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| {{Ventilator-associated pneumonia}}
| | #redirect[[Hospital-acquired pneumonia]] |
| {{CMG}}; '''Associate Editor(s)-In-Chief:''' [[Priyamvada Singh|Priyamvada Singh, M.D.]] [mailto:psingh@perfuse.org]
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| ==[[Ventilator-associated pneumonia overview|Overview]]==
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| ==[[Ventilator-associated pneumonia historical perspective|Historical Perspective]]==
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| ==[[Ventilator-associated pneumonia pathophysiology|Pathophysiology]]==
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| ==[[Ventilator-associated pneumonia causes|Causes]]==
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| ==[[Pneumonia differential diagnosis|Differentiating Hospital acquired-pneumonia from other diseases]]==
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| ==[[Pneumonia epidemiology and demographics|Epidemiology and Demographics]]==
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| ==[[Ventilator-associated pneumonia risk factors|Risk Factors]]==
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| ==[[Pneumonia natural history, complications, and prognosis|Natural History, Complications and Prognosis]]==
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| '''Prognosis predictor scores:''' [[CURB-65]] | [[Pneumonia severity index]] | [[Pneumonia medical therapy#Criteria for severe community acquired pneumonia|Criteria for severe community acquired pneumonia]]
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| ==Diagnosis==
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| [[Ventilator-associated pneumonia diagnostic criteria|Diagnostic criteria]] | [[Pneumonia history and symptoms| History and Symptoms]] | [[Pneumonia physical examination | Physical Examination]] | [[Pneumonia laboratory studies |Laboratory Findings]] | [[Pneumonia chest x ray|Chest X Ray]]
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| ==Treatment==
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| [[Pneumonia medical therapy#Pneumonia site of care decision|Site of care decision]] | [[Pneumonia medical therapy|Medical Therapy]] | [[Pneumonia medical therapy#Other treatments consideration|Other treatments consideration]] | [[Pneumonia prevention|Prevention]] | [[Pneumonia medical therapy#Management of non-responding pneumonia|Management of non-responding pneumonia]]
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| [[Category:Diseaase]]
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| [[Category:Pulmonology]]
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| [[Category:Infectious disease]]
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| [[Category:Pneumonia|Pneumonia]]
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| [[Category:Emergency medicine]]
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| {{WH}}
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| {{WS}}
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| {{pneumonia}}
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| {{CMG}}
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| ==Overview==
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| '''Ventilator-associated pneumonia''' ('''VAP''') is a sub-type of [[hospital-acquired pneumonia]] (HAP) which occurs in people who are on [[mechanical ventilation]] through an [[endotracheal tube|endotracheal]] or [[tracheostomy]] tube for at least 48 hours. VAP is a medical condition that results from [[infection]] which floods the small, [[alveoli|air-filled sacs]] ([[alveoli]]) in the [[lung]] responsible for absorbing [[oxygen]] from the [[Earth's atmosphere|atmosphere]]. VAP is distinguished from other kinds of infectious pneumonia because of the different types of [[microorganisms]] responsible, [[antibiotic]]s used to treat, methods of [[diagnosis]], ultimate [[prognosis]], and effective [[Preventive medicine|preventive]] measures. In the community pneumonia is most often caused by ''[[Streptococcus pneumoniae|S. pneumoniae]]'', ''[[Haemophilus influenzae|H. influenzae]]'', or ''[[Staphylococcus aureus|S. aureus]]''. However, in the hospital the organism associated with pneumonia is most often ''[[Pseudomonas]]'', regardless of whether or not the patient is ventilated. In order for a patient to have VAP they have to be on a ventilator…so it’s not the organism that distinguishes VAP, it's the fact that the patient is on a ventilator.
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| == Symptoms and Signs ==
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| People who are on mechanical ventilation are often sedated and are rarely able to communicate. As such, many of the typical symptoms of pneumonia will either be absent or unable to be obtained. The most important symptoms are [[fever]], [[hypothermia|low body temperature]], new [[purulent]] [[sputum]], and [[hypoxia (medical)|hypoxia]] (decreasing amounts of oxygen in the blood).
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| == Diagnosis ==
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| VAP should be suspected in any person with symptoms of VAP, increasing numbers of [[white blood cell]]s on blood testing, and new shadows (infiltrates) on a chest x-ray. [[Blood culture]]s may reveal the microorganism causing VAP.
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| Two strategies exist for diagnosing VAP. One strategy collects cultures from the [[Vertebrate trachea|trachea]] of people with symptoms of VAP plus a new or enlarging infiltrate on chest x-ray. The other is more invasive and advocates a [[bronchoscopy]] plus [[bronchoalveolar lavage]] (BAL) for people with symptoms of VAP plus a new or enlarging infiltrate on chest x-ray. In both cases, VAP is not diagnosed when cultures are negative and another source of the symptoms is sought.
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| == Pathophysiology ==
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| VAP primarily occurs because the endotracheal or tracheostomy tube allows free passage of bacteria into the lower segments of the lung in a person who often has underlying lung or immune problems. Bacteria travel in small [[droplet]]s both through the endotracheal tube and around the cuff. Often, bacteria colonize the endotracheal or tracheostomy tube and are [[Embolism|embolized]] into the lungs with each breath. Bacteria may also be brought down into the lungs with procedures such as deep suctioning or [[bronchoscopy]].
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| Whether bacteria also travel from the [[sinuses]] or the stomach into the lungs is, as of [[2005]], controversial. However, spread to the lungs from the [[blood stream]] or the [[gut]] is uncommon.
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| Once inside the lungs, bacteria then take advantage of any deficiencies in the [[immune system]] (such as due to malnutrition or chemotherapy) and multiply. A combination of bacterial damage and consequences of the immune response lead to disruption of [[gas exchange]] with resulting symptoms.
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| == Microbiology ==
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| The microbiologic [[Flora (microbiology)|flora]] responsible for VAP is different from that of the more common [[community-acquired pneumonia]] (CAP). In particular, viruses and fungi are uncommon causes in people who do not have underlying [[immunocompromise|immune deficiencies]]. Though any microorganism that causes CAP can cause VAP, there are several bacteria which are particularly important causes of VAP because of their resistance to commonly used antibiotics. These bacteria are referred to as [[multidrug resistance|multidrug resistant]] (MDR).
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| :*''[[Pseudomonas aeruginosa]]'' is the most common MDR [[Gram-negative]] bacterium causing VAP. ''Pseudomonas'' has natural resistance to many antibiotics and has been known to acquire resistance to every antibiotic except for [[polymixin B]]. Resistance is typically acquired through upregulation or mutation of a variety of efflux pumps which pump antbiotics out of the cell. Resistance may also occur through loss of an outer membrane porin channel ([[OprD]])
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| :*''[[Klebsiella pneumoniae]]'' has natural resistance to some [[Beta-lactam antibiotic|beta-lactam antibiotic]]s such as [[ampicillin]]. Resistance to [[cephalosporins]] and [[aztreonam]] may arise through [[Enzyme induction and inhibition|induction]] of a [[plasmid]]-based extended spectrum [[beta-lactamase]] (ESBL) or plasmid-based [[ampC]]-type [[enzyme]]
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| :*''[[Serratia marcescens]]'' has an ampC [[gene]] which can be induced by exposure to antibiotics such as cephalosporins. Thus, culture sensitivities may initially indicate appropriate treatment which fails due to bacterial response.
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| :*''[[Enterobacter]]'' as a group also have an inducible ampC gene. Enterobacter may also develop resistance by acquiring plasmids.
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| :*''[[Citrobacter]]'' also has an inducible ampC gene.
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| :*''[[Stenotrophomonas maltophilia]]'' often colonizes people who have [[endotracheal tube]]s or [[tracheostomy|tracheostomies]] but can also cause pneumonia. It is often resistant to a wide array of antibiotics but is usually sensitive to [[co-trimoxazole]]
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| :*''[[Acinetobacter]]'' are becoming more common and may be resistant to [[carbapenem]]s such as [[imipenem]] and [[meropenem]]
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| :*''[[Burkholderia cepacia]]'' is an important organism in people with cystic fibrosis and is often resistant to multiple antibiotics
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| :*''[[Methicillin-resistant Staphylococcus aureus]]'' is an increasing cause of VAP. As many as fifty percent of ''Staphylococcus aureus'' isolates in the intensive care setting are resistant to methicillin. Resistance is conferred by the [[mecA]] gene.
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| == Treatment ==
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| Treatment of VAP should be matched to known causative bacteria. However, when VAP is first suspected, the bacteria causing infection is typically not known and broad-spectrum antibiotics are given ([[Empiric therapy|empiric therapy]]) until the particular bacterium and its sensitivities are determined. Empiric antibiotics should take into account both the risk factors a particular individual has for resistant bacteria as well as the local prevalence of resistant microorganisms. If a person has previously had episodes of pneumonia, information may be available about prior causative bacteria. The choice of initial therapy is therefore entirely dependent on knowledge of local flora and will vary from hospital to hospital.
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| Risk factors for infection with an MDR strain include ventilation for more than five days, recent hospitalization (last 90 days), residence in a [[nursing home]], treatment in a [[hemodialysis]] clinic, and prior antibiotic use (last 90 days).
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| Possible empirical therapy combinations include (but are not limited to):
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| * [[vancomycin]]/[[linezolid]] and [[ciprofloxacin]],
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| * [[cefepime]] and [[gentamicin]]/[[amikacin]]/[[tobramycin]]
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| * [[vancomycin]]/[[linezolid]] and [[ceftazidime]]
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| * [[Ureidopenicillin]] plus β-lactamase inhibitor such as [[piperacillin/tazobactam|piperacillin/tazobactam]] or [[ticarcillin/clavulanate]]
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| * a carbapenem (e.g., [[imipenem]] or [[meropenem]])
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| Therapy is typically changed once the causative bacteria are known and continued until symptoms resolve (often 7 to 14 days).
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| People who do not have risk factors for MDR organisms may be treated differently depending on local knowledge of prevalent bacteria. Appropriate antibiotics may include [[ceftriaxone]], [[ciprofloxacin]], [[levofloxacin]], or [[ampicillin/sulbactam]].
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| As of [[2005]], there is ongoing research into inhaled antibiotics as an adjunct to conventional therapy. [[Tobramycin]] and [[polymyxin B]] are commonly used in certain centres but there is no clinical evidence to support their use.
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| == Prevention ==
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| Prevention of VAP involves limiting exposure to resistant bacteria, discontinuing mechanical ventilation as soon as possible, and a variety of strategies to limit infection while intubated. Resistant bacteria are spread in much the same ways as any communicable disease. Proper [[hand washing]], [[sterile technique]] for invasive procedures, and isolation of individuals with known resistant organisms are all mandatory for effective infection control. A variety of aggressive weaning protocols to limit the amount of time a person spends intubation have been proposed. One important aspect is limiting the amount of sedation that a ventilated person receives.
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| Other recommendations for preventing VAP include raising the head of the bed to at least 45 degrees and placement of [[Feeding tube|feedings tubes]] beyond the [[Pyloric valve|pylorus]] of the [[stomach]]. Antiseptic mouth washes such as [[chlorhexidine]] may also reduce the incidence of VAP. One study also suggests that using heat and moisture exchangers instead of heated humidifiers, may also reduce the incidence of VAP.<ref>{{cite journal | author=Lorente L, Lecuona M, Jimenez A, Mora ML, Sierra A. | title=Ventilator-associated pneumonia using a heated humidifier or a heat and moisture exchanger: a randomized controlled trial | journal=Crit Care | year=2006 | volume=10 | pages=4 }}</ref>
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| == Epidemiology and prognosis ==
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| VAP occurs in up to 25% of all people who require mechanical ventilation. VAP can develop at any time during ventilation, but occurs more often in the first few days after intubation. This is because the intubation process itself contributes to the development of VAP. VAP occurring early after intubation typically involves fewer resistant organisms and is thus associated with a more favorable outcome. Because respiratory failure requiring mechanical ventilation is itself associated with a high mortality, determination of the exact contribution of VAP to mortality has been difficult. As of [[2006]], estimates range from 33% to 50% death in patients who develop VAP. Mortality is more likely when VAP is associated with certain microorganisms (''Pseudomonas'', ''Acinetobacter''), [[Bacteremia|blood stream infections]], and ineffective initial antibiotics. VAP is especially common in people who have [[acute respiratory distress syndrome]] (ARDS).
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| == See also ==
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| * [[Pneumonia]]
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| * [[Nosocomial infection]]
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| == References ==
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| * {{cite journal | author=American Thoracic Society and the Infectious Diseases Society of America. | title=ATS/IDSA Guidelines: Guidelines for the management of adults with HAP, VAP, and HCAP | journal=Am J Respir Crit Care Med | year=2005 | volume=171 | pages=388 }}
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| [[Category:Pneumonia]]
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| [[Category:Pulmonology]]
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