What is the cause of fever in the Intensive Care Unit (ICU)?

From the Guidelines

Fever in the ICU is most commonly caused by healthcare-associated infections, such as catheter-related bloodstream infections, ventilator-associated pneumonia, and urinary tract infections, as well as non-infectious causes like drug reactions, thromboembolism, or post-surgical inflammation. The evaluation and management of fever in the ICU should prioritize identifying and treating the underlying cause, while also considering the potential benefits and risks of antipyretic therapy 1.

Key Considerations

• The definition of fever in the ICU is typically a single temperature measurement greater than or equal to 38.3°C 1.
• Non-infectious causes of fever, such as malignant hyperthermia, neuroleptic malignant syndrome, and serotonin syndrome, should be considered in the differential diagnosis 1.
• The use of antipyretic medications, such as acetaminophen, may be considered for symptomatic relief, but should not mask the diagnostic workup 1.

Diagnostic Approach

• Obtain blood cultures, urine cultures, sputum cultures, and cultures from any indwelling devices before initiating empiric antibiotics.
• Perform a chest radiograph for patients who develop fever during ICU stay 1.
• Consider performing CT imaging of the operative area for patients who have recently undergone thoracic, abdominal, or pelvic surgery and have a fever of unknown origin 1.

Treatment Approach

• Use broad-spectrum antibiotics, such as piperacillin-tazobactam or meropenem, plus vancomycin, for empiric treatment of suspected infections.
• Consider removing potentially infected catheters and devices.
• Monitor vital signs, including temperature trends, to evaluate treatment response.
• Once culture results return, narrow antibiotic therapy based on identified pathogens and susceptibilities to reduce resistance development and adverse effects.

From the Research

Causes of Fever in the ICU

• Fever in the ICU can be caused by both infectious and non-infectious etiologies 2, 3, 4
• About half of all febrile cases in the ICU are due to non-infectious causes, while the other half are due to infectious causes 2, 4
• Common infectious causes of fever in the ICU include pneumonia, urosepsis, line infections, and intraabdominal infections 3, 4
• Non-infectious causes of fever in the ICU can include deep venous thrombosis, infusion reactions, aspiration, drug fever, and the neuroleptic malignant syndrome 3, 4

Diagnosis and Management of Fever in the ICU

• Any unexplained fever in ICU patients warrants investigation, including complete clinical assessment and blood cultures 2
• The extent of evaluation should be based on the likelihood of the disease process being present and is highly variable for each individual patient 3
• A structured approach is required to correctly diagnose and treat fever in critically ill patients 4
• The use of antipyretics, such as acetaminophen, may not affect the number of ICU-free days in patients with fever due to probable infection 5

Outcomes of Fever in the ICU

• Patients with fever in the ICU have significant morbidity and mortality 6
• The mortality rate of patients with fever in the ICU can be more than double that of patients without fever 6
• Early administration of acetaminophen to treat fever due to probable infection did not affect the number of ICU-free days or mortality 5