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Dosing of Topical Lidocaine During Flexible Bronchoscopy

Morris, Michael J. MD

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doi: 10.1097/LBR.0b013e31818496d7
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What is the optimal dosage and strength of topical lidocaine that should be used during flexible bronchoscopy (FB)? When used in conjunction with intravenous conscious sedation, topical airway anesthesia with lidocaine should be safe and provide a comfortable experience to the patient. Additionally, the bronchoscopist should be able to complete a more rapid and detailed examination when patient coughing and in discomfort is minimized. Uncontrolled coughing during FB limits the duration of the procedure and lessens a bronchoscopist's ability to perform diagnostic and therapeutic interventions.

The primary issue concerning topical lidocaine administration is potential toxicity (seizures, arrhythmias, or methemoglobinemia) related to excessive absorption through the airway mucosa. There is a potential for higher serum lidocaine levels in both the elderly and patients with decreased hepatic clearance due to underlying liver disease.1 The early 1974 survey of nearly 25,000 FBs, only reported 6 patients with complications (respiratory arrest and seizures) related to airway anesthesia and only 1 patient with methemoglobinemia.2 The first bronchoscopy guidelines published in 1985 by the National Institutes of Health conservatively recommended a maximum cumulative lidocaine dose of 400 mg, but subsequent guidelines published in 1991 only indicated minimizing the dose to avoid potential toxicity.3,4 Despite these published guidelines, apprehension was justifiably raised in 1996 when a 19-year-old healthy volunteer died from lidocaine toxicity after undergoing a research FB.5 The recent 2001 bronchoscopy guidelines from the British Thoracic Society recommended no greater than 8.2 mg/kg cumulative dose based primarily on a study of asthmatics undergoing research FB.6,7 As there is no absolute method to determine which patients will have greater lidocaine absorption and therefore be at greater risk for life-threatening toxicity, published guidelines favor the smallest lidocaine dose possible.

Despite these concerns, there exists a significant body of evidence demonstrating the continued safety of topical lidocaine in FB. The recent manuscript by Frey et al8 in the previous issue of the Journal of Bronchology evaluated serum lidocaine and methemoglobin levels in a large cohort (n=154) of patients who received airway anesthesia consisting of 4% nebulized lidocaine, 2% viscous lidocaine for the nares, and as needed 1% lidocaine during the FB. The authors found a mean topical lidocaine dose of 15.4±4.5 mg/kg and mean serum lidocaine levels of 1.55±0.67 μg/mL without evidence of elevated methemoglobin levels or clinical toxicity. There were no significant differences in lidocaine dose (mg/kg) or serum lidocaine level (μg/mL) when compared by indication for FB or age. These results confirmed previous findings from smaller studies concluding higher topical lidocaine doses did not commonly lead to elevated serum lidocaine levels or clinical toxicity.9–15

In the April 2008 issue of Journal of Bronchology, researchers prospectively evaluated the equivalence of 1% versus 2% topical lidocaine during FB.16 Both groups received an upper airway preparation with nasal 2% viscous lidocaine and 10% spray for the oropharynx. Airway anesthesia included 1% versus 2% lidocaine at fixed doses at the vocal cords, carina, and main bronchi with additional as needed doses to control coughing. The investigators counted the cough frequency in addition to perception of coughing (by visual analog scores) for both the patient and bronchoscopist. Both patient groups had a similar cough frequency; there was likewise no significant difference in perception of cough frequency by either the patients or bronchoscopists. The number of as needed doses of lidocaine did not differ, but the 2% lidocaine group received twice the mg/kg dose as the 1% lidocaine group. This data suggests that 1% lidocaine is equally efficacious as 2% lidocaine for cough suppression during FB. While efficacy for suppressing cough by 1% lidocaine was established, safety was not specifically evaluated, as serum lidocaine levels were not drawn to compare groups.

This study contributes some additional information to relatively few studies examining the optimal lidocaine dosing for patient comfort and safety during FB. Mainland et al17 examined various lidocaine amounts (mg/kg) and strengths ranging from 1% to 2% in 96 patients and found no differences between their six groups. They recommended 1% lidocaine for topical airway anesthesia based on similar amounts of supplemental lidocaine doses and serum lidocaine levels. A study by Sutherland et al18 in 1985 demonstrated that a fixed dose of 370 mg of lidocaine had no effect on patient comfort scores when compared with higher lidocaine doses with as needed dosing (mean lidocaine dose=512 mg). Notably, the airway preparation in the fixed dose group used 1% lidocaine versus 2% in the uncontrolled group.

A secondary observation from this study was the lack of a 4% nebulized lidocaine preparation before FB. Although routinely used in clinical practice, several previous studies have failed to demonstrate efficacy for the use of nebulized 4% lidocaine. A comparison by Graham et al19 demonstrated objective evidence of less cough by decreased cough frequency and visual analog scale using intratracheal 2.5% cocaine compared with either nebulized 4% lidocaine or bronchoscopically injected 2.5% cocaine for airway anesthesia. Recently, Stolz and colleagues20 were unable to demonstrate a benefit for nebulized 4% lidocaine compared with saline placebo in terms of cough perception by patients or bronchoscopists, patient discomfort, or use of supplemental lidocaine doses.

For the past 30 years, FB has been proven to be a very safe and well-tolerated procedure. Ultimately, the goal for any FB is a safe and comfortable procedure that allows the bronchoscopists to efficiently perform FB with minimal coughing and maintain safety by minimizing total lidocaine doses. This manuscript reasonably demonstrated that there is no additional benefit gained by using a 2% lidocaine solution to anesthetize the airway during FB. Although not demonstrated in this study, it can be likewise inferred that use of 1% lidocaine may result in less potential toxicity to the patient.


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