A 2020 guideline for awake tracheal intubation published by the Difficult Airway Society discussed the use of lidocaine as a topical anesthetic. Lidocaine is thought to be beneficial compared to other local anesthetic agents due to a safer cardiovascular and systemic toxicity profile. The dose of topical lidocaine is recommended to be 6 to 9.3 mg/kg lean body weight; while lower doses have been shown to be as effective as higher doses, higher concentrations have been associated with a more rapid airway anesthesia onset. Absorption of lidocaine depends on the delivery method used, and one method is not recommended over another due to insufficient evidence. The authors note that nebulized lidocaine can be used, but has variable absorption; as a result, higher doses may be needed to account for this. The optimal route of lidocaine administration for awake tracheal intubation requires further investigation. [1]
A recently published meta-analysis aimed to assess the superiority of airway nerve blocks (ANBs) versus airway anesthesia without nerve blocks for awake tracheal intubation (ATI), including local anesthesia and local anesthetic nebulization. A total of 14 randomized controlled trials (RCTs) with 658 participants (ANBs group: 328 participants; No-ANBs group: 330) were included. Topical anesthesia included 2% atomized lidocaine, 2% nebulized lidocaine, 4% lidocaine by ultrasonic nebulizer, 4% lidocaine by jet nebulization, or lidocaine spray. The meta-analysis revealed that ANBs resulted in a reduced intubation time compared to no-ANBs (standardized mean difference [SMD] -2.57, 95% confidence interval [CI] −3.59 to −1.56; p <0.00001, I2 = 96%). The pooled analysis indicated that ANBs resulted in a greater absence of reaction to the placement of flexible score and tracheal tube compared to no-ANBs (77.18% versus 6.62%, relative risk [RR] 9.87; 95% CI 4.10 to 23.75, p <0.00001, I2 = 47%). The cough or gag reflex during intubation was also significantly lowered in the ANBs group than in the no-ANBs group (25.29% versus 72%, RR 0.35; 95% CI 0.27 to 0.46; p <0.00001; I2 = 17%). The satisfaction of patients was notably higher in the ANBs group compared to the no-ANBs group (68.22% versus 36.15%, RR 1.88; 95% CI 1.05 to 3.34; p = 0.03; I2 = 78%). Additionally, the overall complications was significantly lower in the ANBs group than in the no-ANBs group (15.50% versus 53.13%, RR 0.29; 95% CI 0.19 to 0.45; p <0.00001; I2 = 9%). The findings suggest that ANBs offer improved airway anesthesia quality for ATI, characterized by a shorter intubation time, enhanced intubation conditions with higher tolerance to the placement of the flexible score and tracheal tube, reduced cough or gag reflex during intubation, higher levels of excellent patient satisfaction, and a decrease in overall complication. [2]
A 2020 meta-analysis sought to identify differences in outcomes with or without nebulized lidocaine when used in bronchoscopy. Seven RCTs (N= 1,366) were included, with doses of nebulized lidocaine ranging from 60 mg to 300 mg (mean total dose 235 mg). Nebulized lidocaine, when compared to no nebulized lidocaine, did not amount to a difference in physician-reported cough score (SMD -0.09; 95% CI -0.7 to 0.51; I^2= 95%; p= 0.76). Subgroup analyses showed that in studies that only used local anesthesia, no nebulized lidocaine showed better cough scores (SMD 0.32; 95% CI 0.12 to 0.51; I^2= 77%; p= 0.001), however this difference was not statistically significant when moderate sedation was used. Additionally, for patient-reported cough scores no difference was seen between nebulized lidocaine and no nebulized lidocaine groups (SMD -0.12; 95% CI -0.82 to 0.59; I^2= 95%; p= 0.75). No differences were seen between groups for operator’s satisfaction score, ease or procedure, patient’s discomfort, and unwillingness to repeat the procedure. The additional nebulized lidocaine groups required higher doses of lidocaine in comparison to the no nebulization group (MD 86.9; 95% CI 34.83 to 138.96; I^2= 100%; p= 0.001). In a subgroup analysis of studies which used moderate sedation, the additional nebulized lidocaine group showed a decrease in midazolam dose and duration of procedure. Of note, this analysis is limited by differing scales used among studies to measure cough and significant heterogeneity between studies. Overall, the authors concluded that the additional administration of nebulized lidocaine did not have a significant effect on cough symptoms. [3]