Nutrition Support Blog: Calories or Protein in the ICU?
December 17, 2012
In the last 2 years there has been an encouraging increase in research exploring the basic “meat and potatoes” questions for nutrition support in the ICU. Questions such as how much to feed and when to add supplemental parenteral nutrition (PN)? A new study suggests that optimization of “energy provision” with PN in adult ICU patients may improve outcomes (1).
Of course, there are a number of details of this study that need to be considered. We have fast-tracked this article into our journal club schedule, so you can look to our upcoming e-journal club for the full details. As usual, the reality is more than a bit different than the abstract conclusions. One aspect that I want to mention here is the notion of calorie versus protein inadequacy. It is important to remember that when patients do not receive full enteral feedings, they not only accrue an energy deficit, they also receive very limited protein and micronutrients. The patients who received supplemental PN in the study by Heideggar et al, not only received about 600 additional calories/day, but they also have received approximately 30 gms of additional protein/day.
We know that a major part of the acute phase response is the rapid proteolysis of body tissue to provide amino acids to the liver to support the dramatic increase in hepatic synthesis of acute phase proteins that we need to survive the insult. Considering that the body is efficient in burning endogenous fat calories to make up any deficit, we may find that protein, and not energy supply may be a more crucial issue in critical illness. A review article in the September issue of AJCN makes a cogent argument for protein as the potential rate-limiting nutrient for survival in the ICU (2).
I highly recommend that you read the full text of the article. If you have ever done a review to look at the evidence for protein recommendations in the adult ICU patient, you will be amazed at just how minimal data we have. I suspect it is long past due that we stop emphasizing the potatoes, and start thinking more about researching the meat of our nutrition support.
1) Heideggar et al. Optimisation of energy provision with supplemental parenteral nutrition in critically ill patients: a randomised controlled clinical trial. Lancet. 2012 Dec 3. [Epub ahead of print] http://www.thelancet.com/journals/lancet/article/PIIS0140-6736(12)61351-8/abstract
2) Hoffer LJ. Appropriate protein provision in critical illness: a systematic and narrative review. Am J Clin Nutr. 2012 Sep;96(3):591-600. http://ajcn.nutrition.org/content/96/3/591.abstract.
"This waybread keeps you on your legs in a wonderful way, though it doesn't satisfy the innards proper, as you might say: not to my feeling anyhow, meaning no disrespect to them as made it."
- JRR Tolkien, The Two Towers