[Early enteral nutrition in the critically-ill patient].
Enteral nutrition has demonstrated to be a useful and safe method to nourish critically ill patients admitted to the Intensive Care Unit. Although the time a severely ill patient can stand without nutrition is unknown, accelerated catabolism and fasting may be deleterious in those patients, and the more common recommendation is to start on artificial nutrition when a fasting period longer than seven days is foreseen. At an experimental level, advantages of enteral nutrition over parenteral nutrition are evident since the use of nutritional substrates via the gastrointestinal tract improves the local and systemic immune response and maintains the barrier functions of the gut. Clinical studies have demonstrated that early enteral nutrition administered within the first 48 hours of admission decreases the incidence of nosocomial infections in these patients, but not the mortality, with the exception of special groups of patients, particularly surgical ones. The major inconvenience of enteral nutrition is its digestive intolerance and the transpyloric approach, necessary when there is gastroparesia. Its efficacy is also questioned when the patient has tissue ischemia. For early enteral nutrition to be effective, a treatment strategy must be implemented that includes from simple measures, such as uprising the bed headrest, to more sophisticated ones, such as the transpyloric approach or the use of nutrients with immunomodulatory capabilities. To date, the use of early enteral nutrition is the best method for nutritional support in this kind of patients provided that it is individualized according to each patient clinical status and that is done following an adequate therapeutic strategy.