Pneumonia

Infection of the lung alveoli leading to inflammation and consolidation (air spaces fill with pus/fluid). Often categorized by setting: community-acquired pneumonia (CAP) occurs outside the hospital, hospital-acquired (HAP) occurs ≥48 hours after admission, and ventilator-associated (VAP) occurs ≥48 hours after intubation. Caused by a variety of organisms (bacteria, viruses, fungi) that overcome the lung's defenses.

• Very common and can be life-threatening if untreated. Pneumonia is a leading cause of hospitalization and the deadliest infectious disease (8th overall cause of death in the US and the #1 killer of young children worldwide). High-yield on exams due to classic presentations linking specific pathogens to risk factors (e.g., alcoholics, dorm students, cystic fibrosis, aspiration).

• Typically presents with fever, cough, and difficulty breathing. Typical pneumonia (e.g., pneumococcal) has acute onset of high fever, chills, and productive cough with purulent or rust-colored sputum; exam shows lobar consolidation (dull percussion, crackles). Atypical pneumonia (e.g., Mycoplasma or viral) has a slower onset with dry cough, low-grade fever, and diffuse or interstitial infiltrates (the patient often looks better than the CXR).
• Common CAP bugs & clues: Streptococcus pneumoniae is the most frequent cause of lobar pneumonia in all ages. Haemophilus influenzae often in smokers/COPD; Staph aureus classically after influenza; Klebsiella in alcoholics (aspiration, upper lobe necrosis, "currant jelly" sputum); Mycoplasma pneumoniae in young adults (college, military) with walking pneumonia; Legionella in older smokers (contaminated water, causes GI symptoms and hyponatremia).
• Children: In infants and toddlers, viruses (RSV, influenza, etc.) cause most pneumonias; bacterial pneumonia in kids is usually S. pneumoniae (especially if not fully immunized). School-age kids and teens often get atypical pneumonia from Mycoplasma. Special situations: neonates can get GBS or chlamydial pneumonia; cystic fibrosis patients get Staph aureus and Pseudomonas; immunocompromised children (e.g., HIV) are at risk for Pneumocystis jirovecii.
• Hospital setting: HAP or VAP presents with new fever, purulent sputum, and lung infiltrates in a hospitalized or ventilated patient. These are often caused by resistant gram-negatives (Pseudomonas, Klebsiella, etc.) or MRSA. Aspiration pneumonia (in patients with impaired consciousness or swallowing) typically involves anaerobes and affects dependent lung segments (e.g., right lower lobe) – sputum may be foul-smelling and CXR can show cavitation (abscess).

1. Obtain a chest X-ray whenever pneumonia is suspected, to confirm the presence of an infiltrate and help distinguish pneumonia from bronchitis or heart failure.
2. Assess severity to determine management setting: use clinical judgment or scoring tools (e.g., CURB-65 in adults) to decide if the patient can be treated outpatient or needs hospitalization/ICU. Red flags include respiratory distress, hypoxia, hypotension, or confusion.
3. If admitted, obtain sputum Gram stain & culture and blood cultures *before* starting antibiotics. Order targeted tests as needed (e.g., influenza or RSV PCR, urine antigen tests for Legionella and pneumococcus in severe CAP).
4. Consider complications: if a pleural effusion is present, do thoracentesis to check for empyema (infected fluid requiring drainage). In aspiration cases, be vigilant for lung abscess; bronchoscopy may be warranted if obstruction or foreign body is suspected.

1. Start empiric antibiotics promptly (after cultures if obtained). For CAP, choose coverage for pneumococcus and atypicals: e.g., outpatient can receive a macrolide (like azithromycin) or doxycycline; hospitalized patients often need a beta-lactam (e.g., ceftriaxone) plus a macrolide. (In children, high-dose amoxicillin is first-line for bacterial pneumonia, and add a macrolide if Mycoplasma is suspected.)
2. HAP/VAP: use broad-spectrum antibiotics covering MRSA and Pseudomonas until sensitivities are known (e.g., vancomycin + piperacillin-tazobactam). If aspiration is suspected, ensure anaerobic coverage (e.g., clindamycin or amoxicillin-clavulanate). De-escalate antibiotics based on culture results.
3. Supportive care is important: give oxygen for hypoxia, IV fluids for dehydration, and antipyretics/analgesics for fever and pleuritic pain. Bronchodilators can help if there is wheezing or underlying asthma/COPD. Severe cases may require ICU support (ventilation, vasopressors for septic shock).
4. Special cases: treat influenza pneumonia with antivirals (oseltamivir). Pneumocystis pneumonia (PCP) in immunocompromised patients is treated with high-dose trimethoprim-sulfamethoxazole (often with corticosteroids if respiratory failure).

• Rust-colored sputum → think pneumococcal pneumonia (classic for Strep pneumoniae). "Currant jelly" sputum (thick, bloody mucus) in an alcoholic → Klebsiella pneumonia.
• "Walking" pneumonia = patient looks fairly well despite bad-looking infiltrates on CXR → usually Mycoplasma pneumoniae (common in young adults, dorms/military).
• Legionella pneumonia clue: pneumonia with diarrhea and hyponatremia (often from contaminated water sources like hotel AC systems).

• Respiratory failure signs – e.g., RR ≥30, O₂ sat <90%, cyanosis, or rising CO₂ – indicate need for aggressive intervention (possible ventilation). Altered mental status or septic shock (SBP <90) in a pneumonia patient → ICU-level care is warranted.
• In infants, apnea, grunting, or inability to feed are ominous signs. Any child with severe retractions or low O₂ saturation should be hospitalized for supportive care.

1. Suspected pneumonia (fever + cough + crackles) → get chest X-ray to confirm infiltrate.
2. Confirmed pneumonia → assess severity (vitals, mental status, labs). Use CURB-65 in adults or pediatric criteria to decide outpatient vs hospital (ICU if critical).
3. If inpatient → obtain cultures (sputum, blood) and relevant tests before antibiotics. Consider viral swabs or urine antigen tests based on clinical context.
4. Start empiric antibiotics (guided by CAP vs HAP and patient factors) and provide supportive care (oxygen, fluids, etc.).
5. Reassess at 48–72 hours; if not improving, broaden coverage or investigate complications (e.g., empyema, resistance). Adjust antibiotics when culture results return.

• Alcoholic with high fever, cough, and currant jelly sputum; CXR shows right upper lobe consolidation → Klebsiella pneumonia.
• College student with persistent dry cough, low-grade fever, and patchy interstitial infiltrates on CXR → Mycoplasma pneumoniae (walking pneumonia).
• Infant (6 months old) in winter with wheezing, tachypnea, and intercostal retractions → RSV bronchiolitis (viral pneumonia in a baby).