Nutrition Support Blog: Déjà vu All Over Again
January 17, 2012
It is a bit unsettling to see a popular trend come around a second (or a third) time, because it is an unwelcome sign that years have flown by and you are suddenly more “experienced” than you might feel. The second time around for bell-bottom pants, sideburns, and the Atkins Diet were pretty amazing to witness, in part because they were all pretty silly the first time around. It has been even more amazing to see some nutrition support trends show up a second time, because one would hope that our field is based more on science than fashion.
One question that has recently appeared on our radar again for some reason is the idea that critically ill patients may routinely need, or benefit from, elemental or semi-elemental tube feedings. Thirty years ago I was taught to change the enteral feeding formula to an elemental, or semi-elemental product if my patient had “feeding intolerance” or diarrhea. Of course, this teaching came before it was realized that sorbitol (in liquid, syrup and elixir medications) and clostridium difficile were the most frequent reasons for diarrhea in the ICU1, and that malabsorption in the ICU is rare outside of occasional cases of undiagnosed pancreatic exocrine insufficiency. Today we also realize how efficient the human digestive process is, with a capacity for digesting and absorbing far more than we can ever eat. Knowing that if you have a pancreas and biliary system that functions, a patient will rapidly turn a polymeric formula into peptides and amino acids, it seems a bit silly that we ever turned to semi-elemental formulas so quickly.
There are actually older studies out there that you can reference as “evidence” that peptide formulas cause less diarrhea in ICU patients with hypoalbuminemia.2 However the flaws in this research are so readily apparent that no one who has actually read the study would use it as evidence these days. One study randomized 7 (yes seven) patients to receive a peptide feeding and 5 patients a polymeric feeding.2 Feedings were started at ½ strength at 50 mL/hr and then the rate was advanced by 25 mL/hr per day until 100 mL/hr was reached, then advanced to full strength formula. Stool data for the first 48 hours of the study were compared. (Yes, you read correctly, 12 patients for 48 hours was the study). There was NO significant difference in # of stools/day, or of fecal weight between groups. There were 3 patients in the polymeric formula group and 1 in the peptide group who met the criteria for diarrhea(> 300 gm stool output)in the first 48 hours. The three patients with diarrhea in the polymeric group were switched over to a peptide formula, and they then had decreased volume of stool output for the next 24 hours.
With the benefit of hindsight we see today that these are relatively meaningless results due to the very small number of patients, no control for sorbitol or other medications that cause laxation, and the realization that much diarrhea is self limiting and the passage of time rather than the formula change may have been a factor. Never mind the fact that by 48 hours patients were only receiving 900 calories of formula in 24 hours assuming that they received every single drop of formula with 0 interruptions.
In contrast there are 3 larger studies that have randomized 50 critically ill, 23 acutely ill or 41 hypoalbuminemic patients (respectively) to a standard or peptide formulas.3-5 All of these studies reported no significant difference in incidence of diarrhea, nitrogen balance or any outcome that mattered between the groups. Two studies did result in improved serum proteins with standard feedings or peptide feedings at various points in the study, but we know today that serum proteins are a result of illness and recovery and do not correlate with adequacy of feeding.
I really appreciate vintage items, and I like classic music and movies; heck I would even put on a leisure suit and dance to boogie, oogie, oogie,6 but I just can not see going back and making the same nutrition support errors a second time.
While semi and elemental feedings have their place when there is clear digestive insufficiency causing malabsorption, there is just no justification to spending 5 to 10 times the cost on nutrition products where there is no evidence that they will improve tolerance to feedings or patient outcome.
For more information about elemental and semi-elemental feedings in various other disease states see link to the review article: Elemental and Semi-Elemental Formulas: Are They Superior to Polymeric Formulas?
- Edes TE, Walk BE, Austin JL. Diarrhea in tube-fed patients: feeding formula not necessarily the cause. Am J Med. 1990 Feb;88(2):91-3.
- Brinson RR, Kolts BE. Diarrhea associated with severe hypoalbuminemia: a comparison of a peptide-based chemically defined diet and standard enteral alimentation. Crit Care Med. 1988 Feb;16(2):130-6.
- Mowatt-Larssen CA, Brown RO, Wojtysiak SL, et al. Comparisonof tolerance and nutritional outcome between a peptide and a standard enteral formula in critically ill, hypoalbuminemic patients. JPEN J Parenter Enteral Nutr, 1992;16(1):20-24.
- Viall C, Porcelli K, Teran JC, et al. A double-blind clinical trial comparing the gastrointestinal side effects of two enteral feeding formulas. JPEN J Parenter Enteral Nutr, 1990;14(3):265-269.
- Heimburger DC, Geels VJ, Bilbrey J, et al. Effects of small-peptide and whole-protein enteral feedings on serum proteins and diarrhea in critically ill patients: a randomized trial. JPEN J Parenter Enteral Nutr, 1997;21(3):162-167.
- Boogie, oogie, oogie 1978, A Taste of Honey, Capital Records.
“Convictions are more dangerous foes of
truth than lies.”
- Friedrich Nietzsche