Intubating the Asthmatic: Pre-Treat with Lidocaine?
ABSTRACT & COMMENTARY
Source: Groeben H, et al. Combined intravenous lidocaine and inhaled salbutamol protect against bronchial hyperreactivity more effectively than lidocaine or salbutamol alone. Anesthesiology 1998;89:862-868.
Tracheal intubation in patients with asthma can cause or exacerbate life-threatening bronchospasm. Intravenous lidocaine has been recommended to attenuate the response to airway irritation because it has been shown to mitigate the response to histamine inhalation in asthmatics. For the first time, in this study, the effects of prophylactic lidocaine are compared with standard prophylaxis with sympathomimetic aerosols.
Fifteen volunteers with bronchial hyperreactivity were enrolled in this placebo-controlled, double-blind, randomized study. A histamine threshold concentration necessary for a 20% decrease in FEV1 was calculated for each volunteer. Each subject was then challenged with inhaled histamine on four different days after pre-treatment with either intravenous lidocaine (1.5 mg/kg over 20 minutes then 3 mg/kg/hr), inhalation of salbutamol (1.5 mg diluted in 1.5 mL saline), inhalation of salbutamol plus intravenous lidocaine, or placebo. The mean histamine threshold after intravenous and inhalational administration of placebo was 6.4 ± 4.3 mg/mL. Intravenous lidocaine and inhaled salbutamol each significantly increased the mean histamine threshold to 14.2 ± 9.5 mg/mL and 16.8 ± 10.9 mg/mL, respectively. However, the combination of lidocaine and salbutamol increased the mean histamine threshold even further to 30.7 ± 15.7 mg/mL.
Comment by Stephanie B. Abbuhl, MD, FACEP
This study shows that, in awake volunteers, the combination of intravenous lidocaine and inhaled salbutamol protect against bronchial hyper-reactivity much more effectively than either agent alone. Groeben and colleagues believe that while lidocaine may have some minor direct effect on smooth muscle cells, the main mechanism for the effects of lidocaine is probably neural blockade of vagal reflex pathways. The idea that lidocaine and salbutamol attenuate the response to histamine by different mechanisms may explain the marked effect of the combined pretreatment with both agents. This report provides more evidence to support the use of lidocaine in the pretreatment phase of tracheal intubation in patients with reactive airway disease.
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