Implementing Nutrition Guidelines in the Critical Care Setting

Abstract

Naomi E. Jones, RD, MSc Daren K. Heyland, MD, FRCPC CONSISTENTLY AND REPEATEDLY,OVER TIME AND ACROSS settings,observational studieshavedocumented the inabilities of critical care practitioners to adequately feedcritically illpatients. Critically illpatientswho receive less nutrition are more likely to experience increased complications,prolongedmechanical ventilation, longer time inthe intensivecareunit (ICU),andanincreasedriskofdeath. Patientswhosurvivetheircritical illnessoftenemergeinaweak and disabled condition that requires months to rehabilitate. Several randomizedcontrolledtrials(RCTs)andmeta-analyses of RCTs suggest that strategies to improve the enteral delivery of calories reduce complications and improve survival. However,preliminarydatafromaninternationalobservationalstudy suggest that wide variation in ICU feeding practices persists. Thus, efforts to improve the provision of calories and protein to critically ill patients are warranted. During the past 2 decades, there have been significant advances in understanding the role of nutrition in the treatment of ICU patients. Fifty years ago, when artificial nutrition was first developed, it was conceived as supportive care entailing administration of metabolic support while the patient recoveredfromhisorherunderlyingillness.Duringthisera,fewlargescale trials informed nutrition practice, and there was little expectationthatnutritionaffectedclinically importantoutcomes. Since 1980, the conduct of nearly 200 randomized trials, involvingthousandsofcritically illpatients,has increasedtheevidence base by demonstrating the benefits of various nutrition practices.Thesebenefits includesignificantreductionsinlength of stay, infectious complications, and mortality. Undoubtedly some positive effects attributed to the provision of nutrition are owing to the prevention of malnutrition. But nutrition also may exert effects beyond the correction of nutrient deficiencies by directly supporting the immune system, attenuating oxidative stress, maintaining gastrointestinal tract structure and function, and modifying the inflammatory response. Accordingly, the role of nutrition in patient care has transitioned from supporting patients while they recover from their underlying illness to modulating their disease response and improving their chances of survival. Thus, it is no longer appropriate to speak of “nutrition support” but rather “nutrition therapy.” However, despite this increase in understanding and the evolution of nutrition as primary therapy, many fundamental questions regarding how to optimally feed critically ill patients remain unanswered. Historically, most trials tested nutritional strategies in critically ill patients and those undergoing elective surgery together, but because the underlying pathophysiology of these subgroups is different, it is difficult to detect effects in homogeneous subgroups of critically ill patients. In addition, the poor methodological quality and small sample sizes of many of these studies hampered the ability to detect significant differences in clinical end points. Therefore, this increase in evidence surrounding nutrition therapy has also been associated with much controversy. Moving forward, some of this controversy may be resolved by the conduct of large, rigorously designed RCTs currently under way and powered to detect differences in mortality. Building on this emerging evidence from clinical trials, several clinicalpracticeguidelines (CPGs) that focusonnutrition therapyinmechanicallyventilatedcritically illpatients have beendeveloped.TheseCPGsare intendedtoassist critical care practitioners inmanaging the rapidproliferationofnewinformation and in making informed decisions regarding feeding their patients. In this issue of JAMA, Doig and colleagues report the results of their study designed to improve the practice of nutrition in 27 Australian ICUs through the development andimplementationofanevidence-basedCPGforfeeding.The thrust of the CPG was to promote earlier initiation of feeding andagreater frequencyofdays inwhichprescribednutritional goals were met. The investigators performed a cluster RCT in which the CPG dissemination, consisting of 18 different strategies to change local practice, was randomly allocated to half the sites. The authors’ hypothesis was that, by improving nutrition practice, patient mortality would be reduced by 8%. The study demonstrated that the intervention led to earlier initiation of feeding and to an increased number of days on which prescribed nutritional goals were met. However, the authors were unable to demonstrate an improvement in clinical outcome. These results are somewhat disappointing and prompt reflection on possible explanations. Existing guidelines recommend starting enteral nutrition within 24 to 48 hours, so shifting the average time to initiation of enteral