Assessment of body composition in the intensive care unit patients: advantages and limitations

Abstract

The risk of undernutrition is elevated in the intensive care unit (ICU). This risk will increase during the next decades because of ageing and higher prevalence of obesity, chronic diseases, and cancer, which are associated with a high risk of fat-free mass (FFM) loss. In these situations, the clinical and biological assessment of nutritional status is not accurate to estimate FFM loss. Energy deficit, leading to FFM loss, is correlated with the prognosis and clinical outcome during the ICU stay, and impairs patient’s muscle function and quality of life after ICU stay. Assessment of body composition should be implemented in the clinical practice in the setting of an early and optimized nutritional management. Because of its simplicity, reproducibility, and low cost, bioelectrical impedance (BIA) appears to be the method of choice to assess the body composition in the ICU. BIA also allows to calculate the phase angle, which is directly associated with prognosis. Given the importance of FFM loss during the ICU stay, body water variations less than ± 2 kg should not distort FFM loss identification. BIA could also be used as a method of measurement of body water variations. As recently suggested in oncology patients, body composition could be accurately evaluated by computed tomography images, which are frequently performed at the early phase of critical illness. Repeated FFM measurement could reduce undernutrition-related complications and costs as well as improve the quality of life of ICU patients.