How should I manage a fever in an adult without contraindications?

Management of Fever in Adults Without Contraindications

For critically ill adults with new-onset fever, avoid routine use of antipyretic medications for the specific purpose of reducing temperature; however, if the patient values comfort, use antipyretics (paracetamol or ibuprofen) rather than physical cooling methods. 1

Temperature Measurement

• Use central temperature monitoring when available (pulmonary artery catheter thermistors, bladder catheters, or esophageal probes) as these represent the gold standard for core body temperature measurement 1
• For patients without central monitoring devices, use oral or rectal temperatures rather than less reliable methods like axillary, tympanic membrane, temporal artery thermometers, or chemical dot thermometers 1
• Define fever as a single temperature ≥38.3°C (101°F) based on SCCM/IDSA criteria 1

Antipyretic Therapy Decision-Making

When to avoid antipyretics:

• Do not routinely use antipyretics solely to reduce temperature in critically ill patients, as fever may be a beneficial host response 1
• This recommendation is based on moderate-quality evidence showing no mortality benefit from routine temperature reduction 1

When to use antipyretics:

• Administer antipyretics when patient comfort is a priority and the patient values temperature reduction 1
• Choose pharmacologic agents (paracetamol 1000mg or paracetamol/ibuprofen combination) over physical cooling methods (tepid sponging, removing clothing, environmental cooling) as physical treatments offer minimal additional benefit 1, 2
• For bacterial fever, paracetamol/ibuprofen 500/150mg combination may provide faster temperature reduction within 1 hour compared to paracetamol alone, though both are equally effective at 2 hours 3

Diagnostic Evaluation Framework

Initial assessment priorities:

• Determine if fever requires investigation - not all fevers warrant workup (e.g., immediate postoperative fever is typically non-infectious) 1
• Focus diagnostic studies based on clinical suspicion rather than reflexively ordering cultures for all possible sources 1
• Recognize that temperatures 38.9-41.1°C (102-106°F) are more likely infectious, while temperatures <38.9°C or >41.1°C suggest non-infectious etiologies 4

Blood culture strategy:

• Obtain 3-4 blood cultures within the first 24 hours of fever onset, drawn before initiating antimicrobials when possible 1
• Use 2% chlorhexidine gluconate in 70% isopropyl alcohol for skin disinfection (preferred over povidone-iodine), allowing 30 seconds drying time 1
• Draw 20-30 mL of blood per culture to maximize yield 1
• For patients with intravascular catheters, obtain one culture by venipuncture and at least one through the catheter to distinguish true bacteremia from catheter-related infection versus contamination 1

Imaging approach:

• Perform chest radiograph for all ICU patients with new fever 1
• Order CT scan for post-surgical patients (thoracic, abdominal, or pelvic surgery) when initial workup fails to identify an etiology, in collaboration with surgical services 1
• Consider abdominal ultrasound or point-of-care ultrasound only when abdominal symptoms, abnormal liver function tests, or recent abdominal surgery are present - do not use routinely 1
• Use 18F-FDG PET/CT when other diagnostic tests fail to establish etiology, if transport risk is acceptable 1

Biomarker utilization:

• Measure serum procalcitonin (PCT) or C-reactive protein (CRP) when probability of bacterial infection is low-to-intermediate and no clear focus exists, to help rule out bacterial infection 1
• Do not measure CRP when probability of bacterial infection is high as it will not change management 1
• PCT and endotoxin activity assay can serve as adjunctive tools for discriminating infection as the cause of fever 1

Non-Infectious Fever Considerations

Critical syndromes requiring immediate recognition:

• Malignant hyperthermia - associated with succinylcholine and inhalation anesthetics (especially halothane), presents with intense muscle contraction, elevated creatinine phosphokinase, and can manifest up to 24 hours post-exposure 1
• Neuroleptic malignant syndrome - linked to antipsychotics (haloperidol, phenothiazines, butyrophenones), characterized by muscle rigidity, fever, and elevated creatinine phosphokinase with central mechanism 1
• Serotonin syndrome - caused by excessive 5-HT1A receptor stimulation from serotonin reuptake inhibitors, can be exacerbated by linezolid 1

Drug-induced fever patterns:

• Suspect drug fever when onset occurs 8-21 days (mean) after drug initiation, though it may occur immediately or after prolonged exposure 1
• Fever typically resolves 1-7 days after discontinuing the offending agent 1
• Rash and eosinophilia are uncommon in drug-induced fever 1

Withdrawal syndromes:

• Consider alcohol, opiate, barbiturate, or benzodiazepine withdrawal when fever develops hours to days after ICU admission with associated tachycardia, diaphoresis, and hyperreflexia 1
• History of substance use may not be available at admission 1

Postoperative Fever Timeline

• Fever within 48 hours post-surgery is usually non-infectious, assuming no breaks in sterile technique or aspiration occurred 1
• After 96 hours postoperatively, fever likely represents infection and warrants full evaluation 1
• Early postoperative chest radiographs are not mandatory unless respiratory rate, auscultation abnormalities, abnormal blood gases, or increased pulmonary secretions suggest utility 1
• Urinalysis/culture not required in first 2-3 days postoperatively unless history or examination suggests urinary source 1

Common Pitfalls

• Avoid empiric antimicrobial therapy in fever of unknown origin except in neutropenic, immunocompromised, or critically ill patients, as it has not been shown effective and selects for resistant organisms 5, 4
• Do not delay appropriate antibiotics when infection is suspected, as delay increases mortality despite concerns about resistance 4
• Physical cooling methods (tepid sponging) offer little advantage over antipyretics alone and should not be primary treatment 2
• Single blood cultures are not recommended except in neonates - always obtain paired cultures for meaningful interpretation 1