Accurate determination of energy requirements in hospitalised patients with parenteral nutrition

Background The prescription of parenteral nutrition (PN) in hospitalised patients requires an estimation of the energy requirements. Most studies employing prediction equations (PEs) to estimate energy requirements have focused on critically ill patients. The present study aimed to evaluate several PEs of the resting energy expenditure (REE) to identify the most accurate equation for estimating the REE required for PN. Methods This cross-sectional and descriptive study included patients hospitalised with medical or surgical diagnoses, making them candidates for PN. Epidemiological data, the reason for hospital admission, nutritional screening results, characteristics of the PN administered and REE by indirect calorimetry (IC) were recorded and, subsequently, PEs were calculated. Results In total, 116 patients were recruited with a mean (SD) age of 56.7 (13.8) years and body mass index of 21.3 (4.25) kg m-2 . The diagnosis was medical in 52% of patients and surgical in 48%. The mean (SD) REEs of patients, according to IC, were: 6.11 (1.18) MJ [1461 (281) kcal]; and according to PEs: Mifflin, 5.07 (1.05) MJ [1212 (252) kcal]; Owen, 5.43 (0.72) MJ [1298 (172) kcal]; Harris-Benedict, 5.38 (0.85) MJ [1285 (204) kcal]; Ireton-Jones, 6.20 (1.69) MJ [1481 (403) kcal]; and short equation, 6.12 (0.92) MJ [1464 (220) kcal]. A comparison of the results obtained for the REE by IC and with PEs indicated that the short equation had less bias than the other equations, with an accuracy of 54% CONCLUSIONS: In hospitalised patients who receive PN, determination of the REE should ideally be made by IC. PEs are acceptable but not exact and so their estimation could overfeed or underfeed the patient.