97. Types of pneumonia, symptoms and therapy

Last updated on May 9, 2021 at 21:03

Definition and epidemiology

Pneumonia is an acute inflammation of the lung parenchyme, with involvement of the bronchioli and alveoli, most often caused by microbes.

It’s a very common condition which causes significant mortality. It’s more common in the winter months.

Classification

According to the place where the patient acquired the infection:

  • Community-acquired pneumonia (CAP)
    • Absence of prior hospital admission in the last 7 days
  • Nosocomial pneumonia
    • Hospital-acquired pneumonia (HAP)
      • Acquired > 48 hours after hospital admission
    • Ventilator-associated pneumonia (VAP)
      • Acquired > 48 hours after endotracheal intubation
    • (Healthcare-associated pneumonia (HCAP))
      • Pneumonia in health care facilities other than hospital
      • Nowadays considered a type of CAP

This classification is important because the causative agents and therefore the management are different for each type.

According to the pathological distribution:

  • Bronchopneumonia
    • Exudate in a patchy distribution
  • Lobar pneumonia
    • Exudate involving an entire lobe
  • Interstitial pneumonia (pneumonitis)
    • Inflammation localized to alveolar septae

Special types:

  • Atypical pneumonia
    • Caused by atypical bacteria
  • Aspiration pneumonia
    • Caused by aspiration of gastric fluids
  • Chemical pneumonitis

Etiology

Microbial agents

  • Community-acquired pneumonia
    • Streptococcus pneumoniae
    • Staphylococcus (if after influenza)
  • Nosocomial pneumonia
    • Gram negative enterobacteria (E. coli, Klebsiella)
    • MSSA and MRSA
    • Pseudomonas aeruginosa
    • ESBL-producing gram negatives
  • Atypical pneumonia
    • Chlamydia pneumoniae
    • Mycoplasma pneumoniae
    • Legionella pneumophila

Risk factors

  • Children < 5 years
  • Adults > 40 years
  • Comorbidities (COPD, bronchiectasis, heart disease, renal disease)
  • Swallowing impairment (for aspiration pneumonia)

Clinical features

The clinical features are caused by microbial inflammation, the host inflammatory response which impairs gas exchange, as well as the systemic effects of infection. Patients usually present soon after onset of symptoms.

  • Fever
  • Shivers
  • Pleuritic chest pain
  • Cough
  • Sputum (purulent or bloody)
  • Dyspnoea

In elderly, non-specific symptoms like confusion or delirium can occur. In atypical pneumonia, the symptoms are usually non-specific like nausea, muscle aches, etc., rather than pulmonary.

Diagnosis

In CAP, imaging and microbiology are not necessary, and the condition is rather diagnosed based on clinical features. In nosocomial pneumonia, imaging and microbiology is important judge the severity and to target the treatment.

Physical exam:

  • Crackles
  • Dullness on percussion
  • Hyperresonance
  • Bronchial breathing

The gold standard for diagnosis is the presence of a new lung shadow on chest x-ray in the setting of typical clinical features. In elderly typical lung symptoms are not necessary for diagnosis. The shadow classically conforms to one lobe and is associated with air bronchograms. The chest x-ray findings usually persist for weeks even after symptoms have cleared, so they’re usually not used for follow-up. Chest x-ray is negative in the first 24 – 48 hours.

In nosocomial pneumonia, sputum culture, blood culture, and ABG are important to guide treatment. CRP and leukocytes are usually measured to monitor severity. Procalcitonin can be used to differentiate bacterial from non-bacterial causes.

Differential diagnosis:

  • Acute bronchitis
  • Exacerbation of COPD
  • Pulmonary embolism

Severity assessment

Most CAP are managed outpatient, but many cases require inpatient treatment. To know who can be managed in an outpatient setting, who can be managed in the normal ward, and who must be admitted to ICU, severity assessment is important. Multiple scoring systems exist, like CURB-65, PSI, SMART-COP, CPIS. For CURB65, a point is awarded for each of these factors:

  • Confusion
  • Elevated urea (> 7 mM)
  • Respiratory rate > 30/min
  • Hypotension (SBP < 90 mmHg)
  • Old age (> 65 years)

0 or 1 points can likely be treated outpatient, 2 likely requires in-ward treatment, while 3 – 5 points likely requires ICU.

Treatment

Treatment is initially empirical and is based on guidelines as well as local microbial patterns and resistance rates. The most important components are correcting gas exchange and fluid balance abnormalities, as well as antimicrobial treatment.

In uncomplicated cases, 5 days of antimicrobial treatment is enough. For more severe cases or atypical pneumonia, 7 – 10 days is required. Inpatient, the length of the treatment is based on the clinical features. When they are improving satisfactorily, treatment can be stopped. Also, normalized procalcitonin level can also be used as an indicator for stopping treatment.

Outpatient empiric treatment is usually azithromycin or amoxicillin in young people without comorbidities. In older people or people with comorbidities, amoxicillin + clavulanic acid + azithromycin is used. Atypical pneumonia is treated with doxycycline, macrolides, or respiratory fluoroquinolones.

Inpatient empiric treatment depends on the risk for pseudomonas. If there are no risk factors for it, ceftriaxone + azithromycin. If there are risk factors, meropenem + levofloxacin.

Complications

  • Pleural effusion
  • Abscess
  • Respiratory failure
  • Sepsis

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99. Chronic obstructive pulmonary disease (COPD). Diagnostics, types, therapy

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