para>Risk of aspiration pneumonia is highest among nursing home patients.
Risk of aspiration pneumonia is 6 times higher if ≥75 years of age compared to those <60 years of age.
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Prevalence
- Prevalence data is difficult to assess given variations in the definition of aspiration pneumonia (radiographic, clinical, or bacteriologic classifications have all been used).
- While small volume aspiration is common, even universal, aspiration pneumonia usually requires a degree of physiologic compromise.
- It is difficult to disprove aspiration as a contributing factor in the common pneumonias that develop in the elderly, neurologically damaged, or in those with temporarily reduced consciousness.
ETIOLOGY AND PATHOPHYSIOLOGY
- Aspiration pneumonia occurs when organisms dwelling in the oropharynx or stomach are introduced into the lungs in sufficient volume to cause clinical disease.
- Mechanical factors
- Mechanical ventilation: Endotracheal tube is a direct path to lower respiratory tract, which also prevents clearance of bacteria and secretions from exiting lower airways.
- Nasogastric feeding tubes prevent normal function of esophageal sphincters and increase risk of aspiration events. They are further associated with the appearance of gram-negative bacteria in pharyngeal secretions (1).
- Reduced gag reflex due to sedation, stroke, or normal aging reduces spontaneous coughing and clearance of bacteria.
- Hospitalization has been associated with a change in microflora of stomach and oropharynx with consequences for both the severity and bacteriology of aspiration pneumonia.
- Increased colonization of bacteria in conditions such as malnutrition, alcoholism, diabetes, and proton-pump inhibitor use increase likelihood of infection with each aspiration event (2).
- Gravity affects the distribution of aspiration events. If aspiration occurs while the patient is recumbent, infection is likely in the posterior segments of the upper lobes and the apical segments of the lower lobes. If aspiration occurs while upright or semirecumbent, the basal segments of the lower lobes are most likely to become infected.
- Aspiration pneumonia patients have longer hospital stays and higher in-hospital mortality than patients with pneumonia who did not aspirate (2).
- Both community-acquired pneumonia (CAP) and hospital-acquired pneumonia have a worse prognosis if aspiration (defined by both clinical and radiologic features) is likely to be the inciting event (3).
- If untreated, patients appear to have a higher incidence of cavitation and lung abscess formation than in those with nonaspiration pneumonia.
- Important contrast with chemical pneumonitis, which is due to aspiration of contents toxic to lung, independent of bacterial involvement (e.g., gastric acid), which presents with an abrupt onset of symptoms and prominent dyspnea. Chest x-ray (CXR) changes are seen within 2 hours.
- Pathogens vary according to setting:
- CAP: Gram positives and some gram negatives (e.g., Streptococcus pneumonia, Staphylococcus aureus, Haemophilus influenzae, and enterobacteria)
- Health care " ôassociated pneumonia (HCAP): mostly polymicrobial, including gram-negative bacilli such as Pseudomonas aeruginosa and anaerobes such as Bacteroides fragilis and less commonly, gram positives, including S. aureus
- Ventilator-associated pneumonia (VAP): common nosocomial bacteria, especially P. aeruginosa, Acinetobacter baumannii, methicillin-resistant Staphylococcus aureus (MRSA)
- Specific bacteria are rarely identified.
- Most cases associated with predisposing factors (see "Risk Factors " Ł)
RISK FACTORS
- Reduced consciousness, alcoholism, dementia, old age, poor nutritional status, poor oral hygiene
- Prior aspiration events
- Mechanical ventilation, bronchoscopy, upper endoscopy
- Pulmonary diseases: chronic obstructive pulmonary disease (COPD)
- Dysphagia: due to stroke, neuromuscular diseases, radiation to the neck or oropharynx
- GI diseases: gastroesophageal reflux disease, esophageal disease
- Enteral feeding tubes, nasogastric tube feeding
- Immunosuppressed patients: solid organ transplantation, steroid use >20 mg/day for >2 weeks, HIV
GENERAL PREVENTION
- Treatment can reduce aspiration events, but it is important to recognize that they are not completely preventable.
- Aspiration prevention protocols, including bedside speech and swallow evaluations, progressive oral intake, head of bed elevation, sedation vacations, and ventilator-weaning protocols significantly reduce risk of aspiration pneumonia in the critically ill population.
- A soft diet and nectar-thickened liquids are better than a pureed diet for preventing pneumonia.
- Feeding tubes, often inserted in the malnourished elderly with swallowing dysfunction and dementia, do not prolong lifespan; the American Geriatrics Society recommends against tube feeding in advanced dementia (4).
- A recent Cochrane review found no difference in aspiration pneumonia between nasogastric feeding and gastric tube feeding populations (5).
- Most cases are not preventable and are likely to be recurrent.
- A "goals of care " Ł discussion in a patient who has recurrent aspiration events may be appropriate.
COMMONLY ASSOCIATED CONDITIONS
See "Risk Factors. " Ł é á
DIAGNOSIS
- There is no "gold standard " Ł test for aspiration pneumonia; radiologic, clinical, and bacteriologic criteria have all been used. Most instances of aspiration are not observed (2)[B].
- Diagnosis is inferred when a patient with risk factors for aspiration develops a pneumonia in a characteristic bronchopulmonary segment (6).
- After assessing for aspiration risk, other elements of history, physical, and diagnostic testing are similar to those used to diagnose pneumonia of any cause.
HISTORY
- Common
- Fever and dyspnea
- Prior aspiration event(s)
- Delirium, change in mental status
- Productive cough classically with putrid sputum
- Pleuritic chest pain
- Indolent course
- Less common: rigors and weight loss
PHYSICAL EXAM
- Altered mental status
- Periodontal disease, poor oral hygiene
- Rhonchi
- Decreased resonance to percussion, bronchovesicular breath sounds showing consolidation
- Less common: wheezes, crackles, severe dyspnea, or acute respiratory failure
DIFFERENTIAL DIAGNOSIS
- Aspiration pneumonitis
- CAP
- Viral or fungal pneumonia
- Lung abscess/empyema
- Foreign body aspiration
- Lung cancer, tuberculosis
DIAGNOSTIC TESTS & INTERPRETATION
- WBC >12,000
- Anemia of chronic disease occasionally present.
- Cultures
- Sputum cultures: anaerobic oral flora difficult to culture
- Blood cultures typically low yield
- Urine antigen test for pneumococcus and Legionella (7)[B]
- Arterial or venous blood gas if acidosis suspected
- CXR (posteroanterior and lateral)
- May be normal in early infection
- Involvement of lower lobes favors aspiration as the cause (2)[B].
- May also show a bronchopneumonia pattern with segmental and subsegmental consolidation, usually in lower lobes
- Much new research has shown serum biomarkers (i.e., procalcitonin) to be significant indicators of aspiration. Although increased serum levels are correlated with increased risk of aspiration pneumonia, they cannot be used to distinguish pneumonia from other types of aspiration injury (2,6)[B].
Follow-Up Tests & Special Considerations
Chest CT: more sensitive detection of infiltrates than CXR but should be used only if clinically indicated é á
Diagnostic Procedures/Other
- Bronchoscopy
- Bronchoscopic brush cultures show improved sensitivity of etiologic diagnosis but are affected by preprocedural administration of antibiotics.
- Commonly used for VAP but controversial in clinical practice
- Swallowing evaluation, including possible videofluoroscopic evaluation with modified barium swallow, used in patients with suspected dysphagia
TREATMENT
MEDICATION
- Treatment guidelines are below, although final therapy choices will vary based on local susceptibility and resistance patterns.
- Antibiotics are indicated for aspiration pneumonia and should be tailored to the risk profile (CAP vs. HCAP) of the patient. Many patients at risk for aspiration pneumonia are also at risk for colonization by virulent nosocomial pathogens.
- It is important to initiate antibiotics early. Providers should empirically initiate broad-spectrum antibiotics with gram-negative coverage until the results of cultures are known.
- Although commonly prescribed, new research has shown that antimicrobials with anaerobic coverage are not routinely warranted, unless there is evidence of severe periodontal disease, necrotizing pneumonia, or lung abscess (6,7)[B].
- New data have shown that a long duration of therapy may not be necessary. Treatment should last for 3 to 13 days, with more sources recommending 7 to 8 days, and be based on clinical response, including time to clinical stability (8)[B].
- If no improvement after 3 days of antibiotic treatment, other diagnoses or resistant bacteria should be considered.
- Outpatients or hospitalized patients without risk factors for resistant bacteria (6)[B]
- First line: ceftriaxone 1 g IV once daily plus azithromycin 500 mg IV/PO once daily
- Second line: levofloxacin 750 mg IV once daily or moxifloxacin 400 mg IV once daily
- VAP or patients at risk for resistant bacteria
- All patients should be treated with a Ä ▓-lactam that is active against Pseudomonas (7)[B].
- First line: cefepime 1 to 2 g IV q8 " ô12h
- Second line: imipenem 500 mg IV q6h, meropenem 1 g IV q8h, piperacillin-tazobactam 4.5 g IV q6h
- In addition, consider including a second agent active against Pseudomonas, especially in hemodynamically unstable patients (6,9)[B]:
- First line: ciprofloxacin 400 mg IV q12h
- Second line: gentamicin 4 to 7 mg/kg/day IV once q24h
- Either vancomycin or linezolid should be added for coverage against MRSA (6)[B]:
- First line: vancomycin per pharmacokinetic guidelines
- Second line: linezolid 600 mg IV q12h
- If there is increased risk of anaerobic infection because of severe periodontal disease, necrotizing pneumonia, or lung abscess, then anaerobic coverage can be added (3)[B].
- First line: clindamycin, 600 mg IV BID (q8h for severe cases) or 300 mg PO QID
- Second line: ampicillin/sulbactam, 3 g IV BID
ISSUES FOR REFERRAL
- Consider speech therapy evaluation.
- If patient without dysphagia fails appropriate therapy or aspiration recurs, consider pulmonology evaluation.
ADDITIONAL THERAPIES
- If possible, avoid the use of medications that may increase the risk of aspiration pneumonia.
- Optimize treatment of comorbidities that may increase the risk of aspiration.
- If patient without dysphagia fails appropriate therapy or aspiration recurs, consider bronchoscopy to rule out neoplasm and other treatment-resistant microorganisms.
INPATIENT CONSIDERATIONS
Admission Criteria/Initial Stabilization
Admission recommended for anyone with signs of sepsis, immunosuppression, significant comorbid illness, poor functional or nutritional status é á
- Support ABCs.
- Assess O2 saturation to determine need for supplemental O2.
- Assess for signs of hemodynamic instability.
- Establish goals of care with patient and family.
Nursing
- Aggressive oral hygiene and pulmonary toileting
- Elevate head of bed, semirecumbent position: 30 to 45 degrees.
ONGOING CARE
DIET
- NPO if reduced consciousness
- Aggressive oral hygiene
- Soft diet with thickened liquids
- Encourage smaller bites.
- Chin-down swallowing
- Mechanical strategies
- Elevated head 30 to 45 degrees when eating; especially important if enteral feeding
- There is a lack of evidence that tube feeding prevents aspiration, but tube feeding does improve pulmonary toileting.
PROGNOSIS
- HCAP and VAP have greater morbidity and mortality than CAP. It is likely that the worse outcomes are associated with the increase in age and comorbidities of those at risk for HCAP and VAP.
- VAP has high morbidity and mortality at 15 " ô50%.
- Age, poor functional and nutritional status, and significant comorbid illness are independent predictors of increased mortality.
COMPLICATIONS
- Early: sepsis, acute respiratory distress syndrome
- Late: lung abscess, necrotizing pneumonia, bronchopleural fistula, empyema
REFERENCES
11 Gomes é áGF, Pisani é áJC, Macedo é áED, et al. The nasogastric feeding tube as a risk factor for aspiration and aspiration pneumonia. Curr Opin Clin Nutr Metab Care. 2003;6(3):327 " ô333.22 DiBardino é áDM, Wunderink é áRG. Aspiration pneumonia: a review of modern trends. J Crit Care. 2015;30(1):40 " ô48.33 Komiya é áK, Ishii é áH, Umeki é áK, et al. Impact of aspiration pneumonia in patients with community-acquired pneumonia and healthcare-associated pneumonia: a multicenter retrospective cohort study. Respirology. 2013;18(3):514 " ô521.44 Mitchell é áSL. Clinical Practice. Advanced dementia. N Engl J Med. 2015;372(26):2533 " ô2540.55 Gomes é áCAJr, Andriolo é áRB, Bennett é áC, et al. Percutaneous endoscopic gastrostomy versus nasogastric tube feeding for adults with swallowing disturbances. Cochrane Database Syst Rev. 2015;(5):CD008096.66 Waybright é áRA, Coolidge é áW, Johnson é áTJ. Treatment of clinical aspiration: a reappraisal. Am J Health Syst Pharm. 2013;70(15):1291 " ô1300.77 Bartlett é áJG. How important are anaerobic bacteria in aspiration pneumonia: when should they be treated and what is optimal therapy. Infect Dis Clin North Am. 2013;27(1):149 " ô155.88 Marik é áPE. Pulmonary aspiration syndromes. Curr Opin Pulm Med. 2011;17(3):148 " ô154.99 Watkins é áRR, Lemonovich é áTL. Diagnosis and management of community-acquired pneumonia in adults. Am Fam Physician. 2011;83(11):1299 " ô1306.
ADDITIONAL READING
- Jaoude é áP, Badlam é áJ, Anandam é áA, et al. A comparison between time to clinical stability in community-acquired aspiration pneumonia and community-acquired pneumonia. Intern Emerg Med. 2014;9(2):143 " ô150.
- Lanspa é áMJ, Jones é áBE, Brown é áSM, et al. Mortality, morbidity, and disease severity of patients with aspiration pneumonia. J Hosp Med. 2013;8(2):83 " ô90.
- Luk é áJK, Chan é áDK. Preventing aspiration pneumonia in older people: do we have the " śknow-how '? Hong Kong Med J. 2014;20(5):421 " ô427.
- Ogasawara é áT, Umezawa é áH, Naito é áY, et al. Procalcitonin-guided antibiotic therapy in aspiration pneumonia and an assessment of the continuation of oral intake. Respir Investig. 2014;52(2):107 " ô113.
- Onur é áOE, Onur é áE, Guneysel é áO, et al. Endoscopic gastrostomy, nasojejunal and oral feeding comparison in aspiration pneumonia patients. J Res Med Sci. 2013;18(12):1097 " ô1102.
CODES
ICD10
- J69.0 Pneumonitis due to inhalation of food and vomit
- J69.8 Pneumonitis due to inhalation of other solids and liquids
- J69.1 Pneumonitis due to inhalation of oils and essences
ICD9
- 507.0 Pneumonitis due to inhalation of food or vomitus
- 507.8 Pneumonitis due to other solids and liquids
- 507.1 Pneumonitis due to inhalation of oils and essences
SNOMED
- aspiration pneumonia (disorder)
- Pneumonitis due to inhalation of food or vomitus
- Pneumonitis due to inhalation of oil or essence
CLINICAL PEARLS
- Aspiration pneumonia is usually a clinical diagnosis.
- Initial antibiotic treatment is empiric. Routine coverage of anaerobes is unnecessary in absence of specific risk factors.
- Mechanical strategies may help with prevention. A goals of care discussion in a patient who has recurrent aspiration pneumonia may be appropriate.