From the Guidelines
Hospital-acquired pneumonia (HAP) is defined as a lung infection that develops 48 hours or more after admission to a hospital in patients who did not have pneumonia when they were admitted. This definition is based on the most recent guidelines from the European Respiratory Society (ERS) and other reputable sources 1. HAP is characterized by new lung infiltrates on chest imaging along with clinical signs such as fever, purulent sputum, leukocytosis, and declining oxygenation. It is distinct from ventilator-associated pneumonia (VAP), which specifically occurs in mechanically ventilated patients, and community-acquired pneumonia (CAP), which is present on admission or develops within the first 48 hours of hospitalization.
Some key points to consider when diagnosing HAP include:
- The time of onset: HAP typically develops 48 hours or more after hospital admission 1
- Clinical signs: fever, purulent sputum, leukocytosis, and declining oxygenation are common signs of HAP 1
- Radiographic findings: new lung infiltrates on chest imaging are a key diagnostic criterion for HAP 1
- Microbiological confirmation: identification of a microorganism isolated from respiratory samples or blood cultures can confirm the diagnosis of HAP 1
The condition typically results from aspiration of bacteria colonizing the oropharynx or gastrointestinal tract, or from direct inhalation of pathogens. Common causative organisms include Gram-negative bacteria like Pseudomonas aeruginosa, Klebsiella pneumoniae, and Escherichia coli, as well as Gram-positive bacteria such as Staphylococcus aureus, including methicillin-resistant strains. HAP is associated with increased hospital length of stay, higher healthcare costs, and greater mortality compared to patients without pneumonia. Risk factors include advanced age, impaired consciousness, underlying lung disease, immunosuppression, recent surgery (especially thoracic or abdominal), and prolonged hospitalization 1.
From the Research
Definition of Hospital Acquired Pneumonia
- Hospital acquired pneumonia (HAP) is defined as pneumonia that develops within 48 hours or more of hospital admission and which was not developing at the time of admission 2.
- HAP is also known as nosocomial pneumonia (NP) and is the second most common hospital infection, while ventilator-associated pneumonia represents the most common intensive care unit (ICU) infection 2.
- The symptoms of HAP can present after more than 2 days (> 48 hours) of admission to hospital or as late as 14 days of discharge from hospital 3.
Key Characteristics of HAP
- HAP significantly contributes to morbidity, mortality, and escalating healthcare costs because of increases in antibiotic prescription and administration, length of ICU stay, and length of hospital stay 2.
- The microbiology of HAP depends on the timing of onset, with early-onset HAP generally caused by endogenous community-acquired pathogens and late-onset HAP caused by potentially multi-drug-resistant nosocomial organisms 2.
- Important risk factors for development of HAP include coma, intubation, prolonged mechanical ventilation, repeated intubations, supine positioning, and long-term antibiotic use 2.
Diagnosis and Treatment of HAP
- Accurate diagnosis of HAP is difficult and controversial, warranting consideration for the application of invasive quantitative culture techniques over tracheal aspirates 2.
- Empiric antibiotic treatment should be prompt, starting on clinical suspicion, and based on local ICU pathogen epidemiology and antibiotic resistance patterns and on a deescalating antibiotic strategy 2.
- Various antibiotic regimens have been studied for the treatment of HAP, including piperacillin/tazobactam 4, 5, 6, cefepime 6, and ceftriaxone plus clindamycin 5.