Pneumonia

Chest radiographic finding	Suggested organism
Lobar consolidation	S. pneumoniae, Klebsiella pneumoniae
Patchy infiltrates	Atypical and fungal organisms
Interstitial pattern	Mycoplasma or viral organisms
Miliary pattern	Tuberculosis or fungal organisms
Apical infiltrate	Tuberculosis
Infiltrate in superior part of lower lobes or posterior part of the upper lobes	Aspiration pneumonia, anaerobic organisms
Cavitary lesion	Tuberculosis, S. aureus, anaerobic organisms, Gram-negative bacilli
Pneumothorax or pneumatocele	Pneumocystis jirovecii

Critical management

Provide supplemental oxygen to maintain a saturation higher than 90%.
Some patients will require mechanical ventilation.
The evidence for the use of Bi-PAP and CPAP is mixed.
Noninvasive ventilation should be considered for preoxygenation of hypoxic patients prior to endotracheal intubation.
Patients who are hypotensive are likely suffering from distributive shock and should be aggressively resuscitated with crystalloids.
Place patients whose radiograph and history are suggestive of tuberculosis in respiratory isolation.
All patients with AIDS who have pneumonia should be placed in respiratory isolation because the chest radiograph cannot discriminate between bacterial pneumonia and tuberculosis.
Two clinical decision rules can assist the physician in deciding whether a patient needs to be admitted for inpatient management, or can be discharged home with outpatient follow-up:
- The Pneumonia Severity Index.
- The CURB-65 rule (Table 54.2). Two or more points warrant hospital admission. Three or more points suggests the need for an ICU admission.
Initiate appropriate antibiotic therapy.
- CAP; outpatient therapy:
  - No comorbidities and no antibiotic use in the past 3 months:
    - Macrolides or doxycycline.
  - Comorbidities such as diabetes mellitus, asplenism, chronic liver, lung or kidney disease, immunosuppression, alcoholism, malignancy, and patients who have received antibiotics in the last 3 months:
    - Respiratory fluoroquinolones or a beta-lactam and a macrolide.
- CAP; inpatient therapy, non-ICU:
  - Beta-lactam (ceftriaxone, cefotaxime, ampicillin-sulbactam) and a macrolide or respiratory fluoroquinolone.
- CAP; inpatient therapy, ICU:
  - Beta-lactam (ceftriaxone, cefotaxime, ampicillin-sulbactam) and a macrolide or respiratory fluoroquinolone.
- HCAP; inpatient therapy:
  - Anti-pseudomonal cephalosporin or anti-pseudomonal carbapenem or piperacillin-tazobactam and
  - Anti-pseudomonal fluoroquinolone or aminoglycoside and
  - Linezolid or vancomycin to cover MRSA.
Special situations
- Aspiration pneumonia; add clindamycin or metronidazole.
- AIDS patients with CD4 counts less than 200 cells/microliter should receive coverage for Pneumocystis jirovecii.
  - TMP-SMX is the first-line agent.
  - Pentamidine can be used in cases of allergy to TMP-SMX.
  - Administer steroids if the PaO₂ is <70 mmHg or the A-a gradient is >35 mmHg on arterial blood gas analysis.