Ventilator-associated pneumonia
Encyclopedia
Ventilator-associated pneumonia (VAP) is a sub-type of hospital-acquired pneumonia
(HAP) which occurs in people who are receiving mechanical ventilation
. VAP is not characterized by the causative agents; rather, as its name implies, definition of VAP is restricted to patients undergoing mechanical ventilation while in a hospital. A positive culture after intubation is indicative of ventilator-associated pneumonia and is diagnosed as such. In order to appropriately categorize the causative agent or mechanism it is usually recommended to obtain a culture prior to initiating mechanical ventilation as a reference.
, low body temperature
, new purulent sputum
, and hypoxemia
(decreasing amounts of oxygen in the blood).
s on blood testing, and new shadows (infiltrates) on a chest x-ray as is indicative of a pneumonia. Blood culture
s may reveal the microorganisms causing VAP.
Two strategies exist for diagnosing VAP. One strategy collects cultures from the 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.
into the lungs with each breath. Bacteria may also be brought down into the lungs with procedures such as deep suctioning or bronchoscopy
.
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.
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.
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 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 resistant
(MDR).
) 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.
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).
Possible empirical therapy combinations include (but are not limited to):
Therapy is typically changed once the causative bacteria are known and continued until symptoms resolve (often 7 to 14 days). For patients with VAP not caused by nonfermenting Gram-negative bacilli (like Acinetobacter, Pseudomonas aeruginosa) the available evidence seems to support the use of short-course antimicrobial treatments (< or =10 days).
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
.
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.
. 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 intubated have been proposed. One important aspect is limiting the amount of sedation that a ventilated person receives.
Other recommendations for preventing VAP include raising the head of the bed to at least 30 degrees and placement of feedings tubes
beyond the pylorus of the stomach
. Antiseptic mouth washes such as chlorhexidine may also reduce the incidence of VAP. One recent study suggests that using heat and moisture exchangers instead of heated humidifiers, may increase the incidence of VAP.
American and Canadian guidelines strongly recommend the use of supraglottic secretion drainage (SSD) Special tracheal tubes with an incorporated suction lumen as the EVAC tracheal tube form Covidien / Mallinckrodt can be used for that reason. New cuff technology based on polyurethane material in combination with subglottic drainage (SealGuard Evac tracheal tube from Covidien/Mallinckrodt)showed significant delay in early and late onset of VAP.
A recent clinical trial indicates that the use of silver
-coated endotracheal tubes may also reduce the incidence of VAP.
, and ineffective initial antibiotics. VAP is especially common in people who have acute respiratory distress syndrome
(ARDS).
Hospital-acquired pneumonia
Hospital-acquired pneumonia or nosocomial pneumonia refers to any pneumonia contracted by a patient in a hospital at least 48–72 hours after being admitted. It is usually caused by a bacterial infection, rather than a virus....
(HAP) which occurs in people who are receiving mechanical ventilation
Mechanical ventilation
In medicine, mechanical ventilation is a method to mechanically assist or replace spontaneous breathing. This may involve a machine called a ventilator or the breathing may be assisted by a physician, respiratory therapist or other suitable person compressing a bag or set of bellows...
. VAP is not characterized by the causative agents; rather, as its name implies, definition of VAP is restricted to patients undergoing mechanical ventilation while in a hospital. A positive culture after intubation is indicative of ventilator-associated pneumonia and is diagnosed as such. In order to appropriately categorize the causative agent or mechanism it is usually recommended to obtain a culture prior to initiating mechanical ventilation as a reference.
Signs and symptoms
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 signs are feverFever
Fever is a common medical sign characterized by an elevation of temperature above the normal range of due to an increase in the body temperature regulatory set-point. This increase in set-point triggers increased muscle tone and shivering.As a person's temperature increases, there is, in...
, low body temperature
Hypothermia
Hypothermia is a condition in which core temperature drops below the required temperature for normal metabolism and body functions which is defined as . Body temperature is usually maintained near a constant level of through biologic homeostasis or thermoregulation...
, new purulent sputum
Sputum
Sputum is mucus that is coughed up from the lower airways. It is usually used for microbiological investigations of respiratory infections....
, and hypoxemia
Hypoxemia
Hypoxemia is generally defined as decreased partial pressure of oxygen in blood, sometimes specifically as less than or causing hemoglobin oxygen saturation of less than 90%.-Distinction from anemia and hypoxia:...
(decreasing amounts of oxygen in the blood).
Diagnosis
A diagnosis of ventilator-associated pneumonia is made when the patient has a new diagnosis of pneumonia after having mechanical ventilation initiated. VAP should be suspected in any person on mechanical ventilation exhibiting increasing numbers of white blood cellWhite blood cell
White blood cells, or leukocytes , are cells of the immune system involved in defending the body against both infectious disease and foreign materials. Five different and diverse types of leukocytes exist, but they are all produced and derived from a multipotent cell in the bone marrow known as a...
s on blood testing, and new shadows (infiltrates) on a chest x-ray as is indicative of a pneumonia. Blood culture
Blood culture
Blood culture is a microbiological culture of blood. It is employed to detect infections that are spreading through the bloodstream...
s may reveal the microorganisms causing VAP.
Two strategies exist for diagnosing VAP. One strategy collects cultures from the trachea
Vertebrate trachea
In tetrapod anatomy the trachea, or windpipe, is a tube that connects the pharynx or larynx to the lungs, allowing the passage of air. It is lined with pseudostratified ciliated columnar epithelium cells with goblet cells that produce mucus...
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
Bronchoscopy
Bronchoscopy is a technique of visualizing the inside of the airways for diagnostic and therapeutic purposes. An instrument is inserted into the airways, usually through the nose or mouth, or occasionally through a tracheostomy. This allows the practitioner to examine the patient's airways for...
plus bronchoalveolar lavage
Bronchoalveolar lavage
Bronchoalveolar lavage is a medical procedure in which a bronchoscope is passed through the mouth or nose into the lungs and fluid is squirted into a small part of the lung and then recollected for examination. BAL is typically performed to diagnose lung disease...
(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.
Pathophysiology
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 droplets both through the endotracheal tube and around the cuff. Often, bacteria colonize the endotracheal or tracheostomy tube and are embolizedEmbolism
In medicine, an embolism is the event of lodging of an embolus into a narrow capillary vessel of an arterial bed which causes a blockage in a distant part of the body.Embolization is...
into the lungs with each breath. Bacteria may also be brought down into the lungs with procedures such as deep suctioning or bronchoscopy
Bronchoscopy
Bronchoscopy is a technique of visualizing the inside of the airways for diagnostic and therapeutic purposes. An instrument is inserted into the airways, usually through the nose or mouth, or occasionally through a tracheostomy. This allows the practitioner to examine the patient's airways for...
.
Whether bacteria also travel from the sinuses
Paranasal sinus
Paranasal sinuses are a group of four paired air-filled spaces that surround the nasal cavity , above and between the eyes , and behind the ethmoids...
or the stomach into the lungs is, as of 2005, controversial. However, spread to the lungs from the blood stream or the gut
Gut (zoology)
In zoology, the gut, also known as the alimentary canal or alimentary tract, is a tube by which bilaterian animals transfer food to the digestion organs. In large bilaterians the gut generally also has an exit, the anus, by which the animal disposes of solid wastes...
is uncommon.
Once inside the lungs, bacteria then take advantage of any deficiencies in the immune system
Immune system
An immune system is a system of biological structures and processes within an organism that protects against disease by identifying and killing pathogens and tumor cells. It detects a wide variety of agents, from viruses to parasitic worms, and needs to distinguish them from the organism's own...
(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
Gas exchange
Gas exchange is a process in biology where gases contained in an organism and atmosphere transfer or exchange. In human gas-exchange, gases contained in the blood of human bodies exchange with gases contained in the atmosphere. Human gas-exchange occurs in the lungs...
with resulting symptoms.
Microbiology
The microbiologic floraFlora (microbiology)
In microbiology, flora refers to the collective bacteria and other microorganisms in an ecosystem . While the term microflora is widely used, it is technically a misnomer since the word root flora pertains to the kingdom plantae...
responsible for VAP is different from that of the more common community-acquired pneumonia
Community-acquired pneumonia
Community-acquired pneumonia is a term used to describe one of several diseases in which individuals who have not recently been hospitalized develop an infection of the lungs . CAP is a common illness and can affect people of all ages. CAP often causes problems like difficulty in breathing, fever,...
(CAP). In particular, viruses and fungi are uncommon causes in people who do not have underlying 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 resistant
Multidrug resistance
Multiple drug resistance or Multidrug resistance is a condition enabling a disease-causing organism to resist distinct drugs or chemicals of a wide variety of structure and function targeted at eradicating the organism...
(MDR).
- Pseudomonas aeruginosaPseudomonas aeruginosaPseudomonas aeruginosa is a common bacterium that can cause disease in animals, including humans. It is found in soil, water, skin flora, and most man-made environments throughout the world. It thrives not only in normal atmospheres, but also in hypoxic atmospheres, and has, thus, colonized many...
is the most common MDR Gram-negativeGram-negativeGram-negative bacteria are bacteria that do not retain crystal violet dye in the Gram staining protocol. In a Gram stain test, a counterstain is added after the crystal violet, coloring all Gram-negative bacteria with a red or pink color...
bacterium causing VAP. Pseudomonas has natural resistance to many antibiotics and has been known to acquire resistance to every antibiotic except for polymyxin BPolymyxin BPolymyxin B is an antibiotic primarily used for resistant gram-negative infections. It is derived from the bacterium Bacillus polymyxa. Polymyxin B is a mixture of two closely related compounds, polymyxin B1 and polymyxin B2. It has a bactericidal action against almost all gram-negative bacilli...
. 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) - Klebsiella pneumoniaeKlebsiella pneumoniaeKlebsiella pneumoniae is a Gram-negative, non-motile, encapsulated, lactose fermenting, facultative anaerobic, rod shaped bacterium found in the normal flora of the mouth, skin, and intestines....
has natural resistance to some beta-lactam antibioticBeta-lactam antibioticβ-Lactam antibiotics are a broad class of antibiotics, consisting of all antibiotic agents that contains a β-lactam nucleus in its molecular structure. This includes penicillin derivatives , cephalosporins , monobactams, and carbapenems...
s such as ampicillinAmpicillinAmpicillin is a beta-lactam antibiotic that has been used extensively to treat bacterial infections since 1961. Until the introduction of ampicillin by the British company Beecham, penicillin therapies had only been effective against Gram-positive organisms such as staphylococci and streptococci...
. Resistance to cephalosporins and aztreonamAztreonamAztreonam is a synthetic monocyclic beta-lactam antibiotic , with the nucleus based on a simpler monobactam isolated from Chromobacterium violaceum. It was approved by the U.S. Food and Drug Administration in 1986...
may arise through inductionEnzyme induction and inhibitionEnzyme induction is a process in which a molecule induces the expression of an enzyme.Enzyme inhibition can refer to* the inhibition of the expression of the enzyme by another molecule...
of a plasmidPlasmidIn microbiology and genetics, a plasmid is a DNA molecule that is separate from, and can replicate independently of, the chromosomal DNA. They are double-stranded and, in many cases, circular...
-based extended spectrum beta-lactamaseBeta-lactamaseBeta-lactamases are enzymes produced by some bacteria and are responsible for their resistance to beta-lactam antibiotics like penicillins, cephamycins, and carbapenems . These antibiotics have a common element in their molecular structure: a four-atom ring known as a beta-lactam...
(ESBL) or plasmid-based ampC-type enzymeEnzymeEnzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates... - Serratia marcescensSerratia marcescensSerratia marcescens is a species of Gram-negative, rod-shaped bacterium in the family Enterobacteriaceae. A human pathogen, S. marcescens is involved in nosocomial infections, particularly catheter-associated bacteremia, urinary tract infections and wound infections, and is responsible for 1.4% of...
has an ampC geneGeneA gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...
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. - EnterobacterEnterobacterEnterobacter is a genus of common Gram-negative, facultatively-anaerobic, rod-shaped bacteria of the family Enterobacteriaceae. Several strains of the these bacteria are pathogenic and cause opportunistic infections in immunocompromised hosts and in those who are on mechanical ventilation...
as a group also have an inducible ampC gene. Enterobacter may also develop resistance by acquiring plasmids. - CitrobacterCitrobacterCitrobacter is a genus of Gram-negative coliform bacteria in the Enterobacteriaceae family.The species C. amalonaticus, C. koseri, and C. freundii use solely citrate as a carbon source...
also has an inducible ampC gene. - Stenotrophomonas maltophiliaStenotrophomonas maltophiliaStenotrophomonas maltophilia is an aerobic, nonfermentative, Gram-negative bacterium. It is an uncommon bacterium and human infection is difficult to treat. Initially classified as Pseudomonas maltophilia, S. maltophilia was also grouped in the genus Xanthomonas before eventually becoming the type...
often colonizes people who have tracheal tubes but can also cause pneumonia. It is often resistant to a wide array of antibiotics but is usually sensitive to co-trimoxazoleCo-trimoxazoleTrimethoprim/sulfamethoxazole or co-trimoxazole is a sulfonamide antibiotic combination of trimethoprim and sulfamethoxazole, in the ratio of 1 to 5, used in the treatment of a variety of bacterial infections.The name co-trimoxazole is the British Approved Name, and has been marketed worldwide... - AcinetobacterAcinetobacterAcinetobacter [asz−in−ée−toe–back−ter] is a genus of Gram-negative bacteria belonging to the Gammaproteobacteria. Acinetobacter species are non-motile and oxidase-negative, and occur in pairs under magnification....
are becoming more common and may be resistant to carbapenemCarbapenemCarbapenems are a class of β-lactam antibiotics with a broad spectrum of antibacterial activity. They have a structure that renders them highly resistant to most β-lactamases...
s such as imipenemImipenemImipenem is an intravenous β-lactam antibiotic developed in 1980. It has an extremely broad spectrum of activity.Imipenem belongs to the subgroup of carbapenems. It is derived from a compound called thienamycin, which is produced by the bacterium Streptomyces cattleya...
and meropenemMeropenemMeropenem is an ultra-broad spectrum injectable antibiotic used to treat a wide variety of infections, including meningitis and pneumonia. It is a beta-lactam and belongs to the subgroup of carbapenem, similar to imipenem and ertapenem. Meropenem was originally developed by Sumitomo Pharmaceuticals... - Burkholderia cepacia is an important organism in people with cystic fibrosis and is often resistant to multiple antibiotics
- Methicillin-resistant Staphylococcus aureusMethicillin-resistant Staphylococcus aureusMethicillin-resistant Staphylococcus aureus is a bacterium responsible for several difficult-to-treat infections in humans. It is also called multidrug-resistant Staphylococcus aureus and oxacillin-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 mecAMECAMeca or MECA may refer to:* Maine College of Art* Marriage Equality California* MECA CLUB, students' Mechanical Electrical Civil Architecture group of Ain Shams University Faculty of Engineering, Cairo, Egypt...
gene.
Treatment
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 therapyEmpiric therapy
Empiric therapy is a medical term referring to the initiation of treatment prior to determination of a firm diagnosis. It may be thought of as taking the initiative against an anticipated and likely cause of infectious disease. It is most often used when antibiotics are given to a person before the...
) 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.
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
Nursing home
A nursing home, convalescent home, skilled nursing unit , care home, rest home, or old people's home provides a type of care of residents: it is a place of residence for people who require constant nursing care and have significant deficiencies with activities of daily living...
, treatment in a hemodialysis
Hemodialysis
In medicine, hemodialysis is a method for removing waste products such as creatinine and urea, as well as free water from the blood when the kidneys are in renal failure. Hemodialysis is one of three renal replacement therapies .Hemodialysis can be an outpatient or inpatient therapy...
clinic, and prior antibiotic use (last 90 days).
Possible empirical therapy combinations include (but are not limited to):
- vancomycinVancomycinVancomycin INN is a glycopeptide antibiotic used in the prophylaxis and treatment of infections caused by Gram-positive bacteria. It has traditionally been reserved as a drug of "last resort", used only after treatment with other antibiotics had failed, although the emergence of...
/linezolidLinezolidLinezolid is a synthetic antibiotic used for the treatment of serious infections caused by Gram-positive bacteria that are resistant to several other antibiotics...
and ciprofloxacinCiprofloxacinCiprofloxacin is a synthetic chemotherapeutic antibiotic of the fluoroquinolone drug class.It is a second-generation fluoroquinolone antibacterial. It kills bacteria by interfering with the enzymes that cause DNA to rewind after being copied, which stops synthesis of DNA and of...
, - cefepimeCefepimeCefepime is a fourth-generation cephalosporin antibiotic developed in 1994. Cefepime has an extended spectrum of activity against Gram-positive and Gram-negative bacteria, with greater activity against both Gram-negative and Gram-positive organisms than third-generation agents...
and gentamicinGentamicinGentamicin is an aminoglycoside antibiotic, used to treat many types of bacterial infections, particularly those caused by Gram-negative organisms. However, gentamicin is not used for Neisseria gonorrhoeae, Neisseria meningitidis or Legionella pneumophila...
/amikacinAmikacinAmikacin is an aminoglycoside antibiotic used to treat different types of bacterial infections. Amikacin works by binding to the bacterial 30S ribosomal subunit, causing misreading of mRNA and leaving the bacterium unable to synthesize proteins vital to its growth.-Administration:Amikacin may be...
/tobramycin - vancomycinVancomycinVancomycin INN is a glycopeptide antibiotic used in the prophylaxis and treatment of infections caused by Gram-positive bacteria. It has traditionally been reserved as a drug of "last resort", used only after treatment with other antibiotics had failed, although the emergence of...
/linezolidLinezolidLinezolid is a synthetic antibiotic used for the treatment of serious infections caused by Gram-positive bacteria that are resistant to several other antibiotics...
and ceftazidimeCeftazidimeCeftazidime is a third-generation cephalosporin antibiotic. Like other third-generation cephalosporins, it has broad spectrum activity against Gram-positive and Gram-negative bacteria. Unlike most third-generation agents, it is active against Pseudomonas aeruginosa, however it has weaker activity... - UreidopenicillinUreidopenicillinThe ureidopenicillins are a group of penicillins which are active against Pseudomonas aeruginosa.There are three ureidopenicillins in clinical use:*Azlocillin*Piperacillin*Mezlocillin...
plus β-lactamase inhibitor such as piperacillin/tazobactamPiperacillin/tazobactamPiperacillin/tazobactam is a combination antibiotic containing the extended-spectrum penicillin antibiotic piperacillin and the β-lactamase inhibitor tazobactam. It is marketed as Kilbac by Morepen and Tazocin or, in the USA, as Zosyn by Wyeth Pharms Inc .-External links:*...
or ticarcillin/clavulanate - a carbapenem (e.g., imipenemImipenemImipenem is an intravenous β-lactam antibiotic developed in 1980. It has an extremely broad spectrum of activity.Imipenem belongs to the subgroup of carbapenems. It is derived from a compound called thienamycin, which is produced by the bacterium Streptomyces cattleya...
or meropenemMeropenemMeropenem is an ultra-broad spectrum injectable antibiotic used to treat a wide variety of infections, including meningitis and pneumonia. It is a beta-lactam and belongs to the subgroup of carbapenem, similar to imipenem and ertapenem. Meropenem was originally developed by Sumitomo Pharmaceuticals...
)
Therapy is typically changed once the causative bacteria are known and continued until symptoms resolve (often 7 to 14 days). For patients with VAP not caused by nonfermenting Gram-negative bacilli (like Acinetobacter, Pseudomonas aeruginosa) the available evidence seems to support the use of short-course antimicrobial treatments (< or =10 days).
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
Ceftriaxone
Ceftriaxone is a third-generation cephalosporin antibiotic. Like other third-generation cephalosporins, it has broad spectrum activity against Gram-positive and Gram-negative bacteria. In most cases, it is considered to be equivalent to cefotaxime in terms of safety and efficacy...
, ciprofloxacin
Ciprofloxacin
Ciprofloxacin is a synthetic chemotherapeutic antibiotic of the fluoroquinolone drug class.It is a second-generation fluoroquinolone antibacterial. It kills bacteria by interfering with the enzymes that cause DNA to rewind after being copied, which stops synthesis of DNA and of...
, levofloxacin
Levofloxacin
Levofloxacin is a synthetic chemotherapeutic antibiotic of the fluoroquinolone drug class and is used to treat severe or life-threatening bacterial infections or bacterial infections that have failed to respond to other antibiotic classes. It is sold under various brand names, such as Levaquin and...
, or ampicillin/sulbactam
Ampicillin/sulbactam
Ampicillin/sulbactam is a combination of the common penicillin-derived antibiotic ampicillin and sulbactam, an inhibitor of bacterial beta-lactamase. Two different forms of the drug exist. The first, developed in 1987 and marketed in the United States under the tradename Unasyn, is an intravenous...
.
As of 2005, there is ongoing research into inhaled antibiotics as an adjunct to conventional therapy. Tobramycin and polymyxin B
Polymyxin B
Polymyxin B is an antibiotic primarily used for resistant gram-negative infections. It is derived from the bacterium Bacillus polymyxa. Polymyxin B is a mixture of two closely related compounds, polymyxin B1 and polymyxin B2. It has a bactericidal action against almost all gram-negative bacilli...
are commonly used in certain centres but there is no clinical evidence to support their use.
Prevention
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 intubatedTracheal intubation
Tracheal intubation, usually simply referred to as intubation, is the placement of a flexible plastic or rubber tube into the trachea to maintain an open airway or to serve as a conduit through which to administer certain drugs...
. Resistant bacteria are spread in much the same ways as any communicable disease. Proper hand washing
Hand washing
Hand washing for hand hygiene is the act of cleaning the hands with or without the use of water or another liquid, or with the use of soap, for the purpose of removing soil, dirt, and/or microorganisms....
, 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 intubated have been proposed. One important aspect is limiting the amount of sedation that a ventilated person receives.
Other recommendations for preventing VAP include raising the head of the bed to at least 30 degrees and placement of feedings tubes
Feeding tube
A feeding tube is a medical device used to provide nutrition to patients who cannot obtain nutrition by swallowing. The state of being fed by a feeding tube is called gavage, enteral feeding or tube feeding...
beyond the pylorus of the stomach
Stomach
The stomach is a muscular, hollow, dilated part of the alimentary canal which functions as an important organ of the digestive tract in some animals, including vertebrates, echinoderms, insects , and molluscs. It is involved in the second phase of digestion, following mastication .The stomach is...
. Antiseptic mouth washes such as chlorhexidine may also reduce the incidence of VAP. One recent study suggests that using heat and moisture exchangers instead of heated humidifiers, may increase the incidence of VAP.
American and Canadian guidelines strongly recommend the use of supraglottic secretion drainage (SSD) Special tracheal tubes with an incorporated suction lumen as the EVAC tracheal tube form Covidien / Mallinckrodt can be used for that reason. New cuff technology based on polyurethane material in combination with subglottic drainage (SealGuard Evac tracheal tube from Covidien/Mallinckrodt)showed significant delay in early and late onset of VAP.
A recent clinical trial indicates that the use of silver
Silver
Silver is a metallic chemical element with the chemical symbol Ag and atomic number 47. A soft, white, lustrous transition metal, it has the highest electrical conductivity of any element and the highest thermal conductivity of any metal...
-coated endotracheal tubes may also reduce the incidence of VAP.
Epidemiology
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.Prognosis
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), blood stream infectionsBacteremia
Bacteremia is the presence of bacteria in the blood. The blood is normally a sterile environment, so the detection of bacteria in the blood is always abnormal....
, and ineffective initial antibiotics. VAP is especially common in people who have acute respiratory distress syndrome
Acute respiratory distress syndrome
Acute respiratory distress syndrome , also known as respiratory distress syndrome or adult respiratory distress syndrome is a serious reaction to various forms of injuries to the lung....
(ARDS).