The benefits of fever treatment in critically ill patients remains unclear. The aim of the prospective, randomized clinical trial was to verify the hypothesis that the administration of ibuprofen in order to decrease the fever in septic patients without limited cardiorespiratory reserve leads to decreasing their prognosis.

Fever is a frequently observed part of the organism's response to infection, and it is a well-known fact that it has positive effects, as it inhibits the growth of microorganisms, and potentiates the activity of anti-microbial agents. On the other hand, fever increases the demand of tissues for oxygen and increases the production of carbon dioxide in tissues. Adapting to these metabolic changes requires an efficient cardiorespiratory apparatus. In other words, in patients with a limited cardiorespiratory reserve (typically patients of higher age or patients with a serious disease of the heart or lungs), the beneficial anti-microbial effect of fever may be masked with cardiorespiratory maladaptation to fever-induced metabolic changes. Indeed, one of the randomized clinical trials investigating the effect of "aggressive" antipyretic strategy used in practice (administration of acetaminophen at the temperature > 38.5 degrees Celsius, and addition of physical cooling should the temperature exceed 39.5 degrees Celsius upon the prognosis of critically ill patients showed that the "aggressive" treatment of fever may result in higher mortality when compared with a "permissive" approach, i.e. an approach when the treatment of fever is initiated only after the body temperature has exceeded 40 degrees Celsius. The study differs remarkably from other studies performed among the population of critically ill patients, and also from studies, which did not manifest the effect of fever treatment upon the mortality of patients, with the age of patients. The average age of patients in both arms of the study was only 47 years of age, whereas the average age of patients in other studies was usually around 60 years of age. It is thus possible to presume that, due to the lower age, the patients in this study possessed a sufficient cardiorespiratory reserve for adaptation to metabolic changes induced with fever, which may have enabled a full manifestation of its anti-microbial effect, and may have led to better patient prognosis. The mortality rate in the group of patients with the "permissive" approach to fever treatment was only 2.6 percent, whereas, in the group of patients with the "aggressive" treatment, the mortality rate was 15.9 percent (p=0.06); due to this fact, the study was prematurely terminated by the Ethics Committee. Based on this study, we decided to test the hypothesis that the administration of ibuprofen in order to decrease the fever would lead to a worsening of the patient prognosis. Ibuprofen was selected due to its potent antipyretic effect, and also due to the fact that the favorable effect of its anti-inflammatory effect upon the prognosis of patients with sepsis has not been fully demonstrated.

Inclusion Criteria:

• age >18 years of age
• body temperature >38.3°C within 2 consecutive hours
• anti-microbial therapy for a known or suspected infection

Exclusion Criteria:

• patients admitted after successful cardiopulmonary resuscitation (CPR)
• acute myocardial infarction
• brain injury (traumatic and non-traumatic)
• transfer from another ICU after 72 hours
• pregnancy
• antipyretic medication prior to randomization
• non-obtaining the informed consent
• moribund condition
• high risk of hemodynamic or respiratory maladaptation on the metabolic effect of fever

There exists no plan to make individual participant data available to other researchers.

No masking was used in the study