JDSA Journal Abstracts

Effects of 0.75% Ropivacaine on Infiltration Anesthesia Assessed by Somatosensory Evoked Potentials in Rats: Addition of Sodium Chondroitin Sulfate to Enhance Anesthetic Effect

Abstract

This study was designed to examine the effects of infiltration anesthesia of 0.75% ropivacaine and 0.75% ropivacaine containing sodium chondroitin sulfate (SCS) assessed by using somatosensory evoked potentials (SEP) in rats.

A bipolar stimulating electrode was inserted into the upper incisor pulp. The tooth pulp was stimulated electrically, and SEP was recorded from the contralateral surface of the skull (Fig. 1). The amplitude of the positive peak to the negative peak of the primary component (|P1–N1|) was measured (Fig. 2). Thirty Wistar male rats were divided into five groups; Group C: 1% SCS, Group L: 2% lidocaine, Group LE: 2% lidocaine containing 1 : 73,000 epinephrine, Group R: 0.75% ropivacaine, Group RC: 0.75% ropivacaine containing 1% SCS (Table 1). 50 μl of each local anesthetic was injected into the palate paraperiosteally.

In Group C, a reduction in % of amplitude of | P1–N1 | was not found. In Group L, the value was significantly greater than the control point up to 30 minutes, in Group LE, the difference was significantly greater for up to 90 minutes, in Group R, up to 40 minutes, and in Group RC, up to 70 minutes (Fig. 3). In comparing the groups, the reduction of | P1–N1 | in Group L was significantly greater than that of Group C from 4 minutes to 20 minutes. The reduction in Group R was significantly greater than that of Group C from just after the injection to 40 minutes. Group LE and Group RC had a significant decrease in amplitude of | P1–N1 | compared to the Group C from just after the injection to 80 minutes. Reduction of | P1–N1 | in Group R was significantly greater than that of Group L just after the injection and again from 4 minutes to 30 minutes. Reductions of | P1–N1 | in Group LE and Group RC were significantly greater than that of Group L from just after the injection to 90 minutes. The reduction of Group LE was significantly greater than that of Group R from 40 minutes to 60 minutes and at 80 minutes. The reduction in Group RC was significantly greater than that of Group R from 40 minutes to 70 minutes. No significant difference was found between Group LE and Group RC (Fig. 3, Table 2). The maximum anesthetic effect was as follows: Group L : Group LE : Group R : Group RC=1 : 1.82 : 1.85 : 1.88 (Fig. 4). The duration of the anesthetic effect was the longest in Group LE at 90 minutes followed by Group RC at 70 minutes, Group R at 40 minutes, and Group L at 30 minutes (Fig. 5).

The results indicate that the maximum infiltration anesthetic effect of 0.75% ropivacaine is similar to that of 2% lidocaine containing 1 : 73,000 epinephrine, but the duration of the effect of 0.75% ropivacaine is as short as 40 minutes. Ropivacaine containing SCS extended the duration similar to the time of 2% lidocaine containing 1 : 73,000 epinephrine. Therefore, ropivacaine containing SCS could be a useful dental local anesthetic.

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Anesthetic Efficacy of Ropivacaine in the Inferior Alveolar Nerve Block Compared to 2% Lidocaine with 1/80,000 Epinephrine

Abstract

Considering inferior alveolar nerve block using 2% lidocaine with 1 : 80,000 epinephrine as the standard anesthesia, the present randomized control study sought to confirm the efficacy of inferior alveolar nerve blocks using ropivacaine, a new amide local anesthetic, in the context of clinical dentistry.

The subject group consisted of 43 healthy volunteers: 14 men and 29 women, average aged, 21.0±2.0 years. Using blocked randomization, one of the following three anesthetics was randomly assigned to perform inferior alveolar nerve blocks: 2% lidocaine with 1 : 80,000 epinephrine (1.8 mL, n = 15, hereinafter referred to as the 2%L group); 0.5% ropivacaine (1.8 mL, n = 12, hereafter referred to as the 0.5%R group); and 1% ropivacaine (1.8 mL, n = 11, hereafter referred to as the 1%R group). The subjects were asked to assess the degree of discomfort associated with inferior alveolar nerve blocks, anesthetic onset (when anesthetic began to work), emergence when anesthetic began to wear off, and length of time before the anesthetic effect had worn off completely. The incidence of lower lip anesthesia was also verified. For up to 120 minutes after injection, an electric pulp tester was used to evaluate the anesthetic effects on each tooth of the subjects. The dental pulp was judged as being anesthetized if no response was observed following application of the maximum stimulus. Chronological changes in the rate of successful pulp anesthesia were examined (cases of pulp anesthesia/total cases).

The results showed no significant differences in degree of discomfort associated with inferior alveolar nerve block, anesthetic onset, or incidence of lower lip anesthesia among the 2%L, 0.5%R, and 1%R groups (Tables 1–3). Chronological changes in the rate of successful pulp anesthesia up to 120 minutes following inferior alveolar nerve blocks were comparable among the three groups (Figures 1–1-7). However, there were significant differences in emergence from anesthesia and duration of anesthesia among the three groups (Tables 4 and 5).

These findings suggest that 0.5% or 1.0% ropivacaine is just as effective a local anesthesia as 2% lidocaine with 1 : 80,000 epinephrine in everyday dental practice with respect to: the degree of discomfort associated with inferior alveolar nerve blocks, incidence of lower lip anesthesia, anesthetic onset, the success rates of anesthesia effects up to 120 minutes after administration, and duration of anesthesia. With respect to the time until the anesthetic effects began to wear off and duration of anesthesia until the anesthetic effect had worn off completely, the anesthetic effects in inferior alveolar nerve blocks appear to last longer in patients administered 0.5% or 1.0% ropivacaine than in patients administered 2% lidocaine with 1 : 80,000 epinephrine.

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Evaluation of Topical Anesthetic Activities of Several Agents Using Starch Wafer Method

Abstract

Application of topical anesthetics shielded by a starch wafer (the starch wafer method) and the conventional application method were compared in terms of degree of pain during needle insertion, occurrence of a bitter taste, and leakage of the agent. A total of 105 subjects (24.5±4.0 years) were enrolled in the study, and 7 commercially available topical anesthetics, Copalon^® (6% tetracaine hydrochloride; K-Solution), Hurricaine^® Gel (20% ethyl aminobenzoate; H-Gel), Beezocaine-Jelly^® (20% ethyl aminobenzoate; B-Jelly), Xylocaine^® Jelly (2% lidocaine hydrochloride; L-Jelly), Xylocaine^® Solution (4%) (4% lidocaine hydrochloride; L-Solution), Pronespasta AROMA^® (10% ethyl aminobenzoate, 1% tetracaine hydrochloride, 1% dibucaine hydrochloride; P-Pasta), and Neo Zalocaine^® Pasta (25% ethyl amino-benzoate, 5% p-butylaminobenzoyl diethyl aminoethyl hydrochloride; N-Pasta) were tested. The following results were obtained: 1) Degree of pain: The starch wafer method (starch wafer group) was significantly more effective for pain control during needle insertion than the conventional method for all agents tested. In the starch wafer group, efficacy was greatest with N-Pasta, followed by H-Gel, L-Solution, P-Pasta, B-Jelly, K-Solution, and L-Jelly. 2) Occurrence of a bitter taste: Only 4 of the 105 subjects (3.8%) in the starch wafer group reported a bitter taste, indicating adequate suppression of bitter taste by the starch wafer method. 3) Leakage: Significant suppression of leakage was noted for all agents in the starch wafer group.

The results of this study showed that the starch wafer method significantly controls pain during needle insertion by preventing leakage of topical anesthetics and ensuring their localization. The starch wafer method was also shown to significantly control pain by preventing leakage of local anesthetics from the site of injection and by ensuring their localization. The present study demonstrated the effectiveness of the starch wafer method in dental treatment and its potential as a novel technique for pain management.

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CCI Model and Local Inflammation: Evaluation of Neuropathic Pain Occurrence

Abstract

Neuropathic pain is a form of intractable pain defined as “pain whose causes are temporary injury to the nervous system and functional abnormalities in the nervous system, or pain induced by these causes” (International Association for the Study of Pain, 1994). Various animal models have been developed to elucidate its pathological conditions. A neuropathic pain model, the CCI model, is prepared by loosely ligating the rat sciatic nerve with a 4-0 chromic gut at 4 points. Although there have been reports suggesting the involvement of neuropathy by mechanical stimulation and inflammatory stimulation by chromic gut, there are many unclarified points regarding the development of neuropathic pain in the CCI model. We histologically evaluated the periphery of the sciatic nerve to clarify the pathogenesis in the CCI model.

After the CCI model was prepared, the behavioral assessment of heat hyperalgesia, the main symptom of neuropathic pain, was performed, and the rats were divided into the groups with and without neuropathic pain (Fig. 1). Both the ligated and sham-treatment sides of the sciatic nerve were extirpated, and the histology of the peripheral tissue was compared.

On the sham-treatment side, histology did not suggest inflammation in either group (Fig. 2). On the ligated side, infiltration of a large number of inflammatory cells (eg, lymphocytes) around the sciatic nerve was observed in the two groups. In addition, infiltration of macrophages/foreign body giant cells and formation of collagen fibers around the chromic gut were observed in the two groups. There were no marked differences in the histological findings between the two groups (Figures 3, 4).

Although it was unclear whether inflammation was caused by secondary changes accompanying mechanical stimulation, or by stimulation by chromic gut in this experiment, we obtained results that the possibility of direct involvement of inflammation in the development of neuropathic pain was low, differing from the reports by Maves and Kajander that suggested the importance of inflammation by the chemical components of chromic gut.

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A New Management Method for Intravenous Sedation with Propofol Using TCI Pump: Evaluation in Volunteers

Abstract

The purpose of this study was to investigate the usefulness of a modified propofol intravenous sedation method with a target controlled infusion (TCI) pump and evaluate the level of sedation with constant verbal stimulation in volunteers.

Methods: Fourteen healthy male volunteers were sedated with intravenous propofol. The sedation level aimed for was a state in which the patient's eyes were closed but they responded to mild verbal commands. The TCI was started after the initial target blood concentration had been set at 2.2 μg/mL (Figure 1). Immediately after the aimed sedation level was recognized during induction, the target blood concentration was manually reset to the same value as the calculated brain (effect-site) concentration displayed at that time (A value). Then the infusion rate was automatically regulated to let the calculated blood concentration follow the target blood concentration. The target blood concentration was manually regulated to maintain sedation level described above during the experiment. The main parameters were 1) the calculated brain concentration of pro-pofol at the time when the sedation level aimed for appeared during induction, 2) the maximum discrepancy between the calculated brain concentration at the sedation level aimed for during induction and the calculated blood concentration during the experiment, and 3) Bispectral index (BIS) value from the beginning of infusion to the end of infusion.

Results: The calculated brain concentration at the sedation level aimed for during induction was 1.69±0.08 μg/mL (mean±SD) and the distribution range was wide, from 1.0 to 2.2 μg/mL (Fig. 2). A maximum discrepancy of less than 0.2 μg/mL occurred in 71% (10/14) of the volunteers (Figure 3). The range of BIS was from 70 to 83 (77.1±3.2) between 5 minutes after the beginning of infusion and the end of infusion.

Conclusion: This method has shown to predict the optimal blood concentration within a small error range, using the calculated brain concentration at the optimal sedation level obtained during induction. Moreover, the maintenance of the calculated blood concentration was easy and reliable because the infusion rate was changed automatically according to a validated pharmacokinetic model. Therefore, this TCI pump method is useful.

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Medical Emergencies Treated in Tokyo Dental College Chiba Hospital

Abstract

The authors retrospectively reviewed 106 medical emergency cases that were managed in the Department of Dental Anesthesiology, Tokyo Dental College Chiba Hospital from April 1996 to March 2003. The incidence of medical emergencies among the outpatients was 0.007% (106/1,508,586). There were more female cases than male cases, and their ages ranged from 1 year 10 months to 74 years old (Figure 1). More than one third (36.7%=39/106) of the medical emergency cases occurred during or immediately after local anesthesia (Figure 2). About one third of the medical emergency cases occurred during oral surgery such as tooth extraction (Figure 3). Medical emergency cases occurred more in the morning than in the afternoon. There was no relationship between the time and the kind of emergency cases (Figure 4). The outpatient clinics of the Department of Oral Surgery and Conservative Dentistry were the two main sources of the medical emergency cases. Others included the outpatient clinics of other departments and other places in the hospital. The Chiba-city Dental Association (Figure 5) represents the medical emergencies introduced by general practitioners belonging to Chiba-city Dental Association. Most of the medical emergency cases were mild, such as vasovagal reactions or hyperventilation. Others included accidental ingestion and aspiration, blood pressure elevation, and drug hypersensitivity. In contrast, a few critical cases did occur: acute asthmatic episode occurred after taking diclofenac sodium in a patient who underwent cyst enucleation. The patient lost consciousness and became cyanotic. We intubated and transported the patient to the emergency hospital. Fifteen days later, the patient died because of acute cardiac failure (Figure 6).

Most emergency cases occurred unforeseen, independent of previous diseases and anamnesis. There was no difference between the incidences of our previous report and the present report including critical cases. These results suggest that medical emergencies could occur at anytime in the dental practice. Thus, it is important that the emergency care system be established in order to be able to respond quickly to medical emergency crises.

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Systematic Desensitization in a Patient with Severe Dental Phobia

Abstract

It is said that dental phobia is a conditional response caused by the sensitization of psychological anxiety and fear of dental procedures. We tried intravenous sedation, general anesthesia, and systematic desensitization regarding dental treatment in a patient with severe dental phobia.

The patient was an 18-year-old woman who was referred to our clinic from a local dental clinic. Her main complaint was the inability to receive dental treatment because of excessive phobia about local anesthetic injection. She had had dental needle phobia for more than 10 years. First, intravenous sedation with propofol was selected to reduce her fear. However, she was afraid of venipuncture and stubbornly resisted local anesthetic injection, so bolus administration of propofol was repeated several times, resulting in loss of consciousness. Next, tooth extraction under general anesthesia with sevoflurane was scheduled. She was emotionally very unstable and increasingly distraught over the impending general anesthesia as she was getting closer to the entrance of the operating room. Intermittent intravenous administration of midazolam (total dose: 6 mg) was required to assuage her fear while she was transported from her ward to the operating room. This experience with intravenous sedation and general anesthesia further aggravated her phobia.

We noticed that deep sedation and amnesia induced with sedative and hypnotic drugs during general anesthesia interfered with her memory of successful experience, and it was necessary to maintain communication with her under light sedation through conversation for accumulation of repeated learning. Accordingly, the principle of systemic management was changed to a systematic desensitization based on behavioral modification. The TSD (Tell Show Do) method is a modified systematic desensitization method used in dentistry, especially in pediatric and handicapped patients. We applied the TSD method with simulation facility and image training using a cartridge-type injector provided with a cap. As the intensity of psychological stress gradually increased, she got accustomed to local anesthetic injections.

Approximately one year after her first visit, she overcame dental phobia and accepted dental procedures without resistance. Our experience suggests the importance of the psychological approach in the case of dental phobia.

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The Examination of Sore Throat after Mandibular Osteotomy for Prognathism: The Effect of Lidocaine Gargle before Induction of Anesthesia

Abstract

We examined the effect of lidocaine gargle before induction of anesthesia and the effect of the frequency of sore throat in patients who were operated on mandibular osteotomy for prognathism. There were 60 surgical patients (ASA 1–2, 15 male and 45 female) under general anesthesia using nitrous oxide, fentanyl, and pro-pofol. The patients were divided into the Lidocaine gargle group and the Non-lidocaine gargle group (30 patients each). In the Lidocaine gargle group, 5 mL of 2% lidocaine viscous were gargled before induction of anesthesia. In the Non-lidocaine gargle group, 2% lidocaine viscous were not gargled. The results of examining both groups were compared retrospectively. There were no demographic differences among the patients, such as gender, age, weight, height, or BMI (Table 1). There were no differences in duration of surgery and anesthesia or the time to endotracheal intubation during anesthesia induction (Table 2). The internal diameter size of the nasal endotracheal tube selected tended to be narrower in the Lidocaine gargle group than in the Non-lidocaine group, but there were no significant differences between both groups (Table 3). The cuff volume of nasal endotracheal tube in the Lidocaine gargle group (3.8 mL) was significantly less than in the Non-lidocaine gargle group (4.7 mL) (P = 0.0009). Sore throat was observed in 50% of the Lidocaine gargle group (15/30) and in 70% of the Non-lidocaine gargle group (21/30), but the difference between the two groups was not significant (Table 4). Hoarseness was observed in only one case in the Non-lidocaine gargle group (Table 4).

In conclusion, it is suggested that neither topical anesthesia on mucous membrane using gargled lidocaine before induction of anesthesia nor the cuff volume of the nasal endotracheal tube affect the occurrence of sore throat after mandibular osteotomy for prognathism.

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A Questionnaire Study of Clinical Training of Inferior Alveolar Nerve Blocks

Abstract

A survey was conducted on the clinical training of local anesthesia in Japanese dental colleges. The questions included: 1) Whether clinical training of local anesthesia was conducted, 2) The content of the training of local anesthesia, 3) The technique of inferior alveolar nerve blocks, 4) Complications during the training, 5) Procedures for dealing with complications. Replies were obtained from 28 schools. Local anesthesia training was provided in 25 schools. In 18 schools, the department of dental anesthesiology was responsible for the training.

The results were analyzed based on the data obtained from these 18 schools. In 16 schools, both infiltration and inferior alveolar nerve block were taught, whereas in the other 2 schools, only inferior alveolar nerve block was taught. With respect to the nerve block technique, the direct approach was employed in 12 schools, the indirect approach using three steps was taught in 4 schools, and the indirect approach of two steps was taught in one school. In one school, both direct and indirect approaches were employed. 20 cases of complications were reported by 13 schools (Table 1); 4 general complication cases were reported, including 2 cases of feeling of unwellness, one case of hyperventilation, and one case of vasodepressor syncope; 16 localized complication cases were reported, including 8 cases of hypesthesia of lingual or mental nerve, 4 cases of trismus, one case of facial palsy, one case of inflammation of pterygomandibular space, one case of hematoma formation, and one case of ear division discomfort. Hypesthesia occurred in 6 indirect approach cases and in 2 direct approach cases. Trismus was observed in all the direct approach cases. As for the treatment of the complications, 4 cases of hypesthesia were described in detail as shown in Table 2. In these cases, the treatments applied were stellate ganglion blocks, irradiation of infrared ray, and administration of drugs. Hypesthesia disappeared within 2 to 6 weeks in all cases. Of the remaining 4 cases, only drugs were administered in one case, hypesthesia disappeared without any treatment in the other 3 cases. Prior to the treatment, written or verbal informed consent of agreement was obtained in 7 schools, but it was not obtained in 11 schools. In one school, students lacking confidence were excluded from clinical training, and in one school, the training was carried out only on mannequins. As a measure of safety, the staffs have reported the complications to the student office or person in charge in 9 schools, and insurance procedures were followed in 3 schools. The cost for treatment was borne by the school or the hospital in affiliation in 9 schools and by the insurance in 3 schools.

This study indicates that in the practice of local anesthesia, the safe technique of inferior nerve block should be established and that written consent in case of complications should be obtained before the training. It is also necessary to establish effective procedures for dealing with complications.

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