Bioelectrical impedance assessment of nutritional status in critically ill patients.

The objective of this study was to assess the utility of bioelectrical impedance analysis (BIA) in determining nutritional status in critically ill patients in the intensive care unit (ICU). Data were collected prospectively in 33 mechanically ventilated medical and surgical ICU patients requiring nutrition as part of their care. BIA, with subsequent calculation of body-composition indexes, was performed every other day for the duration of ICU stay. Body cell mass (BCM) changes correlated with energy and protein intakes (r2 = 0.87, P < 0.001 and r2 = 0.67, P < 0.001, respectively). Maintenance of BCM was achieved by a daily provision of 125.5 kJ.kg-1.d-1 (30 kcal.kg-1.d-1) and 1.5 g protein/kg whereas greater intakes allowed restoration of BCM. The mean ratios of exchangeable sodium to potassium (Nae:Ke) improved only in patients achieving positive nitrogen balance (P = 0.013). Body-composition changes determined by BIA represent a feasible adjunctive method for evaluating and monitoring nutritional status in ICU patients.