HOSPITAL-ACQUIRED PNEUMONIA
(HAP)Dr.Redha 2012
Hospital-acquired or nosocomial pneumonia refers to a new episode of pneumonia occurring at least 2 days after admission to hospital.
It is the second most common hospital-acquired infection (HAI) and the leading cause of HAI-associated death.
Older people are particularly at risk, as are patients in intensive care units, especially when mechanically ventilated, in which case the term ventilator-associated pneumonia (VAP) is applied.
Health care-associated pneumonia (HCAP) refers to the development of pneumonia in a person who has spent at least 2 days in hospital within the last 90 days, attended a hemodialysis unit, received intravenous antibiotics, or been resident in a nursing home or other long-term care facility.
Aetiology:
When HAP occurs within 4-5 days of admission (early-onset), the organisms involved are similar to those involved in CAP; however, late-onset HAP is more often attributable to Gram-negative bacteria (e.g. Escherichia, Pseudomonas and Klebsiella species), Staph. aureus (including meticillin-resistant Staph. aureus (MRSA)) and anaerobes.
Factors predisposing to hospital-acquired pneumonia
1- Reduced host defences against bacteria:
• Reduced immune defences (e.g. corticosteroid treatment, diabetes, malignancy)
• Reduced cough reflex (e.g. post-operative)
• Disordered mucociliary clearance (e.g. anaesthetic agents)
• Bulbar or vocal cord palsy.
2-Aspiration of nasopharyngeal or gastric secretions
• Immobility or reduced conscious level
• Vomiting, dysphagia, achalasia or severe reflux
• Nasogastric intubation
3-Bacteria introduced into lower respiratory tract
• Endotracheal intubation/tracheostomy
• Infected ventilators/nebulizers /bronchoscopes
• Dental or sinus infection
4-Bacteraemia
• Abdominal sepsis
• I.v. cannula infection
• Infected emboli
Clinical features and investigations:
HAP should be considered in any hospitalized or ventilated patient who develops purulent sputum (or endotracheal secretions), new radiological infiltrates, an otherwise unexplained increase in oxygen requirement, a core temperature > 38.3°C, and a leukocytosis or leucopenia.
Circulating biomarkers may assist with the diagnosis but are currently non-specific.
Appropriate investigations are similar to those outlined for CAP, although whenever possible, microbiological confirmation should be sought.
In mechanically ventilated patients, bronchoscopy-directed protected brush specimens or bronchoalveolar lavage (BAL) may be performed.
Endotracheal aspirates are easy to obtain but less reliable.
Management:
The choice of empirical antibiotic therapy should be based on local knowledge of pathogens and drug resistance patterns, and variables such as length of hospital stay, recent antibiotics and comorbidity.
Adequate Gram-negative cover is usually provided by:
• A third-generation cephalosporin (e.g. cefotaxime) with an aminoglycoside (e.g. gentamicin)
• Meropenem or
• A monocyclic β-lactam (e.g. aztreonam) and flucloxacillin.
MRSA is treated with intravenous vancomycin, but when appropriate, oral therapy may be considered with doxycycline, rifampicin or linezolid.
The nature and severity of most HAPs dictate that these antibiotics are all given intravenously, at least initially.
Physiotherapy is important in those who are immobile or old.
Adequate oxygen therapy, fluid support and monitoring are essential.
Prevention
Despite appropriate management, the mortality from HAP is high at approximately 30%, emphasizing the importance of prevention.
Good hygiene is paramount, including both hand washing and equipment.
Steps should be taken to minimize the chances of aspiration and limit the use of stress ulcer prophylaxis with proton pump inhibitors.
Oral antiseptic (chlorhexidine 2%) may be used to decontaminate the upper airway and some intensive care units use selective decontamination of the digestive tract when the anticipated requirement for ventilation will exceed 48 hours.
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