Enteral Feeding

Enteral Nutrition. Abad-Sinden A, Sutphen I. In: Walker WA, Goulet O, Kleinman RE, Sherman PM, Schneider BL, Sanderson IR, eds. Pediatric Gastrointestinal Disease. 4th ed. Hamilton, Ontario, Canada: BC Decker; 2004:1981–1991Short-Bowel Syndrome and Intestinal Adaptation. Vanderhoof J. In: Walker WA, Goulet O, Kleinman RE, Sherman PM, Schneider BL, Sanderson IR, eds. Pediatric Gastrointestinal Disease. 4th ed. Hamilton, Ontario, Canada: BC Decker; 2004:750–753Nutrition Support. Tiberio E, Surkhang D, Brusco T. In: Piccini JP, Nilsson KR, eds. The Osler Medical Handbook. 2nd ed. Baltimore, Md: Johns Hopkins University; 2006Nutrition in Gastrointestinal Diseases. DeLegge M. In: Feldman M, Friedman LS, Sleisenger MH, eds. Feldman, Sleisenger & Fordtran's Gastrointestinal and Liver Disease. 8th ed. Philadelphia, Pa: Saunders; 2006:365–378Nutrition support is essential for patients unable to meet daily caloric or fluid requirements orally and can be provided either by an enteral or parenteral route. Enteral support is preferred because it is more “physiologic,” less expensive, safer, and associated with fewer adverse effects than parenteral nutrition. Enteral feeding stimulates gastrointestinal (GI) motility, minimizes atrophy of the GI mucosa, decreases the risk of bacterial overgrowth, and prevents translocation of bacteria or bacterial products into the circulation. Enteral nutrition avoids the need for central venous access, thus diminishing infections and eliminating the thrombotic and hepatic complications of parenteral nutrition.Malnourished children unable to maintain adequate nutrition can benefit from enteral feeding. Conditions warranting enteral nutrition include feeding of preterm infants, prolonged anorexia, severe protein-energy malnutrition, neurologic disease or impairment, liver failure, cardiopulmonary disease, inflammatory bowel disease, short gut syndrome, critical illness, and conditions of hypermetabolism (burn injury, cancer, human immunodeficiency virus infection/acquired immune deficiency syndrome, trauma/head trauma), and renal disease. Enteral feeding also may be indicated for children at high risk for aspiration.Enteral feeding provides calories and fluid to the GI tract by means other than the oral route and requires some type of tube delivery system, either temporary for acute conditions or permanent for chronic disabilities. Parenteral nutrition ranges from supportive therapy, in which the tube supplies a portion of the nutrients, to primary therapy, in which the tube delivers all nutrients.A temporary nasoenteric tube (nasogastric, nasoduodenal, or nasojejunal) is recommended when the anticipated duration of nutrition support is limited (1 to 3 mo). For longer-term needs or for patients who have chronic esophageal abnormalities, tube enterostomy is the preferred access route and includes percutaneous tubes (eg, endoscopic gastrostomy and jejunostomy) and surgically placed feeding tubes (eg, open gastrostomy).Gastric administration of feedings is preferred because of the ease of management, ability to use a bolus feeding regimen, and potential benefits of gastric acid as a bactericidal agent. However, jejunal placement should be considered for patients who have significant upper tract disease or when there is a high risk of aspiration, as in critically ill patients.Enteral feedings can be delivered by bolus or continuously. Bolus feedings deliver formula as rapidly as an oral feeding. This technique is simple, requires minimal supplies, and may facilitate the transition to home care. Most patients tolerate bolus feeding, but vomiting, painful abdominal distention, large gastric residuals, or diarrhea may be evidence of intolerance. When intolerance of bolus feedings is suspected, continuous infusion pump feedings are indicated. Continuous administration also is preferred for patients fed through the small intestine or at high risk of aspirating and appears to be particularly beneficial for patients suffering impaired absorption (chronic diarrhea, short bowel syndrome).When selecting an enteral preparation, formula variables to consider include digestibility and availability of the nutrients, nutritional adequacy, and osmolality. Patient variables include nutritional status and requirements, digestive and absorptive capacity, and disease state. Special attention should be paid to osmolality and carbohydrate content when patients exhibit signs of intolerance. The osmolality of a formula is affected by the concentration of amino acids, carbohydrates, and electrolytes. A formula that has an osmolality greater than that of normal body fluids can produce an osmotic effect in the stomach and small intestine, drawing water into the gut and diluting the formula. This excess water can cause diarrhea, nausea, cramping, and distention. Isotonic formulas are designed to alleviate these problems. The osmolality of full-strength isotonic formulas is similar to that of normal body fluids, approximately 300 mOsm/L.Specialized formulas have been tailored to a wide variety of physiologic circumstances while attempting to minimize specific types of intolerance. A complete discussion of the many formulations is beyond the scope of this review, but examples are worth mentioning. Some formulas address the special nutrient requirements of preterm infants while diminishing osmolality and improving digestibility. Patients who have severe GI disease or protein allergies may require semi-elemental or elemental formulas, which also are free of lactose and fructose, to optimize tolerance. Other specialized formulas include calorie- and protein-dense preparations for fluid-restricted patients and fiber-enriched formulas for patients who have severe constipation.Complications of enteral feeding include GI, mechanical, and metabolic problems. GI complications include nausea, vomiting, constipation, and diarrhea. In addition to formula intolerance, nausea and vomiting can be caused by too rapid an infusion rate, delayed gastric emptying, or GI tract obstruction. Constipation may result from dehydration, obstruction, decreased bowel motility, or a decrease in dietary fiber. Diarrhea can be caused by diminished absorptive capacity, formula hyperosmolality, bacterial overgrowth, or enterally administered medications, including antibiotics, formulations containing sorbitol, and magnesium-containing antacids.Aspiration, tube obstruction (ie, dislodged or occluded feeding tube), and mucosal damage (ie, skin breakdown) are examples of mechanical complications. Aspiration, potentially the most serious complication of enteral feeding, is most likely to occur in patients who have neurologic injury, an incompetent lower esophageal sphincter, large gastric residuals, significant gastroesophageal reflux, impaired gastric emptying, improper tube placement, or migration of the tube tip into the upper stomach or esophagus. Percutaneous feeding tubes also are associated with a risk of infection or erosion at the insertion site. Excessive traction may cause gastric wall necrosis and perforation of the stomach. More commonly, patients may experience chronic drainage, erythema, or excessive build-up of granulation tissue with intermittent bleeding.Metabolic complications are less common with enteral than with parenteral feeding. Dehydration and fluid shifts may occur with formulas of high osmolarity. Overly aggressive caloric administration to severely malnourished patients can lead to “refeeding syndrome,” characterized by the development of hypokalemia, hypophosphatemia, and hypomagnesemia. This disorder can result in cardiac arrhythmias, heart failure, respiratory failure, liver dysfunction, coma, and death.Often when enteral feeding is initiated, medications are administered by tube, but this approach has limitations. For example, phenytoin concentrations can be affected because phenytoin-formula complexes adhere to the wall of the tube. Ciprofloxacin has been shown to bind with tube feedings, reducing its absorption.Special considerations should be given to the patient who is transitioning from parenteral to enteral feedings after bowel resection. The timing of this transition depends on the activity of the underlying disease and whether GI function is sufficient for enteral nutrition. Immediately following resection, parenteral nutrition is necessary, primarily because of bowel ileus. Initially, large volumes of fluid and electrolytes may be secreted and gastric fluid lost from nasogastric suctioning. An ostomy may produce additional significant losses. When fluid and electrolyte losses have resolved, continuous enteral infusion may be started, taking into account the extent and specific portions of resected bowel. The initial rate should be slow, and dilute formulas commonly are used. However, if tolerated, the concentration can be increased rapidly to full-strength. Once full-strength feedings are tolerated, the volume of enteral feedings can be increased gradually until caloric goals are reached, and the volume of parenteral nutrition can be decreased simultaneously.When the oral route is restricted, enteral feeding often is the safest, most cost effective, and most physiologic approach to providing adequate nutrition to both acute and chronically ill patients. Several approaches and multiple formulas are available, and each choice should be individualized for the specific needs and circumstances of the patient.Comment: Within the memory of some of us, enteral tube feeding meant placement and repeated replacement of nasogastric tubes, with fear of misplacement into the airway instead of the GI tract. Surgically placed gastrostomy tubes and inconspicuous “buttons” made G-tubes more cosmetically acceptable. Now we have percutaneous endoscopic gastrostomy, which avoids laparotomy and usually can be accomplished with sedation rather than anesthesia. This procedure involves insufflation of the stomach to bring it into apposition with the abdominal wall, followed by the percutaneous passage of a cannula and subsequently a wire into the stomach, over which the gastrostomy tube is guided into place. Ingenious!

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