Pneumonia based on Schwartz

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Pneumonia - Schwartz's Principles of Surgery (11th Ed.)

Schwartz's covers pneumonia primarily from a surgical perspective, addressing it in the contexts of postoperative complications, ventilator-associated infection, lung abscess, aspiration, and bronchiectasis.

1. Postoperative Pneumonia & Predisposing Factors

Pulmonary atelectasis is a key precursor - it reduces functional residual capacity (FRC) and predisposes to pneumonia. Contributing factors include:

Poor pain control → inadequate inspiratory effort → lower lobe collapse
Inadequate pulmonary toilet → bronchial plugging, lobar collapse
Aspiration (from anesthesia, stroke, drugs/alcohol, esophageal disease)

Prevention of atelectasis/pneumonia:

Sit patient >45° (increases FRC by ≥700 mL)
Early ambulation
Adequate pain control - epidural analgesia significantly lowers pneumonia risk vs. patient-controlled analgesia
Head of bed at 30-45° for ventilated patients
Adequate tidal volumes (8-10 mL/kg) in ventilated patients

2. Ventilator-Associated Pneumonia (VAP)

Pneumonia is the second most common nosocomial infection overall and the most common infection in ventilated patients.

VAP occurs in 15% to 40% of ventilated ICU patients
Probability rate: 5% per day, up to 70% at 30 days
30-day mortality of nosocomial pneumonia: up to 40% (depends on organism and timeliness of antibiotics)

Diagnosis requires:

Abnormal chest X-ray
Fever
Productive cough with purulent sputum
No other obvious fever source

The presence of two clinical findings + CXR changes significantly increases diagnostic likelihood. Bronchoalveolar lavage (BAL) for Gram stain and culture is recommended; quantitative cultures (threshold: ≥100,000 CFU) help confirm diagnosis.

Organisms:

Nosocomial pneumonia: 60-70% gram-negative bacteria
Pseudomonas and Acinetobacter spp. are particularly virulent - double antibiotic coverage may be appropriate if local prevalence is high
Immunosuppressed patients: also susceptible to Salmonella, Legionella, Pneumocystis carinii (jirovecii), atypical mycobacteria, fungi

Treatment:

Begin broad-spectrum antibiotics immediately once pneumonia suspected
Narrow spectrum once culture sensitivities are known
Track the institution's antibiogram every 6-12 months - one of the most helpful tools in managing pneumonia

Prevention of VAP: Wean from mechanical ventilation as soon as oxygenation and inspiratory effort allow. Protocol-driven approaches are recognized as beneficial.

3. Aspiration Pneumonitis vs. Aspiration Pneumonia

Feature	Pneumonitis	Pneumonia
Cause	Chemical injury from aspirated gastric acid	Bacterial infection from aspirated material
Antibiotics	Not indicated	Required (broad-spectrum initially)
Treatment	Supportive care, oxygenation (similar to ARDS management); early aggressive bronchoscopy for suctioning	Antibiotics guided by culture
Mortality	Up to 70-80% in hospitalized patients	Depends on organism and timeliness

Forced diuresis for anasarca/over-resuscitation remains controversial - complications include electrolyte disturbances, metabolic alkalosis, hypotension, and acute kidney injury.

4. Lung Abscess (Necrotizing Pneumonia)

Etiology Classification

Primary (lung as source):

Necrotizing pneumonia - caused by S. aureus, Klebsiella, Pseudomonas, Mycobacterium, Bacteroides, Fusobacterium, Actinomyces, Entamoeba, Echinococcus
Aspiration pneumonia - anesthesia, stroke, drugs/alcohol
Esophageal disease - achalasia, Zenker's diverticulum, GERD
Immunodeficiency - cancer, chemotherapy, diabetes, organ transplantation, steroid therapy, malnutrition

Secondary (lung involved from elsewhere):

Bronchial obstruction (neoplasm, foreign body)
Systemic sepsis (septic pulmonary emboli, seeding of pulmonary infarct)
Pulmonary trauma (infected hematoma/contusion, contaminated foreign body)
Direct extension from extraparenchymal infection (pleural empyema, mediastinal/hepatic/subphrenic abscess)

Microbiology

Post-aspiration lung abscesses are typically polymicrobial (average 2-4 isolates):

≥50% purely anaerobic bacteria
25% mixed aerobes + anaerobes
≤25% aerobes only

Clinical Features

Productive cough, fever (>38.9°C), chills, leukocytosis (>15,000 cells/mm³)
Weight loss, fatigue, malaise, pleuritic chest pain, dyspnea
More indolent course possible: weeks-months of low-grade fever, night sweats, anemia
After aspiration: cavitation in 1-2 weeks; 40-75% produce putrid/foul-smelling sputum
Severe complications (massive hemoptysis, pyopneumothorax, septic shock) are rare in the antibiotic era
Mortality: 5-10% overall; 9-28% in immunosuppressed patients

Diagnosis

CXR is primary tool - shows density/mass with thin-walled cavity; air-fluid level indicates communication with tracheobronchial tree
CT chest when CXR is equivocal - clarifies diagnosis, identifies endobronchial obstruction
Differential: cavitating lung carcinoma, loculated empyema, infected lung cysts/bullae, TB, bronchiectasis, fungal infections, Wegener's granulomatosis
Bronchoscopy for culture (ideally before antibiotics)

Treatment

Medical treatment is primary - spontaneous drainage via the tracheobronchial tree is usual.

Surgical indications (Table 19-18):

Failure of medical therapy
Abscess under tension
Abscess increasing in size during appropriate treatment
Contralateral lung contamination
Abscess >4-6 cm in diameter
Necrotizing infection with multiple abscesses, hemoptysis, abscess rupture, or pyopneumothorax
Inability to exclude cavitating carcinoma

Drainage options:

Tube thoracostomy
Percutaneous (radiographically guided) drainage
Surgical cavernostomy
Surgical resection required in <10% of patients
Lobectomy is preferred for bleeding or pyopneumothorax
Intraoperative: protect contralateral lung with double-lumen tube, bronchial blocker, or contralateral mainstem intubation
Surgical treatment: 90% success rate, mortality 1-13%

5. Pneumonia as a Cause of Bronchiectasis

Diffuse pneumonic processes - including necrotizing bacterial pneumonia, pertussis/measles pneumonia, severe influenza, and varicella pneumonia - can lead to widespread bronchiectasis (permanent dilation of bronchi with wall thickening). This is a key acquired cause of bronchiectasis, particularly in post-infectious settings.

6. Inhalation Injury & Pneumonia (Burn Patients)

Ventilator-associated pneumonia is especially common in patients with inhalation injury
BAL within 24 hours of inhalation injury has a high rate of positive cultures, helping isolate organisms early
"Pneumonia" nomenclature is complicated in this population by the background of inhalation injury

Sources: SCHWARTZ'S PRINCIPLES OF SURGERY, 11th Edition - Chapters on Surgical Complications (Ch. 12), Critical Care (Ch. 13), Chest Wall, Lung, Mediastinum & Pleura (Ch. 19), and Burns (Ch. 8)

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