Page 533 - ACCCN's Critical Care Nursing

510 P R I N C I P L E S A N D P R A C T I C E O F C R I T I C A L C A R E

providing nutrition to the critically ill who cannot have and institutions, 24,58,93-95 primarily as a consequence of
oral feeding is controversial. Infectious complications the shortage of reliable and valid research into the
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have been associated with PN when used alone, but no effective delivery of enteral nutrition. In the absence of
differences in infectious complications were seen with strong research evidence, rituals are embraced and rarely
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concurrent use of EN and PN. In a meta-analysis, PN challenged. Furthermore, the implementation and
was associated with reduced mortality when comparing sustainability of guidelines is influenced by multiple
PN with delayed EN despite the increased risk for infec- factors, e.g. clinicians, patients, context and contents of
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tious complications associated with PN. Meta-analyses guidelines. 96
are limited by the quality of the studies included in the
analyses. 53,54 Recent guidelines advocate early enteral
nutrition 53,55-59 but better evidence is needed. 60 Management of Enteral Feeding
Routes of enteral feeding
ENTERAL NUTRITION The insertion of enteral feeding tubes into the correct
EN has benefits beyond the supply of nutrients to the place in the critically ill can be difficult because of reduced
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body, including: cough reflex, altered sensorium and use of sedative
97
and narcotic medications. Wide-bore nasogastric tubes
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● gut-derived mucosal immunity and decrease in
septic complications 63-65 (sump tubes) are most commonly used in the critically
● preservation of gastrointestinal mucosal integrity 66,67 ill in the early stages of enteral feeding. Because long-term
● improved gastrointestinal mucosal cell growth and use of wide-bore tubes can contribute to sinusitis, a fine-
replacement 68 bore feeding tube is often introduced if enteral feeding is
● increased gastric mucosal blood flow. 69 expected to continue beyond a few days. Should pro-
longed enteral feeding be anticipated (longer than 1
Absence of enteral nutrients (despite the provision of PN) month), gastrostomy, duodenostomy or jejunostomy
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has been linked to atrophy of the intestinal villi, a reduc- tubes may also be used. Postpyloric feeding has not
tion in the number of epithelial cells produced, reduced been shown to be beneficial over gastric feeding, 99,100 but
gastrointestinal mucosal thickness, and ineffective func- is useful for later enteral feeding in patients if gastric
tioning of the intestinal brush border enzymes of the atony is present and the patient has persistent high gastric
gastrointestinal mucosa. 59,70-73 Stimulating and improving residual volumes. 101
gastrointestinal immune function is an important goal of
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early EN. Early enteral feeding (within 48 hours) is For some critically ill patients, gastric secretions may
102
recommended. 55,56 increase when small bowel feeding is initiated. A
double-lumen tube is available, one lumen for gastric
Hypocaloric Intake in the Critically Ill aspiration and decompression and the second for simul-
taneous jejunal feeding, but these tubes are not widely
A significant number of hospitalised patients receiving used in the clinical setting. 103
EN do not have their nutritional needs met. 70,71 Hypoca-
loric feeding in the first few days of critical illness may be
beneficial, 36,74-77 but results are conflicting. 34,78-80 The Assessment of enteral feeding tube placement
belief that early enteral feeding prevents gut dysfunction Correct placement of enteral feeding tubes in the criti-
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independently of calorie intake perpetuates the accep- cally ill can be difficult. 104,105 Misplacement of the feeding
tance of administration of EN below the nutrition tube into the tracheobronchial tree are important
target. 33,70,82,83 In most cases, hypocaloric feeding is unnec- complications of tube insertion. Additional complica-
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essary and avoidable. 84,85 Severe underfeeding over a short tions such as infusion of tube feedings, pneumothorax,
time particularly during the initial week of ICU stay is pneumonitis, hydropneumothorax, bronchopleural
associated with the formation of an energy debt that leads fistula, empyema and pulmonary hemorrhage have been
to increased infections, complications and longer ICU reported. 107-112 While confirmation of tube placement is
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stays. Factors that contribute to unintentional hypoca- routinely done with radiography, this approach does not
loric feeding include staffing shortages, unavailability of prevent incorrect placement occurring during insertion;
feeds/equipment, low priorities for feeding, fasting for less reliable methods of confirming tube placement
clinical investigations, blockages in feeding tubes and include the use of auscultation and aspiration, and other
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variations in feed prescriptions. Delivery issues, such as novel methods such as capnography. 105,113
elective interruption for investigative procedures or oper-
ations, contributed to hypocaloric feeding with only 76% Assessment of feeding tube placement by auscultation of
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of prescribed feeds delivered to critically ill patients. air insufflated into the stomach remains a common clini-
Similar results were observed in mechanically-ventilated cal practice. Auscultation should not be used as the sole
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patients, where more than 36% of patients received less method to determine placement of the gastric tube
than 90% of their caloric requirements. because it is unreliable. Other important points are:
● Aspirate from critically ill patients who receive con-
Enteral Feeding Protocols tinuous feedings may have the appearance of
Enteral feeding protocols improve the delivery of enteral unchanged formula, regardless of the site of the
feeds 87,89,90 and have been shown to improve clinical feeding tube, therefore this method should not be
outcomes. 83,91,92 But protocols vary widely between units used. 114