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Aspiration pneumonia: What you need to know
Although aspiration pneumonia accounts for 5% to 15% of cases of community-acquired pneumonia, difficulties in both diagnosis and differentiating the condition from other types of pneumonia have led this to be an understudied infection, according to a recently published review article in The New England Journal of Medicine.
Healio Primary Care Today spoke with Michael S. Niederman, MD, pulmonary and critical medicine specialist at Weill Cornell Medicine and New York-Presbyterian Hospital and co-author of the review article, touching on a variety of areas related to the condition, including significant risk factors, how primary care physicians can be better prepared to make accurate diagnoses and preventive measures patients can take. – by Melissa J. Webb
Question: How would you characterize aspiration pneumonia? What clinical features differentiate it from other types?
Answer: Aspiration pneumonia refers to patients who have macroaspiration of large volumes of material from the upper respiratory tract or stomach into the lung. Although most pneumonia occurs via microaspiration, this is different, and clinically is recognized by a patient with risk factors who develops a pneumonia in gravity-dependent lung segments such as the lower lobes posteriorly and more on the right than on the left. Aspiration can involve oral and gastric contents that are contaminated with bacteria or can involve gastric acid, the former causing a bacterial pneumonia, the latter a chemical pneumonitis.
Q: What are the most significant risk factors to pay attention to? What types of patients are most at risk?
A: Patients with impaired swallowing or altered level of consciousness are most at risk. Common predisposing conditions include stroke, seizures, alcohol intoxication, dysphagia, tube feeding, esophageal stricture and following cardiac arrest.
Q: What should primary care physicians know about the difficulties of diagnosing aspiration pneumonia and how can they be better prepared to identify the condition in patients?
A: The key issue is to suspect its presence. Although aspiration pneumonia is similar to other pneumonias, recognition of aspiration can lead to efforts at preventing future episodes. Once the diagnosis is suspected and made, all the contributing risks should be identified and efforts made to reduce them. In very specific patients, such as those with head injury and intubation, a short course of prophylactic antibiotics may be useful.
Q: What are some preventive strategies that patients can do to lessen their chances of acquiring aspiration pneumonia?
A: Prevention involves identifying risk factors. Recommended prevention includes no food for 8 hours and no clear liquids for 2 hours before elective surgery; 24 hours of antibiotics in comatose patients after emergency intubation; swallowing evaluation after extubation and after stroke; feeding in a semi-recumbent position after stroke; preference for angiotensin converting enzyme inhibitors (which promote cough) for hypertension control after stroke.
Q: What are some of the most effective treatment options?
A: It is important to determine if the patient has chemical aspiration or liquid/bacterial aspiration. The first should not be treated empirically with antibiotics, while the latter should get antibiotic therapy, selected based on severity of pneumonia, site of aspiration (community or hospital) and associated risk factors for specific drug-resistant pathogens.
Q: What have researchers learned about the condition since the last review article was published 15 years ago?
A: Our review focuses on a number of new concepts including a new understanding of pathogenesis involving alterations in the lung microbiome, newly identified risk factors such as hypothermia therapy post-cardiac arrest, changing microbiology and new concepts on prevention, some of which are outlined above.
Q: What further research is needed in this area?
A: Ideally, we would like to identify a biomarker that can tell when to use antibiotics and when they are not needed. Procalcitonin has been studied for this purpose and not shown to be useful.
We also need better prevention strategies, especially for patients with neurologic illness and impaired swallowing, and we need additional investigation into other clinical scenarios where aspiration can be part of the pathogenesis of recurrent pneumonia.