Anesthetic Efficacy of a Combination of Hyaluronidase: MATERIALS AND METHODS

In: Anesthesia

29 Dec 2009

Thirty adult subjects participated in this study. The subjects were in good health and were not taking any medications that would alter pain perception. The Ohio State University Human Subjects Review Committee approved the study, and written informed consent was obtained from each subject.

Equal numbers of mandibular right and left sides were tested, with the first and second molars, first and second premolars, and lateral and central incisors chosen as the test teeth. The contralateral canine was used as the unanesthetized control to ensure that the pulp tester was operating properly and that the subject was responding appropriately during the experiment. Clinical examinations indicated that all teeth were free of caries, large restorations, and periodontal disease; none had histories of trauma or sensitivity.
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Two appointments at least 1 week apart were scheduled for each of the 30 subjects. Through use of a repeated-measures design, each subject randomly received an IAN block at each of 2 successive appointments. The injections were an IAN block using a solution of buffered lidocaine with epinephrine and a solution of buffered lidocaine with epinephrine plus hyaluronidase. Before the experiment, the two anesthetic solutions were randomly assigned 5-digit numbers from a random number table. Each subject was randomly assigned to 1 of the 2 solutions to determine the sequence of the injections. Only the random numbers were recorded on the data collection and postoperative survey sheets to blind the experiment.

At the beginning of each appointment and before any injections were given, the experimental teeth and control contralateral canine were tested 3 times with the pulp tester (Analytic Technology Corp, Redmond, Wash) to record baseline vitality. After the tooth to be tested was isolated with cotton rolls and dried with gauze, toothpaste was applied to the probe tip, which was then placed midway between the gingival margin and the occlusal/incisal edge of the tooth. The current rate was set at 25 seconds to increase from no output (0) to the maximum output (80). The number associated with the initial sensation was recorded. Trained personnel, blinded to the anesthetic solutions, administered all preinjection and postinjection tests.

The anesthetic solutions were prepared as follows. Under sterile conditions, 0.1 mL of 1:1000 epinephrine (American Regent Laboratories, Inc, Shirley, NY) was withdrawn from a 1-mL ampule using a 1-mL tuberculin syringe and added to a 10-mL single-dose ampule of plain 2% lidocaine (Abbott Laboratories, North Chicago, 111). This produced a final concentration of 1: 100,000 epinephrine. The ampule was inverted 20 times to mix the solutions. One and two-tenths milliliters of the solution were drawn from the ampule and placed in a 3-cm3 Leur-Lok syringe. The 1.2-mL volume of solution contained 24 mg of lidocaine and 12 |xg of epinephrine. Because higher success rates have been observed with a buffered hyaluronidase solution, 0.6 mL of sodium bicarbonate was drawn from a vial containing 50 mL of 8.4% sodium bicarbonate (Abbott Laboratories) using a 1-mL tuberculin syringe. The 0.6 mL of the sodium bicarbonate was added to the lidocaine solution (24 mg of lidocaine and 12 |xg of epinephrine) to produce a final volume of 1.8 mL buffered with 0.33 mEq/mL of sodium bicarbonate. For the lidocaine/hy-aluronidase solution, a 1-mL vial containing 150 USP units of lyophilized hyaluronidase (Wydase, Wyeth Laboratories, Philadelphia, Pa) was added to the lidocaine with epinephrine solution. The lyophilized form was used in order to not change the volume of the solution injected. The anesthetic solutions administered were blinded by masking the Leur-Lok syringes containing the anesthetic solutions with white, opaque tape and labeling the syringes with random 5-digit numbers. The opaque tape did not cover the syringe area next to the needle attachment, which allowed evaluation of aspiration during the IAN blocks. Sample solutions of each anesthetic solution were tested to determine pH values using an Orion pH meter (Orion Research Inc, Boston, Mass).
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Because hyaluronidase may cause a hypersensitivity reaction, each subject received a preliminary mucosal test. The mucosa just inside the vermillion border of the lip was injected with approximately 0.2 mL of a freshly prepared test solution the subjects were to receive at that appointment. Therefore, only half the injections contained hyaluronidase. The contralateral lip was used in order to not interfere with determining lip numbness from the IAN block. Each subject was observed for 5 to 10 minutes to see if a positive reaction consisting of a wheal with pseudopods developed. The site was also checked at the end of the appointment. No patient had a positive reaction.

The standard IAN block was administered with a 27-gauge 1 ^-inch needle (Monoject; Sherwood Medical, St Louis, Mo) using each of the anesthetic solutions. After the target area was reached and aspiration was performed, 1 minute was used to deposit the anesthetic solution and the subject was asked to rate the pain of solution deposition. The pain scale was from 0 to 3. Zero indicated no pain. One indicated mild pain, pain that was recognizable but not discomforting. Two indicated moderate pain, pain that was discomforting but bearable. Three indicated severe pain, pain that caused considerable discomfort and was difficult to bear.
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At 1 minute after the IAN block, the first and second molars were pulp tested. At 2 minutes, the first and second premolars were tested. At 3 minutes, the central and lateral incisors were tested. At 4 minutes, the control canine was tested. This cycle of testing was repeated every 4 minutes. At every fourth cycle, the control tooth, ie, the contralateral canine, was tested by a pulp tester without batteries to test the reliability of the subject. Each subject was asked if his or her lip/tongue were numb every minute for 5 minutes and at every fourth minute during pulp testing. If profound lip numbness was not recorded within 20 minutes, the block was considered unsuccessful; the subject was then reappointed. Two IAN blocks were unsuccessful in this study and these subjects required an additional appointment. All testing was stopped at 60 minutes postinjection.

All subjects completed postinjection surveys after each IAN block administered. The subjects rated pain in the injection area, using the previous pain scale (none, mild, moderate, severe), immediately after the numbness wore off and again each morning upon arising for 3 days. The subjects also recorded any other problems such as difficulty in opening.

No response from the subject at the maximum output (80 reading) of the pulp tester was used as the criterion for pulpal anesthesia. Anesthesia was considered successful when 2 consecutive 80 readings were obtained. Anesthesia was considered a failure if the subject never achieved 2 consecutive 80 readings.
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Comparisons between the buffered lidocaine solution and the buffered lidocaine plus hyaluronidase solution for anesthetic success and incidence of trismus were analyzed nonparametrically using Bonferroni-adjusted McNemar tests. Between-group comparisons on solution deposition discomfort and postinjection discomfort were made using Bonferroni-adjusted Wilcoxon, matched-pairs, signed-ranks test. Comparisons were considered significant at P < .05.

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