Severe Pneumonia in the ICU

Severe Pneumonia in the ICU is a topic covered in the Pocket ICU Management.

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First Things First (assess & treat for the following)

  • Does patient have any respiratory distress that requires immediate attention?
    • PaCO2 > 50 mmHg
    • pH < 7.2
    • PaO2 < 70 mmHg or O2 saturation < 90%
  • Does patient have evidence of low BP: systolic < 90 mmHg and/or diastolic < 60 mmHg?
  • Does patient have mental status changes?
  • Does patient have evidence of renal dysfunction &/or decreased urine output?
  • Is the CXR showing bilateral, multilobar or progression of pulmonary infiltrates?
  • Is the patient immunocompromised?


  • Community-acquired pneumonia (CAP)
  • Severe community-acquired pneumonia (SCAP)
  • Nosocomial pneumonia (NP) or hospital-acquired pneumonia (HAP)
  • Ventilator-associated pneumonia (VAP)
    • Nosocomial pneumonia in a mechanically ventilated patient
  • Healthcare-associated pneumonia (HCAP)
    • A NP in patients from nursing homes, dialysis centers, etc. who are exposed to multidrug-resistant (MDR) bacteria
  • Important to differentiate the different groups of patients who may present with pneumonia in the ICU:
    • Patient origin: from the community, immunocompromised host either from the community or a nursing home, or currently in the hospital
    • Patient in the hospital and/or ICU who develops a pneumonia, and/or receiving mechanical ventilation, who develops a nosocomial pneumonia
  • Demographic characteristics
    • Most relevant are age, comorbid conditions, medication use, history of immunosuppression, geographic & travel history, exposure to animals.
  • SCAP
    • American Thoracic Society (ATS) defines SCAP & need for ICU admission by of at least 2 of the minor criteria parameters (systolic BP 90 mmHg or less, multilobar disease, PaO2/FIO2 < 250 torr) or one of the major criteria (need for mechanical ventilation or septic shock).
    • Mortality due to SCAP: 35-40%
      • NP (HAP, VAP, HCAP)
    • Mortality rate of NP in the ICU is 35-70%.
    • Risk factors for NP are grouped into 3 categories:
      • Underlying acute illness that predisposes to secondary pneumonia
        • Acute lung injury
        • Abdominal, thoracic or cardiac surgery
        • Head injury/coma
        • Immunosuppressive illness
      • Coexisting medical illness
        • Age >60 yo
        • Obesity
        • Cardiac diseases
        • Albumin < 2.2 g/dl
        • Burns
        • Multiple organ failure
        • Chronic pulmonary diseases (chronic obstructive pulmonary disease, asthma, bronchiectasis, etc.)
        • Renal failure
        • Malignancies
        • Diabetes mellitus
        • Splenic dysfunction
      • Factors associated with therapies frequently used in ICU
        • Intubation with mechanical ventilation >2 days: most important, risk factor increases the risk 7- to 21-fold!
        • Antibiotic therapy
        • Bacteriologically virulent pathogens (Pseudomonas aeruginosa, Acinetobacter spp.)
        • Tracheostomy
        • Nasogastric tube use
        • Transfusion >4 units PRBC
        • Use of corticosteroids, immunosuppressants, H2 antagonists
        • Prolonged sedation and/or paralysis
        • Head of bed elevation < 30 degrees


  • SCAP
    • Patients with severe pneumonia in the ICU may have a pneumonia acquired:
      • In the community (SCAP),
      • In the hospital (HAP),
      • While being mechanically ventilated (VAP) or
      • From nursing homes, dialysis centers, etc. who are exposed to MDR bacteria (HCAP)
    • Most common cause of CAP is S. pneumoniae. 40% of S. pneumoniae is resistant to penicillin and is called drug-resistant S. pneumoniae.
    • S. pneumoniae, H. influenzae, Mycoplasma pneumoniae, influenza A virus, coronavirus (SARS), S. aureus, C. pneumoniae, C. psittaci, L. pneumophila, C. burnetii, gram-negative bacilli (Klebsiella spp, E. coli, Pseudomonas aeruginosa, etc). P. aeruginosa infection is a risk factor in patients with underlying lung diseases, as seen in bronchiectasis, cystic fibrosis & chronic corticosteroid use.
    • Opportunistic pathogens: P. carinii, cytomegalovirus, Cryptococcus neoformans, M. tuberculosis, M. avium intracellulare, A. israelii, N. asteroides, Aspergillus spp.
    • Rare pathogens: pertussis, typhoid, paratyphoid, brucellosis, leptospirosis, tularemia, anthrax, plague, Q fever
    • Viruses: Epstein-Barr virus, cytomegalovirus, measles, varicella, herpes, hantavirus
    • In the first 5 days of hospitalization, pneumonia is usually caused by Streptococcus pneumoniae, Haemophilus influenzae, anaerobic bacteria & less frequently Staphylococcus aureus (SA) (including methicillin-resistant SA [MRSA]) & Moraxella catarrhalis.
    • >5 days after admission, pneumonia is more commonly caused by hospital-acquired pathogens such as aerobic gram-negative bacilli, SA (often MRSA), Legionella pneumophila. Less frequent: influenza A & B, respiratory syncytial virus, Aspergillus spp., Pneumocystis carinii, Mycobacterium tuberculosis.
      • Gram-negative rods: Pseudomonas aeruginosa, Enterobacter spp., Acinetobacter spp., & enteric gram-negative rods (Klebsiella, E. coli, Proteus, Serratia) are the predominant pathogens & are at high risk to be drug-resistant.
      • SA (20-30% are MRSA). MRSA is seen in patients with underlying COPD or prior antibiotic use and/or in patients receiving mechanical ventilation.
    • Polymicrobial infections (60%) are common in patients on mechanical ventilation. MRSA, S. pneumoniae & H. influenzae are found in early-onset (before day 5) nosocomial pneumonia.

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Last updated: May 5, 2010