Chapter 073. Enteral and Parenteral Nutrition (Part 3) Efficacy of SNS in Different Disease States Efficacy studies have shown that malnourished patients undergoing major thoracoabdominal surgery benefit from SNS. Critical illness requiring ICU care including major burns, major trauma, severe sepsis, closed head injury, and severe pancreatitis [positive CT scan and Acute Physiology and Chronic Health Evaluation II (APACHE II) > 10] all benefit by early SNS, as indicated by reduced mortality and morbidity. In critical illness, initiation of SNS within 24 h of injury or ICU admission is associated with a ~50% reduction in mortality. Patients with nitrogen accumulation disorders of renal and hepatic failure have a likelihood of PCM of >50% and at least a moderate SRI. Improvements in morbidity, including infection rates, encephalopathy, liver or renal function, and length of hospital stay have been found with SNS. Inflammatory bowel disease— including Crohn's disease particularly, and, to a lesser degree, ulcerative colitis— often produce PCM. In the outpatient setting, SNS in Crohn's disease can improve nutritional status, quality of life, and the likelihood of remission. With pulmonary disease in the critically ill, SNS improves ventilatory status, and in acute lung injury the use of omega 3 fats as a component of SNS improves gas exchange and respiratory dynamics and reduces the need for mechanical ventilation. Low body weight in chronic obstructive pulmonary disease is associated with diminished pulmonary status and exercise capacity and higher mortality rates. However, there is little convincing evidence that SNS as caloric supplementation improves nutrition or pulmonary function. PCM is also common in the course of cancer and HIV disease, although less so in the latter with the advent of highly active antiretroviral therapy. When PCM develops as a consequence of SRI in these conditions, there is limited likelihood of substantial efficacy or benefit from SNS. However, when PCM develops as a consequence of gastrointestinal dysfunction, SNS can be effective. Although no randomized trials have been performed for SNS provided for hyperemesis gravidarum, there is considerable clinical evidence that it improves pregnancy outcomes. Risks and Benefits of Specialized Nutrition Support The risks are determined primarily by patient factors such as state of alertness, swallowing competence, the route of delivery, underlying conditions, and the experience of the supervising clinical team. The safest and least costly approach is to avoid SNS by close attention to oral food intake, by adding an oral liquid supplement, or in certain chronic conditions by using medications to stimulate appetite. Nutrient intake monitoring by frequent calorie counts or oral formula selection is best performed by a nutritionist. Enteral tube feeding is often required in patients with anorexia, impaired swallowing, or bowel disease. The bowel and its associated digestive organs derive 70% of their required nutrients directly from food in the lumen. Arginine, glutamine, short-chain fatty acids, long-chain omega 3 fatty acids, and nucleotides available in some specialty enteral formulas are particularly important for maintaining immunity. Enteral feeding also supports gut function by stimulating splanchnic blood flow, neuronal activity, IgA antibody release, and secretion of gastrointestinal hormones that stimulate gut trophic activity. These factors support the gut as an immunologic barrier against enteric pathogens. For these reasons, some luminal nutrition should be provided, even when PN is required to provide most of the nutritional support. The combination of some enteral feeding either by mouth or by enteral tube with parenteral feeding often shortens the transition to full enteral feeding, which can generally be used when >50% of requirements can be met enterally. Substantial nutritional benefit can be achieved by providing ~50% of energy needs for periods of up to 10 days, if protein and other essential nutrient requirements are met. For longer periods of time, it may be preferable to provide 75–80% of energy needs, rather than full feeding, if this improves gastrointestinal tolerance, glycemic control, and avoidance of excess fluid administration. In the past, bowel rest through PN was the cornerstone of treatment for many severe gastrointestinal disorders. However, the value of providing even minimal amounts of EN is now widely accepted. The development of protocols to facilitate more widespread use of EN include initiation within 24 h of ICU admission; aggressive use of the head-upright position; postpyloric and nasojejunal feeding tubes; prokinetic agents; more rapid increases in feeding rates; tolerance of higher gastric residuals; and nurse-administered algorithms. PN alone is generally necessary only for severe gut dysfunction due to prolonged ileus, obstruction, or severe hemorrhagic pancreatitis. In the critically ill, feeding adequately by PN beginning within the first 24 h of care improves mortality and is more effective than delayed EN. Early feeding of the critically ill in the ICU is associated with a 50% reduction in mortality, but there is also a 50% increase in infection risk. Much of the increase in morbidity related to PN and EN is due to hyperglycemia, which can be significantly reduced by insulin therapy. The level of glycemia necessary to accomplish this goal, whether <110 mg/dL or only <150 mg/dL, is not yet defined. . Chapter 073. Enteral and Parenteral Nutrition (Part 3) Efficacy of SNS in Different Disease States Efficacy studies have. luminal nutrition should be provided, even when PN is required to provide most of the nutritional support. The combination of some enteral feeding either by mouth or by enteral tube with parenteral. injury, and severe pancreatitis [positive CT scan and Acute Physiology and Chronic Health Evaluation II (APACHE II) > 10] all benefit by early SNS, as indicated by reduced mortality and morbidity.