Comparison of Various Scaling Parameters and Energy Expenditure in Peritoneal Dialysis Patients

Peritoneal dialysis (PD) dosing is determined by urea clearance scaled to total body water (TBW). However, studies delivering greater peritoneal Kt/V urea have failed to demonstrate improved survival. Body surface area (BSA) has been suggested as an alternative scaling factor. Cellular metabolism generates toxins, and thus total energy expenditure (TEE) might be a preferable scaling factor. Because TEE is cumbersome to determine, we set out to determine the association of anthropomorphic scaling factors with TEE.The TEE was determined using the Recent Physical Activity Questionnaire combined with resting energy expenditure by validated equations that use doubly labelled isotopic water and body composition by multi-frequency bioimpedance.In 148 adult PD patients [97 men (65.5%)], mean age was 60.6 ± 20.6 years, and median PD treatment duration was 9.1 months (range: 3.5 - 25.2 months). Mean weight in the group was 73.6 ± 16.7 kg, body mass index (BMI) was 26.0 ± 4.9 kg/m², and BSA was 1.86 ± 0.24 m². The mean TEE was 1974 ± 414 kcal daily, and it correlated with BMI (men: r = 0.48, p < 0.001; women r = 0.36, p = 0.018), BSA (men: r = 0.56; women: r = 0.63; both p < 0.001), and TBW (men: r = 0.62; women: r = 0.65; both p < 0.001). Skeletal muscle mass correlated with BMI (men: r = 0.48; women: r = 0.50), BSA (men: r = 0.72; women: r = 0.63), and TBW (men: r = 0.98; women: r = 0.99), all p < 0.001.Comparing scaling factors, correlations with TEE were stronger for TBW and BSA than for BMI. Skeletal muscle mass was most strongly associated with TBW. Our study did not demonstrate any advantage for BSA compared with TBW as a scaling factor to adjust the dose of PD.