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CHAPTER 20: Nutrition Therapy in the Critically Ill 137

frequently than aspiration. A number of risk factors have been identi- ill patients assigned to semirecumbent or supine position. Drakulovic and
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fied that increase risk of aspiration in the ICU. While it is difficult to colleagues demonstrated that providing EN into the stomach in patients kept
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quantify or stratify degree of risk among these factors, a simple categori- in the supine position was associated with a much higher risk of pneumonia
zation differentiates major risk factors for which change in management compared to feeding patients with the head of the bed elevated to 45° (23%
strategy may be needed, versus additional minor risk factors that may vs 5%, p <0.05). In subsequent randomized trial, van Nieuwenhoven et al
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not warrant specific change in therapeutic course. Major risk factors tried to replicate these findings but were unable. They were unsuccessful in
include documented previous episodes of aspiration, decreased level of fully achieving 45° elevation in the intervention group and the supine group
consciousness (including sedation or increased intracranial pressure), was nursed at approximately 20°. These facts may explain the negative find-
neuromuscular disease, structural abnormalities of the aerodigestive ings associated with this study. Thus, a simple maneuver (ie, elevating the
tract, need for endotracheal intubation, overt vomiting or regurgitation, head of the bed to 30°-45°) may reduce the risks associated with enteral feed-
need for prolonged supine position, and persistently high gastric resid- ings and is recommended.
https://kat.cr/user/tahir99/
ual volumes. Additional risk factors include presence of a nasoenteric
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tube, noncontinuous or bolus intermittent feeding, abdominal/thoracic ■ MOTILITY AGENTS
surgery or trauma, delayed gastric emptying, poor oral care, advanced Gastrointestinal prokinetic agents improve gastric emptying, improve
age, inadequate nursing staff, large bore feeding tube, malpositioned tolerance to enteral nutrition, reduce gastroesophageal reflux and pul-
enteral tube (back into the esophagus), or transport out of the ICU. monary aspiration, and therefore may have the potential to improve
1,69
Strategies to prevent aspiration in patients receiving nutrition support outcomes in critically ill patients. While no study has demonstrated
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who have significant risk factors, as outlined below, should be utilized an impact from use of these agents on clinical outcomes, their low
to minimize the risks associated with EN in this setting. probability of harm and favorable feasibility and cost considerations
■ ROLE OF SMALL BOWEL FEEDING warrant their use as a strategy to optimize nutritional intake and
minimize regurgitation. Since cisapride is no longer available and due
A number of strategies may be employed to maximize the delivery of to the concerns of bacterial resistance with the use of erythromycin,
EN while minimizing the risks of gastric colonization, gastroesophageal metoclopramide is probably the drug of choice. It can be prescribed
regurgitation, and pulmonary aspiration (Table 20-1). By delivering with the initiation of enteral feeds or reserved for patients who experi-
enteral feeds into the small bowel, beyond the pylorus, the frequency ence persistently high gastric residuals. It can be discontinued after
of regurgitation and aspiration, and possibly the risk of pneumonia, is four doses if there is no benefit observed, or after tolerance to EN is no
decreased while at the same time nutrient delivery is maximized. There longer a problem clinically. For refractory cases, metoclopramide can
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are 11 randomized trials that evaluated the effect of route of feeding on be used in combination with erythromycin with good effect. Reducing
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rates of VAP. When these results were aggregated, there was a signifi- narcotic dosages and potentially reversing their effect at the level of the
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cant reduction in VAP associated with small bowel feedings (RR 0.77; gut by infusing naloxone or methylnaltrexone through the feeding tube
95% CIs 0.60, 1.00; p = 0.05) compared to gastric feeding. Therefore, may also be effective in improving gastric function and tolerance to EN,
the converse is also true. In some patients, intragastric feeding may be while reducing risk of aspiration. 69
associated with inadequate delivery of nutrition, increased regurgita- Methods not recommended solely to reduce risk of aspiration include
tion, pulmonary aspiration, and pneumonia, particularly if patients are switching to PN, adding acid to the enteral formula, switching from a
cared for in the supine position. large bore to a small bore nasoenteric tube, or converting a nasogastric
The clinical implications of these findings are influenced by the inherent tube to a percutaneous endoscopic gastrostomy tube. 69
difficulties in obtaining small bowel access. Given that some patients will
tolerate intragastric feeds, it seems more prudent to reserve small bowel ■ FEEDING PROTOCOLS
feeds for patients at high risk for intolerance to EN (due to use of inotro- Several observational studies document that EN is frequently inter-
pes, continuous infusion of sedatives, paralytic agents, high gastric residual rupted for high gastric residual volumes, procedures, nausea and vomit-
volumes, or patients with high nasogastric drainage) or at high risk for ing, and other miscellaneous reasons. Over the duration of ICU stay,
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regurgitation and aspiration (nursed in prolonged supine position). this may result in inadequate delivery of EN to a critically ill patient and
■ BODY POSITION the associated complications of inadequate nutrition. Nurse-directed
feeding protocols or algorithms have been shown to increase the amount
While several studies document that elevation of the head of the bed is of EN delivered on a daily basis. Instituting a feeding protocol in ICUs
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associated with less regurgitation and pulmonary aspiration, only one ran- that provides specific instructions on the patient’s management related
domized controlled trial compared the frequency of pneumonia in critically to EN to the bedside nurse has the potential to improve nutrient delivery
and decrease complications. At what volume of gastric residuals should
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EN be held, in the context of implementing these protocols, remains a
controversial subject. Recent studies suggest that inappropriately low
TABLE 20-1 Summary of Strategies to Optimize the Benefits and Minimize the thresholds do not protect the patient from aspiration, but simply result
Risks of Enteral Nutrition and Total Parenteral Nutrition
in more frequent cessation of EN delivery. Higher thresholds (>400)
Enteral Nutrition Total Parenteral Nutrition may be just as safe as lower thresholds (<250). 79,80
Initiate early, within 24-48 hours of admission Hypocaloric dose ■
Use small bowel feedings Do not use lipids for short-term use ROLE OF IMMUNE ENHANCING NUTRIENTS AND ANTIOXIDANTS
Elevate head of the bed (<10 days) An additional strategy to maximize the benefits of enteral nutrition is
to consider using products supplemented with specific nutrients that
Use motility agents Tight control of blood sugars modulate the immune system, facilitate wound healing, and reduce
Use feeding protocol that enables consistent Supplement with glutamine oxidative stress. Enteral formulas developed to such an extent contain
evaluation of gastric residual volumes and selected substrates such as glutamine, arginine, and omega-3 fatty acids,
specifies when feeds should be interrupted as well as selenium, vitamins E, C, and A, and β-carotene in supra-
Use concentrated feeding formulas in cases of Continue to trickle concentrated physiologic concentrations. Unfortunately, with the possible exception
intolerance amounts of enteral nutrition if able of glutamine, the nutrients by themselves have not been adequately
studied in critically ill patients, so their individual efficacy remains
Consider formulas with immune additives unknown. Nevertheless, these nutrients have been combined together

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