stratification, clinical evaluation and other applications, but its use in everyday practice for CKD patients is scarce. This article describes the basic principles and methodology of CPET and provides an overview of important studies that utilized CPET in patients with ESKD, in an effort to increase awareness of CPET capabilities among practicing nephrologists.

Reduction of functional cardiovascular reserve in the stages of chronic kidney disease

SUMMARY OBJECTIVE Patients with chronic kidney disease (CKD) present reduced oxygen consumption at peak exercise (VO2 peak). No studies have evaluated objective measures of the cardiovascular reserve, besides VO2 peak and VO2 at the anaerobic threshold (VO2 AT), and compared these measures among ckd patients at different stages of the disease. METHODS Fifty-eight patients [pre-dialysis group (PD)=26, hemodialysis group (HD)=20, and post-kidney transplant group (KT)=12] were included. The following measures of cardiovascular reserve were obtained: 1) peak heart rate (HR); 2) peak systolic blood pressure (SBP); 3) VO2 peak and % predicted; 4) VO2 AT and % of predicted VO2; 5) peak circulatory power; 6) ventilatory efficiency for the production of carbon dioxide (VE/VCO2 slope); 7) oxygen uptake efficiency slope (OUES); and 8) recovery of gas exchange. RESULTS The VO2 peak and VO2 AT in the PD, HD, and KT groups were reduced to 86% and 69%, 70% and 57%, and 79% and 64% of the predicted value, respectively. Patients in the HD group had lower VO2 peak (17.5±5.9 vs. 23.2±8.2 [p-value=0.036]) and VO2 AT (14.0±5.2 vs. 18.3±4.7 [p-value=0.039]) compared to patients in the KT group. OUES was significantly lower in the HD group compared to the KT group (p-value=0.034). Age in the PD, HD, and KT groups and sedentary lifestyle in the KT group were predictors of VO2 peak. CONCLUSIONS CKD patients presented a reduction in cardiovascular reserve regardless of the stage of the disease. However, hemodialysis patients presented a greater reduction of cardiovascular reserve when compared to post-kidney transplant patients.

Characterising recovery from renal transplantation and live-related donation using cardiopulmonary exercise testing

BACKGROUND

An association between end-stage renal failure and exercise intolerance exists. Whether live kidney donation impacts on exercise tolerance is unknown. Here recovery post renal transplant and donation using cardiopulmonary exercise testing is investigated.

METHODS

Renal donors (n = 28) and recipients (n = 24) undertook a cardiopulmonary exercise test, Duke activity score index and patient reported health score questionnaires pre-operatively and in the 7th and 14th week post-operatively. Anaerobic threshold, peak oxygen uptake and ventilatory equivalents were measured in relation to activity and reported health scores. Haemoglobin and renal function was recorded.

RESULTS

Recipients showed impaired cardiopulmonary function compared to donors with lower anaerobic threshold (10.5 vs. 14.4 ml/kg/min) and peak oxygen uptake (18.5 vs 23.0 ml/kg/min). Post-operatively the anaerobic threshold of recipients improved and normalised by the 14th week, whereas that in donors fell by ∼20% by the 7th (mean 11.4 ml/kg/min), recovering by the 14th (mean 15.6 ml/kg/min). Reported health but not activity scores showed similar changes.

CONCLUSIONS

Recovery following renal transplantation and donation differ. Transplantation improves renal function resulting in an increase in anaerobic threshold and peak oxygen uptake which essentially normalise by the 14th week post-operatively. Donors suffer a 20% reduction in cardiopulmonary reserve post-operatively, which recovers by the 14th week, suggesting no associated chronic exercise intolerance.IMPLICATIONS FOR REHABILITATIONCardiopulmonary exercise testing is a real-time predictor of functional capacity and thus is used as a pre-operative tool to measure physiological fitness and predict outcomes.Renal failure is associated with exercise intolerance and transplantation is transformational in terms of quality of life, longevity and healthcare cost.Live - related renal donation is increasingly available but whether donation itself carries a long-term health burden has not been previously well established.This study suggests that renal donation is not associated with long-term cardiopulmonary compromise and patients who donate their kidneys recover their previous fitness within 14 weeks.

Subclinical cardiopulmonary dysfunction in stage 3 chronic kidney disease

OBJECTIVE

Reduced exercise capacity is well documented in end-stage chronic kidney disease (CKD), preceded by changes in cardiac morphology in CKD stage 3. However, it is unknown whether subclinical cardiopulmonary dysfunction occurs in CKD stage 3 independently of heart failure.

METHODS

Prospective observational cross-sectional study of exercise capacity assessed by cardiopulmonary exercise testing in 993 preoperative patients. Primary outcome was peak oxygen consumption (VO2peak). Anaerobic threshold (AT), oxygen pulse and exercise-evoked measures of autonomic function were analysed, controlling for CKD stage 3, age, gender, diabetes mellitus and hypertension.

RESULTS

CKD stage 3 was present in 93/993 (9.97%) patients. Diabetes mellitus (RR 2.49 (95% CI 1.59 to 3.89); p<0.001), and hypertension (RR 3.20 (95% CI 2.04 to 5.03); p<0.001)) were more common in CKD stage 3. Cardiac failure (RR 0.83 (95% CI 0.30 to 2.24); p=0.70) and ischaemic heart disease (RR 1.40 (95% CI 0.97 to 2.02); p=0.09) were not more common in CKD stage 3. Patients with CKD stage 3 had lower predicted VO2peak (mean difference: 6% (95% CI 1% to 11%); p=0.02), lower peak heart rate (mean difference:9 bpm (95% CI 3 to 14); p=0.03)), lower AT (mean difference: 1.1 mL/min/kg (95% CI 0.4 to 1.7); p<0.001) and impaired heart rate recovery (mean difference: 4 bpm (95% CI 1 to 7); p<0.001)).

CONCLUSIONS

Subclinical cardiopulmonary dysfunction in CKD stage 3 is common. This study suggests that maladaptive cardiovascular/autonomic dysfunction may be established in CKD stage 3, preceding pathophysiology reported in end-stage CKD.

Impact of Resistance Training on Factors Involved in the Development of New-Onset Diabetes After Transplantation in Renal Transplant Recipients: An Open Randomized Pilot Study

OBJECTIVES

New-onsetdiabetes after transplant (NODAT) is a major contributor to cardiovascular disease after transplantation. Kidney transplantation (KT) recipients have low levels of exercise capacity. Resistance training (RT) might be of special benefit in this population because underlying disease and immunosuppressive drugs favour muscle loss and insulin resistance. The aim of this study was to assess the feasibility of implementing an RT program within a population of KT recipients and its impact on the incidence of NODAT and cardiometabolic risk factors.

METHODS

This pilot study was an open-randomized study. We randomized 24 patients with a 1:1 allocation to 2 parallel groups, the exercise group (E) or the control group (C). The E group was submitted to RT 3 times a week for 16 weeks. Anthropometric, body composition, cardiometabolic risk factors, muscle strength, cardiorespiratory fitness and well-being were measured before and after 16 weeks.

RESULTS

Of the 24 recruited participants, 20 completed the study (10 in the E group and 10 in the C group). No injuries were reported. The intervention was associated with a significant increase in muscle strength (p=0.003). A significant group effect, in favour of the E group, was detected for the well-being score (p=0.03). However, no changes in body composition, cardiometabolic risk factors or cardiorespiratory fitness were noted for either group after the intervention.

CONCLUSIONS

This pilot study suggests that RT appears to be secure and feasible and improves strength and well-being in patients after KT. However, it does not improve cardiometabolic risk factors.

Intra-dialytic training accelerates oxygen uptake kinetics in hemodialysis patients

BACKGROUND

End-stage renal disease is associated with several hemodynamic and peripheral muscle abnormalities that could slow the rate of change in oxygen uptake ([Formula: see text]O2) at the onset and at the end of exercise. This study was performed to determine whether an intra-dialytic aerobic training program would speed [Formula: see text]O2 kinetics at the transition to and from moderate and high-intensity exercise.

DESIGN

This study was a randomized controlled trial.

METHODS

Twenty-four patients with end-stage renal disease (14 females; 47.0 ± 11.9 years) were randomly assigned to either 12-week cycle ergometer-based training at moderate exertion or a similar control period. At initial and final evaluations, patients underwent 6 min moderate and high-intensity tests to exercise intolerance (Tlim).

RESULTS

Training improved Tlim by ∼90% (median (inter-quartile range) = 232 (59) s to 445 (451) s, p < 0.05); in contrast, Tlim decreased by ∼30% in controls (291 (134) s to 202 (131) s). [Formula: see text]O2 kinetics at the onset of moderate-intensity exercise were significantly accelerated with training leading to lower oxygen (O2) deficit (mean ± standard deviation (SD) = 3.2 ± 1.3 l vs 2.3 ± 1.2 l). Similar positive effects were found at the high-intensity test either at the onset of, or recovery from, exercise (p < 0.05). "Excess" [Formula: see text]O2 at the high-intensity test was also lessened with training. Changes in Tlim correlated with faster [Formula: see text]O2 kinetics and lower "excess" [Formula: see text]O2 (Spearman's ρ = -0.56 and -0.75, respectively; p < 0.01).

CONCLUSIONS

A symptom-targeted intra-dialytic training program improved sub-maximal aerobic metabolism and endurance exercise capacity. [Formula: see text]O2 kinetics are valuable in providing relatively effort-independent information on the efficacy of exercise interventions in this patient population.

Reduced functional measure of cardiovascular reserve predicts admission to critical care unit following kidney transplantation

BACKGROUND

There is currently no effective preoperative assessment for patients undergoing kidney transplantation that is able to identify those at high perioperative risk requiring admission to critical care unit (CCU). We sought to determine if functional measures of cardiovascular reserve, in particular the anaerobic threshold (VO₂AT) could identify these patients.

METHODS

Adult patients were assessed within 4 weeks prior to kidney transplantation in a University hospital with a 37-bed CCU, between April 2010 and June 2012. Cardiopulmonary exercise testing (CPET), echocardiography and arterial applanation tonometry were performed.

RESULTS

There were 70 participants (age 41.7±14.5 years, 60% male, 91.4% living donor kidney recipients, 23.4% were desensitized). 14 patients (20%) required escalation of care from the ward to CCU following transplantation. Reduced anaerobic threshold (VO₂AT) was the most significant predictor, independently (OR = 0.43; 95% CI 0.27-0.68; p<0.001) and in the multivariate logistic regression analysis (adjusted OR = 0.26; 95% CI 0.12-0.59; p = 0.001). The area under the receiver-operating-characteristic curve was 0.93, based on a risk prediction model that incorporated VO₂AT, body mass index and desensitization status. Neither echocardiographic nor measures of aortic compliance were significantly associated with CCU admission.

CONCLUSIONS

To our knowledge, this is the first prospective observational study to demonstrate the usefulness of CPET as a preoperative risk stratification tool for patients undergoing kidney transplantation. The study suggests that VO₂AT has the potential to predict perioperative morbidity in kidney transplant recipients.

Exercício aeróbico durante a hemodiálise: relato de cinco anos de experiência

INTRODUÇÃO: Nos pacientes portadores de doença renal crônica (DRC) submetidos à hemodiálise (HD), o sedentarismo compromete a capacidade funcional e se associa a aumento da mortalidade por doenças cardiovasculares. Apesar da demonstração dos benefícios da prática de exercícios físicos para estes pacientes, poucos centros de diálise desenvolvem esta atividade. O objetivo deste estudo foi descrever a experiência de cinco anos de um programa de exercício aeróbico intradialítico, com ênfase na adesão e na segurança do procedimento. MÉTODOS: Foram incluídos pacientes adultos, de ambos os sexos, que participaram de um programa de exercícios realizado no período de agosto de 2004 a agosto de 2009. O exercício foi realizado nas duas horas iniciais da HD, empregando-se um cicloergômetro horizontal, sendo constituído de aquecimento, condicionamento e resfriamento. Foram realizadas análises descritivas dos dados coletados ao longo dos cinco anos do programa. RESULTADOS: No período de cinco anos, 34 pacientes (48,26 ± 11,44 anos; 20 mulheres) participaram do programa de exercício. Foram realizadas 3.077 sessões individuais de exercício aeróbico durante as sessões de HD. O tempo médio de participação no programa foi de 15,65 ± 13,86 meses e a aderência às sessões de exercício foi de 64,87 ± 19,47%. Apesar do registro de alguns episódios de hipotensão, sem repercussões hemodinâmicas significativas, não foram observadas complicações clínicas importantes. CONCLUSÃO: A realização de exercício aeróbico durante a sessão de HD é uma prática bem aceita pelos pacientes, segura e não acompanhada de complicações graves.

Association of Malnutrition-Inflammation Score with quality of life and mortality in hemodialysis patients: a 5-year prospective cohort study

BACKGROUND

The Malnutrition-Inflammation Score (MIS), an inexpensive and easy-to-assess score of 0 to 30 to examine protein-energy wasting (PEW) and inflammation, includes 7 components of the Subjective Global Assessment, body mass index, and serum albumin and transferrin concentrations. We hypothesized that MIS risk stratification of hemodialysis (HD) patients in predicting outcomes is better than its components or laboratory markers of inflammation.

STUDY DESIGN

5-Year cohort study.

SETTING & PARTICIPANTS

We examined 809 stable HD outpatients and followed them for up to 5 years (October 2001 to December 2006).

PREDICTORS

MIS and other nutritional and inflammatory markers.

OUTCOMES & MEASUREMENTS

Prospective all-cause mortality, health-related quality of life using the 36-Item Short Form Health Survey (SF-36), and tests of body composition.

RESULTS

The MIS correlated with logarithm of serum interleukin 6 level (r = +0.26; P < 0.001), logarithm of C-reactive protein level (r = +0.16; P < 0.001), and several measures of nutritional status. Patients with a higher MIS had lower SF-36 scores. After multivariate adjustment for case-mix and other measures of PEW, HD patients in the second (3 to 4), third (5 to 7), and fourth (>or=8) quartiles of MIS had worse survival rates than those in the first (0 to 2) quartile (P < 0.001). Each 2-unit increase in MIS was associated with a 2-fold greater death risk, ie, adjusted death hazard ratio of 2.03 (95% confidence interval, 1.76 to 2.33; P < 0.001). Cubic spline survival models confirmed linear trends. Adding MIS to the constellation of age, sex, race/ethnicity, and vintage significantly improved the area under the receiver operating characteristic curve developed for predicting mortality (0.71 versus 0.67; P < 0.001).

LIMITATIONS

Selection bias and unknown confounders.

CONCLUSIONS

In HD patients, the MIS is associated with inflammation, nutritional status, quality of life, and 5-year prospective mortality. The mortality predictability of the MIS appears equal to serum interleukin 6 and somewhat greater than C-reactive protein levels. Controlled trials are warranted to examine whether interventions to improve the MIS can also improve clinical outcomes in HD patients.