Introduction
Hospital-acquired pneumonia is also known as nosocomial pneumonia.
It is defined as pneumonia occurring ≥48 hours after admission and excluding
any infection that is incubating at the time of admission. Ventilator-associated pneumonia is described as
pneumonia occurring >48-72 hours after endotracheal intubation and within 48
hours after the removal of endotracheal (ET) tube.
Multidrug-resistant is defined as an acquired non-susceptibility
to at least one agent in three different antimicrobial classes. Extensively
drug resistant refers to non-susceptibility to at least one agent in all
but two antimicrobial classes. Pandrug resistant refers to
non-susceptibility to all antimicrobial agents that can be used for treatment.
Epidemiology
Hospital-acquired pneumonia is one
of the most common causes of nosocomial infection in hospitalized and intensive
care patients. Hospital-acquired pneumonia
is more common in the elderly; however, the mean age of patients with
early-onset hospital-acquired pneumonia is lower
than that of patients with late-onset hospital-acquired
pneumonia.
Asian epidemiologic data on hospital-acquired
pneumonia are scarce but various health care
facilities reported incidences ranging from 1 to 21 per 1000 hospital
admissions.
Pathophysiology
Hospital-acquired pneumonia develops from an imbalance of the normal host defenses and the ability of the microorganism to colonize and invade the lower respiratory tract. Aerobic gram-negative pathogen may cause destructive effects on the lung tissue such as cavitation, microabscess formation, blood vessel invasion and hemorrhage.
Risk Factors
Risk Factors for Hospital-acquired Pneumonia/Ventilator-associated Pneumonia
- Patient-related: Age, chronic pulmonary disease, multiple organ system failure, depressed consciousness
- Treatment-related: Intubation/mechanical ventilation, reintubation, prolonged intubation, previous exposure to antibiotics, thoracoabdominal surgery
- Triggers of aspiration: Positioning, nasogastric tube insertion, enteral feeding, low ET tube pressure
- Oropharyngeal colonization
Risk
Factors for Multidrug-resistant Pathogens
- Duration of ≥5 days stay for the current hospitalization prior to occurrence of ventilator-associated pneumonia
- Septic shock at the time of hospital-acquired pneumonia/ventilator-associated pneumonia
- ARDS preceding ventilator-associated pneumonia
- Acute renal replacement therapy before ventilator-associated pneumonia onset
- IV antibiotics within the preceding 90 days (risk factor for multidrug-resistant, Methicillin-resistant Staphylococcus aureus (MRSA), and multidrug-resistant Pseudomonas ventilator-associated pneumonia and hospital-acquired pneumonia)
- Intensive care unit (ICU) admission
- Structural lung disease (eg bronchiectasis, cystic fibrosis) for hospital-acquired pneumonia
- Colonization with or prior isolation of multidrug-resistant Pseudomonas or other Gram-negative bacilli