What is the initial evaluation and management for an adult patient presenting with fever, chills, and rigors?

Initial Evaluation and Management of Fever with Chills and Rigors

Immediate Clinical Assessment

Begin with immediate risk stratification focusing on hemodynamic stability, oxygen saturation, mental status, and signs of organ dysfunction, as these determine whether empiric antibiotics must be started within 1 hour. 1

High-Risk Features Requiring Urgent Intervention

• Hypotension, altered mental status, respiratory distress (oxygen saturation <92%), tachycardia, or signs of end-organ dysfunction mandate immediate hospitalization and empiric antibiotic therapy. 1, 2
• Rigors and chills increase the likelihood of bacteremia significantly, with patients ≥50 years having a 55% probability of serious bacterial infection when combined with other risk factors. 1
• Confusion, seizures, severe thrombocytopenia, or reduced Glasgow Coma Scale are absolute indications for hospital admission. 1

Diagnostic Workup (Before Antibiotics)

Obtain blood cultures immediately—within 30-90 minutes of presentation—as bacteria are rapidly cleared from the bloodstream and diagnostic yield drops precipitously after antibiotic administration. 1

Essential Laboratory Tests

• Draw at least 2-3 sets of blood cultures from separate venipuncture sites (never from central lines due to contamination risk). 1, 2
• Complete blood count with differential looking for neutropenia, thrombocytopenia (occurs in 70-79% of malaria cases), or left shift with band forms. 1, 3
• Comprehensive metabolic panel, lactate level (serial measurements if elevated), urinalysis, and urine culture. 1
• Consider SARS-CoV-2 PCR testing based on community transmission levels and clinical presentation. 4

Biomarker Utilization

• If bacterial infection probability is low-to-intermediate and no clear focus exists, measure procalcitonin (PCT) or C-reactive protein (CRP) to guide antibiotic discontinuation decisions. 4
• Do not use PCT or CRP to rule out bacterial infection when clinical probability is high—proceed directly to treatment. 4
• PCT >0.5 ng/mL suggests bacterial infection; >10 ng/mL suggests septic shock. 2

Imaging Studies

• Obtain chest radiography for all patients to evaluate for pneumonia, tuberculosis, or mediastinal lymphadenopathy. 2
• Use ultrasonography and other imaging modalities based on clinical suspicion of specific infection sources. 4

Temperature Measurement

Use oral or rectal temperatures over less reliable methods (axillary, tympanic, temporal artery, or chemical dot thermometers). 4

• For critically ill patients where precise measurements are essential, use central methods: pulmonary artery catheter thermistors, bladder catheters, or esophageal balloon thermistors if already in place. 4

Empiric Antibiotic Decision Algorithm

Start Antibiotics Immediately (Within 1 Hour) If:

• Hemodynamic instability or signs of septic shock present 1
• Systemic inflammatory response syndrome criteria met 1
• Immunocompromised state (neutropenia <500 cells/mm³, chemotherapy, transplant) 1
• Suspected meningitis (altered mental status, meningismus) 1
• Suspected cholangitis (Charcot's triad: fever, jaundice, right upper quadrant pain) 1
• Oxygen saturation <92% or evidence of organ dysfunction 1

Antibiotic Selection

• Use anti-pseudomonal monotherapy (ceftazidime or carbapenem) or combination therapy based on local resistance patterns for neutropenic patients. 1
• Add vancomycin only if catheter-related infection suspected, skin/soft tissue infection present, hemodynamic instability exists, or mucositis in centers with high viridans streptococci rates. 2
• For suspected enteric fever in travelers from Asia, use intravenous ceftriaxone as first-line therapy. 1

When Antibiotics Can Be Withheld

In stable, immunocompetent patients without sepsis or organ dysfunction, complete the diagnostic workup and observe for 1-2 hours before initiating antibiotics, provided blood cultures are obtained and close monitoring is in place. 1

• When uncertain, err on the side of early antibiotic administration after cultures, as each hour of delay in cirrhotic patients with septic shock increases mortality by 10%. 1

Supportive Care

• Initiate immediate fluid resuscitation with 250-500 mL crystalloid boluses for hypotensive patients. 1
• Implement continuous monitoring: vital signs, pulse oximetry, strict intake/output, and serial lactate measurements. 1
• Administer antipyretics for fever control and consider prophylactic acetaminophen to reduce severity of rigors. 1

Special Considerations

Travel History

If recent travel to endemic areas, immediately exclude malaria, dengue fever, enteric fever, and rickettsial diseases. 1, 3

• Obtain thick and thin blood films (Giemsa stained) immediately for malaria diagnosis. 3
• Fever with chills increases likelihood ratio for malaria to 5.1 in febrile travelers from endemic areas. 3
• Initiate doxycycline empirically if rickettsial infection suspected (African tick bite fever, Mediterranean spotted fever). 1

Medication Review

• Document all medications started within the past 3 weeks, as drug-induced fever has a mean lag time of 21 days and can persist 1-7 days after stopping the offending agent. 2

Device-Related Infections

• Presence of indwelling urinary catheters or vascular access increases bacteremia risk 39-fold. 2

Critical Pitfalls to Avoid

• Never delay blood cultures until after antibiotic administration—this significantly reduces diagnostic yield. 1
• Do not assume "toxic appearance" or high fever reliably predicts bacterial infection. 1
• Avoid obtaining blood cultures from central venous catheters due to increased contamination rates. 1
• Do not miss atypical presentations in elderly or cirrhotic patients who may lack fever or localizing symptoms. 1
• Recognize that rigors can cause transient laryngeal dyskinesia and negative pressure pulmonary edema, mimicking aspiration or allergic reactions. 5
• Consider occult dental abscess in patients with no clear infection focus, particularly if facial pain develops. 6