Authors: Arabi YM et al., N Engl J Med 2015 Jun 18; 372:2398
Outcomes did not differ among patients who received permissive underfeeding or full feeds.
What is the right amount of nutrition for a critically ill patient? Two randomized, controlled trials demonstrated that higher-rate enteral nutrition was not necessarily better than low-rate enteral feeds (CMAJ 2004; 170:197 and JAMA 2008; 300:2731). With these results in mind, investigators in Saudi Arabia and Canada evaluated the potential benefit of permissive underfeeding (i.e., restricted nonprotein calories but preserved protein intake) in 894 predominantly medical intensive care unit (ICU) patients at seven tertiary medical centers. Patients’ average body-mass index was 29 kg/m2.
Patients were randomized to permissive underfeeding or standard feeding. Patients who received high-dose vasopressors or parenteral nutrition were excluded. On average, underfeeding patients received 46% of their calculated caloric requirements and standard-feeding patients received 71% of their goal (mean daily intakes, 835 vs. 1299 kcal). Ninety-day mortality, ICU-free days, and ventilator-free days were all similar between the groups.
The underfeeding patients had lower glucose levels, required less insulin, and exhibited a lower mean daily fluid balance than standard-feeding patients, but all other secondary outcomes were similar.
This study, in conjunction with earlier trials, demonstrates that achieving full caloric intake in critically ill patients does not afford any clear benefit. Although permissive underfeeding didn’t lower 90-day mortality, it is worth considering for patients in whom better glucose control and lower fluid intake have important clinical implications.