The Real-World Boards: Question #34
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A 56-year-old man has been admitted to the ICU with sepsis due to pyelonephritis. He developed gram-negative bacteremia, with worsening shock, respiratory failure, and encephalopathy, and was intubated six days ago.
He was weaned off vasopressors, but continues to require mechanical ventilation. He is receiving enteral nutrition through an orogastric tube at 50 mL/hour. He had an episode of emesis three days ago, after which enteral feedings were interrupted for several hours and then resumed.
The nurse informs you that his gastric residual volumes are 420 mL. It has been five days since his last bowel movement. His abdominal exam shows unchanged mild distension, with occasional audible bowel sounds. An abdominal film shows mildly dilated loops of small bowel, unchanged from previous films.
For many years, gastric feeding was considered risky in critically ill patients. When postpyloric feeding was infeasible, gastric residual volume checks were used to reduce the perceived risk, with >100 mL considered to be a sign of intolerance of feedings. The 100 mL number, arbitrary to begin with, crept up over the years, but gastric volumes are still commonly checked in ICUs; if “elevated” (e.g., >250 mL, >400 mL, or >500 mL), enteral feedings are interrupted.
Two mid-sized randomized trials concluded that in patients receiving enteral feedings, regularly checking gastric residual volumes does not affect outcomes:
NUTRIREA1, n=452, France (JAMA 2013): Numerically similar VAP rates using >250 mL residual volume as a trigger to stop feedings in the control group, vs. not checking; more calories were delivered to patients in the unchecked arm
REGANE, n=329, Spain (Int Care Med 2010): No difference in calories delivered or VAP in patients using >500 mL residuals as feeding-stopping trigger, vs 200 mL
In NUTRIREA1 and some other trials, patients whose gastric volumes were not checked received more total calories.
As a result, U.S. and European nutrition guidelines advised not withholding enteral feedings for gastric volumes <500 mL, and U.S. guidelines advised not checking gastric volumes at all.
Checking gastric volumes is an ingrained nursing practice, however, and is performed in many if not most ICUs. About one-third of patients will have gastric volumes >200 mL during their ICU stays.
But Why Force-Feed Ventilated Patients?
NUTRIREA had an interesting finding of significantly more vomiting in the intervention patients (whose gastric volumes were not checked). About 7% of the intervention patients vomited 5 or more times during the trial—twice as many as in controls, whose feedings were stopped for gastric volumes >250 mL.
Authors seem to consider this to be insignificant, because the (supposedly) more important goal was achieved: more total calories delivered in the intervention arm.
But caloric targets in mechanically ventilated patients have no basis in evidence. They were arbitrarily invented by nutritionists based on theoretical metabolic assumptions.
In multiple large randomized trials, providing as little as half the nutritionist-defined goal to ventilated patients had no detectable influence on outcomes. This has been one of the stronger signals in critical care research.
Enteral Nutrition in the ICU and Wards: Review
Nutrition is complex, and so it should not be surprising that the data on nutritional support in hospitalized patients represent something of a paradox.
Not checking gastric volumes in critically ill patients is guideline-compliant. It follows the evidence.
It also probably results in force-feeding a lot of very ill people who aren’t hungry, who don’t need a healthy person’s full day’s worth of calories (as anorexia is a natural aspect of illness and may be adaptive), and making many of them nauseous.
Assuming mechanically ventilated patients are receiving at least 50-75% of a healthy person’s daily calories, either checking gastric volumes or not is equally reasonable.
Reflect to earn CME with Learner+
Sample reflection: I reviewed and reflected on the evidence of and against the use of gastric residual volume checks to manage enteral feedings in mechanically ventilated critically ill patients.
References
Reignier J. Effect of Not Monitoring Residual Gastric Volume on Risk of Ventilator-Associated Pneumonia in Adults Receiving Mechanical Ventilation and Early Enteral Feeding. JAMA. 2013;309(3):249. doi:https://doi.org/10.1001/jama.2012.196377
Montejo JC, Miñambres E, Bordejé L, et al. Gastric residual volume during enteral nutrition in ICU patients: the REGANE study. Intensive Care Medicine. 2010;36(8):1386-1393. doi:https://doi.org/10.1007/s00134-010-1856-y
Zoeller S, Bechtold ML, Burns B, et al. Dispelling Myths and Unfounded Practices About Enteral Nutrition. Nutrition in Clinical Practice. Published online January 29, 2020. doi:https://doi.org/10.1002/ncp.10456
Marr AB, McQuiggan MM, Kozar R, Moore FA. Gastric Feeding as an Extension of an Established Enteral Nutrition Protocol. Nutrition in Clinical Practice. 2004;19(5):504-510. doi:https://doi.org/10.1177/0115426504019005504
Lindner M, Padar M, Merli Mändul, et al. Current practice of gastric residual volume measurements and related outcomes of critically ill patients – a secondary analysis of the iSOFA study. Journal of Parenteral and Enteral Nutrition. 2023;47(5). doi:https://doi.org/10.1002/jpen.2502