Intravenous induction agents used in asthmatic patients include oxybarbiturates, thiobarbiturates, ketamine, and propofol. Thiobarbiturates constrict airways in laboratory investigations and may have a loose association with clinical bronchospasm. The most common cause of bronchospasm is the stimulus of intubation, and large doses of barbiturates are required to block this effect successfully. Ketamine has well-known bronchodilatory effects secondary to the release of endogenous catecholamines with p2-agonist effects. Ketamine also has a small, direct relaxant effect on smooth muscles. Propofol decreases both airway resistance and airway reflexes after administration. Intravenous lidocaine is a useful adjunct for blunting the response to laryngoscopy and intubation.
Mask induction with halothane or sevoflurane is an excellent method to block airway reflexes and to relax airway smooth muscles directly. These agents are much more palatable to the airway than isoflurane or desflurane.
Atracurium and mivacurium are commonly used muscle relaxants that have demonstrated histamine release and may cause bronchoconstriction. Vecuronium, rocuronium, pancuronium are not associated with histamine release. Cis-atracurium is associated with less histamine release relative to atracurium.
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If you suffer with asthma, you will no doubt be familiar with the uncomfortable sensations as your bronchial tubes begin to narrow and your muscles around them start to tighten. A sticky mucus known as phlegm begins to produce and increase within your bronchial tubes and you begin to wheeze, cough and struggle to breathe.