[Optimization of energy intake in artificial nutrition: second lecture Jesús Culebras].

A primary goal of nutritional support is to provide the energy requirements needed to sustain metabolic processes, maintain body temperature and tissue repair. The beginnings of artificial nutrition were characterized by high calorie nutritional formulae. The assimilation of physiological concepts, accumulating research data and clinical experience led to a progressive reduction of this intake. During the decade of the 90s of the past century, the concept of permissive underfeeding was proposed. Since then, there has been a controversy between supporters of an initial reduction of energy intake for the critical patient and advocates of a full administration of the estimated calorie needs since the very first days of admission to the Intensive Care Unit. This controversy has extended into clinical practice guidelines, showing a clear disagreement between recent recommendations of ASPEN and ESPEN. In the future we will see the publication of new studies that might better define the evidence on which to base the recommendations of caloric intake. There is also a clear need to deepen the knowledge about the optimal caloric intake in the non-critically ill patient requiring artificial nutrition. It is of great importance that these new concepts, which will arise undoubtedly, are incorporated quickly in the design of nutritional formulas produced by the pharmaceutical industry. Finally, it is important to encourage active participation in continuous educational activities in the field of Nutrition for achieving a rapid incorporation in daily practice of these new concepts of optimal caloric intake.