Page 232 - Hall et al (2015) Principles of Critical Care-McGraw-Hill

136 PART 2: General Management of the Patient

■ ACHIEVING ACCESS to the ICU) to some form of delayed nutrient intake (ie, delayed EN

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Unfortunately, obtaining enteral access early in the course of the critical or oral diet). When results from these studies were aggregated,
early EN was associated with a trend toward a reduction in mortality
illness may be very difficult. With greater severity of illness, patients
become more prone to ileus with gastroparesis, high residual volumes, (RR 0.60; 95% CIs 0.46, 1.01; p = 0.06) when compared to delayed nutri-
ent intake. Seven studies reported infectious complications.
When
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and intolerance of gastric feeds. Early on, the hypermetabolic response,
SIRS, high doses of narcotic analgesics, and electrolyte abnormalities these were aggregated, early EN was associated with a significant reduc-
tion in infectious complications (RR 0.76; 95% CIs 0.59, 0.98; p = 0.04)
may potentiate gastroparesis. Compounding the problem is the fact that
disuse of the gut reduces the secretion of prokinetic hormones such as when compared to delayed nutrient intake. No differences in length of
stay were observed between groups. All 13 studies reported nutritional
gastrin, bombesin, and motilin. 26,27
The ability to obtain enteral access may be vital to the success of end points and showed a significant improvement in the groups receiv-
https://kat.cr/user/tahir99/
nutritional therapy in the critically ill patient. Each institution needs ing early EN (eg, improvements in calorie intake, protein intake, per-
specialists who have the skills to place tubes at the appropriate levels of centage of goal achieved, and better nitrogen balance achieved). There
were no differences in other complications between the groups.
the GI tract, with techniques that can usually be done at the bedside with
Although the results lack statistical significance, they do suggest a
minimal or no sedation. A number of newer tubes and techniques have large improvement in clinical outcome and a significant increase in
been described for blind postpyloric placement at the bedside, which in
the hands of a dedicated nurse, dietitian, or intensivist should be suc- nutrient delivery associated with early enteral feeding. However, before
endorsing the concept of early enteral feeding, one must consider the
cessful in >85% of cases. 48-51 Newer guidance systems using magnets on
the tip of the feeding tube (guided by handheld magnets on the outside), potential risks of such a strategy. Two recent nonrandomized stud-
ies suggest that early enteral feeds delivered into the stomach may be
tracking systems with a GPS device in the tip of the tube (visualized by 64,65
a monitor on the outside), and optical guidance systems using fiberoptic associated with increased complications. In contrast, Taylor and
colleagues combined an aggressive early feeding protocol with the use
strands or the CMOS camera chip from cell phones placed within the
feeding tube, all should serve to enhance the safety and success rate of of small bowel feedings and documented that head-injured patients fed
aggressively, compared to standard (slower) provision of EN, not only
bedside placement. In cases where bedside placement is unsuccessful
or deeper jejunal placement is required (such as in patients with severe had better nutritional status, but also had fewer complications and a
more rapid recovery from their illness. Moreover, in a large multicenter
10
acute pancreatitis), enteral access to the small bowel may require endo-
scopic or fluoroscopic placement. For these latter patients, transport out observational study, Artinian and colleagues demonstrated that early EN
(within 48 hours) was associated with a small increase in pneumonia
of the ICU should be avoided to prevent an increased risk of mishaps
(eg, cardiopulmonary arrest, new dysrhythmias, or loss of central IV line rates but not withstanding, these patients who were fed early had a lower
mortality rate compared to patients who received delayed EN.
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access) and pulmonary aspiration. 52-54 Synthesizing these discordant results, it would seem that early EN may
■ ASSESSING TOLERANCE be associated with improved clinical outcomes when done in such a way
Physical examination by the clinical nutritionist may be the most that maximizes the benefits and minimizes the risks (see below). Careful
early EN, particularly if delivered distal in the small bowel, will reduce
important element of monitoring the patient on enteral tube feed- the risk of EN and provide the benefits of maintaining gastrointestinal
ing. Abnormalities on physical examination usually reflect segmental structure and function. Furthermore, it should be noted that the goal of
abnormalities in contractility of the GI tract. Bloating, abdominal dis- early EN, while critically ill patients are still early in the acute phase of
tention, hyperresonance, and increased residual volumes may signify their illness, is to provide enough critical nutrients to the gut to modulate
delayed gastric emptying. In patients placed on nasogastric drainage, the disease process and enhance gut barrier structure and function, not
output of >1200 mL/d may indicate relative gastroparesis. Contractility to meet their caloric requirements as soon as possible. Thus for some
of the colon may be assessed by passage of stool and gas. The presence patients with evidence of inadequate oxygen delivery, specific nutrients
of bowel sounds is a poor indicator of contractility in the small bowel, (eg, glutamine and antioxidants) may be more important to provide in
as evidenced by the fact that nasogastric suction will reduce its detec- the first few days of critical illness. If patients are still on high-dose ino-
tion. Studies performed on the postoperative return of bowel func- tropes to maintain adequate blood pressure, the risk of providing EN may
tion or contractility have provided valuable findings for the clinician. outweigh the benefits. However, recent data suggest that even patients on
Invariably, contractility in the stomach stops initially, followed next by vasopressors may benefit from early EN. Khalid and colleagues used a
colonic contractility. Small bowel function or contractility appears to be multi-institutional database to identify mechanically ventilated patients
retained the longest. In most critically ill patients (particularly patients on vasopressors and compared the outcomes of those who received early
55
with trauma), who on baseline evaluation have grossly abnormal physi- EN to those were received delayed EN, using sophisticated propensity
cal examinations, tolerance to enteral tube feeding may be defined by matching analysis to adjust for confounding variables. They demon-
67
slight decreases in abdominal distention and abdominal discomfort in strated that the group of patients that received early EN had a much
the absence of high gastric residual volumes, metabolic acidosis, third- lower mortality rate than those that received delayed EN. Moreover,
spacing of fluids, or a worsening clinical condition. These findings on they described that the sickest patients, those on multiple vasopressors
serial physical examinations determine whether the position of the feed- experienced the largest benefit. This is the strongest available evidence
ing tube needs to be changed (ie, placing the tip of the tube lower down to support the safety and efficacy of feeding the hemodynamically chal-
in the GI tract at or below the ligament of Treitz), whether a tube with lenged patient. By no means are we advocating that EN has any role in
simultaneous aspirating and feeding capabilities needs to be added, or the unresuscitated, unstable patient. But once fully resuscitated, despite
whether the feeds need to be temporarily discontinued. the presence of vasopressors, EN should be initiated. If there are concerns
about tolerating high-volume intragastric nutrition in such patients,
STRATEGIES TO MAXIMIZE THE BENEFITS either direct jejunal feeding or initiating low-volume feeds (trophic feeds)
AND MINIMIZE THE RISKS OF ENTERAL NUTRITION at 10 to 20 mL/h for 24 hours then reassessing could be considered.
■ TIMING OF ENTERAL NUTRITION ■ REDUCING RISK OF ASPIRATION
While enteral feeding is the preferred route of nutrient administration, It is important on initial evaluation to assess the patient’s risk for aspi-
how soon it should be started after an acute injury or insult is not clear. ration on EN. Aspiration may occur from the antegrade passage of
In critically ill patients, there were 14 randomized controlled trials contaminated oropharyngeal secretions or the retrograde passage of con-
comparing early EN (ie, that started within 24-48 hours of admission taminated gastric contents into the larynx. Regurgitation occurs more

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