Resp Care
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Ventilator-associated pneumonia (VAP), which is usually defined as an infection occurring greater than 48 hours after hospital admission in a patient requiring mechanical ventilation, is an entity that should be viewed as a subcategory of health-care-associated pneumonia, which includes any patient who was hospitalized in an acute care hospital for 2 or more days within 90 days of the infection; resided in a nursing home or long-term care facility; received recent antibiotic therapy, chemotherapy, or wound care within the past 30 days of the current infection; or attended a hospital or hemodialysis clinic. VAP is the most frequent intensive-care-unit (ICU)-acquired infection among patients receiving mechanical ventilation. In contrast to infections of other frequently involved organs (eg, urinary tract and skin), for which mortality is low, the mortality rate for VAP ranges from 20% to 50% and can reach 70% in some specific settings or when lung infection is caused by high-risk pathogens and/or when initial antibiotic therapy is inappropriate. ⋯ Antimicrobial therapy of patients with VAP should follow a 2-stage process. The first stage involves administering broad-spectrum antibiotics to avoid inappropriate treatment in patients with true bacterial pneumonia. The second stage focuses on trying to achieve this objective without over-using and abusing antibiotics, combining a number of different steps, such as stopping therapy in patients with a low probability of the disease, streamlining treatment once the etiologic agent is known, switching to monotherapy after days 3-5, and shortening duration of therapy to 7-8 days, as dictated by the patient's clinical response to therapy and information about the bacteriology of the infection.
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Pooling of contaminated secretions above the cuff of the endotracheal tube predisposes patients to ventilator-associated pneumonia (VAP). Subglottic secretion drainage requires a special endotracheal tube that has a separate lumen that opens in the subglottic region above the tracheal tube. A recent meta-analysis of the 5 randomized clinical trials that evaluated the efficacy of removing these secretions found that this technique significantly reduces the incidence of VAP. ⋯ While silver-coated endotracheal tubes reduce pseudomonas pneumonia in intubated dogs and delay airway colonization in intubated patients, evaluation of studies with a variety of case mixes is warranted to identify subsets likely to benefit from the technique before it is implemented on a large scale. A patient who has a colonized airway and who undergoes percutaneous tracheotomy has an increased risk of VAP, particularly due to Pseudomonas aeruginosa, in the week following the procedure. As many studies suggest that incidence of VAP is highly dependent on the strategies of airway management, health care workers should be alerted to issues related to the artificial airway.
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Historically, the relationship between the ventilator circuit and pulmonary infection was accepted as fact, without any scientific evidence. Hence the term, "ventilator"-associated pneumonia. Recent evidence, however, has demonstrated that the major sources of pneumonia in the ventilated patient are colonization of the gastrointestinal tract, with subsequent aspiration around the endotracheal tube cuff, and contamination by caregivers. ⋯ A number of clinical trials have demonstrated that routine changing of the ventilator circuit fails to impact the incidence of pneumonia in the ventilated patient. Additional studies evaluating the type of humidification device, type of suctioning device, and frequency of change of the devices have resulted in conflicting evidence. This paper reviews the role of the humidifier, ventilator circuit, and airway suctioning equipment on the pathogenesis and prevention of ventilator-associated pneumonia.
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Ventilator management strategies can affect the risk for ventilator-associated pneumonia in 3 ways: the development of ventilator-induced lung injury; the need for potentially harmful tradeoffs in providing lung-protective ventilatory strategies; and the prolongation of the duration of mechanical ventilation from iatrogenic factors. Strategies to reduce ventilator-induced lung injury include a smaller tidal volume and careful attention to reducing the maximum pressures in the lung. ⋯ However, the weight of evidence suggests that beneficial outcomes from lung-protective strategies outweigh any potential harm from these tradeoffs. Finally, properly performed weaning protocols based on clinical evidence should reduce any iatrogenic delays in ventilator weaning and thereby minimize prolongation of unneeded mechanical ventilatory support.
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Ventilator-associated pneumonia (VAP) is the most common nosocomial infection in the intensive care unit and is associated with major morbidity and attributable mortality. Strategies to prevent VAP are likely to be successful only if based upon a sound understanding of pathogenesis and epidemiology. The major route for acquiring endemic VAP is oropharyngeal colonization by the endogenous flora or by pathogens acquired exogenously from the intensive care unit environment, especially the hands or apparel of health-care workers, contaminated respiratory equipment, hospital water, or air. ⋯ Measures to prevent epidemic VAP include rigorous disinfection of respiratory equipment and bronchoscopes, and infection-control measures to prevent contamination of medical aerosols. Hospital water should be Legionella-free, and high-risk patients, especially those with prolonged granulocytopenia or organ transplants, should be cared for in hospital units with high-efficiency-particulate-arrestor (HEPA) filtered air. Routine surveillance of VAP, to track endemic VAPs and facilitate early detection of outbreaks, is mandatory.