Epidemiology
Due to improvements in the prevention of urinary tract infections in the hospital, HAP and ventilator-associated pneumonia (VAP) are now the most common nosocomial infections (accounting for 22% of the total).[3] Ventilator-associated events, but not HAP or VAP per se, are reportable to the Center for Medicare and Medicaid Services via the National Healthcare Safety Network, managed by the Division of Healthcare Quality Promotion at the Centers for Disease Control and Prevention in Atlanta, GA. When HAP occurs in the intensive care unit (ICU), it is primarily VAP. Reports have stated that 5 to 10 per 1000 patients admitted to the hospital develop HAP. Mechanical intubation is associated with higher rates, and one half of all antibiotics prescribed in an ICU are for HAP or VAP.[4] HAP extends admission to the hospital by 7 to 11 days.[5][6] Risk factors for MRSA include exposure to antibiotics within the last 90 days, hospitalization in a unit where >20% of Staphylococcus aureus isolates are MRSA or a high risk for mortality.[1] The crude mortality for VAP may be as high as 20% to 50%, while the attributable mortality is estimated at 13%.[1] Increased mortality is associated with bacteremia, especially due to Acinetobacter or Pseudomonas.[7] It is also associated with medical, as opposed to surgical, illness and ineffective empiric antimicrobials.[7] Approximately 10% to 20% of burn patients have inhalational injury, which predisposes to VAP.[8]
Risk factors
Pathogens that cause HAP, such as Acinetobacter baumannii, are transmitted to patients from healthcare workers' hands.
The most common introduction of bacteria into alveoli is microaspiration of oropharyngeal pathogens, or leakage of secretions containing bacteria around an endotracheal tube cuff.[15]
Sources of pathogens for HAP include healthcare devices (infected biofilm in the endotracheal tube), the environment (air, water, equipment, and fomites), and the transfer of microorganisms from patient to patient through healthcare workers.[18][19]
For patients who are intubated, the rate of ventilator-associated pneumonia is 6 to 20 patients per 1000 patients admitted to the hospital. This is higher than the rate of HAP, which is 5 to 10 patients per 1000 patients admitted to the hospital. Patients with nasotracheal intubation are at higher risk than those with orotracheal intubation.
Studies using radioactive-labeled enteral feeding in mechanically ventilated patients have found that a supine position promotes aspiration.[22] Another study found that the rate of ventilator-associated pneumonia was significantly reduced among patients maintained in the semi-recumbent position compared with those who were supine.[23] Therefore, elevating the head of the bed, unless medically contraindicated, is recommended by the American Thoracic Society, SHEA/IDSA/APIC (The Society for Healthcare Epidemiology of America/Infectious Diseases Society of America/Association for Professionals in Infection Control and Epidemiology), the Centers for Diseases Control and Prevention, and is supported by most experts despite poor-quality evidence to support the practice.[24][25] Efforts are continuing to collect better-quality evidence.
Oral care is the most commonly studied strategy to prevent HAP, although there is a paucity of robust data.[25] SHEA/IDSA/APIC (The Society for Healthcare Epidemiology of America/Infectious Diseases Society of America/Association for Professionals in Infection Control and Epidemiology) recommend daily oral care without chlorhexidine to prevent HAP.[25][26] Evidence shows that chlorhexidine mouthwash or gel, as part of oral hygiene care (OHC), probably reduces the incidence of developing ventilator-associated pneumonia (VAP) in critically ill patients from 26% to about 18%, when compared with placebo or usual care. Chlorhexidine made no difference to mortality, duration of mechanical ventilation or duration of stay in the intensive care unit (ICU), although the evidence was low certainty. OHC including both antiseptics and toothbrushing may be more effective than OHC with antiseptics alone to reduce the incidence of VAP and the length of ICU stay, but, again, the evidence is low certainty.[26]
Sedation of ventilated patients should be minimized whenever possible.[25] Potential strategies to minimize sedation include nurse-driven protocols for targeted light sedation and daily sedative interruptions (i.e., spontaneous awakening trials) for patients without contraindications.[25] Interrupting sedation has been shown to shorten the duration of intubation and thus decrease ventilator-associated pneumonia.[27] Using a sedation vacation requires more intensive care unit staffing, so the availability of resources should be anticipated before adding the practice to protocols.
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