Body temperature and mortality in patients with acute respiratory distress syndrome.

The relationship between body temperature alterations (both hypothermia and fever) in critically ill patients and outcomes is not well understood, despite the fact that clinicians often intervene to achieve normothermia in these patients.1-6 Fever is common in critically ill patients and occurs as an adaptive response to inflammation that results from injury or infection.7-9 Fever is defined as a regulated increase in body temperature above the normal thermal set point in response to injury and inflammation.10 studies that have examined the relationship between fever and mortality in critically ill patients have yielded disparate results.1,7,9,11-13 high fever, typically defined as 39.5°C or greater, has been associated with increased mortality in critically ill patients.7-9,12 A large multinational observational study evaluating the relationship between temperature and mortality in critically ill patients with and without infection showed a reduced risk of in-hospital mortality with fever relative to normothermia in critically ill patients with infection.11 The noninfection group from this study also had reduced risk of mortality with elevated temperatures up to 39°C, after which mortality increased. hypothermia was associated with increased mortality in both infection and noninfection groups. In another recent multisite observational study,9 the presence of fever on admission to the intensive care unit (ICU) had no significant association with ICU case-fatality among patients in medical and surgical ICUs. In a large, randomized, double-blind, placebo-controlled trial evaluating the effects of ibuprofen on outcomes in critically ill patients with sepsis, body temperature was significantly reduced in the febrile group that received ibuprofen.14 however, despite the significant reductions in fever, heart rate, lactate levels, and oxygen consumption values in the treatment group, no differences in oxygen delivery, organ failure–free days, or mortality were found. In a recent observational trial,1 researchers investigated the association of fever and antipyretic interventions with mortality in critically ill patients with and without sepsis. In the cohort with sepsis, fever was an independent predictor of decreased mortality and use of acetaminophen and ibuprofen was an independent predictor of increased mortality. In the cohort without sepsis, only high fever (≥39.5°C) was independently associated with increased mortality, and no associations were found with use of antipyretic medication and mortality. Thus, robust evidence to guide management of fever in critically ill patients is lacking. Nonetheless, the use of antipyretic medications and physical cooling interventions to treat fever is widespread in clinical practice.1-4 Acute respiratory distress syndrome (ARDS) is one of several forms of critical illness characterized by the presence of the acute phase response, a series of complex neuroimmunologic reactions that include stimulation of fever and the release of cytokines and other immunologically activated proteins in response to injury or infection in an attempt to reestablish homeostasis.15,16 The acute phase response stimulates leukocytosis, complement activation, coagulation activation, opsonization, cytotoxicity, vascular permeability, and chemotaxis of monocytes, neutrophils, and T cells.17 Fever is a hallmark sign of the acute phase response to infectious and noninfectious sources of tissue injury, so one would expect fever to be common in patients with ARDS. however, little is known about the incidence of fever in patients with ARDS and whether body temperature has an association with the trajectory of illness and recovery. Thus, a better understanding of the impact of body temperature on outcomes for ARDS patients can inform future research. specifically, because the relationship between body temperature and patients' outcomes is unknown, it is unclear whether temperature-altering interventions are beneficial, detrimental, or neutral in patients with ARDS. The purpose of this study was to examine the relationship between body temperature in early ARDS and mortality.