The metabolic response to stress is part of the adaptive response to survive critical illness. Several mechanisms are well preserved during evolution, including the stimulation of the sympathetic nervous system, the release of pituitary hormones, a peripheral resistance to the effects of these and other anabolic factors, triggered to increase the provision of energy substrates to the vital tissues. The pathways of energy production are altered and alternative substrates are used as a result of the loss of control of energy substrate utilization by their availability. The clinical consequences of the metabolic response to stress include sequential changes in energy expenditure, stress hyperglycaemia, changes in body composition, and psychological and behavioural problems. The loss of muscle proteins and function is a major long-term consequence of stress metabolism. Specific therapeutic interventions, including hormone supplementation, enhanced protein intake, and early mobilization, are investigated. This review aims to summarize the pathophysiological mechanisms, the clinical consequences, and therapeutic implications of the metabolic response to stress.

The results of recent large-scale clinical trials have led us to review our understanding of the metabolic response to stress and the most appropriate means of managing nutrition in critically ill patients. This review presents an update in this field, identifying and discussing a number of areas for which consensus has been reached and others where controversy remains and presenting areas for future research. We discuss optimal calorie and protein intake, the incidence and management of re-feeding syndrome, the role of gastric residual volume monitoring, the place of supplemental parenteral nutrition when enteral feeding is deemed insufficient, the role of indirect calorimetry, and potential indications for several pharmaconutrients.

Introduction: Hyperglycemia, hypoglycemia, and increased glycemic variability have each beenindependently associated with increased risk of mortality in critically illpatients. The role of diabetic status on modulating the relation of these threedomains of glycemic control with mortality remains uncertain. The purpose of thisinvestigation was to determine how diabetic status affects the relation ofhyperglycemia, hypoglycemia, and increased glycemic variability with the risk ofmortality in critically ill patients. Methods: This is a retrospective analysis of prospectively collected data involving 44,964patients admitted to 23 intensive care units (ICUs) from nine countries, betweenFebruary 2001 and May 2012. We analyzed mean blood glucose concentration (BG),coefficient of variation (CV), and minimal BG and created multivariable models toanalyze their independent association with mortality. Patients were stratifiedaccording to the diagnosis of diabetes. Results: Among patients without diabetes, mean BG bands between 80 and 140 mg/dl wereindependently associated with decreased risk of mortality, and mean BG bands> 140 mg/dl, with increased risk of mortality. Among patients withdiabetes, mean BG from 80 to 110 mg/dl was associated with increased risk ofmortality and mean BG from 110 to 180 mg/dl with decreased risk of mortality. Aneffect of center was noted on the relation between mean BG and mortality.Hypoglycemia, defined as minimum BG <70 mg/dl, was independently associatedwith increased risk of mortality among patients with and without diabetes andincreased glycemic variability, defined as CV > 20%, was independentlyassociated with increased risk of mortality only among patients without diabetes.Derangements of more than one domain of glycemic control had a cumulativeassociation with mortality, especially for patients without diabetes. Conclusions: Although hyperglycemia, hypoglycemia, and increased glycemic variability is eachindependently associated with mortality in critically ill patients, diabeticstatus modulates these relations in clinically important ways. Our findingssuggest that patients with diabetes may benefit from higher glucose target rangesthan will those without diabetes. Additionally, hypoglycemia is independentlyassociated with increased risk of mortality regardless of the patient's diabeticstatus, and increased glycemic variability is independently associated withincreased risk of mortality among patients without diabetes. See related commentary by Krinsley,http://ccforum.com/content/17/2/131 See related commentary by Finfer and Billot,http://ccforum.com/content/17/2/134

Intensive care survivors often experience post-intensive care sequelae, which are frequently gathered together under the term “post-intensive care syndrome” (PICS). The consequences of PICS on quality of life, health-related costs and hospital readmissions are real public health problems. In the present Viewpoint, we summarize current knowledge and gaps in our understanding of PICS and approaches to management.