Emergency Medicine Hub / Pulmonary Emergencies • 3 min read • 3 sections

Community-Acquired Pneumonia & Pleural Space Infections

Comprehensive emergency management of community-acquired pneumonia (CAP), severe viral pneumonias (Influenza, COVID-19), aspiration syndromes, and pleural space infections. Covers clinical risk scores (CURB-65, PSI/PORT), ATS/IDSA empiric antimicrobial regimens, thoracentesis indications, and Light's criteria for complicated parapneumonic effusions and empyema.

Resuscitation Quick Actions • First 2 Minutes

High-Acuity

CURB-65 Score

Confusion, Uremia (BUN > 20), RR >= 30, BP (SBP < 90 or DBP <= 60), Age >= 65; 0-1 = Outpatient, 2 = Inpatient floor, >= 3 = ICU consideration

Outpatient CAP Regimen

No comorbidities: Amoxicillin 1g PO TID OR Doxycycline 100mg BID. Comorbidities: Augmentin + Macrolide/Doxycycline OR Respiratory Fluoroquinolone

Inpatient CAP Regimen

Ceftriaxone 1-2g IV q24h + Azithromycin 500mg IV q24h (or Doxycycline); add Vancomycin/Cefepime if MRSA/Pseudomonas risk factors

Empyema Fluid Criteria

pH < 7.20, Glucose < 60 mg/dL, LDH > 1000 IU/L, or frank pus -> Mandatory immediate chest tube drainage

Severe Influenza

Start Oseltamivir 75mg PO BID immediately in hospitalized/high-risk patients, even if symptom duration > 48 hours

Bottom-Line Clinical Pearl

Risk-stratify all pneumonia patients using CURB-65 or PSI/PORT to determine outpatient vs. inpatient vs. ICU disposition. In patients with significant pleural effusions (> 10 mm on lateral decubitus or ultrasound), perform diagnostic thoracentesis: pleural fluid pH < 7.20, glucose < 60 mg/dL, LDH > 1000 IU/L, or positive Gram stain/frank pus defines empyema/complicated effusion mandating immediate tube thoracostomy drainage.

1. Risk Stratification & Disposition: CURB-65 vs. PSI/PORT

Community-acquired pneumonia (CAP) remains a leading cause of infectious death in the emergency department. Clinical judgment alone frequently underestimates mortality; standardized decision tools guide objective admission versus safe outpatient discharge decisions.

Score Feature	CURB-65 Criteria (1 Point Each)	PSI/PORT Score Risk Stratification	Clinical Disposition Recommendation
Score 0 to 1	C: Confusion (AMTS <= 8 or new disorientation) U: Urea > 7 mmol/L (BUN > 20 mg/dL) R: Respiratory rate >= 30 breaths/min B: Blood pressure (SBP < 90 or DBP <= 60 mmHg) 65: Age >= 65 years	Class I or II (Score <= 70 points): 30-day mortality < 1.0% Based on age, nursing home status, comorbidities, vitals, labs, and arterial pH.	Outpatient management safe if patient has oral tolerance, stable home support, and adequate pulse oximetry (SpO2 >= 92% on room air).
Score 2	Presence of any 2 CURB-65 factors: 30-day mortality approximately 6-9%	Class III (Score 71–90 points): 30-day mortality 2.8% Borderline cohort requiring individualized clinical decision-making.	Short-stay observation unit or medical floor admission. Initiate parenteral antibiotics within 4 hours of ED arrival.
Score >= 3	Presence of 3 to 5 factors: Score 3 = 14% mortality Score 4-5 = 27-40% mortality	Class IV (Score 91–130, 8.2% mortality) or Class V (Score > 130, 29% mortality).	Inpatient medical floor or Intensive Care Unit (ICU). Evaluate ATS/IDSA Major/Minor ICU criteria for direct ICU admission.

ATS/IDSA Severe CAP ICU Criteria: Direct ICU transfer is mandatory if 1 Major Criterion is present (Septic shock requiring vasopressors OR respiratory failure requiring mechanical ventilation). ICU care is also indicated if >= 3 Minor Criteria are met: RR >= 30, PaO2/FiO2 ratio <= 250, multilobar infiltrates, confusion/disorientation, uremia (BUN >= 20 mg/dL), leukopenia (WBC < 4,000/mcL), thrombocytopenia (platelets < 100,000/mcL), hypothermia (core temp < 36°C), or hypotension requiring aggressive fluid resuscitation.

2. ATS/IDSA Guideline-Directed Antimicrobial Regimens

Patient Population	First-Line Empiric Antimicrobial Options	Mechanistic & Coverage Rationales	Treatment Duration
Outpatient (Healthy, No Comorbidities)	1. Amoxicillin 1g PO TID OR 2. Doxycycline 100 mg PO BID (Macrolide monotherapy [Azithromycin 500mg day 1, 250mg days 2-5] only if local pneumococcal resistance < 25%)	Targets Streptococcus pneumoniae, Mycoplasma pneumoniae, Chlamydia pneumoniae, and Haemophilus influenzae. High-dose amoxicillin overcomes penicillin-intermediate pneumococci.	5 days minimum (patient must be afebrile for 48 hours with stable vitals before discontinuation).
Outpatient (With Comorbidities: COPD, CKD, DM, CHF, Cirrhosis, Alcoholism)	Combination Therapy: Amoxicillin-Clavulanate (Augmentin) 875/125 mg PO BID (or Cefuroxime 500 mg BID) PLUS Azithromycin 500 mg day 1 then 250 mg daily (or Doxycycline 100 mg BID) OR Respiratory Fluoroquinolone Monotherapy: Levofloxacin 750 mg PO daily or Moxifloxacin 400 mg PO daily	Broad coverage against gram-negative bacilli, beta-lactamase producing H. influenzae, Moraxella catarrhalis, plus atypicals. Fluoroquinolones reserved for penicillin-allergic patients due to tendonopathy/aortic aneurysm risks.	5 to 7 days.
Inpatient (Non-Severe, Medical Floor)	Beta-Lactam + Macrolide: Ceftriaxone 1g to 2g IV daily PLUS Azithromycin 500 mg IV/PO daily OR Respiratory Fluoroquinolone: Levofloxacin 750 mg IV daily	Covers typical bacteremic pneumococcus and atypicals. Beta-lactam/macrolide combination demonstrates consistent survival benefit over fluoroquinolone monotherapy in multicenter trials.	5 to 7 days.
Inpatient (Severe/ICU)	Ceftriaxone 2g IV daily (or Ampicillin-Sulbactam 3g IV q6h) PLUS Azithromycin 500 mg IV daily (or Levofloxacin 750 mg IV daily). If MRSA Risk: Add Vancomycin 15-20 mg/kg IV q8-12h (target trough 15-20) or Linezolid 600 mg IV q12h. If Pseudomonas Risk: Substitute Cefepime 2g IV q8h, Piperacillin-Tazobactam 4.5g IV q6h, or Meropenem 1g IV q8h.	Dual antipseudomonal/anti-MRSA therapy indicated only if prior respiratory isolation of pathogen or recent hospitalization with parenteral antibiotics in last 90 days. Obtain stat nasal MRSA PCR to de-escalate vancomycin within 24 hours.	7 to 14 days.

3. Pleural Space Infections: Light's Criteria & Empyema Drainage

Up to 40% of hospitalized pneumonia patients develop a parapneumonic effusion. Diagnostic thoracentesis is indicated for any parapneumonic effusion measuring > 10 mm depth on upright lateral decubitus radiograph or bedside ultrasound. Fluid analysis differentiates an uncomplicated effusion from a complicated parapneumonic effusion or frank empyema requiring urgent tube thoracostomy:

Effusion Stage	Macroscopic & Microscopic Appearance	Biochemical Parameters (Light's & Markers)	Mandatory Emergency Intervention
Transudate (CHF, Cirrhosis, Nephrosis)	Clear, straw-colored fluid; non-viscous; no odor.	Meets NONE of Light's criteria: 1. Pleural/Serum Protein ratio <= 0.5 2. Pleural/Serum LDH ratio <= 0.6 3. Pleural LDH <= 2/3 upper limit of normal serum LDH	Treat underlying systemic disease (diuretics for CHF, albumin/paracentesis for cirrhosis). No chest tube required.
Uncomplicated Parapneumonic Effusion	Turbid or serous; sterile on Gram stain and culture; predominantly neutrophils.	Meets at least one of Light's criteria (Exudate): - Pleural fluid pH > 7.20 - Glucose > 60 mg/dL - LDH elevated but < 1,000 IU/L - Negative Gram stain and culture	Systemic antibiotic therapy alone is sufficient. Serial bedside POCUS to monitor for loculation or volume progression.
Complicated Parapneumonic Effusion	Cloudy or turbid fluid; bacterial invasion of the pleural space with fibrin deposition and loculations.	Severe biochemical acidosis and consumption: - Pleural fluid pH < 7.20 - Pleural fluid glucose < 40-60 mg/dL - Pleural fluid LDH > 1,000 IU/L - Gram stain or culture may be positive or negative	MANDATORY CHEST TUBE DRAINAGE: Antibiotics cannot penetrate acidic, fibrin-rich pleural spaces. Insert 14-28 Fr chest tube under ultrasound guidance.
Empyema (Frank Pus)	Thick, purulent, foul-smelling fluid ('frank pus'); high viscosity; extensive loculations and pleural peel.	Frank pus overrides all biochemical criteria. - Positive bacterial Gram stain and culture - Extreme leukocyte lysis and acidosis	URGENT TUBE THORACOSTOMY + THORACIC SURGERY CONSULT. Early intrapleural fibrinolytic therapy (tPA + Dornase alfa) or Video-Assisted Thoracoscopic Surgery (VATS) decortication.

Complicated Parapneumonic Effusion & Empyema: Never Treat with Antibiotics Alone

An infected or highly acidic pleural space (pH < 7.20, glucose < 60 mg/dL, LDH > 1,000 IU/L, or visible purulence) will NEVER resolve with systemic intravenous antibiotics alone. The thick pleural fibrinous peel and acidic microenvironment neutralize antimicrobial activity and trap bacteria. Failure to perform immediate tube thoracostomy or image-guided catheter drainage leads to trapped lung, fibrothorax, sepsis, and multiorgan failure requiring emergent open thoracotomy or VATS decortication. Always place an ultrasound-guided chest tube promptly upon identifying complicated biochemical criteria.

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