Oct 042012

Image: EIMJM.com

Evidence-based practice guidelines adopted by critical care societies in Canada, Germany, Australia and New Zealand recommend starting enteral nutrition for critical illness shortly after admission to an ICU. In observational studies, critically ill adults get only about 50-70% their caloric goals from enteral feeding; reduced gastric motility is often responsible for the limited caloric intake. Impaired gastric motility also raises concerns for aspiration pneumonia and pneumonitis. Although post-pyloric enteral feeding through a naso-jejunal tube has been shown to improve caloric delivery in some randomized trials, most recently by Hsu et al in 2009, other trials showed no benefit. These trials were generally in "all comers," so Andrew Davies, Siouxzy Morrison, and Michael Bailey set out to answer the question better by exploring whether there would be a benefit of nasojejunal feeding in the patients at highest apparent risk -- those with impaired gastric motility.

What They Did

Authors randomized 181 mechanically ventilated patients who had high gastric "residuals" of > 150 mL aspirated while receiving their initial nasogastric tube feeds (<72 hours) in 17 Australian ICUs, to either receive:

  • Continued tube feedings through a nasogastric tube, or
  • Placement of a post-pyloric nasojejunal tube for ongoing enteric nutrition.

Treatment assignment was thereafter unblinded. The primary end point was the proportion of calculated caloric requirement received. Secondary end points included incident VAP (adjudicated blindly), gastrointestinal (GI) intolerance, ICU and hospital length of stay, duration of mechanical ventilation, and in-hospital mortality.

Patients getting nasojejunal tubes received erythromycin to stimulate peristaltic passage of the tube through the pylorus. Erythromycin and metoclopramide (Reglan) were given to the patients in the nasogastric tube feeding group who developed "high residuals," to stimulate gastric emptying and gut motility.

What They Found

There was no difference between groups in the percentage of intended calories delivered: patients getting nasojejunal tube feeding and those with nasogastric tube feeds both received ~70% of their caloric goals. There was no difference in secondary outcomes, either, including ventilator-associated pneumonia (VAP) incidence (~20%), ICU length of stay, duration of mechanical ventilation, in-hospital mortality, vomiting, abdominal distention, or diarrhea. Patients in the nasojejunal feeding group had higher rates of minor gastrointestinal bleeding (12% vs. 3%). Nasojejunal tubes were placed in 8 (9%) of the nasogastric tube patients (i.e., they crossed over) for persistent slow gut motility.

What It Means

The previous four randomized trials that demonstrated increased caloric delivery and/or improvement in pneumonia rates with postpyloric nasojejunal feedings were smaller (n~40-80 each) [1, 2, 3, 4] This larger and well-conducted trial in an at-risk group strongly suggests that post-pyloric enteral feeding does not improve calorie delivery during enteral nutrition, or improve meaningful clinical outcomes. The 8 patients that crossed over from NG to NJ tubes were unlikely to reduce any real benefit of NJ tubes.

With ~70% of their mechanically ventilated patients receiving goal caloric needs through nasogastric feeding, one wonders how much better we should expect to get. Keep in mind that caloric goals in hospitalized patients are (to my knowledge) not backed by any outcomes research, and are rather based on general principles of nutrition and metabolism. The minor bleeding increase with nasojejunal placement could be considered a strike against its routine use, as well. There is an FDA black-box warning and lawsuits in the U.S. for tardive dyskinesia resulting from Reglan use, but the warning is only for "long-term or high-dose use."

Clinical Takeaway: Nasojejunal tube placement for enteral feedings doesn't provide a detectable benefit in most critically ill patients, even those with clearly impaired gastric motility. Nasogastric tube feedings seem to achieve similar caloric goals, if pro-motility agents like metoclopramide and erythromycin are used. Certain patients (e.g., severe pancreatitis, post-abdominal surgery, gut stenosis), may still benefit from postpyloric tube feedings.

Davies AR, Morrison SS, et al. A Multicenter, Randomized Controlled Trial Comparing Early Nasojejunal With Nasogastric Nutrition in Critical Illness. Crit Care Med; 2012;40 (August): 2342-2348

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Post-pyloric feeding no better than usual NG tube in vented patients (RCT)