he inferior alveolar nerve block does not always result the anesthetic agent to diffuse effectively into the nerve.5

Transcription

1 An Evaluation of Lidocaine Hydrocarbonate Compared with Lidocaine Hydrochloride for Inferior Alveolar Nerve Block Michael A. Chaney, DDS,* Ronald Kerby, DDS,t Al Reader, DDS, MS,* F. Michael Beck, DDS, MA,:t William J. Meyers, DMD, MEd,* and Joel Weaver, DDS, PhD *Department of Endodontics, tdepartment of Restorative Dentistry, -tdepartment of Diagnostic Services, and Department of Oral and Maxillofacial Surgery, The Ohio State University, Columbus, Ohio The purpose of this study was to measure the degree of anesthesia obtained with 2.2% lidocaine hydrocarbonate, 2.2% lidocaine hydrocarbonate with 1:1, epinephrine, and 2% lidocaine hydrochloride with 1: 1, epinephrine for inferior alveolar nerve block. Using a repeated-measures design, 3 subjects randomly received an inferior alveolar injection of each solution over the course of three successive appointments. The first molar, first premolar, lateral incisor, and contralateral canine (control) were blindly tested with an Analytic Technology pulp tester at 3-min cycles for 6 min. Anesthetic success was defined as no subject response to the maximum output (8 reading) of the pulp tester within 16 min and maintenance of this reading for the remainder of the testing period. Although subjects felt numb subjectively, anesthetic success as defined here ranged from 3% to 1% for the plain lidocaine hydrocarbonate; for the lidocaine hydrocarbonate and lidocaine hydrochloride solutions with epinephrine, success ranged from 37% to 63%. We conclude that 2.2% lidocaine hydrocarbonate without vasoconstrictor is not as effective as the other two preparations for inferior alveolar nerve block. The 2.2% lidocaine hydrocarbonate with epinephrine and 2% Received November 12, 1991; accepted for publication January 27, Address correspondence to Dr. Al Reader, Department of Endodontics, College of Dentistry, The Ohio State University, 35 W. 12th Avenue, Columbus, OH This article was adapted from a research project submitted by Dr. Chaney in partial fulfillment of the requirements for certification in endodontics at The Ohio State University. This study was supported by research funding from the J. David Brilliant Memorial Fund, Ohio Association of Endodontists by the American Dental Society of Anesthesiology lidocaine hydrochloride with epinephrine preparations are equivalent for inferior alveolar nerve block of 6-min duration. he inferior alveolar nerve block does not always result in successful pulpal anesthesia.1-4 Although many reasons have been cited for this failure (including accessory innervation, cross-innervation, and inaccurate location), perhaps another reason may be the inability of the anesthetic agent to diffuse effectively into the nerve.5 Carbonated anesthetic solutions may provide more effective anesthesia by trapping the anesthetic within the nerve,6 and studies7'- have demonstrated a synergistic relationship between carbon dioxide (CO2) and local anesthetics. CO2 also has been shown to have a direct depressant action on nerves. 12 Theoretically, carbonated anesthetic preparations would result in a quicker onset and a greater intensity and extent of anesthesia than current preparations. However, controversy exists on the claimed superiority of carbonated local anesthetics. l Gupta et a113 subjectively evaluated carbonated lidocaine in surgical procedures and found an increased rate of onset and duration compared with noncarbonated solutions. There have been no objective studies, using standardized stimuli, of carbonated lidocaine in dentistry. The purpose ofthis study was to measure the degree of anesthesia obtained with 2.2% lidocaine hydrocarbonate and 2.2% lidocaine hydrocarbonate with 1: 1, epinephrine as compared with 2% lidocaine hydrochloride with 1: 1, epinephrine after inferior alveolar nerve block. METHODS Thirty adult male subjects, ranging in age from 22 to 41 yr and with an average age of 28 yr, participated in this ISSN 3-36/91/$5. 212

2 study. The subjects were in good health and were not taking any medications that would alter pain perception. The study was approved by The Ohio State University Human Subjects Review Committee, and written informed consent was obtained from each subject. Sixteen mandibular left and 14 right sides were tested, with the first molar, first premolar, and lateral incisor chosen as the test teeth. The contralateral canine was used as the unanesthetized control to ensure that the pulp tester was operating properly and the subject would respond during the experiment. Clinical examinations indicated that all teeth were free of caries, large restorations, and periodontal disease and that none had a history of trauma or sensitivity. Using a repeated-measures design, each subject randomly received each anesthetic solution over a course of three successive appointments spaced at least 1 wk apart. The anesthetic solutions tested were (A) 1.8 ml of 2.2% lidocaine hydrocarbonate (Xylocaine CO2; Astra Pharmaceutical Products, Inc., Worchester, MA); (B) 1.8 ml of 2.2% lidocaine hydrocarbonate with 1: 1, epinephrine; and (C) 1.8 ml of 2% lidocaine hydrochloride (Xylocaine; Astra) with 1:1, epinephrine. Each subject was randomly assigned to one of six letter (ABC) combinations to determine the sequence of solution administration. The 2.2% lidocaine hydrocarbonate solution was prepared by slowly drawing 1.8 ml of the hydrocarbonate solution (ph = 6.6; PCO2 value was approximately 267 mm Hg) from a 5-mL vial into a 3-cc Luer-Lok syringe (Becton, Dickinson, and Co., Rutherford, NJ) using an 18-gauge needle. The 18-gauge needle was replaced with a 27-gauge, 1 1/2 inch needle (Monoject, Sherwood Medical, St. Louis, MO) prior to injection. The 2.2% lidocaine hydrocarbonate with epinephrine solution was prepared in an identical manner, and 18 /.L of epinephrine (1:1 solution with a ph of 3.1; Elkins-Sinn, Inc., Cherry Hill, NJ) was added using a Hamilton Syringe (Microliter Syringe 71-N, Hamilton Co., Reno, NV). The 2% lidocaine hydrochloride solution was prepared by diluting.9 ml of 4% lidocaine HCl (ph = 6.2; PCO2 value was approximately 3 mm Hg) with an equal amount of sterile saline solution (.9% sodium chloride injectable, Abbott Labs, North Chicago, IL) in a 3-cc Leur-Lok syringe. Eighteen /L of epinephrine was then added to the syringe. Following all preparations, the solution was mixed by gently inverting the syringe for 1 sec. Each vial of hydrocarbonate, hydrochloride, saline, and epinephrine was used only once. Each syringe was taped and coded with a four-digit random number that corresponded to the anesthetic letter designation. After solution preparation, sample volumes were tested (Orion 61; Orion Research Inc., Boston, MA) to ensure that the solutions were within a ph of 6.1 to 7.. This Chaney et al 213 would be important with the hydrocarbonate solution as a broken seal would affect the CO2 content. No variations were recorded. All injections were given within 3 min of solution preparation. At each appointment prior to injection, the experimental teeth and control canine were tested three times with an Analytic Technology pulp tester (Analytic Technology Corp., Redmond, WA) to record baseline vitality. Following isolation with cotton rolls and drying with gauze, toothpaste was applied to the probe tip, which was placed midway between the gingival margin and the occusal edge. The current rate was set to increase from no output () to the maximum output of 8 in 25 sec. The number at initial sensation was recorded. Soft tissue responsiveness labial and lingual to the canine and buccal to the first molar was tested by sticking the alveolar mucosa with a sharp explorer. All pre- and postinjection tests were performed by trained personnel who were blinded to the solutions administered. For all injections, a standard inferior alveolar nerve block, as described by Jorgensen and Hayden,14 was administered with a 27-gauge 1 1/2-inch needle (Monoject; Sherwood Medical, St. Louis, MO). After reaching the target area and performing aspiration, the solution was deposited over a period of 2 min. At 1 min postinjection, the first molar was pulp tested, and alveolar mucosal sticks were performed. At 2 min, the first premolar and lateral incisor were tested. At 3 min, the control canine was tested, and the subject asked if the lip and tongue were numb. This cycle of testing was repeated every 3 min. If lip numbness was not recorded within 2 min, the block was considered missed, and reinjection took place at least a week later. All testing was stopped at 6 min postinjection. Lip and tongue anesthesia were considered successful when the subject felt subjectively numb within 2 min. Lip, tongue, and buccal anesthesia were considered successful when two consecutive negative responses (no feeling of pain) to mucosal sticks were recorded. The onset of lip anesthesia occurred at the first of two consecutive positive (feeling numb) or negative (no feeling of pain with mucosal sticks) responses. A lack of subject response to the maximum output (8 reading) of the pulp tester was used to indicate complete pulpal anesthesia. The onset of pulpal anesthesia occurred at the first of two consecutive 8 readings. Anesthesia was considered successful when an 8 reading was obtained within 16 min and this reading was sustained for the remainder of the 6-min test period. Anesthesia was considered a failure if the subject never achieved two consecutive 8 readings during the 6-min test period. Anesthesia was of slow onset if the subject achieved two consecutive 8 readings after 16 min. Anesthesia was of short duration when the

3 214 Carbonated Lidocaine Anesth Prog 38: Table 1. Number and Percentages of Subjects Who Experienced Subjective Lip and Tongue Anesthesia Drug Solution Lip Tongue A-HCO2 3 (1) 27 (9) B-HCO2 (1:1,) 3 (1) 25 (83) C-HCl (1: 1,) 3 (1) 28 (93) subject achieved two consecutive 8 readings, lost this reading, and never regained it during the 6-min period. Onset times were analyzed using a one-way repeated measures analysis of variance. Anesthetic success and failure, and incidence of pulpal anesthesia, were analyzed nonparametrically using Bonferroni-adjusted McNemar tests. Comparisons were considered significant at P <.5. RESULTS One hundred percent of the subjects had subjective lip numbness and 83% to 93% had tongue numbness (Table 1). Mental and lingual anesthesia, as evaluated by mucosal sticks, occurred in 83% to 97% of subjects, and buccal anesthesia ranged from 23% to 63% (Table 2). The mean baseline pulp test readings were as follows: first molar, 38; first premolar, 34; lateral incisor, 3; and control canine, 35. All control canines responded positively during the experiment, and the pulp test readings were uniformly within 5 points of baseline readings over the 6 min. The mean onset time of lip anesthesia is shown in Table 3. The mean onset time of pulpal anesthesia for each experimental tooth is shown in Table 4. There were no significant differences in onset among the solutions. Anesthetic success, failure, slow onset, and short duration, and significant differences are presented in Table 5. For all subjects with anesthetic failure, the mean elevation of pulp test readings (for the 6 min) above baseline readings were as follows: first molar, 8 points; first premolar, 7 points; lateral incisor, 1 points. The incidence of pulpal anesthesia and significant differences are presented in Figures 1, 2, and 3. The highest incidences for lidocaine hydrocarbonate plain, lidocaine Table 2. Number and Percentages of Subjects Who Experienced Soft Tissue Anesthesia to Mucosal Probing ~~Drug ~Probing Area Drug Solution Mental Lingual Buccal A-HCO2 25 (83%) 25 (83%) 7 (23%) B-HCO2 (1:1,) 28 (93%) 27 (9%) 19 (63%) C-HCl (1:1,) 29 (97%) 28 (93%) 14 (47%) Table 3. Mean Onset of Lip Anesthesiaa Drug Patient Response Mucosal Sticks Solution (min) (min) A-HCO ± ±.8 B-HCO2 (1: 1,) 4.6 ± ±+ 1.2 C-HCI (1:1,) 4.7 ± ±+ 1.5 There were no significant differences among the solutions (P >.5). a Values are the mean +± SE. hydrocarbonate with epinephrine, and lidocaine hydrochloride with epinephrine, respectively by tooth, were as follows: first molar, 4%, 73%, and 77%; first premolar, 57%, 8%, and 83%; lateral incisor, 4%, 47%, and 63%. DISCUSSION The 1% incidence of lip numbness (Table 1) indicated that the inferior alveolar nerve block was "clinically successful." There also was a fairly high incidence of anesthesia with the mental and lingual mucosal sticks (Table 2). Figures 1, 2, and 3 demonstrate a lower incidence of pulpal anesthesia; therefore, lip numbness and negative mucosal responses did not always indicate onset or guarantee successful pulpal anesthesia as defined in this study. Experimentally, the 8 reading standard for pulpal anesthesia is an endpoint that can be used to measure complete anesthesia over time. This approach allows comparisons of anesthetic solutions without the clinical variations of depth of cavity preparation, tooth location, or procedure. The 8 reading is a rigorous definition of pulpal anesthesia. Clinically, the 8 reading will provide complete pulpal anesthesia in asymptomatic vital teeth.15 However, readings less than 8 may provide clinical anesthesia, and this would depend on the type of procedure preformed, the tooth involved, and the requirements for complete pulpal anesthesia. Therefore, the results presented in this study may not reflect clinical success or failure. Buccal mucosal sticks (Table 2) indicated that some degree of anesthesia may be obtained with only the stan- Table 4. Mean Onset Time of Pulpal Anesthesiaa First First Lateral Drug Molar Premolar Incisor Solution (min) (min) (min) A-HCO ± B-HCO2 (1:1,) 8.8 ± ±+ 5.6 C-HCl (1: 1,) 8.2 +± ± ±+ 2.4 There were no significant differences among the solutions (P >.5). Values are the mean ±+ SE.

4 Table 5. Number and Percentages of Subjects Who Experienced Anesthetic Success, Anesthetic Failure, Slow Onset of Anesthesia, and Anesthesia of Short Duration First First Lateral Drug Solution Molar Premolar Incisor Anesthetic success A-HCO2 1 (3%) 3 (1%) 2 (7%)a B-HCO2 (1:1,) 17 (57%) 16 (53%) 11(37%) C-HCI (1:1,) 17 (57%) 19 (63%) 13 (43%) Anesthetic failure A-HCO2 15 (5%)a 12 (4%) 17 (57%) B-HCO2 (1:1,) 5 (17%) 4 (13%) 16 (53%) C-HCl (1:1,) 6 (2%) 5 (17%) 11(37%) Slow onset of anesthesia A-HCO2 3 (1%) 3 (1%) 2 (7%) B-HCO2 (1:1,) 5 (17%) 7 (23%) 3 (1%) C-HCl (1:1,) 5 (17%) 6 (2%) 6 (2%) Anesthesia of short duration A-HCO2 11 (37%)a 14 (47%)a 11 (37%)a B-HCO2 (1:1,) 3 (1%) 3 (1%) (%) C-HCl (1:1,) 1 (3%) (%) (%) Denotes significant difference from other two anesthetic solutions (P <.5). dard inferior alveolar injection, which agrees with previous studies.2-4 The lower incidence with the plain hydrocarbonate solution is probably related to a decreased effectiveness. The onset of lip anesthesia did not vary significantly among the test solutions (Table 3). The onset of pulpal anesthesia was not significantly different either (Table. Although the plain hydrocarbonate solution appears to have a quicker onset, subjects with anesthetic failure (Ta- Figure 1. Incidence of first molar anesthesia as determined by lack of response to electrical pulp testing at the maximal setting (percentage of 8/8's) at each postinjection time interval, for the three solutions. There were no significant differences (P>.5) between the solutions with epinephrine at any time interval. Significant differences (P <.5) between HCO2 and HCO2 (1: 1,), and between HCO2 and HCl (1:1,), are marked, respectively, with t and *. CD co co co ) (U C4- U C. 1 '1 Chaney et al A = 2.2% Lldocaine HCO2 * = 2% Lidocaine HCI a = 2.2% Lldocaine HCO2 (1:1, Epi) (1-1nnnnnf Fni, ob 75 GO co 5 CO (U O. 25 U I. I. I Figure 2. Incidence of first premolar anesthesia as determined by lack of response to electrical pulp testing at the maximal setting (percentage of 8/8's) at each postinjection time interval, for the three solutions. There were no significant differences (P >.5) between the solutions with epinephrine at any time interval. Significant differences (P <.5) between HCO2 and HCO2 (1: 1,), and between HCO2 and HCI (1: 1,), are marked, respectively, with t and * ble 5) were excluded from the onset times analysis, and this may account for the lack of statistical difference. Instances of slow onset of anesthesia (Table 5) also would increase the mean time of onset. These cases of slow onset indicate that a waiting period of even 16 min after an inferior alveolar injection may not guarantee complete pulpal anesthesia. Clinically, pulp testing vital teeth would provide a measure of pulpal anesthesia onset. Figure 3. Incidence of lateral incisor anesthesia as determined by lack of response to electrical pulp testing at the maximal sefting (percentage of 8/8's) at each postinjection time interval, for the three solutions. There were no significant differences (P >.5) between the solutions with epinephrine at any time interval. Significant differences (P <.5) between HCO2 and HCO2 (1: 1,), and between HCO2 and HCl (1: 1,) are marked, respectively, with t and *.. I b Go co c (-- C) s.,

5 216 Carbonated Lidocaine Anesth Prog 38: The plain hydrocarbonate solution had a low incidence of anesthetic success (Table 5). This may be due to the inherent vasodilatory effect of plain lidocaine combined with the vasodilatory effect of CO2. When comparing the plain hydrocarbonate with the other solutions, statistical differences were shown for anesthetic success, failure (except the lateral incisor), short duration, and incidence (Table 5, Figures 1-3). Therefore, a hydrocarbonate solution without epinephrine may not provide effective pulpal anesthesia. The results (Table 5) with the lidocaine hydrochloride (1: 1,) were similar to the findings of previous studies.3,4 Theories for inadequate anesthesia with the inferior alveolar nerve block (accessory innervation, crossinnervation, central core theory) and clinical solutions to these problems are discussed by Vreeland et al.3 There were no statistical differences between lidocaine hydrocarbonate and lidocaine hydrochloride, both with epinephrine, in any of the parameters measured (Tables 4, and 5 and Figures 1-3). Therefore, we did not confirm the superiority of carbonated solutions as found in previous studies. 11,13 In medicine, large volumes of carbonated lidocaine have been used for epidural, caudal, and brachial plexus blocks. 1 It may be that an increased amount of the hydrocarbonate, or an increased carbon dioxide content, would result in better anesthesia with the inferior alveolar injection. Hydrocarbonate solutions have not been approved by the Food and Drug Administration for use in the United States but are available in Canada. Whether they will be marketed in the future must await further research. CONCLUSIONS Concerning the anesthetic efficacy obtained with 2.2% lidocaine hydrocarbonate, 2.2% lidocaine hydrocarbonate (1: 1, epinephrine), and 2% lidocaine hydrochloride (1: 1, epinephrine) in inferior alveolar nerve blocks of 6-min duration, the following conclusions were reached: 1. Lip numbness and negative response to mucosal probing may not indicate onset or complete pulpal anesthesia as measured by the electric pulp tester in this study. 2. Plain 2.2% lidocaine hydrocarbonate was not as effective as the other two preparations in providing complete pulpal anesthesia. 3. The 2.2% lidocaine hydrocarbonate with 1: 1, epinephrine solution and 2% lidocaine hydrochloride with 1: 1, epinephrine solution were equivalent in blocking the inferior alveolar nerve. ACKNOWLEDGMENT The authors thank Dr. Joe Oakley and Astra Pharmaceutical Products for their invaluable help during the study and for supplying the hydrocarbonate solutions. REFERENCES 1. Kaufman E, Weinstein P, Milgrom P: Difficulties in achieving local anesthesia. J Am Dent Assoc 1984;18: Agren E, Danielsson K: Conduction block analgesia in the mandible. Swed Dent J 1981;5: Vreeland DL, Reader A, Beck M, Meyers W, Weaver J: An evaluation of volumes and concentrations of lidocaine in human inferior alveolar nerve block. J Endod 1989;15: Hinkley SA, Reader A, Beck M, Meyers WJ: An evaluation of 4% prilocaine with 1:2, epinephrine and 2% mepivacaine with 1: 2, levonordefrin compared to 2% lidocaine with 1: 1, epinephrine for inferior alveolar nerve block. Anesth Prog 1991;38: Strichartz G: Molecular mechanisms of nerve block by local anesthetics. Anesthesiology 1976;45: Catchlove RFH: The influence of CO2 and ph on local anesthetic action. J Pharmacol Exp Ther 1972;181: Condouris GA, Shakalis A: Potentiation of the nerve depressant effects of local anesthetics by carbon dioxide. Nature 1964;24: Catchlove RFH: Potentiation of two different local anaesthetics by carbon dioxide. Br J Anaesth 1973;45: Gissen AJ, Covino BG, Gregus J: Differential sensitivity of fast and slow fibers in mammalian nerve. IV. Effect of carbonation of local anesthetics. Reg Anesth 1985;1: Bokesch PM, Raymond SA, Strichartz GR: Depedence of lidocaine potency on ph and PCO2. Anesth Analg 1987;66: Bromage PR, Nickel PM, Winnie AP, Sukhani R: Local anesthetics: The carbonation controversy. Int Anesth Res Soc 1986; Necheles H, Gerard RW: The effect of carbon dioxide on nerve. Am J Physiol 193;93: Gupta YK, Doval DC, Nath C, Saimbi CS, Saxena RC: Evaluation of carbonated solution of Xylocaine as local anaesthetic. Indian J Med Res 1982;75: Jorgensen NB, Hayden J Jr: Sedation, Local and General Anesthesia in Dentistry, 2nd ed. Philadelphia, Lea & Febiger, 1967: Dreven LJ, Reader A, Beck FM, Meyers WJ, Weaver J: An evaluation of an electric pulp tester as a measure of analgesia in human vital teeth. J Endod 1987;13: