Use of Bioelectrical Impedance Analysis for the Assessment of Nutritional Status in Critically Ill Patients

Malnutrition is common in the critically ill patients and known to cause a variety of negative clinical outcomes. However, various conventional methods for nutrition assessment have several limitations. We hypothesized that body composition data, as measured using bioelectrical impedance analysis (BIA), may have a significant role in evaluating nutritional status and predicting clinical outcomes in critically ill patients. We gathered clinical, biochemical, and BIA data from 66 critically ill patients admitted to an intensive care unit. Patients were divided into three nutritional status groups according to their serum albumin level and total lymphocyte counts. The BIA results, conventional indicators of nutrition status, and clinical outcomes were compared and analyzed retrospectively. Results showed that the BIA indices including phase angle (PhA), extracellular water (ECW), and ECW/total body water (TBW) were significantly associated with the severity of nutritional status. Particularly, PhA, an indicator of the health of the cell membrane, was higher in the well-nourished patient group, whereas the edema index (ECW/TBW) was higher in the severely malnourished patient group. PhA was positively associated with albumin and ECW/TBW was negatively associated with serum albumin, hemoglobin, and duration of mechanical ventilation. In non-survivors, PhA was significantly lower and both ECW/TBW and %TBW/fat free mass were higher than in survivors. In conclusion, several BIA indexes including PhA and ECW/TBW may be useful for nutritional assessment and represent significant prognostic factors in the care of critically ill patients.