Nutrition Support Blog: Controversial Critical Care Calorie Conundrum
August 6, 2013
A number of consensus statements and society guidelines have advocated early and full feedings in critically ill adult patients. The 2009 joint guidelines of the American Society of Critical Care Medicine and Society of Critical Care Medicine recommend that >50% to 65% of goal calories be provided over the first week of hospitalization “in order to achieve the clinical benefit of EN” (1). The 2013 update to the Canadian Clinical Practice Guidelines recommends enteral nutrition begin with 24-48 hours after admission, with strategies to optimize the provision of nutrition in critically ill patients (2). The current Canadian Guidelines also recommend against “an initial strategy of trophic feeds for 5 days” in acute lung injury, and concluded that there was insufficient data to make recommendations on the use of hypocaloric nutrition in critically ill patients (2).
While guidelines to provide full nutrition to critically ill patients is supported by observational studies and appears to make intuitive sense, research in the past several years has started to cast doubt on the wisdom of pushing for early full feedings in critically ill adults. A 2011 study of 240 patients reported significantly decreased hospital mortality with reduced-calorie, protein supplemented feedings compared to attempting to feed the full nutrition target (3). A very large (1000 patients) multi-center study that compared “trophic” to full feeding in patients with ALI/ARDS did not find any apparent negative effect on outcome of reduced-feedings compared to ordering full feedings (4). Trophic feeding also had the advantage of significantly fewer episodes of regurgitation, vomiting, elevated gastric residuals, and required less anti-diarrheal and prokinetic medications compared with the full-feeding group (4). Early supplemental TPN to meet full calorie needs in critically ill adults certainly does not appear to improve patient outcomes, and results primarily in more infectious complications (5,6). In view of the limited data to support full feedings, and the increase in minor GI “complications” seen in full feeding groups, the Surviving Sepsis Campaign published nutrition guidelines in February 2013 that included a recommendation to avoid mandatory full caloric feeding to critically ill adults, and provide only up to 500 calories/day in the first week of critical illness.
Naturally, after years of attempting to meet full nutrition needs as early as possible, the recommendations for very limited feedings for the first week of illness has been somewhat controversial. Some of the controversy arises because severely malnourished patients were not allowed into the hypocaloric feeding studies and the average BMI of patients in the multicenter study of ALI/ARDS was 30 kg/M2 (3, 4). Additionally, the average length of ICU stay was relatively short in patients enrolled in the studies of hypocaloric feeding (3, 4). All of the patients in one study (3), and many of the patients with ALI/ARDS received supplemental protein (4), but the surviving Sepsis guidelines do not address protein adequacy during the initial part of the admission. Concerns about increased loss of muscle and decreased functional status of patients with extended ICU or hospital admissions and those patients with pre-existing malnutrition have not yet been adequately addressed in randomized studies. Clinicians realize that some patients have unforeseen problems with feeding for an extended period, require additional surgeries, tests or other procedures that recurrently interrupt nutrition. There are already a host of existing barriers to adequate nutrition, such as inadequate education and outdated ideas about bowel sounds, residuals, aspiration risk, etc. that lead to a cumulative nutrition deficit in the ICU. Clinicians are leery of recommendations that will encourage inertia to address nutrition issues and allow an early nutrition deficit to start in all critically ill patients.
Nonetheless, intensivists are acutely aware of the dangers of clinging to current practices and preconceived (“logical”) notions when randomized studies reveal surprising truths about survival and outcomes in the ICU. It is certainly conceivable that our sickest, and unavoidably catabolic patients may benefit from a period of reduced calories when they are most acutely ill, with severe insulin resistance and decreased gastrointestinal motility. Providing some enteral nutrients for GI protection plus protein to support the production of acute phase proteins initially, and delaying full calories until patients are capable of mounting an anabolic response may turn out to be the best nutritional approach to critical illness. Unfortunately, the current data is inadequate to allow the formulation of a Grand Unified Theory of calories, protein and micronutrient provision (amounts, timing and route) for all ICU patients. In the meantime, it is helpful to know that in the adult critical care patient it may not be necessary (or desirable) to rapidly feed full calories to all patients.
“In all affairs it's a healthy thing now and then to hang a question mark on the things you have long taken for granted.”
“The young man knows the rules, but the old man knows the exceptions.”
-Oliver Wendell Holmes
1. McClave SA, Martindale RG, Vanek VW, et al. Guidelines for the Provision and Assessment of Nutrition Support Therapy in the Adult Critically Ill Patient: Society of Critical Care Medicine (SCCM) and American Society for Parenteral and Enteral Nutrition (A.S.P.E.N.). JPEN J Parenter Enteral Nutr. 2009;33(3):277-316.
2. Canadian Clinical Practice Guidelines: Critical Care Nutrition.com. Retrieved July 30, 2013 from http://www.criticalcarenutrition.com/
3. Arabi YM, Tamim HM, Dhar GS, et al. Permissive underfeeding and intensive insulin therapy in critically ill patients: a randomized controlled trial. Am J Clin Nutr. 2011;93(3):569-577.
4. Rice TW, Wheeler AP, Thompson BT, et al. Initial Trophic vs. Full Enteral Feeding in Patients with Acute Lung Injury: The EDEN Randomized Trial. JAMA. 2012;307(8):795-803.
5. Casaer MP, Mesotten D, Hermans G, et al. Early versus Late Parenteral Nutrition in Critically Ill Adults. NEJM 2011, 2011;365(6):506-517.
6. Singer P, Anbar R, Cohen J, et al. The tight calorie control study (TICACOS): a prospective, randomized, controlled pilot study of nutritional support in critically ill patients. Intensive Care Med 2011;37(4):601-609.