The Asthma and Allergy Foundation of America describes asthma as a process whereby the airways become narrowed. Narrowing results from chronic inflammation and increased sensitivity of tubes in the lungs called bronchioles. According to the Centers for Disease Control and Prevention, 20 million people in the U.S. have received a diagnosis of asthma. A study in the journal Anesthesiology in 1994 by David Warner, M.D., asserts that although specific effects of anesthesia occur in people with asthmatic, they rarely cause serious problems.
Wheezing, a hallmark of most variants of asthma, can be triggered by anesthesia and results when a person with asthma tries to exhale through airways that are swollen and narrowed. Many anesthetics require the use of a breathing tube, which is stimulating to irritable airways, causing them to swell and narrow with resultant wheezing. Some medications, such as certain muscle relaxants used in anesthesia, also cause histamine release, further contributing to narrowed airways and wheezing, explains the third edition of the text Anesthesia and Co-Existing Disease, edited by Robert Stoelting.
Coughing results from the need to clear fluid, irritants or mucous from the airways. When the bronchioles become irritated from anesthesia tube or medicines, more secretions build up and the protective cough reflex increases. Aside from being uncomfortable, coughing can further irritate the airways and cause worsening of an asthma attack. Interestingly, some intravenous agents such as fentanyl used mostly during the early stages of anesthesia, can induce mild, transient coughing in up to 28% of patients with or without asthma, according to the text Clinical Anesthesia, edited by Paul Barash. Usually just an annoyance, in a person with asthma the effect might be of more consequence if it starts the pathologic process of cough leading to irritation, leading to spasm of the airway leading to more coughing and a full-blown asthma attack.
Even in patients with normal lungs, collapse of parts of the lung, called atelectasis, can result from surgery and anesthesia. Many sources quote this as an increased risk for people with asthma after anesthesia but newer studies seem to refute this, as discussed in Clinical Anesthesia by Paul Barash and confirmed in a 1994 study by Dr. Warner in the journal Anesthesiology.
While most of the effects and after-effects of anesthesia seem to involve risk or complications, anesthetics have actually been used in the treatment of asthma that doesn't respond to other therapies, as described by case studies reported in Clinical Anesthesia, edited by Paul Barash. With deep gas anesthesia, the bronchioles eventually relax allowing time for treatment of the underlying disease process. Before a planned surgery people with asthma should work with a doctor or asthma specialist to optimize asthma treatment and control symptoms. This makes the anesthetic much safer and means that the patient and the anesthesia provider can be confident in knowing the risks are minimized.
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- Centers for Disease Control, FastStats for Asthma
- "Clinical Anesthesia", 6th edition; Paul Barash, editor; 2009
- "Anesthesiology"; Perioperative Respiratory Complications in Patients with Asthma; Warner, DO; 1996
- "Anesthesia and Co-Existing Disease", 3rd edition; Robert K. Stoelting and Stephen Dierdorf, editors; 1998