Initial calorie targets for enteral feeding fail to influence outcomes
MedWire News: Outcomes of patients with acute lung injury who require mechanical ventilation are not affected by whether initial enteral feeding supplies the full recommended calorie allowance or a reduced amount, shows a randomized trial.
Previous evidence has been mixed, with some studies showing better outcomes in patients given full calorie requirements and others showing better outcomes in those given restricted nutrition.
The authors of the current study, which appears in JAMA, hypothesized that initial restricted calorie intake, for up to 6 days, would improve patient outcomes. But their trial showed no differences for number of ventilator-free days or mortality.
However, they note: "This study does not address the safety or efficacy of foregoing all enteral intake, of trophic feeding for more than 6 days, or of trophic feeding in patients with preexisting malnutrition."
The 492 patients randomly assigned to receive full enteral feeding were started on 25 mL/hour and moved as soon as possible to rates that supplied 25 to 30 kcal/kg per day of nonprotein calories and 1.2 to 1.6 g/kg per day of protein. The 508 patients given restricted enteral feeding were fed at a rate of 20 kcal/hour. The full-feeding protocol resulted in patients receiving about 1300 kcal/day, whereas those given restricted feeding received about 400 kcal/day.
"Providing approximately 25% of goal feeding clearly resulted in less group separation than would have occurred with a 'no feeding' comparator," comment Todd Rice (Vanderbilt University School of Medicine, Nashville, Tennessee, USA) and colleagues.
They explain: "We did not believe it feasible to have a group receiving no feeding at all, even though previous studies of usual practice indicate that many critically ill patients receive no enteral nutrition for many days."
All patients started enteral feeding within 48 hours of injury and continued in their allocated group for up to 6 days, at which point all who still required mechanical ventilation received full nutrition.
Patients given restricted feeding had an average of 14.9 ventilator-free days to day 28 (the primary outcome measure), compared with 15.0 in the full-feeding group. Feeding strategy also failed to influence 60-day mortality, which occurred in 23.2% of the restricted-feeding group and 22.2% of the full-feeding group.
However, patients given restricted feeding did have less frequent vomiting than those given full feeding, at 1.7% versus 2.2% of patient-feeding days, gastric residual volumes, at 2.2% versus 4.9% of patient-feeding days, and constipation, at 2.1% versus 3.1% of patient-feeding days. This was despite patients in the full-feeding group receiving more prokinetic agents than those in the restricted-feeding group.
The researchers note that they used gastric tubes, rather than postpyloric tubes, in most patients "despite near-universal use of sedatives and narcotics and a substantial proportion in shock."
They add that regurgitation, constipation, vomiting, and aspiration were uncommon despite a "higher than commonly accepted" gastric residual volume (GRV) limit, of 400 mL.
Rice et al conclude: "These findings raise questions about routine use of postpyloric tubes and more conservative GRV limits when gastric tubes are used."
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By Eleanor McDermid