ASPIRATION PNEUMONIAASPIRATION PNEUMONIA&&

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 ・ 671

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.

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

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

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

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.

ASPIRATION PNEUMONITISASPIRATION PNEUMONITISSIGNS & 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

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.

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.

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.

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

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

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

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

MANAGEMENTMANAGEMENTAspiration 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 contents2) Aspiration pneumonitis that fails to resolve within 48 hours

MANAGEMENTMANAGEMENTAspiration 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

MANAGEMENTMANAGEMENTAspiration 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