Strategies of combined minimally enteral and total parenteral nutrition of the critically ill patient

The advantages of minimally enteral nutritional support (MEE) during critical illness, compared to total parenteral nutrition, are based on a more physiologic route of application and a more complete supply of substrates. Recent investigations have shown a protective effect of MEE with regard to intestinal barrier integrity and decreased infection-related morbidity. There is also evidence of reduced stress response, optimized substrate utilization, and better formula tolerance. However, MEE is an invasive therapeutic procedure with the potential risk of gastric colonization, aspiration, and feeding tube complications. Its clinical use can further be complicated by reflux, diarrhea, and intestinal impact. To overcome most of these problems, the jejunal route of administration is essential. Practicability and efficacy of MEE are dependent on the preexisting extent of the mucosal trauma (ischemic mucosal damage, mucosal atrophy) and the current degree of intestinal hypoperfusion. When absolute contraindications have been ruled out, MEE should be started at a rate of 5-10 ml/h and has to be adjusted according to clinical feasibility. The use of combined enteral and parenteral nutritional support is mandatory. Total supply of energy and nitrogen should be guided by monitoring of blood urea nitrogen, urea production rate, serum concentrations of triglycerides and glucose. This strategy of nutritional support may precipitate a hypoenergetic nutritional therapy; however, the offered variety of nutrients should be as complete as possible. This, in particular, is of importance as far as the supply of conditionally essential substrates, vitamins and trace elements is concerned. During severe stress metabolism the goal of nutritional support has to focus on the preservation of organ function and yet has to avoid the side effects of hyperalimentation.