How would you give 2-agonists? What is their mechanism of action on asthma?
Answer:
Historically, it was fashionable to treat episodes of severe asthma with intravenous sympathomimetics such as isoproterenol. This approach no longer appears justifiable. Isoproterenol infusions can induce ventricular arrhythmias during halothane anesthesia and is clearly associated with myocardial damage. Even the intravenous administration of 2-selective agents such as terbutaline and albuterol offers no advantage over the inhaled route.
2-Agonists such as albuterol, levalbuterol, and terbutaline may be administered through MDI adapters or small-volume jet nebulizers to the anesthetic circuit. Because MDI adapters are not very efficient in the intubated patient due to rain-out in the endotracheal tube, 8 to 10 puffs are needed to break acute bronchospasms.
Adrenergic stimulants produce bronchodilation through action on -adrenergic receptors. -Agonists increase intracellular cAMP by activating adenyl cyclase, which produces cAMP from adenosine triphosphate. Increased cAMP promotes bronchial relaxation and inhibits the release of mediators from mast cells (Fig. 1.4).
Reference(s):
- Fanta CH. Asthma. N Engl J Med. 2009;360:1002-1014.
- Hines RL, Marschall KE, eds. Stoelting’s Anesthesia and Co-existing Disease. 7th ed. Philadelphia, PA: Elsevier; 2018:19-22.
- Jameson JL, Fauci AS, Kasper DL, et al, eds. Harrison’s Principles of Internal Medicine. 20th ed. New York: McGraw-Hill; 2018:1957-1969.
- Woods BD, Sladen RN. Perioperative considerations for the patient with asthma and bronchospasm. Br J Anaesth. 2009;103(suppl 1):i57-i65.