EMLA cream is an effective topical anesthetic for bronchoscopy

587 1Departments of Anesthesiology and 2Respirology; 3Respiratory Therapy, The Ottawa Hospital, Ottawa, Ontario Correspondence: Dr B Sohmer, Department of Anesthesiology, The Ottawa Hospital-Civic Campus, 1053 Carling Avenue, Ottawa, Ontario K1Y 4E9. Telephone 613-761-4169, fax 613-761-5209, e-mail bensohmer@hotmail.com B Sohmer, GL Bryson, S Bencze, MM Scharf. EMLA cream is an effective topical anesthetic for bronchoscopy. Can Respir J 2004;11(8):587-588.

A nesthesia of the oropharyngeal airway before bronchoscopy is required to minimize the gag reflex and coughing, and to facilitate a comfortable, yet thorough, evaluation of the patient's airway.Local anesthetics have been sprayed, aerosolized, atomized and applied as a viscous gel to achieve topical anesthesia of the oropharynx (1,2).These techniques, although effective, are limited by the ease of application, time required, amount of local anesthetic used and patient discomfort.
EMLA cream (AstraZeneca Inc, Canada) is a 1:1 eutectic mixture of lidocaine 2.5% and prilocaine 2.5%.Both lidocaine and prilocaine are amide-type local anesthetics and function by preventing the initiation and conduction of nerve impulses.The depth of anesthesia is dependent on the dose of the drug and its time of application.Absorption, onset and duration of anesthesia with EMLA will vary based on blood flow, thickness and pathology of the tissue to which it is applied.Traditional indications for the use of EMLA include topical anesthesia for venipuncture (3), laser excision of condylomata (4) and dressing changes (5).The safe use of EMLA for topical anesthesia of the oral mucosa has also been described (6,7).
Clinicians at The Ottawa Hospital (Ottawa, Ontario) have recently adopted EMLA cream for oropharyngeal anesthesia.The purpose of the present study was to evaluate the use of EMLA cream for topical anesthesia of the oropharyngeal mucosa for diagnostic bronchoscopy.

MATERIALS AND METHODS
After The Ottawa Hospital research ethics board approval, the charts of 57 consecutive patients (both inpatients and outpatients) that underwent diagnostic bronchoscopy using EMLA for oropharyngeal topical anesthesia were reviewed retrospectively.All patients arrived in the bronchoscopy suite with intravenous access.No premedication or supplemental intravenous sedation were administered.Oxygen was applied to patients via nasal prongs at 3 L/min.Three-lead electrocardiography and oxygen saturation monitors were applied.EMLA cream (4 mL; 100 mg lidocaine and 100 mg prilocaine) was dispensed into a disposable syringe.Patients were asked to open their mouths with their tongues extended and the cream was applied all at once to the posterior third of the tongue.The cream became less viscous as it mixed with saliva.Patients were encouraged to mix and gargle the cream within their oropharynx.Bronchoscopists then gowned, gloved and positioned patients for the procedure.The time from initial EMLA cream application to insertion of bronchoscope was recorded.
Patients were asked to expel any remaining oral contents before bronchoscope insertion.For dose calculation purposes, it was assumed that no remaining contents were expelled and the maximal mass of administered drug was recorded.All bronchoscopies were performed orally.On visualization of the larynx, liquid lidocaine was applied through the bronchoscope for laryngeal anesthesia.Adequacy of anesthesia (excellent, fair, good or poor), need for supplemental airway anesthesia, the amount of liquid lidocaine used for laryngeal anesthesia and procedural complications were recorded.

RESULTS
Fifty-seven consecutive patients received topical oral airway anesthesia with EMLA cream.Indications for bronchoscopy were varied and not recorded.Patients ranged in age from 28 to 91 years and their characteristics are described in Table 1.
The mass of lidocaine administered at the larynx was 79.65±14.39mg.Bronchoscopy conditions were described as 'excellent' in 55 cases (96.5%) and 'good' in the remaining two cases (3.5%).Supplemental oral anesthesia, in the form of four sprays of 2% lidocaine spray, was administered to the oropharynx in one case (1.8%).The remaining 56 cases (98.2%) required no supplementation.The total mass of local anesthetic administered (prilocaine in EMLA, lidocaine in EMLA, laryngeal topical lidocaine and supplemental lidocaine spray) was 280.8±16.8mg (range 240 mg to 345 mg).The mean time from the application of EMLA cream to insertion of the bronchoscope was 5.10±0.48min.

DISCUSSION
The scope of EMLA cream's use is slowly expanding and now includes a recent report (8) of its use for awake fibre optic endoscopy and oral endotracheal intubation.To date, we have not found any published literature describing EMLA cream use in diagnostic bronchoscopy.Bronchoscopy is an invasive procedure commonly performed on an outpatient basis that requires adequate airway anesthesia and patient compliance to be successful.Inadequate analgesia may lead to repeated doses of local anesthetics, narcotic analgesia or sedative hypnotics.Seizures and airway obstruction following repeated attempts to provide analgesia for bronchoscopy have been reported (9,10).A 400 mg total dose limit of lidocaine is presently recommended for fibre optic bronchoscopy (11).Much of this mass (approximately 75%) is often used for oropharyngeal anesthesia alone.With the requirement of tracheobronchial anesthesia, the likelihood of toxic lidocaine dose administration increases (10,12).It may be difficult to account for local anesthetics applied when nebulizers, tonsil tip sprays and gargles are used.In the present study, every milligram of local anesthetic was accounted for (70% of recommended maximum), decreasing the likelihood of accidental toxic administration.Previous reports (8) showed that with oral mucosa administration of 4 mL of EMLA, the peak plasma concentration of both lidocaine and prilocaine did not reach toxic levels (8).As well, methemoglobin levels did not exceed normal values, which is of concern with prilocaine administration (8).
Anxiolysis and amnesia are two indications for supplemental intravenous medication during bronchoscopy.It is the gag and choke experience, often the most unpleasant aspect, that requires amnesia.It can be argued that much of patient anxiety stems from the unpleasant 'freezing' portion of the procedure.Patients have characterized EMLA as being the least unpleasant method of airway topicalization (13).We achieved simple, pleasant and effective topical anesthesia that blunted any significant gag reflex.This, in turn, should decrease requirements for additional intravenous sedation, reducing the risk of excess sedation and respiratory depression.Our cohort did not require any supplemental intravenous sedation.
The present study has shown EMLA cream to be an alternative for oropharyngeal topical anesthesia that is effective and well-tolerated by patients, and which decreases the overall mass of local anesthetic required for successful bronchoscopy.

TABLE 1
Patient characteristics and local anesthetic consumption (n=57)