How to enterally refeed a critically ill patient
Small bowel atrophy begins within three days of nothing per os (NPO), but is necessary in the management of some patients.
NPO is a common procedure for patients with vomiting and/or diarrhea, pancreatitis, parvoenteritis, megaesophagus, inflammatory bowel/lymphoma, intestinal surgery/short bowel syndrome.
Clinical consequences of an atrophied small bowel are reduced local synthesis and repair, and decreased local and systemic immunocompetence. This patient is more susceptible to systemic infections with the translocation of bacteria and toxins from the bowel.A septic patient is more likely to be anorectic which results in the continued downward spiral of protein-calorie deficiencies unless there is interventional feeding.
Food nutrients and dietary ingredients maintain normal GI morphology and function via chemical and mechanical stimulants.
The type and quantity of nutrients alter mucosal cell mass by affecting the rate of stem cell division. Physical presence of food in the intestines stimulates the release of endogenous and hormonal secretions. Gastric, duodenal and pancreatiobiliary secretions promote mucosal structure and function.
Intestinal integrity is maintained by trophic hormones, blood flow, neurologic input, enteral nutrients and dietary ingredients. What nutrient and dietary characteristics would we want in a product used to begin refeeding an atrophied small bowel?
Small bowel atrophy is characterized by decreased villus height and crypt depth, decreased surface area and motility, decreased brush border enzymes for digestion, decreased secretions and immunity with increased translocation of bacteria, endotoxin and cytokines.
During NPO, there is an absence of positive intraluminal nutrient and dietary factors which lead to decreased hormonal and neurologic stimuli and blood flow.
The small bowel has lost 22 percent of its total weight, 28 percent of its mucosal weight, 35 percent of its mucosal protein, and 25 percent of its mucosal DNA by day seven of NPO. When refeeding these patients, what would logically be the most desirable characteristics of the first food product fed to a patient with an atrophied small bowel?
Protein: Protein digestion is begun in the gastric mucosa with pepsin, but completed by pancreatic enzymes secreted into the intestine via the common bile duct and mucosal brush border enzymes (endopeptidases and exopeptidases). Metabolism of dietary protein is dependent upon the complete digestion and then absorption of single, di- and tripeptides using a sodium-dependent gradient active transport system.
With NPO treatments, gastric and pancreatic protein digestion may remain functional. However, with an atrophied mucosal lining, the complete digestion and absorption of dietary amino acids has to be questioned.
Currently, the recommendation is to provide a hydrolyzed protein source such that dietary di- and tripeptides are fed. These are the most readily absorbable forms of protein in the absence of digestion.
The intestinal uptake of glutamine by the small bowel is known to increase with surgery and trauma to the intestines.
Glutamine is the preferred fuel source for enterocytes. In 80 percent of the published animal data, there is a positive effect with glutamine- enriched feedings over those not containing glutamine. Specifically in dogs, there was an increased intestinal requirement for glutamine during the immediate postoperative phase (<7 d) of intestinal surgery. Intestinal uptake rates returned to normal after day 10 postoperative. Glutamine is a not an essential amino acid, according to AAFCO and is not found in all pet food products. Glutamine is considered a conditionally essential nutrient, probably needed only during periods of physiologic stress to stimulate DNA synthesis and increase mucosal mass early in recovery.
Although glutamine may stimulate stem cells, all essential nutrients will be required for the enterocyte to complete division and maturation. Therefore, a complete and balanced food product specific for the dog or cat containing approximately 2 percent glutamine is recommended.