Scaling hemodialysis target dose to reflect body surface area, metabolic activity, and protein catabolic rate: A prospective, cross-sectional study

Background:Women and small men treated by haemodialysis (HD) have reduced survival. This may be due to the practice of using total body water (V) as the normalising factor for dialysis dosing. Our aim in this study was to explore the use of alternate parameters for scaling dialysis dose. Study Design: Prospective, cross-sectional study. Setting and Participants: 1500 HD patients on thrice weekly schedule were recruited across five different centres. Predictors: Age, sex, weight, ethnicity, comorbidity level and employment status. Outcomes: Kt was estimated by multiplying V by 1.2. Kt/BSA, Kt/REE and Kt/TEE equivalent to a target Kt/V of 1.2 were then estimated by dividing Kt by the respective parameters. Measurements: Anthropometric and HD adequacy details were obtained from direct measurements and medical records of patients. Body surface area (BSA) was estimated using Haycock formula. Resting energy expenditure (REE) was estimated using a novel validated equation. Total energy expenditure (TEE) was calculated from physical activity data obtained using Recent Physical Activity Questionnaire. Results: Mean BSA was 1.87 m2, mean REE 1545 kcal/day and mean TEE 1841 kcal/day. For Kt/V of 1.2, there was a wide range of equivalent doses expressed as Kt/BSA, Kt/REE and Kt/TEE. The mean equivalent dose was lower in women for all 3 parameters (p<0.001). Small men would also receive lower doses compared to larger men. Younger patients, those with low comorbidity, those employed and those of South Asian ethnicity would receive significantly lower dialysis doses with current practice. Limitations: Cross-sectional study and the physical activity data has been collected by an activity questionnaire. Conclusion:Our data suggest that current dosing practices risk under-dialysis in women and men of lower body size and in specific subgroups of patients. Using BSA, REE or TEE based dialysis prescription would result in higher dose delivery in these patients.