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ساعت ٩:٥۱ ‎ق.ظ روز ۱۳٩٠/۱۱/۱۱   کلمات کلیدی:
 
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Consider Early Enteral Feeding
Bryan A. Cotton MD
If the gut works, use it!
As with other basic principles in patient care, this simple maxim of nutrition has sometimes been inexplicably ignored as our technological and pharmacological advances have exponentially increased over the past several decades. However, to ignore this simple idea is often to the detriment of the patient. Numerous studies have demonstrated a correlation with poor nutritional status and poor postoperative outcome. The current literature supports the preferential use of enteral feeding over parenteral nutrition (total parenteral nutrition, TPN) in intensive care unit (ICU) patients whenever possible. The reasons for this include not only the beneficial effects of enteral support but also the detrimental effects of TPN.
Beneficial Effects of Enteral Feeding
Several recent studies have demonstrated that gut mucosal dysfunction, in the form of increased permeability and villous sloughing, occurs early in the absence of enteral feedings. In the critically injured patient, several authors have demonstrated improvements in the catabolic state, specifically through improved nitrogen balance, when enteral nutrition is utilized instead of TPN. Physiological advantages of enteral nutrition over TPN include its stimulation of gallbladder emptying and release of pancreatic secretions, as well as maintenance of gut-associated lymphoid tissue (GALT) and mucosal immune function. The improved gut mucosal integrity noted with enteral feedings is likely responsible for the decreased bowel perforation rate, improved intestinal anastomotic healing, and decreased septic complications. In addition, enteral feeding is significantly less expensive (even when excluding the costs associated with TPN complications) than parenteral formulations.
Detrimental Effects of Parenteral Nutrition
The intestinal mucosa and submucosa is an area of intense metabolic and immunologic activity, especially in the critically ill and severely injured patient. Utilization of TPN in these patients further
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compromises an already tenuous situation, with loss of mucosal mass and weight, increased villous sloughing, and disturbed mucosal enzyme activity. TPN use has been shown to decrease IgA in the gut, as well as in upper respiratory secretions. From a metabolic standpoint, TPN causes metabolic acidosis, hyperglycemia, hyperlipidemia, and significant electrolyte disturbances. In addition, TPN has been associated with hepatic steatosis and cellular injury leading to liver dysfunction and failure. Systemically, the effects of TPN include impairment of leukocyte chemotaxis, impaired phagocytosis, and an attenuated inflammatory response. Other authors, however, have shown TPN associated alterations may actually potentiate the systemic inflammatory state by allowing increased bacterial translocation and increasing free-radical formation. Some studies have demonstrated higher mortality, especially among the critically ill, in those receiving parenteral nutrition compared with enteral feeding, with TPN almost doubling the risk of dying. Of note, the risks of TPN toxicity can be reduced by the addition of low-rate (sometimes referred to as trophic) tube feedings (10 to 30 mL/h).
When and How to Give Enteral Feedings
Several authors have investigated the impact and timing of early enteral nutrition. In the trauma and burn setting, delays of as little as 24 hours have been demonstrated to impact morbidities and outcomes. In fact, no evidence exists to support withholding enteral feedings in those patients with an open abdomen. Among the emergency surgery population, enteral feedings should be utilized early in the postoperative period. Although tube feedings are routinely held because of concerns of bowel-wall edema and nonperistalsis, this is not supported by the literature. With the exception of bowel obstruction and proximal enteric fistulae, early enteral nutrition has been demonstrated to be tolerated and of benefit even among those presenting with significant peritonitis and premorbid malnutrition. Early enteral support is also recommended following surgery for gastrointestinal malignancies and even in cases of severe pancreatitis, with evidence of attenuated organ dysfunction and improved outcomes.
When possible, the postpyloric position should be utilized for enteral feeding, with the nasojejunal location preferred in pancreatitis. Although many patients experience gastroparesis and some evidence suggests increased risk for aspiration, numerous studies support safety and tolerance of the gastric route. Most importantly, aggressive attention to placing enteral access (whether surgical or nasal route) should
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be considered prior to completion of the operative procedure. It is at this time that placement is most likely to be successful from a technical standpoint and best tolerated with regard to patient comfort.
One final note is that some experienced clinicians who believe in early and aggressive enteral feedings do not support the use of high volume enteral feedings during the initial phase of active resuscitation from shock or sepsis or in high-dose pressor use.
Suggested Readings
Jabbar A, McClave SA. Pre-pyloric versus post-pyloric feeding. Clin Nutr. 2005;24:719–726.
Kaur N, Gupta MK, Minocha VR. Early enteral feeding by nasoenteric tubes in patients with perforation peritonitis. World J Surg. 2005;29:1023–1027.
Marik PE, Pinsky M. Death by parenteral nutrition. Intens Care Med. 2003;29:867–869.
Simpson F, Doig GS. Parenteral vs. enteral nutrition in the critically ill patient: a meta-analysis of trials using the intention to treat principle. Intens Care Med. 2005;31:12– 23.