What is the approach to evaluating pyrexia (fever)?

From the Guidelines

Evaluating pyrexia (fever) in adult patients in the ICU should be approached with a rigorous diagnostic evaluation, as fever is frequently an early indicator of infection and often requires prompt identification and management. When evaluating fever, it is essential to consider the patient's clinical context and use evidence-based guidelines to inform diagnostic and therapeutic decisions. According to the Society of Critical Care Medicine and the Infectious Diseases Society of America guidelines for evaluating new fever in adult patients in the ICU 1, a comprehensive approach to evaluating fever is crucial. The guidelines recommend using central temperature monitoring methods, such as thermistors for pulmonary artery catheters, bladder catheters, or esophageal balloon thermistors, when these devices are in place or accurate temperature measurements are critical to diagnosis and management 1. Additionally, the guidelines suggest avoiding routine use of antipyretic medications for the specific purpose of reducing the temperature, unless the patient values comfort by reducing temperature, in which case antipyretics may be used over nonpharmacologic methods to reduce body temperature 1. Some key recommendations for evaluating fever in the ICU include:

• Performing a chest radiograph for patients who develop fever during ICU stay 1
• Performing CT (in collaboration with the surgical service) as part of a fever workup if an etiology is not readily identified by initial workup for patients who have recently undergone thoracic, abdominal, or pelvic surgery 1
• Collecting at least two sets of blood cultures (ideally 60 mL of blood total) one after the other, from different anatomical sites, without a time interval between them when performing blood cultures in adult ICU patients 1
• Replacing the urinary catheter and obtaining urine cultures from the newly placed catheter for febrile ICU patients with pyuria and in whom urinary tract infection is suspected 1 Overall, a thorough and evidence-based approach to evaluating fever in the ICU is critical to ensuring optimal patient outcomes, reducing morbidity and mortality, and improving quality of life.

From the Research

Approach to Evaluating Pyrexia (Fever)

The approach to evaluating pyrexia (fever) involves a comprehensive and structured process to determine the underlying cause of the fever.

• The evaluation of fever should consider both infectious and non-infectious causes, as fever can result from the body's natural response to exogenous or endogenous pyrogens 2, 3.
• Laboratory tests, including complete blood count, differential blood count, C-reactive protein, erythrocyte sedimentation rate, and procalcitonin, may be used to aid in the evaluation, but these tests do not have sufficient sensitivity and specificity to definitively detect or rule out an infectious cause of fever 2, 3.
• Blood cultures should be carried out when bacteremic or septic illnesses are suspected, and core temperatures should be taken to confirm the presence of fever 2, 3.

Considerations in Specific Patient Populations

• In young infants with fever, a decision analysis model can be used to evaluate different strategies for diagnosis and treatment, including the use of laboratory tests and clinical judgment to exclude low-risk patients from hospitalization and antibiotic treatment 4.
• In elderly and immunocompromised patients, fever may not always be present in true infection, and a high index of suspicion is necessary to avoid missing the diagnosis 2, 3.
• In intensive care unit (ICU) patients, a meticulous and attentive approach is required to evaluate fever, and a more restrictive approach to antibiotic therapy should be considered to avoid inappropriate use of antibiotics and antibiotic resistance 5.

Key Principles in Fever Evaluation

• A broad differential diagnosis should be maintained to avoid pitfalls in fever evaluation 3.
• Consideration of non-infectious causes of elevated temperature is necessary based on the clinical situation 2, 3.
• An understanding of the pathophysiology, causes, and assessment of fever is important for healthcare providers to ensure appropriate evaluation and management 3, 6.