Nutritional supplementation is vital to the recovery process for most disease processes and after traumatic injury. However,
many of these patients do not receive sufficient nutrition during the healing and recovery process. Over time, this lack
of proteins, minerals, and energy substrates can lead to a state of general illness, malnutrition, and profound disability,
a condition defined as cachexia. A cachexic patient has the potential to develop anemia, reduced cardiac mass and function,
decreased pulmonary function and respiratory drive, and altered intestinal morphology and impaired absorptive ability. In
human studies, the early use of enteral nutrition has resulted in a decrease in infectious and noninfectious complications,
development of SIRS or MODS, length of stay in the ICU and hospital, and mortality. However, some patients are not able to
tolerate full nutritional requirements by an enteral route due to intractable vomiting or other significant gastro-intestinal
disease states. In these situations, providing small amounts of nutrients to the cells lining the gastro-intestinal tract,
complications of disease such as gut derived sepsis may be avoided. Micro-enteral nutrition is the delivery of small amounts
of water, electrolytes, and readily absorbed nutrients directly to the gastro-intestinal tract to maintain mucosal cell integrity.
The gastro-intestinal tract receives it's nutrients from intra-luminal absorption. Food within the gastrointestinal tract
serves as a direct source of nutrients to the mucosa. There are specific "gut fuels" that are preferentially used as energy
substrates by enterocytes, colonocytes, and immune cells that may be present depending upon the composition of the diet. The
enteral route of feeding also stimulates mesenteric blood flow, the autonomic nervous system, secretion of various digestive
enzymes, hormones, and growth factors, increases GI mucus production, and helps prevent ileus. Finally, the sources and processing
of nutrients in a diet can influence the make-up of the gastrointestinal microflora. When the gastro-intestinal tract does
not receive sufficient nutrients, several pathologic consequences can occur. These include villous atrophy leading to increased
mucosal permeability, decreases in gut-associated lymphoid tissue (GALT), and decreased surface area for absorption of nutrients
for systemic use.
When gut barrier failure occurs in critical illness secondary to shock, trauma, or sepsis, this allows translocation of bacterial
and endotoxin into the portal and, sometimes, systemic circulations. This gut derived sepsis may lead to a systemic inflammatory
response (SIRS). SIRS can alter the function of distant organs, possibly leading to multi-organ failure and death.
Patients that are candidates for micro-enteral nutrition include those patients that are predisposed to or already have developed
stress gastric ulceration, patients with oro-facial or cervical injury, patients that are actively vomiting, and those patients
that are early in recovery from severe gastro-intestinal disease or gastro-intestinal surgery. Microenteral nutrition is commonly
delivered by naso-esophageal or naso-gastric feeding tubes. Naso-esophageal and naso-gastric tubes are among the easiest
and least expensive forms of feeding tubes available for use. Argyle infant feeding tubes are ideal, are soft and pliable,
and are well tolerated after placement by most patients. Red rubber feeding tubes are a viable alternative, although they
can more reactive with the nasal mucosa.