Background: Awake tracheal intubation may evoke reflex bronchoconstriction in asthmatics. Whether this effect is altered by the choice of the local anesthetic used or by pretreatment with a beta2-adrenoceptor agonist is unknown. Therefore, we assessed the effect of awake fiberoptic intubation after lidocaine or dyclonine inhalation with or without pretreatment with salbutamol on lung function in asthmatic volunteers.
Methods: Bronchial hyperreactivity was verified by an inhalational histamine challenge. On four different days in a randomized, double blind fashion the volunteers (n = 10) inhaled either dyclonine or lidocaine with or without salbutamol pretreatment. FEV1 was measured at baseline, following salbutamol or saline inhalation, after lidocaine or dyclonine inhalation, while intubated, and after extubation. Lidocaine and dyclonine plasma concentrations were also measured.
Statistics: Two-way ANOVA, post hoc tests with Bonferroni correction, results are presented as mean +/- SD.
Results: Neither lidocaine nor dyclonine inhalation changed FEV1 significantly from baseline compared with placebo inhalation (4.43 +/- 0.67 l vs. 4.29 +/- 0.72 l, and 4.53 +/- 0.63 l vs. 4.24 +/- 0.80 l, respectively). Salbutamol slightly but significantly increased FEV1 (4.45 +/- 0.76 l vs. 4.71 +/- 0.61 l, P = 0.0034, and 4.48 +/- 0.62 l vs. 4.71 +/- 0.61 l, P = 0.0121, respectively). Following awake intubation FEV1 significantly decreased under lidocaine topical anesthesia (4.29 +/- 0.72 l to 2.86 +/- 0.87 l) but decreased even more under dyclonine anesthesia (4.24 +/- 0.80 l to 2.20 +/- 0.67 l; P < 0.0001). While salbutamol pretreatment significantly attenuated the response to intubation, it did not eliminate the difference between the effects of lidocaine and dyclonine. Only minutes after extubation FEV1 was similar compared with baseline.
Conclusion: In asthmatics, awake fiberoptic intubation evokes a more than 50% decrease in FEV1 following dyclonine inhalation. Using lidocaine for topical anesthesia the decrease in FEV1 is significantly mitigated (35%) and can be even further attenuated by salbutamol pretreatment. Therefore, combined treatment with lidocaine and salbutamol can be recommended for awake intubation while the use of dyclonine, despite its excellent and longer lasting topical anesthesia, may be contraindicated in patients with bronchial hyperreactivity.