Intranasal anesthetic effects of lidocaine and tetracaine compared ALLEN D. NOORILY, MD, RANDALA. OTTO, MD, and SUSAN H. NOORILY, MD, San Antonio, Texas The quality of nasal anesthesia obtained with two local anesthetic solutions (2% iidocaine in oxymetazoline and I% tetracaine in oxymetazoline] was evaluated in this double-blind, randomized study. Each local anesthetic mixture was applied to the nasal septum of healthy volunteers with medication-soaked pledgets. Measurements of anesthetic effect [sensation threshold and pain perception] were made with Semmes-Weinstein monofllaments [North Coast Medical, San Jose, Calif.]. Measurements were performed before local anesthetic application and at 10 and 70 minutes after local anesthetic application. Subjects had greater increases in sensation threshold with tetracaine than with lidocaine at both 10 and 70 minutes [p = 0.0005 and p = 0.0001, respectively]. Subjects had greater decreases in pain perception with tetracaine than with lidocaine at both time intervals [p = 0.0003 and p < 0.0001, respectively]. Tetracaine mixed with oxymetazoline appears to be a superior topical anesthetic for nasal procedures. [OTOLARYNGOLHEAD NECK SURG 1995;113:370-4.] Cocaine has been used to provide topical nasal gists for spinal anesthesia but is suitable for infil- anesthesia and vasoconstriction for more than 100 tration, peripheral nerve block, and topical anesthe- years) It was favored by otolaryngologists and an- sia on accessible mucous membranes¢ Tetracaine is esthesiologists because of its availability, low cost, one of the ingredients in Cetacaine, a commercially and inherent vasoconstrictor properties at clinically available topical anesthetic spray. Because tetra- useful doses. 1'2 Recently, however, the routine use of caine is very potent and capable of providing anes- cocaine has been criticized because of increasing thesia for long durations, it would appear to be costs, abuse potential, side effects, and availability desirable as a topical nasal anesthetic. The purpose restrictions. 3'4 For these reasons, alternative topical of this study was to compare the anesthetic effect of anesthetics for intranasal procedures are desirable. tetra/oxy with that of lido/oxy when applied intra- We have shown that no difference exists between nasally. the intranasal anesthetic or vasoconstrictive effects Few controlled clinical studies of topical anes- of cocaine and those of a lidocaine-oxymetazoline thetics have been performed because it is difficult to (lido/oxy) mixture2 The combination of tetracaine design objective techniques to evaluate the quality of and oxymetazoline (tetra/oxy) is another mixture local anesthesia. Semmes-Weinstein monofilaments that has been used as a cocaine substitute. Its quality (North Coast Medical, San Jose, Calif.) have been as a nasal local anesthetic has not been reported. successfully used to measure and compare intrana- Tetracaine is most commonly used by anesthesiolo- sal sensation thresholds and pain perception. The specifics of their use have been described previously From the Departments of Otolaryngology-Headand Neck Sur- and will be only briefly discussed here/ gery (Drs. A. Noorily and Otto) and Anesthesiology (Dr. S. Noorily),The Universityof Texas Health ScienceCenter at San METHODS AND MATERIAL Antonio. The study protocol was reviewed and approved by Presented at the Annual Meeting of the American Academy of the Institutional Review Board at The University of Otolaryngology-Head and Neck Surgery, San Diego, Calif., Sept. 18-21, 1994. Texas Health Science Center at San Antonio. All Received for publication July 28, 1994; accepted March 10, 1995. subjects gave informed consent before enrollment. Reprint requests: Allen D. Noorily, MD, Department of Oto- Fifteen healthy volunteers participated in the study. laryngology-Head and Neck Surgery, The Universityof Texas Subjects ranged in age from 24 to 64 years (mean, Health Science Center at San Antonio, 7703 Floyd Curl Dr., 35.7 years). Subjects with a history of active sinona- San Antonio, TX 78284-7777. Copyright © 1995 by the American Academyof Otolaryngology- sal disease or local anesthetic sensitivity were ex- Head and Neck Surgery Foundation, Inc. cluded. 0194-5998/95/$5.00 + 0 23/1/64767 Each subject participated in two sessions, which 370 Otolaryngology - Head and Neck Surgery Volume 113 Number 4 NOORILY et al. 371 took place at least 48 hours apart. Seven subjects against the anterior nasal septum. The subject was received lido/oxy during the first session and instructed to remember this stimulus as 10 on the tetra/oxy during the second session. The other eight VAS, to be used for comparison later in the session. subjects received the agents in reverse order. The Fresh anesthetic solutions were prepared within order of drug administration was determined by 30 minutes of use. The lido/oxy mixture was pre- computer-generated pair-wise randomization. Both pared by mixing 5 cm3 of 4% lidocaine with an equal the subjects and the investigators were blinded (both volume of 0.05% oxymetazoline, yielding a final solutions are colorless) to this order. concentration of 2% lidocaine and 0.025% oxymeta- Baseline measurements of sensation thresh- zoline. The tetra/oxy mixture was prepared by dis- old were made before application of local anes- solving 20 mg of tetracaine in 2 cm3 of 0.05% thetic with the Semmes-Weinstein monofilaments. oxymetazoline, yielding a final concentration of 1% Semmes-Weinstein monofilaments are based on the tetracaine and 0.05% oxymetazoline. A cottonoid von Frey hairs, which were developed in 1898. Each pledget (1.3 x 3 cm) was saturated with local anes- monofilament is calibrated to a specific stiffness.7'8 thetic solution. Each pledget absorbed approxi- The tip of the monofilament is placed on the surface mately 0.5 em3 of solution. The medication-soaked to be tested, and pressure is applied until the fila- pledget was placed in the nasal cavity against the ment bends. When the monofilament bends, a stan- septum at time zero and removed, at 10 minutes, dardized force is applied to the surface, in this case Measurements of sensation threshold were re- the nasal septum. The units of the Semmes-Wein- peated at 10 minutes, as previously described. Pain stein monofilaments are expressed as log (10 × force perception was determined in the following manner. in milligrams), where force is the force applied by the The 5.18 filament was pushed against the nasal monofilament when it bends. Most often, the septum until it bent. The subject was asked to mark monofilaments are used to determine the sensation the VAS, rating the pain felt: 0 on the scale indicated threshold for touch and pressure? Because the nasal no pain felt, and 10 indicated the same amount of mucosa has no pressure receptors, application of the pain felt before administration of the anesthetic. monofilaments to the nasal septum measures the Both sensation threshold and pain perception mea- threshold of free nerve endings within the nasal surements were again repeated at 70 minutes. mucosa. A large monofilament can provide a base- Changes in sensation threshold were calculated by line standardized "maximal" painful stimulus to be subtracting the baseline threshold from the thresh- used for comparison purposes after local anesthetic old measured at 10 and 70 minutes. Changes in pain application. perception were measured as the centimeters of line Subjects were asked to close their eyes to prevent on the VAS between 10 and the mark made by the any visual clues. A large filament (5.18; 12.5 gin) was subject. The aforementioned trials were compared gently applied to the nasal ala, vestibule, nasal hairs, by use of a paired t test. and septum to help the subject discriminate between these structures. The nasal ala was gently retracted RESULTS laterally with a blunt-ended, single-pronged retrac- All 15 subjects completed both sessions. No ad- tor to provide easy access to the nasal septum during verse side effects were noted. No significant differ- measurements. The smallest filament (1.65; 0.008 ence was found in the baseline measurements of the gin) was pushed against the anterior nasal septum subjects between the two anesthetic trials. The mean until the filament bent. The subject was then asked change in sensation threshold is shown in Fig. 1. The to state whether the filament could be felt on the tetra/oxy trial showed a significantlygreater increase septum, with any sensation from adjacent structures in sensation threshold than the lido/oxy trial at both ignored. If the subject could not feel the filament, 10 and 70 minutes. The mean change in sensation the next larger filament was applied. This process threshold at 10 minutes for tetra/oxy was 2.27 and was repeated until a filament was felt. The small- for lido/oxy was 1.36 (p = 0.0005), with the units est filament felt was recorded as the sensation representing log (10 × force in milligrams). The threshold. mean change in sensation threshold at 70 minutes Pain perception was rated on a visual analog scale for tetra/oxy was 1.56 and for lido/oxy was 0.57 (VAS). The scale consisted of a 20-cm line with a 0 (p = 0.0001). During the course of the study, one (zero) on one end and a 10 on the other. No anesthetized subject had a threshold shift surpassing intermediate marks were present. Before the local the 6.10 (84.96 gm) filament. When this occurred, anesthetic was applied, the 5.18 filament was pushed larger filaments were not tested for fear of damaging Otolaryngology - Head and Neck Surgery 372 NOORILY et al. October 1995 2.5 ................................................................................................................................................................................................ .,~ T I [] Lido/oxyI l:::: ~ ] [] Tetra/oxyI l'~ 2. T m .:..:..:.:..;.S'.%'- P < 0.000 Lo ¢""~'~;~,..g.g. 'r" ~:.~:-~'-~ Error bar = ] 0.5 ~,~..:.~..~"///////,//j- 'i""~~.,'-.~y//////.//7~ 'i standard error I .,.,:.;."'~'4'~ i F~!~ °f the mean I 10 70 Time (minutes) Fig. 1. Means(+_SEMlforthechangeinsensationthresholdsasmeasuredbytheSemmes-Weinstein filaments at 10 and 70 minutes after application of either tetra/oxy or Udo/oxy.