Enteral nutrition (EN) refers to the act of taking nutrients into the body through the gastrointestinal (GI) tract. When a patient cannot ingest the necessary nutrients by eating food, either because of illness, injury, surgery, dysphagia, or changes in absorption, EN can be used to fill the void. In medical terms, we typically think of EN as supplying specialized nutrition support via tube feedings. Parenteral nutrition (PN) provides nutrition intravenously, entirely bypassing the GI tract. In general, if the GI system is functional, it is preferable to use EN rather than parenteral feedings.
EN is used in various clinical situations. It may be used to provide nutrition acutely when a patient cannot ingest or absorb adequate nutrition from oral intake or to provide nutrition during periods of extended illness. In general, if an otherwise well-nourished patient cannot take food by mouth for 7 to 14 days, EN should be considered. EN may be the only means of energy intake, or may be used as a supplement to food when oral intake alone is insufficient. Enteral feedings are preferred to parenteral feedings (provision of nutrients through the venous system) for several reasons. Enteral feedings make use of a functional or partially functional gut, reducing the risk of gut atrophy. EN also reduces the risk of infection by removing the need for venous access, and it is also less costly than PN. Additionally, EN is associated with significantly less metabolic complications, particularly glucose intolerance and increased requirements for insulin given it is more physiologic compared to PN in terms of nutrient utilization.
The decision to initiate EN therapy must be based on determination of risk:benefit ratio. The potential benefit for the patient must outweigh the risks of tube placement as well as risk of complications. There are a variety of factors that must be considered when initiating EN in any patient. These issues are discussed below.
Several considerations dictate the route of administration. The level of GI dysfunction and disease state determines where nutrients should enter the GI tract. Feeding should be initiated at the highest level of functional gut, consistent with the patient’s disease. This will maximize the nutrient absorption as well as maintain the gut function at the highest level possible. Patients with gastroparesis or other motility disorders may benefit from tube placement in the jejunum or duodenum as opposed to the stomach. Another consideration is anticipated length of treatment; short-term therapy is typically achieved through use of a nasogastric, orogastric, nasojejunal, or orojejunal tube, but longer therapy usually requires percutaneous placement of a gastrostomy or jejunostomy tube (Table 37-1). Feeding tubes that are intended for short-term therapy are typically placed manually at the bedside as opposed to surgical or endoscopic placement of gastrostomy or jejunostomy tubes that are intended for provision of long-term EN.