Asthma
Asthma is one of the most common chronic disease across the world. It affects around 300 million people. In the United States, it has a prevalence of 8.7% in adults and 8.2% in children. It can occur at all ages, but has a peak incidence between ages 5 and 9. Asthma is characterized as periodic episodes or attacks that result in difficulty breathing, coughing, and wheezing.
Patient’s typically have a family history of asthma or atopic (allergic) diseases. Smoking is the biggest modifiable risk factor for asthma. Other non-modifiable risk factors include income (inversely proportional), ethnicity (higher incidence in African Americans and Hispanics), and environmental exposures (ie. Jobs like coal mining).
Bronchospasm in asthma is a result of hypersensitivity of the airway to various irritants. Asthma can be broken down into two groups based on the etiology: allergic vs. idiosyncratic (intrinsic). Allergic triggers would include dust, pollen, and dander. Intrinsic triggers would include infections, pollution, exercise, cold, and psychogenic.
Asthma can present on a spectrum of severity. The more severe a patient’s underlying disease, the higher risk of intraoperative bronchospasm and complications. Indicators of patients with poor asthma control are:
frequency of symptoms
Use of rescue inhalers
Hospital admissions
ICU admissions
Use of steroids
If you suspect high risk for pulmonary complications due to severe asthma, there are some intraoperative steps to take that help mitigate risk:
Normal inhaler schedule on day of surgery
Avoid lower airway manipulation (ie. Endotracheal intubation, deep endotracheal suctioning)
Use regional anesthesia and/or LMA if general anesthesia is required
Avoid medications that release histamine (ie. Morphine)
Use anesthetic drugs that promote bronchodiliation (ie. Ketamine, sevoflurane, propofol)
In an acute asthma attach, a typical ABG would show hypoxemia (PaO2 < 80 mmHg). In order to compensate for this, patients tend to breath faster, creating a respiratory alkalosis with hypocapnia. If the attack persists and the patient begins to fatigue, hypercapnea can be a late and distressing sign.
The treatment of an acute asthma attack with bronchospasm is albuterol, a beta-agonist. They are usually administered through measured-dose inhalers (MDI) or nebulizers. 8-10 puffs with the MDI is usually necessary to break bronchospasms. The beta-agonism causes bronchodilation by increasing intracellular cAMP by activating adenyl cyclase. Increased cAMP promotes bronchial relaxation and habits the release of inflammatory mediators from mast cells.
