Unintentional overfeeding of ICU patients with acute respiratory distress syndrome (ARDS) may increase the risk for infections, prolong mechanical ventilation and boost hospital length of stay (LOS), according to a study presented at the 2017 American Society for Parenteral and Enteral Nutrition Clinical Nutrition Week (CNW).
The study, from Rush University Medical Center and the University of Illinois at Chicago, was judged a CNW “Abstract of Distinction.”
The study included 95 patients from the control group in the INTACT study. After controlling for severity of illness, every increase of 1 kcal per estimated lean body mass (ELBM) in calorie delivery increased the duration of mechanical ventilation by 0.32 day, increased ICU LOS by 0.37 day and increased hospital LOS by 0.63 day. There also was a trend between kilocalories per ELBM and higher likelihood of infection (odds ratio, 1.09). But there was no relationship between mortality and increased kilocalories per ELBM in calorie delivery.
As for why the unintentional overfeeding occurred, the investigators pointed to indirect calorimetry—the method used to assess caloric needs in these patients—as the likely culprit. Although the test is the gold standard for measuring calorie needs, it requires expensive equipment and a team to perform these measurements, explained Sarah J. Peterson, PhD, RDN, an assistant professor in the Department of Food and Nutrition at Rush.
What’s more, the predictive equations that are the basis of the test “were developed using regression analysis in populations that might not represent patients in your ICU,” Dr. Peterson said. “For example, over 70% of patients in our study had low muscle mass, and muscle mass is the strongest predictor of energy expenditure. So when someone has low muscle mass and we use their body weight as a surrogate to calculate calorie needs, we can overestimate their calorie needs, leading to toxic effects.”
A Common Problem
This was a single-institution study, but Dr. Peterson said since there is a high prevalence of low muscle mass in ICU patients, overfeeding may be common in other ICUs. “Clinicians need to think about this when prescribing calorie needs for ICU patients,” she said. “If a patient is acutely ill in the initial presentation to the ICU—a point at which they’re on multiple vasopressors and are hemodynamically unstable—that’s not the time to feed them aggressively. Wait until the patient’s condition is stabilized and only then try to maximize calorie delivery.”
David Evans, MD, the medical director of nutrition support services at Ohio State University, in Columbus, said the new study confirms earlier data suggesting that problems with caloric testing and overfeeding are real.
“The INTACT study and others suggested that ARDS and acute lung injury populations are more sensitive to the risk of over-delivery, and that nutritional over-delivery may frequently be detrimental,” Dr. Evans said. “When those data were first presented, that really surprised the nutrition community. This new study has once again shaken our foundation, showing that in myopenic patients, extra nutrition delivery increases duration of mechanical ventilation, length of stay and the likelihood of infection. This tells us there may not be consensus on the understanding of this issue.”
The study “also points to the acute process of malnutrition and nutrition risk in the ICU as being different from the chronic body mass issue, and we can’t just lump those together,” he said.
However, Dr. Evans thought unintentional overfeeding in the ICU may not be as common as Dr. Peterson suggested. “In this high-quality clinical trial, these patients were probably getting closer to their intake goals, but in real-world applications it is uncommon that patients get more than 60% to 70% of their predicted goals.”