[Nutritional assessment of the severely ill patient]. / Valoración del estado nutricional en el paciente grave.

There are different parameters aimed at assessing nutritional status. These parameters may be of some help to assess nutritional status prior to patients' admission. However, their application in the critically ill patient is troublesome since results interpretation is interfered by changes originated by the acute disease or treatment measures. This is particularly true in relation to anthropometrical variables that are severely affected by changes in water distribution in the critical patient. Biochemical markers (creatinine/height index, serum albumin, etc.) are also interfered as a result of the metabolic changes that modify the synthesis and degradation processes. Short half-life proteins (prealbumin, retinol-bound protein) are not indicative of the nutritional status although they do inform about an appropriate response to nutrients intake and concurrence of new conditions of metabolic stress. Functional assessment parameters, such as muscular function test, are also difficult to apply in a great number of patients. Subjective global assessment, although it requires some degree of expertise, may be an appropriate tool. Some theoretically more accurate methods, such as bioelectrical impedance, need further investigation in these patients before being recommended.