Introduction

Katherine Liu, MD, CNSP, FACS, Guest Editor

Enteral nutrition support (ENS) has been used successfully in treatingmany diseases, such as cancer, AIDS, pancreatitis, respiratory failure,inflammatory bowel disease, trauma, burns, neurological impairment,bone marrow transplant, and in the perioperative period. ENS is therecommended method of nutritional support in patients who have afunctional gastrointestinal (GI) tract but are unable to eat or maintainadequate oral intake to meet their nutritional requirements. Enteralfeeding is the preferred method of nutritional support in patients withfunctional gastrointestinal tracts for a number of reasons, includingmaintenance of gut function and low cost.

The type of enteral access is determined by where the functional GItract starts, how long ENS will be required, and whether the patient islikely to aspirate. Generally, the gastric route is preferable to small bowelfeeding, nasal feeding tubes may be used when short-term enteral feedingis required, and jejunal feeding is preferable when a patient is at risk ofaspiration. Nasogastric (NGT) or nasoenteric feeding tubes may be safelyinserted at the bedside, although nasojejunal tube placement usuallyrequires endoscopic or radiologic assistance. NGT feeding is associatedwith significant complications and should be used when ENS is requiredfor only a few days. Nasoduodenal feeding has not resulted in asignificant complication rate reduction compared to NGT, and is moredifficult to place. Nasojejunal feeding appears to be superior to eithernasogastric or nasoduodenal feeding with a significant decrease ingastrointestinal complications and gastric residuals.

Recently, percutaneous endoscopic gastrostomy (PEG) has rapidlybecome the most popular route of enteral feeding in patients requiringlong-term ENS. Because the types of patients requiring PEG often havesignificant underlying medical problems, the immediate complication ratemay be as high as 16%, and long-term morbidity may reach 44%.Although PEG feeding is an option for elderly patients, it is associatedwith a high 30-day mortality rate and poor long-term functional status.Similarly, the use of PEG in patients with dementia has not improved theoverall outcome. Percutaneous gastrostomy or jejunostomy may also beplaced radiologically. When all of these methods fail, gastrostomy or

DM, December 2002 749

jejunostomy may be performed surgically, preferably using a laparo-scopic approach.

Prior to initiating ENS, the energy and protein requirements aredetermined by patient specific factors, such as age, height, weight, gender,and underlying illness. In general, indirect calorimetry provides the mostaccurate assessment of energy requirement, although it can be roughlycalculated using available formulas, such as the Harris-Benedict equation.The needs of most patients requiring ENS can be met with a standardenteral formula, although specialty formulas have been developed forspecific disease states, such as liver, renal, and pulmonary disease,glucose intolerance, and healing wounds. Immune enhancing formulasalso have been developed to possibly reduce infection, patient mortality,and overall hospital stay in high-risk patients. Enteral feeding may beinitiated at full strength at a low rate with step-wise increments toeventually deliver the entire requirement. Monitoring intervals should befrequent at initiation and longer after tolerance is demonstrated.

During ENS, the most common complication is failure to meetnutritional goals, especially in critically ill patients, commonly due tointerruption of feeding caused by significant gastric residuals, diagnostictesting, clogged tube, tube displacement, or gastrointestinal intolerance.Aspiration is always a potential risk, though lower with jejunal thangastric feeding. Contrary to common belief, the usual causes of diarrheaare medications, formula composition, rate of administration, and infec-tion, rather than the osmolarity of the formula. ENS is safe in acutepancreatitis, beneficial in critically ill patients, and useful in patients withcancer undergoing surgical treatment, as well as in postoperative support.There are similar considerations in pediatric patients requiring ENS.However, special instructions for formula dilution in infants should begiven, and deprivation of normal oral feeding experience may lead topsychological consequences.

ENS reduces infection rates and is less costly than parenteral nutritionsupport. Nonetheless, the decision to use ENS is often made withoutadequate discussion, either with the patient or the family, regarding itsbenefit, risk, and long-term outcome. It is unlikely to be beneficial withpatients of dementia, untreatable cancer, or terminal disease. Apart fromthe lack of improved survival, ENS may actually contribute to patientsuffering because of the necessity for patient restraint. Therefore, wheninitiating ENS, the eventual outcome and ethical considerations should beaddressed.

750 DM, December 2002