AUTHOR AND EDITOR INFORMATION

Section 1 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Multimedia
• References

INTRODUCTION

Section 2 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Multimedia
• References

Background

Aspiration is defined as the inhalation of either oropharyngeal or gastric contents into the lower airways. Inhalation of these contents can lead to aspiration pneumonia and aspiration pneumonitis. Although these two entities are managed differently, they are often interchangeably referred to as aspiration pneumonia.

Aspiration pneumonitis represents chemical damage to the tracheobronchial tree caused by acute, often witnessed, inhalation of regurgitated gastric contents in patients with an acute change in mental status. Aspiration pneumonia results from chronic, usually unwitnessed, inhalation of small amounts of oropharyngeal contents leading to an infectious process.

For more information, see Medscape’s Pneumonia Resource Center.

Pathophysiology

Aspiration pneumonitis represents an acute, chemical lung injury resulting from the inhalation of gastric contents. This disease occurs in people with altered levels of consciousness resulting from seizures, cerebrovascular accident (CVA), CNS mass lesions, drug intoxication or overdose, and head trauma.

The risk of aspiration is indirectly related to the level of consciousness of the patient (ie, decreasing Glasgow Coma Scale [GCS] score is related with increased risk of aspiration).¹ The extent and severity of this disease is directly related to the volume and acidity of the fluid aspirated. Aspiration of a massive amount of gastric contents, also know as Mendelson syndrome, can produce acute respiratory distress within 1 hour. The acidity of gastric contents results in chemical burns to the tracheobronchial tree involved in the aspiration.

Because of the relative sterility of normal gastric contents, bacteria do not play an important role in the early stages of the disease. This does not hold true in patients with gastroparesis or small-bowel obstruction or in those using antacids (proton pump inhibitor [PPI], H2-receptor antagonists). Regardless of the bacterial load of the inoculum, bacterial superinfection may occur after the initial chemical injury.

Aspiration pneumonia is defined as the development of an infiltrate in a patient at increased risk of oropharyngeal aspiration. It occurs when a patient inhales material from the oropharynx that is colonized by upper airway flora.

Initial bacteriologic studies into the causative organisms revealed the anaerobic species to be the predominant pathogens in community-acquired aspiration pneumonia. However, subsequent studies revealed that Streptococcus pneumoniae, Staphylococcus aureus, Haemophilus influenzae, and Enterobacteriaceae are the most common organisms. Hospital-acquired aspiration pneumonia, on the other hand, is often caused by gram-negative organisms including Pseudomonas aeruginosa, particularly in intubated patients. These studies demonstrated a limited role of anaerobic pathogens in both the community and nosocomial variants of the disease.

This syndrome most commonly occurs in individuals with chronically impaired airway defense mechanisms. This includes gag reflex, coughing, ciliary movement, and immune mechanisms, all of which aid in removing infectious material from the lower airways. Other risk factors include poor dentition and poor oral care, which both increase the bacterial burden of oropharyngeal secretions. Clinicians must thus surmise this diagnosis when a patient presents with risk factors and radiographic evidence of an infiltrate suggestive of aspiration pneumonia. The location of the infiltrate on chest radiograph depends on the position of the patient when the aspiration occurred.

Frequency

United States

Few studies have been designed that distinguish between aspiration pneumonia and aspiration pneumonitis. Several studies suggest that 5-15% of the 4.5 million cases of community-acquired pneumonia result from aspiration pneumonia.

Approximately 10% of patients who are hospitalized after drug overdoses will have an aspiration pneumonitis.

International

Aspiration pneumonia is considered a common disease, but no statistics are available.

Mortality/Morbidity

• The mortality associated with aspiration pneumonia mimics that of community-acquired pneumonia: approximately 1% in the outpatient setting and up to 25% in those requiring hospitalization. This mortality range depends on complications of the disease.
• The mortality rate for severe chemical pneumonitis (Mendelson syndrome) can be up to 70%.
• Without treatment, aspiration pneumonia is associated with a high incidence of cavitation and abscess formation in comparison to community-acquired pneumonia. Other complications of both aspiration pneumonia and pneumonitis include empyema, acute respiratory distress syndrome, and respiratory failure. Aspiration pneumonitis can rapidly progress to respiratory failure.

Sex

Aspiration pneumonia is more common in males than in females.

Age

Aspiration pneumonia is more common in extremely young or old patients.

CLINICAL

Section 3 of 10  

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History

The clinical presentation of both aspiration pneumonitis and pneumonia ranges from mildly ill and ambulating to critically ill with signs and symptoms of septic shock and/or respiratory failure.

Patient history in aspiration pneumonia is similar to that of community-acquired pneumonia and may include the following:

• Cough
• Fever or chills
• Malaise, myalgias
• Shortness of breath, dyspnea on exertion
• Pleuritic chest pain
• Putrid expectoration
• Nonspecific symptoms including headache, nausea/vomiting, anorexia, weight loss
• Host factors - Chronic conditions resulting in decreased ability to protect one's airway
• • Previous CVA
  • History of esophageal diseases including achalasia, esophageal web
  • Nursing home patients
  • Patients chronically fed by feeding tube (NG tube or gastric tube)
• Patients brought in after witnessed large-volume vomitus and subsequent aspiration pneumonitis will have a history consistent with an acute change in mental status. This history may include the following:
• • Seizure
  • Alcohol abuse
  • Drug overdose
  • Head trauma

Physical

Physical examination findings vary depending on severity of the disease, presence of complications, and host factors. Patients with aspiration pneumonitis secondary to seizure, head trauma, or drug overdose should be inspected for signs related to these processes. Both aspiration pneumonia and pneumonitis can present with the following:

• Fever or hypothermia
• Tachypnea
• Tachycardia
• Decreased breath sounds
• Dullness to percussion over areas of consolidation
• Rales
• Egophony and pectoriloquy
• Decreased breath sounds
• Pleural friction rub
• Altered mental status
• Hypoxemia
• Hypotension (in septic shock)
• In addition, patients may exhibit signs associated with the underlying disease that lead to their aspiration.

Causes

Any condition that reduces a patient's gag reflex, ability to maintain an airway, or both increases the risk of aspiration pneumonia or pneumonitis.

• CVA
• Intracranial mass lesion
• Head trauma
• Alcohol abuse
• Drug overdose
• Isolated alteration of the swallowing reflex associated with pharyngeal disease

DIFFERENTIALS

Section 4 of 10  

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• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Multimedia
• References

Other Problems to be Considered

Hypersensitivity pneumonitis

WORKUP

Section 5 of 10  

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• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Multimedia
• References

Lab Studies

The lab studies obtained should be guided by the clinical presentation. Patients with signs or symptoms of sepsis or septic shock require further lab testing than those with uncomplicated aspiration syndromes. The following lab tests are useful in both aspiration pneumonia and pneumonitis.

• Complete blood count with differential
• • Determine white count as marker of possible infection.
  • Determine band count; a left shift further supports the diagnosis of bacterial pneumonia.
  • Determine baseline hemoglobin/hematocrit and platelets for further management.
• Basic metabolic panel
• • Serum electrolytes, BUN, and creatinine levels can be used to assess fluid status and the need for intravenous hydration. This is especially important in patients who present with fever, vomiting, or diarrhea who may have significant fluid loss.
  • Serum BUN and creatinine levels can also be used to assess renal function in order to appropriately dose antibiotics. In addition, these values can be used to assess end-organ damage in patients who present with sepsis or septic shock.
• Arterial blood gas analysis
• • Arterial blood gas analysis is used to assess oxygenation and adds information to guiding oxygen supplementation.
  • Assess the patient's pH status.
  • Lactate level (often included with blood gases) can be used as an early marker of severe sepsis or septic shock.
• Mixed venous gas measurement
• • This should be obtained in any patient in whom septic shock is suspected.
  • Decreased mixed venous oxygen saturation is a marker for septic shock.
• Blood cultures
• • Baseline screening for bacteremia
  • In uncomplicated pneumonia (no signs of sepsis or septic shock), blood cultures have a low yield and are not necessary for initial management and treatment.
• Sputum culture and Gram stain - These are generally not helpful in initial diagnosis or treatment.

Imaging Studies

• Chest radiograph - Posteroanterior (PA) and lateral
• • Location of infiltrate
  • • The right middle and lower lung lobes are the most common sites of infiltrate formation due to the larger caliber and more vertical orientation of the right mainstem bronchus.
    • Patients who aspirate while standing can have bilateral lower lung lobe infiltrates.
    • Patients lying in the left lateral decubitus position are more likely to have left-sided infiltrates.
    • The right upper lobe is a common area of consolidation in alcoholics who aspirate in the prone position.
  • Presence of pleural effusion may indicate the need to perform thoracentesis to rule out empyema.
• Chest CT scan
• • This is not usually necessary on an emergent basis.
  • In the presence of pleural effusion or empyema, CT may aid in further characterization of the infiltrate.

Procedures

• Bronchoscopy with protected brush or protected bronchial sample
• • Bronchoscopy may be helpful in nosocomial aspiration pneumonia for guiding antibiotic therapy.
  • This is not useful in the treatment of community-acquired aspiration pneumonia.
• Thoracentesis
• Chest tube placement (for drainage of large empyema)

TREATMENT

Section 6 of 10  

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• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Multimedia
• References

Prehospital Care

Prehospital care should focus on stabilizing the patient's airway, breathing, and circulation.

• In patients found with signs of gastric aspiration (ie, vomitus) suctioning of the upper airway may remove a significant amount of aspirate or potential aspirate.
• Intubation should be considered in any patient who is unable to protect his or her airway. The ability of paramedics to provide this intervention depends on the level of training. In addition, EMTs trained in intubation may choose to intubate patients with poor gag reflex prior to aspiration.
• Oxygen supplementation
• Cardiac monitoring and pulse oximetry
• Intravenous catheter placement and intravenous fluids as indicated

Emergency Department Care

Emergency department care should start with stabilizing the patient's airway, breathing, and circulation.

• Oropharyngeal/tracheal suctioning may be indicated to further remove aspirate.
• Reassess the need for intubation on a frequent basis depending on oxygenation, patient's mental status, signs of increased work of breathing, or impending respiratory failure.
• Continue supplemental oxygenation as needed.
• Continue cardiac monitoring and pulse oximetry.
• Provide continued supportive care with intravenous fluids and electrolyte replacement.
• Antibiotic therapy
• • Aspiration pneumonia: Antibiotics are always indicated.
  • Aspiration pneumonitis
  • • Prophylactic antibiotics are not recommended in most cases.
    • In addition, those patients with recent aspiration, fever, and leukocytosis should not be treated even in the presence of a pulmonary infiltrate due to the risk of development of resistant organisms.
    • When to use antibiotics: (1) Pneumonitis fails to resolve within 48 hours. (2) Patients with small-bowel obstruction–lower; bacteria may colonize gastric contents. (3) Antibiotics should be considered for patients on antacids due to the potential for gastric colonization.
• Antibiotic choice
• • Patients without a toxic appearance
  • • Cover typical community-acquired pathogens.
    • Ceftriaxone plus azithromycin, levofloxacin, or moxifloxacin are appropriate options.
  • Patients with a toxic appearance or who were recently hospitalized  
  • • Although community-acquired pathogens are still the most common, gram-negative bacteria including Pseudomonas aeruginosa and Klebsiella pneumoniae as well as methicillin-resistant Staphylococcus aureus must be covered as well.
    • Piperacillin/tazobactam or imipenem/cilastatin plus vancomycin would be appropriate.
    • Add clindamycin for purulent sputum.
• Corticosteroids
• • Historically corticosteroids have been used in the treatment of aspiration pneumonitis, but randomized control studies have been unable to demonstrate a benefit to using high-dose corticosteroids.
  • Patients with septic shock that requires vasoactive substances to maintain blood pressure should receive stress-dose steroids.

Consultations

• Pulmonary/critical care specialist in severe cases of respiratory failure requiring ventilatory support
• Infectious disease specialist for advice about proper antibiotic therapy

MEDICATION

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• References

The antibiotics of choice should be tailored to the setting in which the aspiration occurred (community vs nosocomial); however, antibiotic agents with activity against gram-negative organisms as well as gram-positive organisms is usually required.

Microbiological evidence indicates that empiric coverage of anaerobes is not indicated unless the patient presents with putrid sputum, severe oropharyngeal disease, or evidence of lung abscess or necrotizing pneumonia on chest radiograph or CT scan.

Drug Category: Antibiotics

Empiric antimicrobial therapy must be comprehensive and should cover all likely pathogens in the context of the clinical setting.

FOLLOW-UP

Section 8 of 10  

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• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Multimedia
• References

Further Inpatient Care

• Admit patients with severe hemodynamic compromise and/or persistent respiratory distress to the ICU.
• Admit the patient to a general-care floor if the patient's respiratory status is stabilized.

Transfer

• Intubated and ventilated patients must be transferred to a hospital with an ICU.
• Patients with signs or symptoms indicating severe sepsis or septic shock should be transferred to a hospital with an ICU.

Deterrence/Prevention

• Keep the head of the bed at a 30° angle. The semirecumbent body position reduces the risk or aspiration leading to pneumonia.
• Patients with dysphagia and/or a poor gag reflex should not be fed orally; feeding through a nasogastric or gastric tube may be required.

Complications

• Acute respiratory failure
• Acute respiratory distress syndrome
• Empyema
• Pulmonary abscess
• Superinfection

Prognosis

• The mortality associated with aspiration pneumonia mimics that of community-acquired pneumonia: approximately 1% in the outpatient setting and up to 25% in those requiring hospitalization.
• The mortality rate of massive aspiration pneumonitis (Mendelson syndrome) approaches 70%.
• The mortality rate for aspiration pneumonitis complicated by empyema is approximately 20%.
• The mortality for uncomplicated pneumonitis is approximately 5%.

Patient Education

• For excellent patient education resources, visit eMedicine's Pneumonia Center. Also, see eMedicine's patient education article Chemical Pneumonia.

MULTIMEDIA

Section 9 of 10  

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• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Multimedia
• References

Media file 1:  Chest radiograph of a patient with aspiration pneumonia of the left lung after a benzodiazepine overdose. The patient was probably positioned to the left at the moment of aspiration.
	View Full Size Image
Media type:  Radiograph

Media file 2:  Chest radiograph of a patient with massive aspiration pneumonia of the right lung.
	View Full Size Image
Media type:  Radiograph

REFERENCES

Section 10 of 10

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
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• References

1. Adnet F, Baud F. Relation between Glasgow Coma Scale and aspiration pneumonia. Lancet. Jul 13 1996;348(9020):123-4. [Medline].
2. Akritidis N, Gousis C, Dimos G. Fever, cough, and bilateral lung infiltrates. Achalasia associated with aspiration pneumonia. Chest. Feb 2003;123(2):608-12. [Medline].
3. Drakulovic MB, Torres A, Bauer TT, et al. Supine body position as a risk factor for nosocomial pneumonia in mechanically ventilated patients: a randomised trial. Lancet. Nov 27 1999;354(9193):1851-8. [Medline].
4. Lumpkin JR, Westfall MD. Aspiration pneumonia. In: Emergency Medicine: Concepts and Clinical Practice. 1992:1112-20.
5. Marik PE. Aspiration pneumonitis and aspiration pneumonia. N Engl J Med. Mar 1 2001;344(9):665-71. [Medline].
6. Marik PE, Careau P. The role of anaerobes in patients with ventilator-associated pneumonia and aspiration pneumonia: a prospective study. Chest. Jan 1999;115(1):178-83. [Medline].
7. Marom EM, McAdams HP, Erasmus JJ. The many faces of pulmonary aspiration. AJR Am J Roentgenol. Jan 1999;172(1):121-8. [Medline].
8. Mier L, Dreyfuss D, Darchy B. Is penicillin G an adequate initial treatment for aspiration pneumonia? A prospective evaluation using a protected specimen brush and quantitative cultures. Intensive Care Med. 1993;19(5):279-84. [Medline].
9. Moll J, Kerns W 2nd, Tomaszewski C. Incidence of aspiration pneumonia in intubated patients receiving activated charcoal. J Emerg Med. Mar-Apr 1999;17(2):279-83. [Medline].
10. Pennza PT. Aspiration pneumonia, necrotizing pneumonia, and lung abscess. Emerg Med Clin North Am. May 1989;7(2):279-307. [Medline].
11. Preston AJ, Gosney MA, Noon S. Oral flora of elderly patients following acute medical admission. Gerontology. Jan-Feb 1999;45(1):49-52. [Medline].
12. Sasaki H, Sekizawa K, Yanai M. New strategies for aspiration pneumonia. Intern Med. Dec 1997;36(12):851-5. [Medline].
13. Vadeboncoeur TF, Davis DP, Ochs M. The ability of paramedics to predict aspiration in patients undergoing prehospital rapid sequence intubation. J Emerg Med. Feb 2006;30(2):131-6. [Medline].

Article Last Updated: Mar 26, 2008