What is the management approach for community-acquired pneumonia (CAP)?

Management of Community-Acquired Pneumonia

The cornerstone of CAP management is severity-based risk stratification to determine site of care, followed by prompt empirical antibiotic therapy tailored to the treatment setting, with β-lactam plus macrolide combination therapy for hospitalized patients and respiratory fluoroquinolone or macrolide monotherapy for outpatients. 1, 2

Initial Assessment and Severity Stratification

Severity assessment must be performed immediately upon presentation using validated tools such as CURB-65 or the Pneumonia Severity Index (PSI) to guide all subsequent management decisions. 3, 1, 2

Key Adverse Prognostic Features to Assess:

• Hypoxemia: SaO₂ <92% or PaO₂ <8 kPa regardless of FiO₂ 3
• Bilateral or multilobar involvement on chest radiograph 3
• Hemodynamic instability, altered mental status, or respiratory failure 1, 2

Site of Care Decision:

• PSI risk classes I-III: Outpatient management is safe 2, 4
• PSI risk classes IV-V or CURB-65 ≥2: Hospital admission required 1, 2
• Severe pneumonia with ICU criteria: Immediate ICU admission 3, 1

Clinical judgment remains essential as prediction models cannot definitively categorize all patients, and reassessment every 48-72 hours is mandatory. 3

Empirical Antibiotic Therapy

Outpatient Management (Non-Severe CAP)

For previously healthy patients without recent antibiotic use within 3 months:

• First-line: Amoxicillin 1 g three times daily 3, 1, 5
• Alternative: Macrolide (azithromycin or clarithromycin) or doxycycline 100 mg twice daily 1, 2, 6

For patients with comorbidities (chronic heart/lung/liver/renal disease, diabetes, alcoholism, malignancy) or recent antibiotic use:

• Respiratory fluoroquinolone (levofloxacin 750 mg daily or moxifloxacin) alone 1, 2, 6
• Alternative: β-lactam plus macrolide combination 2, 6

Hospitalized Non-ICU Patients

Standard regimen: β-lactam (ceftriaxone 1-2 g every 24 hours, cefotaxime, or ampicillin-sulbactam) PLUS macrolide (azithromycin or clarithromycin) 1, 2, 6, 4

Alternative: Respiratory fluoroquinolone monotherapy (levofloxacin or moxifloxacin) 1, 2

Critical timing: First antibiotic dose must be administered within 8 hours of hospital arrival, ideally while still in the emergency department for ED admissions. 1, 2

Severe CAP/ICU Patients

For patients WITHOUT Pseudomonas risk factors:

• β-lactam (ceftriaxone, cefotaxime, or ceftaroline) PLUS either azithromycin OR respiratory fluoroquinolone 1, 2, 6

For patients WITH Pseudomonas risk factors (structural lung disease, recent hospitalization, recent broad-spectrum antibiotics):

• Antipseudomonal β-lactam (piperacillin-tazobactam, cefepime, imipenem, or meropenem) PLUS ciprofloxacin 400 mg IV every 8-12 hours OR levofloxacin 750 mg daily 1, 2, 6
• Alternative: Antipseudomonal β-lactam PLUS aminoglycoside PLUS azithromycin 2, 6

For suspected MRSA (recent hospitalization, IV drug use, known colonization):

• Add vancomycin 15-20 mg/kg every 8-12 hours OR linezolid 600 mg every 12 hours to the above regimens 1, 6

Adjunctive therapy with ceftazidime or piperacillin-tazobactam was used in 88% of documented Pseudomonas cases in clinical trials. 7

Supportive Care Measures

In Hospital Setting:

• Oxygen therapy to maintain PaO₂ >8 kPa and SaO₂ >92%; high concentrations are safe in uncomplicated pneumonia 3
• For COPD patients with ventilatory failure: Titrate oxygen carefully with repeated arterial blood gas monitoring 3
• Assess for volume depletion and provide IV fluids as needed 3
• Monitor vital signs (temperature, respiratory rate, pulse, blood pressure, mental status, oxygen saturation) at least twice daily, more frequently in severe cases 3

In Community Setting:

• Advise smoking cessation, rest, and adequate fluid intake 3, 1
• Simple analgesia (paracetamol/acetaminophen) for pleuritic pain 3
• Mandatory clinical review at 48 hours or earlier if deteriorating 3

Transition to Oral Therapy and Duration

Switch from IV to oral antibiotics when the patient meets ALL criteria:

• Hemodynamically stable 2, 5
• Clinically improving with decreased cough and dyspnea 2
• Afebrile for 48-72 hours 2, 5
• Able to take oral medications with functioning GI tract 2, 5

This typically occurs within the first 2-3 days of hospitalization. 2, 4

Treatment Duration:

• Minimum 5 days for most responding patients 1, 2
• Patient must be afebrile for 48-72 hours with no more than one sign of clinical instability before discontinuation 2, 5
• Extended therapy (7-14 days) for suspected/proven MRSA or Pseudomonas aeruginosa 1
• 14-21 days for severe pneumonia or confirmed Legionella, staphylococcal, or gram-negative enteric bacilli 1

Levofloxacin 750 mg daily for 5 days demonstrated equivalent efficacy to 500 mg daily for 10 days in clinical trials, with 90.9% clinical success rates. 7

Management of Treatment Failure

Do NOT change initial antibiotic therapy in the first 72 hours unless marked clinical deterioration occurs. 1, 2

For patients not progressing satisfactorily after 72 hours:

• Remeasure CRP level 3
• Repeat chest radiograph 3
• Consider diagnostic evaluation for drug-resistant pathogens, unusual organisms, non-pneumonia diagnoses, or complications (empyema, abscess) 2

Up to 10% of CAP patients will not respond to initial therapy. 2

Follow-Up and Prevention

Clinical review should be arranged at 6 weeks post-treatment for all patients, with chest radiograph for those with persistent symptoms or higher malignancy risk. 2

Bronchoscopy should be considered for patients with persisting signs, symptoms, and radiological abnormalities 6 weeks after completing treatment. 3

Prevention Strategies:

• Pneumococcal vaccination (23-valent polysaccharide) for all patients ≥65 years and at-risk populations 1, 6
• Annual influenza vaccination for all at-risk patients 1, 6
• Smoking cessation counseling eliminates an important CAP risk factor 1, 6

Critical Pitfalls to Avoid

• Delayed antibiotic administration increases mortality; ensure first dose within 8 hours of arrival 2
• Inadequate coverage of causative pathogens (particularly atypical organisms) is associated with worse outcomes and longer hospitalization 2, 8
• Antimicrobial overtreatment is common in mild-moderate CAP (49-55% of cases), leading to unnecessary adverse effects and resistance 8
• Failure to reassess severity regularly can result in inappropriate escalation or de-escalation of care 3
• Radiological improvement lags behind clinical recovery; do not perform unnecessary investigations in clinically improving patients 3