Pathophysiology of Critical Illness and Role of Nutrition

Critical illness is a hypercatabolic state. It has been hypothesized that timely and adequate nutrition support may optimize the host response and thereby minimize nutritionally related complications while improving overall outcome. Any illness in due course can lead to a malnourished state-critical illness can worsen this state as patients may become immunocompromised and unable to mount an adequate inflammatory response and therefore susceptible to poor outcomes. Data indicate that prevalence of malnutrition in the ICU ranges from 38% to 78% and is independently associated with poor outcomes. Hence, exploring the role of nutrition as a way to mitigate critical illness is important. In this review, the basic pathophysiology of critical illness and how it alters carbohydrate, protein, and fat metabolism are discussed. This is followed by a discussion of malnutrition and how it affects patient and hospital outcomes. Finally, a summary of the available evidence regarding nutrition support and its impact on outcomes are provided. This review is not intended to provide practice-based guidelines; instead, it intends to highlight available data on the role of nutrition support in critically ill patients.