Increasing the energy density of the diet of tube-fed-ICU patients increases the risk of vomiting and doesn’t improve survival, a major study has found.

The study sought to answer the longstanding concern of ICU professionals on just how important nutrition was to survival of patients on mechanical ventilation and how energy dense should their liquid diet be to maximise their chance of recovery?

The combined New Zealand and Australian research called the TARGET study, the largest intensive care nutrition trial ever undertaken, indicates efforst made by intensive care staff to ensure critically ill patients receive their recommended ‘goal’ calorie intake may be unnecessary and make no difference to patient survival or recovery.

Current international guidelines recommend that patients on life support are provided with enough nutrition (via a nasogastric tube from the nose to the stomach) to ensure that their energy intake matches energy expenditure. However, in reality, patients typically receive less than 60% of this recommended daily intake, due to factors such as nausea and vomiting as well as the safety need for fasting before surgery.

Study co-author Dr Paul Young from Wellington’s Medical Research Institute of New Zealand (MRINZ) says the new research shows there’s no real cause for concern if a patient doesn’t meet their recommended daily ‘goal’ calorific amount.

“When patients are sick they don’t feel hungry and this research shows that if you feed them extra calories in order to boost their nutritional intake, the end result is that they are just more likely to vomit, and, most significantly, no more likely to get better” says Dr Young.

“Up until now, a lot of time and effort has been spent on interventions to try to achieve these calorie goals such as using medicines to aid stomach emptying and inserting special feeding tubes” he says. “This study suggests that these interventions are often unnecessary”.

The Health Research Council-funded study, published in the New England Journal of Medicine, enrolled nearly 4000 patients admitted to 46 intensive care units in Australia and New Zealand last year. More than one-third of all patients studied were from New Zealand.

All were given the same hourly volume of liquid nutrition via nasogastric tube. Half received an energy-dense nutrition which contained 1.5 kcal/ml, while the other half who received the usual recommended 1.0 kcal/ml nutrition formula. The more energy-dense formula had added fat and carbohydrate to boost calorific intake by 47.6%. However, patients who received the higher nutritional amount experienced no improved survival after 90 days, nor did the extra calories improve key secondary outcomes such as organ support or duration of stay in the intensive care unit or hospital. They also experienced more vomiting and required more drugs to treat vomiting.

“While we do not know for sure why the nutrition formula with more calories resulted in more vomiting, it may simply be that vomiting is the body’s response to receiving more calories than needed” says Dr Young.

Auckland Hospital Intensive Care specialist Dr Shay McGuinness says the findings will help improve patient care in critical care units worldwide.

“This TARGET study has shown that using higher energy feed to try to get the calculated goal amount of food absorbed by the patient does not improve important outcomes and may actually result in more feeding complications” says Dr McGuinness. “As many of us know from personal experience when we are sick we often lose our appetite – allowing critically ill patients to self-regulate how much food they absorb may well be a better approach to artificially trying to boost energy delivery”.

Chief Executive of the Health Research Council Professor Kathryn McPherson says she was surprised by these findings and mindful of their widespread implications.

“Questioning fundamental assumptions about just what level of nutrition is actually needed – and getting closer to definitive answers- means we are making real progress in our ability to support people when they are vulnerable and dependant on our health service to support life” says McPherson.

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