Management of fever in critically ill patients with infection
Body temperature is one of the important vital signs to evaluate the whole-body condition. It is common that new examinations or treatments was triggered by hypothermia or fever in critically ill patients. In a clinical setting, fever is an important indicator that suggests the presence of infection. However, fever in seriously ill patients is caused not only by infection but also by non-infective pathology or multiple factors. In critically ill patients, fever may have detrimental effects. It can cause discomfort, increase minute ventilation and oxygen consumption, and worsen neurological outcomes. Therefore, antipyretics are usually administered. There are two methods for treating febrile patients: administration of an antipyretic drug and physical cooling. An antipyretic drug may lower body temperature by decreasing the threshold of body temperature control in the hypothalamus. Therefore, antipyretic drugs can decrease body temperature both in patients taking sedatives and those not taking sedatives. Sedation should suppress cold reactions, and sedation combined with physical cooling should therefore be effective for body temperature reduction. However, if the patient is not under sedation, the set point of body temperature does not change, and physical cooling may therefore cause a cold reaction such as shivering or vasoconstriction. In that case, it would be difficult to lowering body temperature, and oxygen consumption and minute ventilation may increase. There is growing evidence regarding the benefits and harmful effects of antipyretics in febrile critically ill patients, especially in those with infection. However, there is no definitive conclusion regarding antipyretic therapy for febrile critically ill patients. Until results of large-scale randomized trials on the effects of antipyretic therapy in critically ill patients are reported, it seems that antipyretic therapy should be performed according to each patient’s situation. If the fever itself is within a normal physiological response accompanied by compensating changes in vital signs including heart rate and respiratory rate, it might be better not to treat the fever. However, if there is decompensation of vital signs including tachycardia, tachypnea or patient suffering caused by fever, antipyretics should be used to prevent derangement. In doing so, it is necessary to understand the effects of antipyretic drugs and physical cooling on the physiology and to use an appropriate method. Since fever and antipyretic therapy may have merits and demerits, routine antipyretics triggered by certain body temperature might be better to be avoided.