What is the best approach to managing a suspected infection?

Managing a Suspected Infection

Initiate empiric antimicrobial therapy within 1 hour of recognizing sepsis after obtaining blood cultures, prioritizing patients with hemodynamic instability, signs of septic shock, or immunocompromised states. 1, 2

Immediate Assessment and Diagnostic Workup

Before administering any antibiotics, obtain the following diagnostic tests 2:

• Blood cultures (≥3 sets from peripheral vein and all indwelling catheters) 1, 2
• Complete blood count with differential
• Comprehensive metabolic panel and lactate level
• Urinalysis and urine culture
• Gram stain and culture from suspected infection site when accessible 1

Perform a detailed patient history and thorough clinical examination to identify the infection source, including 1:

• Travel history to endemic areas (malaria, dengue, enteric fever, rickettsial diseases) 2
• Recent antibiotic exposure (consider Clostridium difficile) 1
• Immunosuppression status (chemotherapy, transplant, HIV, corticosteroids) 1, 3
• Presence of indwelling devices or catheters 1

Use imaging techniques (chest X-ray, CT, ultrasound) when clinically indicated to localize infection source 1.

Criteria for Immediate Empiric Antibiotic Therapy

Start antibiotics within 1 hour after obtaining cultures if any of the following are present 1, 2:

• Hemodynamic instability or septic shock (systolic BP <90 mmHg in adults)
• Signs of systemic inflammatory response or organ dysfunction
• Immunocompromised state (neutropenia, chemotherapy, transplant, HIV with CD4 <200) 1, 3
• Suspected meningitis (altered mental status, meningismus) 1, 2
• Suspected cholangitis (Charcot's triad: fever, jaundice, right upper quadrant pain) 2
• Age ≥50 years with fever and chills (55% likelihood of serious bacterial infection) 2

In cirrhotic patients with septic shock, mortality increases by 10% for every hour of antibiotic delay. 2

Empiric Antibiotic Selection

Base antibiotic selection on 1:

• Local pathogen epidemiology and resistance patterns
• Suspected infection source
• Recent travel history
• Patient's immunocompromised status

For suspected bacterial sepsis in adults: Use fluoroquinolone (ciprofloxacin) or azithromycin depending on local susceptibility patterns and travel history 1. For severe sepsis, consider anti-pseudomonal coverage (ceftazidime or carbapenem) 3.

For children <3 months with suspected bacterial etiology: Use third-generation cephalosporin 1.

For neutropenic fever: Use anti-pseudomonal monotherapy (ceftazidime or carbapenem) or combination therapy based on local resistance patterns 3.

For suspected enteric fever in travelers from Asia: Use intravenous ceftriaxone as first-line 2.

Fluid Resuscitation and Supportive Care

In patients with tissue hypoperfusion 1:

• Infuse crystalloids and/or colloids aggressively
• Continue liberal infusions for 24-48 hours (>4L may be required in first 24 hours for adults)
• Target systolic arterial blood pressure ≥90 mmHg in adults
• Monitor for clinical indicators of adequate perfusion: normal capillary refill, warm extremities, well-felt peripheral pulses, urine output >0.5 mL/kg/hour (adults)

Use dopamine or epinephrine in patients with persistent tissue hypoperfusion despite liberal fluid resuscitation 1.

Administer intravenous hydrocortisone (up to 300 mg/day) or prednisolone (up to 75 mg/day) to adult patients requiring escalating dosages of vasopressors 1.

Oxygen and Ventilation Support

Apply oxygen to achieve oxygen saturation >90% 1. If no pulse oximeter available, administer oxygen empirically in patients with severe sepsis or septic shock 1.

Place patients in semi-recumbent position (head of bed raised to 30-45°) 1, 4. Unconscious patients should be placed in lateral position with clear airway 1.

Use non-invasive ventilation in patients with dyspnea and/or persistent hypoxemia despite oxygen therapy when staff is adequately trained 1.

When to Withhold Empiric Antibiotics

In stable, immunocompetent patients without signs of sepsis or organ dysfunction, it is reasonable to complete diagnostic workup and observe for 1-2 hours before initiating antibiotics, provided blood cultures have been obtained and close monitoring is in place 2.

Do NOT treat 1:

• Asymptomatic contacts of patients with infections
• Aspiration pneumonitis without evidence of bacterial pneumonia 4
• Infections attributed to STEC O157 and other STEC producing Shiga toxin 2 1

Source Control

Whenever possible 1:

• Drain or debride the source of infection
• Remove any foreign body or device that may be the infection source
• Remove all indwelling intravenous catheters promptly at end of therapy 1

Critical Pitfalls to Avoid

Do NOT delay antibiotic administration while awaiting diagnostic workup in patients meeting criteria for immediate treatment 2. When in doubt, err on the side of early antibiotic administration after cultures are obtained 2.

Do NOT perform blind stone basketing or invasive procedures without direct visualization 1.

Signs and symptoms of infection may be minimal or absent in neutropenic patients, especially those on corticosteroids—maintain high clinical suspicion even with low-grade fever 3.

Do NOT obtain blood cultures from central venous catheters alone as this increases contamination rates 2. Always obtain peripheral blood cultures 2.

Do NOT initiate empirical antimicrobial therapy for suspected infection in patients with history of infective endocarditis unless the patient's condition warrants it 1.

Monitoring and Follow-up

Monitor patients for 1:

• Vital signs, pulse oximetry, strict intake and output
• Serial lactate measurements
• Development of complications including relapse and heart failure
• Response to therapy at 48-72 hours

Modify or discontinue antimicrobial treatment when a clinically plausible organism is identified from diagnostic tests 1.