P155
FATIGUE IN PATIENTS WITH CHRONIC KIDNEY DISEASE: PHYSIOLOGICAL
AND PSYCHOLOGICAL RESPONSES DURING ACTIVITIES OF DAILY LIVING
Macdonald, J1, Fern, L1, Jibani, M2, Marcora S3
1
College of Health and Behavioural Sciences, Bangor University, Bangor, 2Ysbyty
Gwynedd Renal Unit, Betsi Cadwaladr University Health Board, Bangor, 3Centre for
Sports Studies, University of Kent at Medway, Kent
INTRODUCTION: Fatigue is one of the most prevalent symptoms in chronic kidney disease
(CKD). However fatigue is poorly identified and treated, due to unspecific definitions and poor
understanding of mechanisms. This purpose of this study was to identify why patients with
CKD suffer from fatigue. The first objective was to determine whether patients reported
excessive exertional fatigue during activities of daily living. The second objective was to
determine the cause of exertional fatigue, focusing on oxygen delivery and utilization.
METHODS: An “explanatory” prospective case control observational study was completed. 13
CKD patients, stage 3-4, age mean 62 ± 13 years, were compared to 13 healthy controls
matched for age, height, mass, and physical activity level. Participants completed a submaximal incremental cycle ergometer test to simulate the energy expenditure of typical
activities of daily living. Four exercise intensities were investigated: 1, 1.8, 2.4, and 3.1
metabolic equivalents (METs), where 1 MET equates to sitting quietly and 3.1 METs equates to
putting away household items. The primary outcome measure was exertional fatigue by rating
of perceived exertion (RPE),self-reported using a Borg 6 – 20 number and verbal descriptor
scale. Other multidimensional assessments of fatigue included the UK Short-Form 36 (SF-36)
vitality and Functional Assessment of Chronic Illness Therapy-Fatigue (FACIT-Fatigue) subscales. Physiological measures of the oxygen transport chain were also obtained, including
expired gas analysis, cardiac output, arterial oxygen content, and blood lactate. Data were
analyzed by t-tests and repeated measures analysis of variance.
RESULTS: RPE was increased in patients compared to controls at 2.4 METs (10.5Light ± 2.7 vs.
8.7Very light ± 1.7 units) and 3.1 METs (12.5Somewhat hard ± 2.6 vs. 10.2Light ± 1.7 units) (interaction P
= 0.03), which was consistent with higher chronic fatigue in patients by both SF-36 vitality (P =
0.01) and FACIT-Fatigue (P = 0.004) sub-scales. Due to mild anaemia (13.3 ± 1.5 vs. 15.4 ±
1.4 g/dL, P < 0.001), arterial oxygen content was decreased in patients (P = 0.001), but cardiac
output and oxygen extraction ratio were inappropriately normal, decreasing oxygen delivery (P
= 0.04). Respiratory exchange ratio (P=0.004) and blood lactate production (P = 0.002) were
consequently increased.
CONCLUSION: Pre-dialysis CKD patients reported considerable fatigue. Exertional fatigue
(RPE) obtained during a standardized exercise test offers a novel outcome measure to further
study this symptom. CKD patients had low whole body oxygen delivery, resulting in greater
anaerobic energy production and increased exertional fatigue. This study implies that the
currently recommended below normal haemoglobin target for CKD patients increases fatigue
symptoms and reduces quality of life. The study further implies that the entire oxygen transport
chain, rather than just anaemia, needs to be targeted to successfully treat fatigue in CKD.