Comparison of resting energy equations and total energy expenditure in haemodialysis patients and body composition measured by multi-frequency bioimpedance

Background Waste products of metabolism are retained in haemodialysis (HD) patients. Cellular metabolism generates energy, and patients with greater energy expenditure may therefore require more dialysis. To determine the amount of dialysis required, equations estimating resting and total energy expenditure (REE,TEE) are required. Methods We compared estimates of REE in HD patients using established equations with a novel equation recently validated in HD patients (HD equation). TEE was derived from REE (HD equation) and estimates of physical activity obtained by questionnaire. REE and TEE relationships with bioimpedance measured body composition were then determined. Results We studied 317 HD patients; 195 males (61.5%), 123 diabetic (38.9%), mean age 65.0 ± 15.3 and weight 73.1 ± 16.8 kg. REE from HD Equation was 1509 ± 241 kcal/day, which was greater than for Mifflin St Joer 1384 ± 259, Harris-Benedict 1437 ± 244, Katch-McArdle 1345 ± 232 (all p < 0.05 vs HD Equation), but less than Cunningham 1557 ± 236 kcal/day. Bland Altman mean bias ranged from −263 to 55 kcal/day. TEE was 1727 (1558–1976) kcal/day, and on multi-variable analysis was positively associated with skeletal muscle mass (β 23.3, p < 0.001), employment (β 406.5, p < 0.001), low co-morbidity (β 105.1, p = 0.006), and protein nitrogen appearance (β 2.7, p = 0.015), and negatively with age (β -7.9, p < 0.001), and dialysis vintage (β -121.2, p = 0.002). Conclusions Most standard equations underestimate REE in HD patients compared to the HD Equation. TEE was greater in those with higher skeletal muscle mass and protein nitrogen appearance, lower co-morbidity, age, and dialysis vintage, and the employed. More metabolically active patients may require greater dialytic clearances.