As mentioned in one of our earlier entries two important trials (Hermanns et al. The Lancet and Caesar et al. NEJM) have indicated that early parenteral nutrition (PN) might actually be harmful and a late PN strategy should be the standard of care.
Despite this the debate has continued and remains highly controversial. This is nicely reflected in recent guidelines regarding the timing of supplemental PN. While the European Society for Clinical Nutrition and Metabolism (ESPEN) recommends PN within 24-48h in patients who are expected to be intolerant to enteral nutrition (EN), the American Society for Parenteral and Enteral Nutrition (ASPEN) recommends postponing the initiation of PN until day 8 after ICU admission.
In order to clarify things a little Bost et al. have now published a systematic review on the timing of parenteral nutrition in critical care (Open access). From 3520 initially screened articles only four randomised controlled trials and two prospective observational studies remained after critical appraisal.
"In conclusion it seems to be reasonable to assume that in critically ill patients, when full enteral support is contraindicated or fails to reach caloric targets, there are no clinically relevant benefits of early PN compared to late PN with respect to morbidity or mortality end points.
Considering that infectious morbidity and resolution of organ failure may be negatively affected through mechanisms not yet clearly understood and acquisition costs of parenteral nutrition are higher, the early administration of parenteral nutrition cannot be recommended."
The Review in one short sentence: Early PN has no advantage over late PN, but might be actually harmful.
Bost et al. Annals of Intensive Care 2014, 4:31
ESPEN Guidelines on parenteral nutrition, 2009
A.S.P.E.N. Guidelines for the provision and assessment of nutrition support therapy in the adult critically ill patient
BIJC.org on: Starting early PN weakens the critically ill