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N Engl J Med. 2015 Jun 18;372(25):2398-408. doi: 10.1056/NEJMoa1502826. Epub 2015 May 20.

Permissive Underfeeding or Standard Enteral Feeding in Critically Ill Adults.

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From King Saud bin Abdulaziz University for Health Sciences and King Abdullah International Medical Research Center (Y.M.A., A.S.A., S.H.H., H.M.A.-D., H.M.T., M.H.S., M.S., L.A.), and King Faisal Specialist Hospital and Research Center (O.S.) - all in Riyadh, Saudi Arabia; the Department of Internal Medicine, American University of Beirut Medical Center, Beirut, Lebanon (H.M.T.); and the Department of Medicine, Division of Critical Care Medicine, University of Ottawa, Ottawa Hospital Research Institute, Ottawa (G.J., L.M.), and the Interdepartmental Division of Critical Care Medicine, Department of Medicine, Division of Respirology, University of Toronto, and Mount Sinai Hospital, Toronto (S.M.) - all in Canada.



The appropriate caloric goal for critically ill adults is unclear. We evaluated the effect of restriction of nonprotein calories (permissive underfeeding), as compared with standard enteral feeding, on 90-day mortality among critically ill adults, with maintenance of the full recommended amount of protein in both groups.


At seven centers, we randomly assigned 894 critically ill adults with a medical, surgical, or trauma admission category to permissive underfeeding (40 to 60% of calculated caloric requirements) or standard enteral feeding (70 to 100%) for up to 14 days while maintaining a similar protein intake in the two groups. The primary outcome was 90-day mortality.


Baseline characteristics were similar in the two groups; 96.8% of the patients were receiving mechanical ventilation. During the intervention period, the permissive-underfeeding group received fewer mean (±SD) calories than did the standard-feeding group (835±297 kcal per day vs. 1299±467 kcal per day, P<0.001; 46±14% vs. 71±22% of caloric requirements, P<0.001). Protein intake was similar in the two groups (57±24 g per day and 59±25 g per day, respectively; P=0.29). The 90-day mortality was similar: 121 of 445 patients (27.2%) in the permissive-underfeeding group and 127 of 440 patients (28.9%) in the standard-feeding group died (relative risk with permissive underfeeding, 0.94; 95% confidence interval [CI], 0.76 to 1.16; P=0.58). No serious adverse events were reported; there were no significant between-group differences with respect to feeding intolerance, diarrhea, infections acquired in the intensive care unit (ICU), or ICU or hospital length of stay.


Enteral feeding to deliver a moderate amount of nonprotein calories to critically ill adults was not associated with lower mortality than that associated with planned delivery of a full amount of nonprotein calories. (Funded by the King Abdullah International Medical Research Center; PermiT Current Controlled Trials number, ISRCTN68144998.).

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