A core function of the upper airway is to protect the lungs from aspiration via various reflexes, one of which is bronchospasm, or the temporary narrowing of the bronchi via involuntary contraction of the local smooth muscle. However, not all episodes of bronchospasm protect the airways–ill-timed bronchospasm can prevent the physician’s ability to ventilate a patient. In fact, bronchospasm accounted for 2% of claims in the ASA Closed Claims Study, half in patients without a previous history of asthma.
Tracheal intubation is one of the main triggers for ill-timed bronchospasm. It can be reduced by prophylactic bronchodilator therapy or in patients with asthma, prophylactic steroids and bronchodilators. In cases of flexible fiberoptic intubation, the risk of bronchospasm can be decreased as well with topical lidocaine.
Risk of bronchospasm occurs again at extubation. Extubation may be performed awake, with light anesthesia, or deep (iight implying recovery of airway reflexes and deep implying their absence). Sometimes, deep extubation is performed to avoid ill-timed bronchospasm by tracheal tube stimulation with removal. But this is at the price of a higher risk of hypoventilation and upper airway obstruction. Upper airway obstruction and hypoventilation are less likely during light extubation, but at the price of adverse hemodynamic reflexes and bronchospasm.
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Harald Groeben, Markus Schlicht, Sven Stieglitz, Goran Pavlakovic, Jürgen Peters Both local anesthetics and salbutamol pretreatment affect reflex bronchoconstriction in volunteers with asthma undergoing awake fiberoptic intubation. Anesthesiology: 2002, 97(6);1445-50