Severe Community-Acquired Pneumonia (Severe CAP)
When pneumonia becomes life-threatening and overwhelming, it is termed "severe community-acquired pneumonia" or "severe CAP," which is defined practically as pneumonia requiring ICU admission due to respiratory infection. 1
Clinical Definition and Mortality
Severe CAP is characterized by a mortality rate of up to 50%, necessitating immediate recognition and aggressive intervention 1
The American Thoracic Society and Infectious Diseases Society of America (IDSA/ATS) define severe CAP using major and minor criteria, with patients meeting ≥3 minor criteria or any major criteria requiring ICU-level care 2
A practical clinical approach defines all patients admitted to the ICU because of respiratory infection as having severe illness, regardless of specific scoring criteria 1
Recognition and Risk Stratification
The CURB-65 score (≥3 points) identifies patients at high mortality risk who should be considered for ICU admission, incorporating Confusion, Urea nitrogen elevation, Respiratory rate ≥30, Blood pressure <90/60 mmHg, and age ≥65 years 2, 3
Delayed ICU admission significantly increases mortality - patients admitted to ICU within 2 days of hospital admission had 46.3% mortality versus 57.6% for those admitted after 7 days 1
Even with appropriate antibiotic therapy, severe CAP mortality remains unacceptably high at 24.2%, underscoring the critical nature of this condition 1
Key Clinical Pitfalls
The Pneumonia Severity Index (PSI) can dangerously underestimate severity in younger patients without comorbidities who develop severe respiratory failure, making it less reliable than CURB-65 or IDSA/ATS criteria for identifying severe cases 2
Physician experience remains vital - objective criteria should guide but not replace clinical judgment in recognizing patients who need immediate ICU-level care 1
Prompt recognition using severity assessment tools combined with clinical judgment improves outcomes compared to clinical judgment alone 2