title: Exertional fatigue in patients with CKD.
abstract: BACKGROUND
  Fatigue is one of the most prevalent symptoms in chronic kidney disease (CKD). However, fatigue mechanisms are poorly understood due in part to nonspecific definitions. This study investigates exertional fatigue during simulated activities of daily living, focusing on oxygen delivery and utilization.
  
  
  METHODS
  "Explanatory" matched-cohort study.
  
  
  METHODS
  13 patients with CKD (stages 3b-4; mean age, 62 ± 13 [SD] years) and 13 healthy controls, mean matched for age, height, body mass and composition, and physical activity level. Participants completed an incremental cycle ergometer test to simulate energy expenditure of typical activities of daily living.
  
  
  METHODS
  4 exercise intensities: 1, 1.8, 2.4, and 3.1 metabolic equivalent tasks (METs).
  
  
  RESULTS
  The primary outcome was exertional fatigue by rating of perceived exertion (RPE) on a 6-20 scale.
  
  
  METHODS
  Other multidimensional measures of fatigue: UK Short Form Health Survey 36 (UK SF-36) Vitality and Functional Assessment of Chronic Illness Therapy-Fatigue (FACIT-Fatigue) subscales. Physiologic measures of the oxygen transport and utilization chain (expired gas analysis, cardiac output, and arterial oxygen content) and blood lactate.
  
  
  RESULTS
  RPE was increased in patients compared with controls at 2.4 (10.5 [ie, light] ± 2.7 vs 8.7 [very light] ± 1.7 units) and 3.1 (12.5 [somewhat hard] ± 2.6 vs 10.2 [light] ± 1.7 units) METs (interaction P = 0.03), which was consistent with higher chronic fatigue in patients by both the UK SF-36 Vitality (P = 0.01) and FACIT-Fatigue (P = 0.004) subscales. Arterial oxygen content was decreased in patients (P = 0.001), but cardiac output and oxygen extraction ratio were unchanged, decreasing oxygen delivery (P = 0.04). Respiratory exchange ratio (P = 0.004) and blood lactate production (P = 0.002) were increased.
  
  
  CONCLUSIONS
  Those inherent to a matched-cohort study.
  
  
  CONCLUSIONS
  Using a novel application of the outcome measure RPE, patients with non-dialysis-dependent CKD reported considerable exertional fatigue during simulated activities of daily living. Poor compensation for mild anemia contributed to this symptom. In addition to anemia, the entire oxygen transport chain needs to be targeted to treat fatigue in patients with CKD.
authors.affiliation: College of Health and Behavioural Sciences, Bangor University, Bangor, United Kingdom. j.h.macdonald@bangor.ac.uk
authors.forename: Jamie H
authors.initials: JH
authors.lastname: Macdonald
authors.forename: Lee
authors.initials: L
authors.lastname: Fearn
authors.forename: Mahdi
authors.initials: M
authors.lastname: Jibani
authors.forename: Samuele M
authors.initials: SM
authors.lastname: Marcora
mesh_terms: D000203:Activities of Daily Living; D000368:Aged; D015331:Cohort Studies; D004734:Energy Metabolism / Q000502:physiology; D005080:Exercise Test / Q000379:methods; D005221:Fatigue / Q000175:diagnosis / Q000453:epidemiology* / Q000503:physiopathology*; D005260:Female; D006306:Health Surveys / Q000379:methods; D006801:Humans; D008297:Male; D008875:Middle Aged; D005082:Physical Exertion / Q000502:physiology*; D051436:Renal Insufficiency, Chronic / Q000453:epidemiology* / Q000503:physiopathology*