The Significance of Enteral Nutrition in the Intensive Care Unit Patient

Nutritional intake in the critically ill: Improving practice through research

Enteral feeding is the preferred method of nutritional support in the critically ill; however, evidence suggests that many critically ill patients do not meet their nutritional goals. The implementation of enteral feeding protocols has improved nutritional delivery, although protocols can be widely variable. Similarly, enteral feeding related nursing practice is also inconsistent within and between intensive care units (ICUs). These variations in enteral feeding practice can be linked to the shortage of reliable and valid research into the many issues associated with the effective delivery of enteral nutrition. In the absence of a strong research tradition and practice, rituals are embraced and rarely challenged, further contributing to the wide variations in enteral feeding practice. Of particular importance are practice issues related to the commencement of enteral feeding and the assessment of feeding tolerance. This article seeks to review the literature related to commencing enteral feeding, with particular reference to the suitability of enteral nutrition, methods of enteral feeding and adjustment of enteral feeding rates. Issues relating to feeding intolerance, including the assessment of gastric residual volume and the development of diarrhoea, will also be explored.

Nutrition in critical care

Many hospitalized patients with cancer are malnourished. Some become critically ill and experience delayed wound healing, loss of muscle strength, and reduced infection fighting ability as a consequence of the loss of nutritional reserves. Complications of critical illness may cause interruption in normal gastrointestinal function and result in shock, sepsis, hypochlorhydria, systemic inflammatory response syndrome, and other disorders. As a result, critically ill patients may require nutritional support.

Intolerance to intragastric enteral nutrition in critically ill patients: complications and management

Compared with parenteral nutrition, early administration of enteral nutrition (EN) to critically ill patients improves clinical outcomes and reduces infection rates. Intragastric EN often is complicated by intolerance, as indicated by elevated volumes of aspirated gastric residuals. Conflicting data are available for the volume of residual that represents intolerance, but most clinicians use 150-200 ml to signify gastrointestinal motility dysfunction. Intolerance is associated with mortality. Data support an association between intragastric EN and aspiration pneumonia, but little information is available regarding the contributory effect of intolerance. Transpyloric migration of the feeding tube may facilitate tolerance but does not reduce the likelihood of aspiration pneumonia. Prokinetic agents (cisapride, erythromycin, metoclopramide) promote gastric emptying. Results of most studies are limited because patients did not receive or tolerated intragastric EN. Metoclopramide is the agent of choice for treating intolerance. Further studies are necessary before prokinetic drugs can be recommended for preventing intragastric EN-associated aspiration pneumonia.

Sequential single doses of cisapride, erythromycin, and metoclopramide in critically ill patients intolerant to enteral nutrition: a randomized, placebo-controlled, crossover study

OBJECTIVE

To evaluate the comparative efficacy of enteral cisapride, metoclopramide, erythromycin, and placebo for promoting gastric emptying in critically ill patients with intolerance to gastric enteral nutrition (EN).

DESIGN

A randomized, crossover study.

SETTING

Adult medical intensive care unit at a university-affiliated private hospital and trauma intensive care unit at a university teaching hospital.

PATIENTS

Ten adult, critically ill, mechanically ventilated patients not tolerating a fiber-containing EN product defined as a single aspirated gastric residual volume >150 mL or two aspirated gastric residual volumes >120 mL during a 12-hr period.

INTERVENTIONS

Patients received 10 mg of cisapride, 200 mg of erythromycin ethylsuccinate, 10 mg of metoclopramide, and placebo as 20 mL of sterile water every 12 hrs over 48 hrs. Acetaminophen solution (1000 mg) was administered concurrently. Gastric residual volumes were assessed, and plasma acetaminophen concentrations were serially determined by TDx between 0 and 12 hrs to evaluate gastric emptying.

MEASUREMENTS AND MAIN RESULTS

Gastric residual volumes during the study were not significantly different between agents. No differences in area under the concentration vs. time curve or elimination rate constant were identified between agents. Metoclopramide and cisapride had a significantly shorter mean residence time of absorption than erythromycin (6.3+/-4.5 [SEM] mins and 10.9+/-5.8 vs. 30.1+/-4.5 mins, respectively [p<.05]). Metoclopramide (9.7+/-15.3 mins) had a significantly shorter time to peak concentration compared with erythromycin and placebo (60.7+/-8.1 and 50.9+/-13.5 mins, respectively [p<.05]). The time to onset of absorption was significantly shorter for metoclopramide vs. cisapride (5.7+/-4.5 vs. 22.9+/-5.7 mins [p<.05]).

CONCLUSION

In critically ill patients intolerant to EN, single enteral doses of metoclopramide or cisapride are effective for promoting gastric emptying in critically ill patients with gastric motility dysfunction. Additionally, metoclopramide may provide a quicker onset than cisapride.

Air insufflation technique of enteral tube insertion: a randomized, controlled trial

OBJECTIVE

To test air insufflation as an adjunct to placement of enteral feeding tubes.

DESIGN

Prospective, randomized study.

SETTING

Intensive care unit in a tertiary hospital.

SUBJECTS

Sixty-four consecutive patients requiring enteral nutrition, in whom a decision to insert a nasoenteral feeding tube was made.

INTERVENTIONS

A 12-Fr feeding tube was inserted to the level of the fundus of the stomach. A 60-mL syringe was used to pump 500 mL of air into the stomach. The tube was then advanced. An abdominal flat plate was obtained within 2 hrs of completion of the procedure and the tube position noted. If the tube was not in the duodenum, the patient was placed on a promotility agent and a repeat radiograph was performed the next day. The technique varied from our control technique only by the instillation of air.

MEASUREMENTS AND MAIN RESULTS

Using the study technique, 21 of 32 tubes were successfully placed, as seen on the initial radiograph, in our study patients compared with only 12 of 34 tubes in our control patients (p< .02). In addition, the success rate at 24 hrs was 25 of 32 vs. 16 of 34 (p< .02). Only 3 of 21 tubes placed in the antrum, body, or fundus of the stomach advanced to the duodenum the following day, compared with 5 of 12 tubes initially placed in the pylorus (p< .075). No complications were noted.

CONCLUSION

Instilling air into the stomach may facilitate the ability to get the feeding tube to the level of the pylorus, at which point it is more likely to advance into the duodenum and beyond.