Enteral nutrition in severe acute pancreatitis. Questions looking for answers

Abstract

The nutritional policy in acute severe pancreatitis changed dramatically in the last two decades. After years of recommendations for nihil per os combined with total parenteral nutrition, the policy moved to enteral nutrition delivered by jejunostomy combined with total parenteral nutrition, than changed to only (if possible) enteral nutrition. Than enteral nutrition by nasojejunal tube was advocated. Lately intragastric nutrition in acute severe pancreatitis is under scrutiny. The “classical” recommendation nihil per os aimed the pancreatic rest. Meanwhile the caloric needs should be delivered by total parenteral nutrition. Fasting has a lot of deleterious consequences: villous atrophy, decreased splanhnic blood flow, loss of epithelial tight junctions, decreased secretion of bile salts and IgA, decreased gut associated lymphoid tissue(GALT), bacterial overgrowth and bacterial translocation. The impaired GALT alters the macrophage priming, promotes the release of cytokines, free oxygen species and arahidonic acid metabolits, all of them resulting in enhanced inflammatory reaction and systemic inflammatory response syndrome (1,4,6). By contrast, enteral nutrition preserves the integrity and the barrier function of intestinal epithelium, enhances blood flow, avoids bacterial overgrowth and bacterial epithelial adhesion and prevents bacterial translocation. It is important to stress that infection of pancreatic necrosis is due to enteral bacteria (1,4,6). Thus, enteral nutrition is not only a support intervention, but a therapeutic one because it may directly influence the evolution of the disease by preventing infection of necrotic tissue. It also promotes bowel movements, shortening the duration of paralitic ileus and decreasing intra-abdominal pressure. Taking into account that 65% of total immune tissues and 80% of immunoglobulin producing tissues belong to the digestive tract (gut-associated lymphoid tissue –GALT and mucosal-associated lymphoid tissue –MALT), enteral nutrition has an important effect upon the local and systemic immune response during acute severe pancreatitis. In conclusion, fasting promotes inflammation and enteral nutrition promotes appropriate immune function. Several studies and meta-analysis investigated different parameters (infection rate, morbidity, mortality, rate of surgery, ICUand hospital length-of-stay, costs) in patients with acute pancreatitis comparing enteral versus parenteral nutrition (1,4,8,10). The last (2008) Cochrane meta-analysis showed that rates of mortality, hospital length-of-stay, local or systemic infections and of other complications favor enteral nutrition (19). Parameters of immune response also favor enteral nutrition, which results in lower rates of SIRS, sepsis, multiple organ dysfunction syndrome and mortality. All these evidences translated into guideline recommendations of the European Society of Enteral and Parenteral Nutrition (7). Whenever possible in acute severe pancreatitis enteral nutrition should be used (grade A). If needed, parenteral nutrition may be associated to support energy and nutrients requirements. Whenever possible, the oral route should be used, if not, the alternative is endoscopically placed naso-jejunal feeding. Feeding jejunostomy may be performed during surgery. Standard enteral formula are well tolerated. Today a consensus has been reached considering early enteral nutrition as standard of care in acute severe pancreatitis due to promotion of appropriate immune response, shortening and improvement of disease evolution, decreased infection and surgery rates and diminished costs. However, despite knowledge and commitment, the application of these principles into the daily practice is not an easy task. Enteral nutrition in acute severe pancreatitis is still associated with many questions, which are looking for answers.