1. ASPIRATION PNEUMONIAASPIRATION PNEUMONIA
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ASPIRATION PNEUMONITISASPIRATION PNEUMONITIS
Tahseen J. Siddiqui, M.D
ASPIRATION PNEUMONITIS AND ASPIRATION PNEUMONIA
PAUL E. MARIK, M.B., B.CH, N Engl J Med, Vol. 344, No. 9 ・ March 1, 2001 ・ www.nejm.org ・
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2. INTRODUCTIONINTRODUCTION
• Aspiration is defined as the inhalation of oropharyngeal or gastric contents into the larynx and lower
respiratory tract.
• Aspiration pneumonitis (Mendelson’s syndrome)
a chemical injury caused by the inhalation of sterile gastric contents,
• Aspiration pneumonia is an infectious process caused by the inhalation of oropharyngeal
secretionsthat are colonized by pathogenic bacteria.
• Both conditions can overlap in one patient
• Other aspiration syndromes include airway obstruction, lung abscess, exogenous lipoid
pneumonia, chronic interstitial fibrosis, and Mycobacterium fortuitum pneumonia.
• Four common problems are:
1) Failure to distinguish aspiration pneumonitis from aspiration pneumonia is usually due to:
2) Tendency to consider all pulmonary complications of aspiration to be infectious,
3) Failure to recognize the spectrum of pathogens in patients with infectious complications, and
4) Misconception that aspiration must be witnessed for it to be diagnosed.

3. EPIDEMIOLOGYEPIDEMIOLOGY
• Aspiration pneumonia is the most common cause of death
in patients with dysphagia due to neurologic disorders
• 5 to 15 percent of cases of community acquired pneumonia
(CAP) are aspiration pneumonia
• Incidence of aspiration pneumonia is 18 percent in nursing
home acquired pneumonia (HCA)
• Aspiration pneumonitis occurs in approximately 10
percent of patients who are hospitalized after a drug
overdose
• Occurs in approximately 1 of 3000 operations in which
general anesthesia is administered and accounting for 10 to
30 percent of all deaths associated with anesthesia

5. ASPIRATION PNEUMONITISASPIRATION PNEUMONITIS
(Mendelson’s syndrome)(Mendelson’s syndrome)
• Acute lung injury after the inhalation of regurgitated
gastric contents
• In 1946, Mendelson first showed that acidic gastric
contents introduced into the lungs of rabbits caused severe
pneumonitis and reported in patients who aspirated while
receiving general anesthesia during obstetrical procedures
• Occurs in patients who have a marked disturbance of
consciousness resulting e.g from intoxication or drug
overdose, seizures, massive stroke, or the use of anesthesia

6. ASPIRATION PNEUMONITISASPIRATION PNEUMONITIS
• Severity of lung injury increased significantly as the volume of the
aspirate increased ((20 to 25 ml in adults) and as its pH decreased
(<2.5)
• Aspiration of particulate food matter may cause severe pulmonary
damage, even if the pH of the aspirate is > 2.5
• Aspiration of gastric contents results in a chemical burn of the
tracheobronchial tree and pulmonary parenchyma, causing an intense
parenchymal inflammatory reaction
• Biphasic pattern of lung injury:
• 1) The first phase peaks at one to two hours after aspiration and results
from the direct, caustic effect of the aspirate on the cells lining the
alveolar-capillary interface.
• 2) The second phase, which peaks at four to six hours, is associated
with infiltration of neutrophils into the alveoli and lung interstitium

7. ASPIRATION PNEUMONITISASPIRATION PNEUMONITIS
• Bacterial infection does not have an important role in the
early stages of acute lung injury after the aspiration since
gastric acid prevents the growth of bacteria
• Infection may occur at a later stage
• Colonization of the gastric contents by pathogenic
organisms may occur when the pH in the stomach is
increased by the use of antacids, histamine H2 receptor
antagonists, or proton-pump inhibitors.
• Gastric colonization by gram-negative bacteria in patients
who receive enteral feedings, patients with gastroparesis or
small-bowel obstruction.

8. ASPIRATION PNEUMONITISASPIRATION PNEUMONITIS
SIGNS & SYMPTOMSSIGNS & SYMPTOMS
• Patients who have aspirated may present with dramatic
signs and symptoms
• Wheezing, coughing, shortness of breath, cyanosis,
pulmonary edema, hypotension, and hypoxemia, with
rapid progression to severe acute respiratory distress
syndrome and death
• Silent aspiration, manifests only as arterial desaturation
with radiologic evidence of aspiration
• Complications include lung abscesses, necrotizing
pneumonia, or empyema

10. ASPIRATION PNEUMONITISASPIRATION PNEUMONITIS
• Aspiration pneumonia develops after the inhalation of colonized
oropharyngeal (Haemophilus influenzae and Streptococcus) (or
gastric- GNB) material
• Approximately half of all healthy adults aspirate small amounts of
oropharyngeal secretions during sleep
• Low burden of virulent bacteria in normal pharyngeal secretions,
together with forceful coughing, active ciliary transport, and
normalhumoral and cellular immune mechanisms, results in clearance
of the infectious material
• Any condition that increases the volume or bacterial burden of
oropharyngeal secretions in a person with impaired defense
mechanisms may lead to aspiration pneumonia.

11. ASPIRATION PNEUMONITISASPIRATION PNEUMONITIS
• Risk of aspiration pneumonia is lower in patients without teeth and in
elderly patients in institutional settings who receive aggressive oral
care
• The diagnosis is made when a patient at risk for aspiration has
radiographic evidence of an infiltrate in a characteristic
bronchopulmonary segment
• In recumbent position, the most common sites of involvement are the
posterior segments of the upper lobes and the apical segments of the
lower lobes
• In upright or semirecumbent position, the basal segments of the lower
lobes are usually affected.
• Usual course is that of an acute pneumonic process
• Without treatment these patients have a higher incidence of cavitation
and abscess formation in the lungs.

12. Risk Factors for Oropharyngeal AspirationRisk Factors for Oropharyngeal Aspiration
• Elderly, neurologic dysphagia, disruption of the
gastroesophageal junction leads to gastroesophageal reflux
(GERD), or anatomical abnormalities of the upper
aerodigestive tract,
• Poor oral- dental hygiene, resulting in oropharyngeal
colonization by respiratory tract pathogens, including
Enterobacteriaceae, Pseudomonas aeruginosa, and
Staphylococcus aureus
• Silent aspiration is common in stroke, as the prevalence of
swallowing dysfunction ranges from 40 to 70 percent.

13. Risk Assessment of Oropharyngeal AspirationRisk Assessment of Oropharyngeal Aspiration
• Assessment of the cough and gag reflexes at bed side is unreliable
• A comprehensive swallowing evaluation,by speech & language
pathologist, supplemented by either a videofluoroscopic swallowing
study or a fiberoptic endoscopic evaluation, is required
• In patients with swallowing dysfunction, a
• soft diet should be introduced, and the patient should be taught
compensatory feeding strategies (e.g., reducing the bite size, keeping
the chin tucked and the head turned while eating, and swallowing
repeatedly)
• Tube feeding is usually recommended in patients who continue to
aspirate pureed food

14. Feeding Tubes and Aspiration PneumoniaFeeding Tubes and Aspiration Pneumonia
• Aspiration pneumonia is the most common cause of death
in patients fed by gastrostomy tube
• PEG (percutaneous endoscopic gastrostomy tube) is more
effective than nasogastric tube feeding in delivering
nutrition but is not superior to the use of a nasogastric tube
for preventing aspiration
• Incidence of aspiration pneumonia with post-pyloric tubes
(those placed in the small bowel-J-Tube) has been shown
to be similar to that with intragastric tubes
• Feeding tubes offer no protection from colonized oral
secretions

15. Aspiration in Critically Ill PatientsAspiration in Critically Ill Patients
• Factors increase the risk of aspiration in ICU patients,
including a supine position, gastroparesis, and NG tube
• 30 percent of patients who are kept in the supine position
are estimated to have gastroesophageal reflux
• A high gastric residual volume due to gastroparesis,
leading to gastric distention and regurgitation
• Risk is especially high after removal of an endotracheal
tube, because of the residual effects of sedative drugs, the
presence of a NG tube, and swallowing dysfunction, which
usually resolves within 48 hours post extubation
• Authors recommend the discontinuation of oral feeding for
at least 6 hours after extubation (in case re-intubation is
required), followed by institution of a pureed diet and then
soft food for at least 48 hours

16. BACTERIOLOGYBACTERIOLOGY
• In early 1970s, anaerobic organisms were considered the
predominant pathogens, alone or with aerobes
• Recent studies shown Strep. pneumoniae, Staph. aureus,
H. influenzae, and Enterobacteriaceae predominated in
patients with a community-acquired aspiration syndrome,
• In patients with hospital acquired aspiration syndrome
gram-negative organisms, including P. aeruginosa,
predominated.
• No anaerobic organisms

17. MANAGEMENTMANAGEMENT
Aspiration PneumonitisAspiration Pneumonitis
• The upper airway should be immediately suctioned after a witnessed
aspiration
• Endotracheal intubation for airway protection in patients with a
decreased level of consciousness e-g (seizure,stroke,coma,
intoxication/Overdose)
• Prophylactic antibiotics are not recommended
• Antibiotics shortly after aspiration in patients in whom a fever,
leukocytosis, or a pulmonary infiltrate develops is discouraged
• Empirical antibiotic therapy is appropriate in two conditions::
1) Patients who aspirate gastric contents and have small-bowel
obstruction or other conditions associated with colonization of the
gastric contents
2) Aspiration pneumonitis that fails to resolve within 48 hours

18. MANAGEMENTMANAGEMENT
Aspiration PneumonitisAspiration Pneumonitis
• Sampling of the lower respiratory tract (by bronchoalveolar lavage or
with a protected brush specimen) and quantitative culture in intubated
patients may allow targeted antibiotic therapy and, in patients with
negative cultures, the discontinuation of antibiotics
• Corticosteroids have been used for decades, however, there are limited
data on their role and are not routinely recommended
• In the patients given corticosteroids, Acute lung injury may improve
more quickly but they may have a longer stay in the ICU, no
significant differences in the incidence of complications or the
outcome,and pneumonia due to gram-negative bacteria is more
frequent after aspiration

19. MANAGEMENTMANAGEMENT
Aspiration PneumoniaAspiration Pneumonia
• Antibiotic therapy is unequivocally indicated
• The choice of antibiotics should depend on the setting in which the
aspiration occurs
• Broad spectrum antibiotics with activity against gram-negative
organisms, such as third-generation cephalosporins (Rocephin),
fluoroquinolones (Levaquin), and piperacillin-tazobactam (zosyn) are
usually required
• Penicillin and clindamycin, often called the standard antibiotic agents
aspiration pneumonia, are inadequate
• Antibiotic with specific anaerobic activity are not routinely warranted
except in patients with severe periodontal disease, putrid sputum, or
evidence of necrotizing pneumonia or lung abscess