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INTRODUCTION

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Critically ill patients are often in hypermetabolic states with increased nutritional needs. At the same time, however, such patients are often unable to take adequate oral intake, necessitating the use of supplementary nutrition. Maintaining adequate nutrition in the critically ill patient has shown to decrease infectious complications.1 Early enteral nutrition in the critically ill mechanically ventilated patient has shown to decrease ICU and hospital mortality rates with the greatest benefit derived in the sickest of patients.2 Malnutrition on the other hand is known to adversely impact the length of ICU and hospital stay.3 It is because of the benefits seen with providing optimal nutrition in the ICU that nutritional support therapy has now become an indispensable component in the management of the critically ill patient. Although nutrition can be provided via the enteral or parenteral route, the enteral route is preferred over the latter due to its lower cost, ease of institution and decreased infectious complications.4 Not using the gastrointestinal tract predisposes to gut mucosal atrophy, resulting in translocation of the bacteria across the gut wall leading to bacteremia.

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Shock, sepsis, traumatic brain injury as well as pharmacologic agents commonly used in the ICU setting (opioid analgesics, vasoactive, and paralytic agents), all predispose critically ill patients to develop impaired gastric emptying and decreased enteral motility that is seen in up to 60% of this patient population.7 As a consequence of impaired gastrointestinal motility, high gastric residual volumes (GRVs) are frequently encountered. Finding high GRVs is often used clinically, as an indication of intolerance to enteral feeds. Feeds are thus held or stopped altogether upon encountering high GRVs. It is thought that feeding past the pylorus may result in a lower incidence of high GRVs leading to fewer interruptions in enteral feeding and ultimately in increased nutritional delivery to the patient. However, whether routine monitoring of GRVs is warranted in the critically ill is yet another area of controversy.

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ENTERAL NUTRITION: SITES OF DELIVERY

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Enteral nutrition in the critically ill is usually delivered via an enteric tube which is inserted either through one of the nares or through the oral cavity. The distal tip of this tube may terminate in the stomach (nasogastric or orogastric tube) or in the duodenum (nasoduodenal tube) or alternatively in the jejunum (nasojejunal tube). These feeding tubes can be placed by surgical techniques as well, namely, gastrostomy (percutaneous endoscopic gastrostomy (PEG) if placed via an endoscopic technique) and jejunostomy (percutaneous endoscopic jejunostomy (PEJ) when placed via an endoscopic technique).

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Feeding into the stomach is often termed pyloric or prepyloric feeding, where as feeding into the duodenum or the jejunum is appropriately called postpyloric feeding because the distal end of the feeding tube rests past the pylorus. Although there are a relatively few clinical conditions (Table 70–1) in which feeding via the postpyloric route may be indicated, in a ...

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