Nutrition Support Blog: Early Enteral Feeding in the ICU?
April 29, 2014
I started working in ICUs at an exciting time for nutrition support. Evidence was emerging that nutrition support could have an impact on critically ill patients that went beyond just providing calories, protein and micronutrients. The concepts of nourishing the gut lumen, bacterial translocation and potential detrimental effects of parenteral nutrition (PN), beyond line infections, were just reaching clinical medicine and surgery journals.1,2 Some of these concepts were quite contentious and even volatile at the time. The first ASPEN chapter meeting I attended in 1989 witnessed an audience member attempting to shout down a speaker (not me btw…just saying) for daring to suggest that PN might be bad, or even dangerous for some patients. I left that MASPEN meeting enthralled with how passionate (and loud) everyone was about nutrition support, and only later, disappointingly, found out that was not the norm for ASPEN chapter meetings.
Today, there is much greater acceptance of EN (and we are way better at it!) and we are starting to have a better appreciation for the role of the GI tract and the microbiome in critical illness. The ASPEN/SCCM and Canadian critical care guidelines currently recommend early EN in the first 24-48 hours in adult critically ill patients. I have even heard some speakers suggest, and some articles remark about the, “known benefits” of early EN. However, it is important to remember that the potential benefits of very early EN remain open to debate. The data supporting early EN in critically ill adult patients is based on small studies with methodological weaknesses. One meta-analysis of 8 studies had a total of only 317 patients, and the other meta-analysis had a total of 234 patients in 6 studies.3,4 As I have mentioned in a past blog, critical care physicians have learned the hard way that studies with only 300 patients can be misleading, and even lead to patient harm (never mind only 300 patients in all studies put together): http://www.healthsystem.virginia.edu/pub/dietitian/inpatient/dh/nutrition-support-team-blog/nutrition-support-blog-4
Also, several of the key studies provided PN to the late EN groups, so it is hard to know if the results of some early EN studies represent the benefits of early EN, or is simply the known detrimental effects of early PN. The ASPEN guidelines recognized the limitations of current data by assigning the lukewarm “Grade C” for early EN in the ICU.5 A recent review article correctly pointed out that we still do not have high-quality randomized studies providing us with robust evidence that early EN in the adult ICU improves patient outcome.6
Especially in an era of improving ICU care with shorter stays, we may need to rethink our approach to early enteral feeding in some populations.
We have no desire for patients to accrue a large nutrition deficit, or experience hospital-acquired malnutrition, but we should be weighing the potential, but not proven benefits of early EN, with the small, but known risks associated with providing enteral nutrition support. You may quibble about what I consider an “exciting time”, but I think we can agree that we need to remain objective about what we really know and be honest about the limitations of current evidence if we hope to advance the field and make good clinical decisions.
“Losing an illusion makes you wiser than finding a truth.”
- Ludwig Borne
1. Alverdy JC1, Aoys E, Moss GS. Total parenteral nutrition promotes bacterial translocation from the gut. Surgery. 1988 Aug;104(2):185-190.
2. Moore FA, Moore EE, Jones TN, et al. TEN versus TPN following major abdominal trauma‑reduced septic morbidity. J Trauma 1989:29:916‑922.
3. Heyland DK, Dhaliwal R, Drover JW, Gramlich L, Dodek P; Canadian Critical Care Clinical Practice Guidelines Committee. Canadian clinical practice guidelines for nutrition support in mechanically ventilated, critically ill adult patients. JPEN J Parenter Enteral Nutr.2003 ;27:355 -373.
4. Doig GS, Heighes PT, Simpson F, Sweetman EA, Davies AR. Early enteral nutrition, provided within 24 h of injury or intensive care unit admission, significantly reduces mortality in critically ill patients: a meta-analysis of randomised controlled trials. Intensive Care Med. 2009;35(12):2018-2027.
5. McClave SA, Martindale RG, Vanek VW, et al. Guidelines for the Provision and Assessment of Nutrition Support Therapy in the Adult Critically Ill Patient: Society of Critical Care Medicine (SCCM) and American Society for Parenteral and Enteral Nutrition (A.S.P.E.N.). JPEN J Parenter Enteral Nutr. 2009; 33(3):277-316.
6. Casaer MP, Van den Berghe G. Nutrition in the acute phase of critical illness. N Engl J Med. 2014;370(13):1227-1236.