How should unexplained chills be evaluated and managed?

Evaluation and Management of Unexplained Chills

Unexplained chills, particularly shaking chills, are highly specific for bacteremia and warrant immediate blood culture collection and empiric antibiotic initiation, even though their absence does not exclude serious infection.

Initial Risk Stratification

The severity and character of chills directly correlates with bacteremia risk and should guide your urgency of evaluation:

• Shaking chills (whole-body shaking even under a thick blanket) carry a 12-fold increased risk of bacteremia compared to no chills, with 90% specificity and a positive likelihood ratio of 4.65 1
• Moderate chills (requiring a thick blanket) carry a 4-fold increased risk 1
• Mild chills (cold-feeling requiring an outer jacket) show minimal association with bacteremia 1
• Recent meta-analysis confirms shaking chills have 87% specificity but only 37% sensitivity for bacteremia, meaning their presence is highly predictive but their absence does not rule out infection 2

Immediate Actions for Patients with Shaking Chills

Blood cultures and early antibiotic initiation should be considered for any patient with shaking chills, as the absence of shaking chills must not lead to exclusion of bacteremia or delay in treatment 2. Patients with shaking chills and at least one abnormal vital sign (tachypnea, tachycardia, altered mental status, hypotension, or hypoxia) have a 5.9-fold increased odds of bacteremia 3.

Diagnostic Workup Algorithm

Temperature Measurement

• Use oral or rectal temperatures over less reliable methods (axillary, tympanic, temporal artery, or chemical dot thermometers) 4
• Central temperature monitoring (pulmonary artery catheter thermistors, bladder catheters, esophageal thermistors) is preferred when these devices are already in place 4

Imaging Studies

• Obtain chest radiograph for all patients with fever during evaluation 4
• Perform CT imaging for patients with recent thoracic, abdominal, or pelvic surgery if initial workup does not identify an etiology 4
• Abdominal ultrasound is indicated only if abdominal symptoms, abnormal physical examination, or liver function abnormalities are present—do not perform routinely without these findings 4
• Thoracic bedside ultrasound should be performed when chest radiograph is abnormal and expertise is available to identify pleural effusions or parenchymal pathology 4

Advanced Imaging

• Consider 18F-fluorodeoxyglucose PET/CT when other diagnostic tests fail to establish etiology and transport risk is acceptable 4

Critical Pitfalls and Caveats

Do Not Overlook Non-Infectious Causes

While pyogenic infections are the most common cause of fever with chills 5, consider:

• Focal seizures presenting as autonomic symptoms (sweating, chills, shivering) in patients with episodic symptoms, particularly when routine tests are normal—obtain brain MRI and EEG if clinical suspicion exists 6
• Drug reactions, malignancy, and inflammatory conditions can also present with chills 5

Avoid These Common Errors

• Do not withhold blood cultures or antibiotics based on absence of shaking chills—sensitivity is only 37% 2
• Do not routinely use antipyretics for temperature reduction in critically ill patients unless the patient values comfort 4
• Do not perform routine abdominal imaging without localizing signs, symptoms, or laboratory abnormalities 4

Management Priorities

Focus treatment on the underlying cause rather than symptomatic fever management 5. The inflammatory response triggered by endogenous pyrogens (interleukin-1, tumor necrosis factor) serves to amplify immune response through T- and B-cell activation 5.

When to Hospitalize

Immediate hospitalization is required for patients with:

• Compromised vital functions
• Central nervous system involvement
• Prolonged fever with chills but no localizing findings
• Symptoms suggesting intraabdominal sepsis 5