The Efficacy of Two Different Concentrations of Local Anaesthetic on Pain in Mandibular Third Molar Surgery

@#Mepivacaine is a common local anaesthetic used with claims of a high safety profile. There are two commercial types, 2% mepivacaine with vasoconstrictor and 3% without vasoconstrictor. There are many suggestions regarding the usage of plain 3% without vasoconstrictor for systemic medical problems, however, there have not been any previous studies to confirm this necessity in impacted lower third molar surgery (ILTMS). This study aims to evaluate the anaesthetic efficiency and the effect on the patient of 2% and 3% mepivacaine, adding vasoconstrictor to the 3% mepivacaine. This crossover study comprised of 24 patients with bilateral, symmetrically positioned, impacted lower third molars. Patients received either 2% or 3% mepivacaine for the inferior alveolar nerve block (IANB). Onset and duration of anaesthesia, and haemodynamic considerations were analysed as primary outcomes. Furthermore, pain, duration of postoperative anaesthesia and pulp vitality were analysed as secondary outcomes. Different concentrations of mepivacaine showed similar anaesthetic onset time (p > 0.05). There was no statistically significant difference regarding the duration of anaesthesia, as well as the postoperative analgesia (p > 0.05). The two concentrations did not lead to any haemodynamic changes or complications during ILTMS. Thus, adding the vasoconstrictor to mepivacaine 3% did not cause any adverse effects on the patients intra or postoperatively. Therefore, it is possible for dentists to use only 2% mepivacaine with vasoconstrictor for IANB effectively and safely when the case necessitates the need for a vasoconstrictor, or in other words, longer duration of haemostasis.

Mepivacaine-induced intracellular calcium increase appears to be mediated primarily by calcium influx in rat aorta without endothelium / 대한마취과학회지

BACKGROUND: Mepivacaine induces contraction or decreased blood flow both in vivo and in vitro. Vasoconstriction is associated with an increase in the intracellular calcium concentration ([Ca2+]i). However, the mechanism responsible for the mepivacaine-evoked [Ca2+]i increase remains to be determined. Therefore, the objective of this in vitro study was to examine the mechanism responsible for the mepivacaine-evoked [Ca2+]i increment in isolated rat aorta. METHODS: Isometric tension was measured in isolated rat aorta without endothelium. In addition, fura-2 loaded aortic muscle strips were illuminated alternately (48 Hz) at two excitation wavelengths (340 and 380 nm). The ratio of F340 to F380 (F340/F380) was regarded as an amount of [Ca2+]i. We investigated the effects of nifedipine, 2-aminoethoxydiphenylborate (2-APB), gadolinium chloride hexahydrate (Gd3+), low calcium level and Krebs solution without calcium on the mepivacaine-evoked contraction in isolated rat aorta and on the mepivacaine-evoked [Ca2+]i increment in fura-2 loaded aortic strips. We assessed the effect of verapamil on the mepivacaine-evoked [Ca2+]i increment. RESULTS: Mepivacaine produced vasoconstriction and increased [Ca2+]i. Nifedipine, 2-APB and low calcium attenuated vasoconstriction and the [Ca2+]i increase evoked by mepivacaine. Verapamil attenuated the mepivacaine-induced [Ca2+]i increment. Calcium-free solution almost abolished mepivacaine-induced contraction and strongly attenuated the mepivacaineinduced [Ca2+]i increase. Gd3+ had no effect on either vasoconstriction or the [Ca2+]i increment evoked by mepivacaine. CONCLUSIONS: The mepivacaine-evoked [Ca2+]i increment, which contributes to mepivacaine-evoked contraction, appears to be mediated mainly by calcium influx and partially by calcium released from the sarcoplasmic reticulum.

Minimum effective volume of mepivacaine for ultrasound-guided supraclavicular block / 대한마취과학회지

BACKGROUND: The aim of this study was to estimate the minimum effective volume (MEV) of 1.5% mepivacaine for ultrasound-guided supraclavicular block by placing the needle near the lower trunk of brachial plexus and multiple injections. METHODS: Thirty patients undergoing forearm and hand surgery received ultrasound-guided supraclavicular block with 1.5% mepivacaine. The initial volume of local anesthetic injected was 24 ml, and local anesthetic volume for the next patient was determined by the response of the previous patient. The next patient received a 3 ml higher volume in the case of the failure of the previous case. If the previous block was successful, the next volume was 3 ml lower. MEV was estimated by the Dixon and Massey up and down method. MEV in 95, 90, and 50% of patients (MEV95, MEV90, and MEV50) were calculated using probit transformation and logistic regression. RESULTS: MEV95 of 1.5% mepivacaine was 17 ml (95% confidence interval [CI], 13-42 ml), MEV90 was 15 ml (95% CI, 12-34 ml), and MEV50 was 9 ml (95% CI, 4-12 ml). Twelve patients had a failed block. Three patients received general anesthesia. Nine patients could undergo surgery with sedation only. Only one patient showed hemi-diaphragmatic paresis. CONCLUSIONS: MEV95 was 17 ml, MEV90 was 15 ml, and MEV50 was 9 ml. However, needle location near the lower trunk of brachial plexus and multiple injections should be performed.

Análise comparativa entre articaína e mepivacaína na anestesia da região palatina: estudo-piloto / Comparative analysis between articaine and mepivacaine anesthesia in the palatine region: pilot study

Em um estudo analítico, do tipo ensaio clínico randomizado, prospectivo, quantitativo, comparativo, descritivo, duplo-cego, de amostras pareadas, comparou-se e analisou-se a difusibilidade dos anestésicos locais Articaína e Mepivacaína, através da anestesia no sulco vestibular e de exame clínico na região palatina, para cirurgia de terceiros molares superiores bilaterais. Uma amostra de 50 pacientes foi estudada, sendo que os resultados de 5 pacientes foram excluídos, porque eles não satisfizeram as exigências. Para o anestésico Mepivacaína, o percentual de pacientes com dor variou de 68,9% com 30 segundos a 37,8% na avaliação com 3 minutos, enquanto que, para o anestésico Articaína, o percentual de pacientes com dor variou de 37,8% com 30 segundos para 20,0% com 3 minutos. Em cada tempo de avaliação, comprova-se diferença significante entre os dois anestésicos em relação à ocorrência da dor ao nível de 5,0% (p < 0,05). Comprova-se, portanto, uma maior difusibilidade da Articaína nos tecidos, diminuindo a necessidade de uma complementação anestésica por palatino, região de grande sensibilidade dolorosa.

In an analytical study, the randomized clinical trial, prospective, quantitative, comparative, descriptive, doubleblind, paired samples, we compare and analyze the diffusibility of local anesthetics Articaine and Mepivacaine, through anesthesia on vestibular and examination clinician in the palate to upper third molar surgery bilateral. A sample of 50 patients was studied, and the results of 5 patients were excluded because they did not have met. For the anesthetic Mepivacaine, the percentage pain patients ranged from 68.9% with 30 seconds to 37.8% in the assessment to 3 minutes. While for the anesthetic Articaine, the percentage of pain patients ranged from 37.8% to 20.0% for 30 seconds and 3 minutes; each evaluation time shows a significant difference between the two anesthetics in relation to the occurrence of pain at the level of 5.0% (P <0.05). Proves, therefore, greater diffusibility of Articaine by tissue, reducing the need for anesthetic supplementation on the palatal, region of great soreness.

An unusual systemic toxicity of mepivacaine following axillary brachial plexus block or femoral/sciatic nerve block in patients with chronic renal failure and/or hypertension: A report of 2 cases

There are few reports about the systemic toxicity of mepivacaine, which is widely used for regional nerve blocks, because of its short onset time and intermediate duration, during or after blockades. We report two cases. In the first, a 70 year-old female with chronic renal failure and hypertension was scheduled for arteriovenous fistula formation under axillary brachial plexus block using 30 ml of 1.5% mepivacaine. In the second, a 69 year-old female with hypertension who was scheduled for total knee replacement under femoral/sciatic nerve block with lateral femoral cutaneous nerve block using 45 ml of 1.5% mepivacaine. Both had an exaggerated hemodynamic response (of increased blood pressure and heart rate) with symptoms and signs of central nervous system excitation not evolving to convulsions, which was induced by mepivacaine during or soon after the blockades. Possible causes and mechanisms of the events are discussed based on the literature.

The changes of heart rate variability after unilateral stellate ganglion block / 대한마취과학회지

BACKGROUND: The effect of the unilateral stellate ganglion block (SGB) on cardiovascular regulation remains controversial. We wished to evaluate the changes in heart rate variability (HRV) after a unilateral stellate ganglion block in patients with head and neck pain in the present study. METHODS: Patients with head and neck pain (n = 89) were studied. HRV was determined before and after a C6 unilateral stellate ganglion block (right-sided SGB, 40; left-sided SGB, 49) using a paratracheal technique with 1% mepivacaine (6 ml). RESULTS: There were no significant differences in HRV indices before and after right-sided SGB. The log scale of power in the high frequency range (lnHF) was increased and ratio of power in the low frequency range (LF) to power in the high frequency range (HF) ratio was decreased after left-sided SGB. CONCLUSIONS: These results demonstrated that left-sided SGB increased parasympathetic activities in patients with head and neck pain.

Influência da solução anestésica na percepção de dor após cirurgia periodontal: um estudo piloto / Infuence of anesthetic solution on pain perception after periodontal surgery: a pilot study

As características farmacológicas de agentes anestésicos locais estão entre os diversos fatores que podem infuenciar a percepção de dor pós-operatória. O objetivo deste estudo piloto foi avaliar a infuência de dois agentes anestésicos na percepção de dor pós-operatória após cirurgia a retalho para raspagem e alisamento radicular (RAR). Neste ensaio clínico randomizado, paralelo, duplo-cego, foram realizadas 12 cirurgias para RAR em pacientes com doença periodontal que apresentassem sinais clínicos de infamação após terapia periodontal básica em pelo menos um sextante. Os pacientes foram aleatoriamente alocados em um dos seguintes grupos: G1- mepivacaína 2% com norepinefrina 1:100.000; G2- lidocaína 2% com epinefrina 1:100.000. A intensidade da dor foi avaliada por meio de escala visual analógica (EVA) e escala numérica de 101 pontos (NRS-101), durante oito horas após a cirurgia. Os resultados demonstraram que a intensidade de dor pós-operatória foi estatisticamente inferior no grupo G2 em determinados períodos após a cirurgia, conforme indicam as respectivas medianas (Md). No período de uma hora: Md G1: 2,5; G2:18; p = 0,01; de duas horas: Md G1:2; G2:28,5; p = 0,009; de três horas: Md G1:6; G2:28; p = 0,01. Desta forma, os dados deste estudo piloto indicam que a utilização de mepivacaína 2% com norepinefrina 1:100.000 promove maior controle da dor no período pós-operatório imediato que a lidocaína 2% com epinefrina 1:100.000, após cirurgia de RAR a retalho.

Pharmacologic characteristics of local anesthetics agents are among several features that may infuence postoperative pain intensity. The aim of this study was to evaluate the infuence of two anesthetic agents on postoperative pain perception after open fap debridement surgeries. For this parallel-group, double-masked, placebo-controlled randomized clinical trial, 12 surgeries for open fap debridement were performed on patients who presented periodontal disease with clinical signs of infammation after nonsurgical treatment on at least one sextant. Patients were allocated in one of the following groups: G1- 2% mepivacaine with 1:100.000 norepinephrine; G2- 2% lidocaine with 1:100.000 epinephrine. Pain intensity was assessed using visual analog scale (VAS) and 101-point numerical rate scale (NRS-101) during the frst 8 hours after surgery. The results demonstrated that postoperative pain intensity was statistically lower in G2 at 1 (Median (Md) G1:2.5; G2:18; p = 0.01), 2 (Md G1:2; G2:28.5; p = 0.009) and 3 (Md G1:6; G2:28; p = 0.01) hours-period after surgery. Therefore, data from this pilot study indicate that 2% mepivacaine with 1:100.000 norepinephrine might promote more pain control at immediate postoperative period than does 2% lidocaine with 1:100.000 epinephrine after open fap debridement surgery.

The Effect of Preoperative Interscalene Block Using Low-Dose Mepivacaine on the Postoperative Pain after Shoulder Arthroscopic Surgery

BACKGROUND: Shoulder arthroscopic surgery is frequently associated with severe postoperative pain, which can be difficult to manage without the use of high-dose opioids. Although an interscalene brachial plexus block (ISBPB) can be used to provide anesthesia for shoulder arthroscopic surgery, its effect using low-dose mepivacaine on postoperative pain management has not been reported. We hypothesized that ISBPB using a low-dose mepivacaine can provide effective postoperative analgesia for shoulder arthroscopic surgery without the need for high-dose opioids and act as a significant motor or sensory block. METHODS: This study examined a total of 40 patients, who underwent shoulder arthroscopic surgery, and received ISBPB with 10 ml of normal saline (group NS; n = 20) or 10 ml of 1% mepivacaine with epinephrine 1:200,000 (group MC; n = 20). The block was performed preoperatively. The postoperative pain score, opioid consumption, and side effect were recorded. RESULTS: The visual analog scale scores were significantly lower in group MC than in group NS at 120 minutes after shoulder arthroscopic surgery (1.9 +/- 1.0 versus 4.0 +/- 1.4). Group MC showed significantly lower fentanyl consumption after shoulder arthroscoic surgery than group NS (27 +/- 32.6 versus 79 +/- 18.9microgram). The degree of motor and sensory block after surgery was minimal. CONCLUSIONS: ISBPB using low-dose mepivacaine reduced the level of postoperative pain and fentanyl consumption without significant side effects. ISBPB using low-dose mepivacaine is a useful analgesic technique for shoulder arthroscopic surgery.

The Effect of Distal Tourniquet in the Axillary Brachial Plexus Block / 대한마취과학회지

BACKGROUND: We investigated the effect of distal tourniquet to the proximal spread of local anesthetics in the axillary brachial plexus block. METHODS: In this prospective, randomized, controlled trial, 60 patients undergoing elective surgery were divided into two equal groups; Group I (2% mepivacaine 20 ml plus 1% lidocaine 20 ml with 250 mmHg of distal tourniquet) and Group II (2% mepivacaine 20 ml plus 1% lidocaine 20 ml alone). Patients were left for 30 minutes after an axillary brachial plexus block with paresthesia and single injection technique. Sensory blockades were evaluated by pin prick test at each nerve dermatome. RESULTS: There was no significant difference of sensory blockade in radial nerve, but there were significant differences of sensory blockade in ulnar, median, musculocutaneous, medial antebrachial cutaneous, and axillary nerves (P < 0.05). CONCLUSIONS: Our findings suggest that the quality and effect of axillary brachial plexus block in group with distal tourniquet is better than the control group.

Intravenous Regional Anesthesia Using Mepivacaine and Tramadol / 대한마취과학회지

BACKGROUND: Tramadol, an opioid n receptor agonist and monoaminergic reuptake inhibitor, has been studied as an adjunct to general and regional anesthesia. Tramadol has been added to local anesthetic regimens for various peripheral nerve blocks, resulting in prolonged anesthesia and analgesia. The purpose of this study was to evaluate the effectiveness of using tramadol as a component of intravenous regional anesthesia (IVRA) to enhance postoperative analgesia. METHODS: Thirty-six patients undergoing hand surgery received IVRA with mepivacaine 0.5%, and were assigned randomly and blindly to one of the following groups: Group I (n = 12) received only 0.5% mepivacaine 40 ml, Group II (n = 12) was given 0.5% mepivacaine 40 ml and 50 mg tramadol, and Group III (n = 12) received 0.5% mepivacaine 40 ml and 100 mg tramadol. After the completion of the operations, analgesic effects were evaluated by using the visual analogue scale (0 - 10). Sedation scores (0 - 3), supplemental analgesic use, and side effects were also evaluated. RESULTS: Patients who received IVRA with 100 mg tramadol reported a significantly lower pain score after tourniquet deflation compared with other groups, and a decreased need for analgesics in the postanesthesia care unit. No significant postoperative sedation, nausea, vomiting, or headache developed in any of the patients. CONCLUSIONS: The addition of 100 mg tramadol to 0.5% mepivacaine for IVRA provided improved analgesia in the postanesthesia care unit after the operation and decreased the need for analgesic supplements after the operation.

Epidural Block of Bupivacaine and Mexiletine for Erythromelalgia / 대한마취과학회지

Erythromelalgia is a rare disease characterized by palmar and plantar erythema, burning pain and local increase in temperature. Secondary erythromelalgia most commonly appears secondary to myeloproliferative disorders, essential thrombocytosis and polycythemia vera. The pain associated with erythromelalgia is often severe and recalcitrant. So far no properly performed therapeutic trials have been published. We present a case of erythromelalgia of both hands and feet in a 52 year old man. A twice daily cervical and lumbar epidural block of mepivacaine 0.5% and mexiletine 100 mg given orally resuletd in complete resolution of the syndrome. After 3 months, the symptom recurred mildly.

Comparison of Onset Time and Postoperative Analgesic Effects of Mepivacaine and Bupivacaine with Morphine on Caudal Block / 대한마취과학회지

BACKGROUND: Caudal injection of local anesthetics with morphine is the most common anesthetic technique for perianal operation and postoperative analgesia. This study was purposed to compare the onset time of caudal analgesia, postoperative analgesic effect and side effects. METHOD: Sixty healthy patients scheduled for perianal operation were divided into 2 groups randomly. Group I was given 2 mg of morphine in 20 ml of 2% mepivacaine via sacral hiatus. Group II was also given 2 mg of morphine in 20 ml of 0.5% bupivacaine caudally. We measured the onset time of caudal block, time to the first request of analgesics, the number of analgesics within 24 hours and the incidence of postoperative side effects. Analgesic effect was evaluated by visual analogue scales (VAS) at 1, 2, 6, 12 and 24 hours postoperatively. RESULT : The onset time of caudal block for operation and the first request time of analgesic for postoperative pain was significantly shorter in group I than group II. The analgesic use in the first 24 hours was significantly more in group I than group II. The side effects were similar in both groups. CONCLUSION: We concluded that the combined use of morphine and bupivacaine provided better postoperative analgesia than the combined use of morphine and mepivacaine.

Comparison of Mepivacaine and Bupivacaine as an Adjuvant of Morphine for Benign Anorectal Surgery under Caudal Anesthesia

BACKGROUND/AIMS: The caudal anesthsia is most commonly used for benign anorectal surgery, The combination of long-acting anesthetics and opiates has been used for longer duration and successful control of postoperative pain. But the side effects of peridural anesthesics and morphine have commonly occured in caudal anesthesia. This study was performed to assess the difference in clinical effects between peridural mepivacaine and bupivacaine with morphine. METHODS: We evaluated the clinical effects in 60 patients who had anal operation with Jack-Knife position under caudal anesthesia. We divided randomly these 60 patients into two groups, M and B groups (in each group, 30 patients included). Group M (n=30) was given 2% mepivacaine 20 ml with morphine 2 mg caudally, and Group B (n=30) was given 0.5% bupivacaine 20 ml with morphine 2 mg in the same manner. We measured the onset time, duration, postoperative analgesia, and side effects including urinary retention. RESULTS: The onset time for analgesia was significantly shorter in group M than in group B. The duration of postoperative pain complaints was significantly longer in group M than in group B. The postoperative analgesic effects and side effects were not significantly different between two groups. CONCLUSIONS: Caudal mepivacaine and morphine mixture is effective for control of postoperative pain without significant side effects.

Spinal Anesthesia with Hyperbaric 1.5% Lidocaine and 1.5% Mepivacaine / 대한마취과학회지

BACKGROUND: Lidocaine has been used for spinal anesthesia in short surgical procedure. However, transient neurologic symptoms (TNS) frequently occur after spinal anesthesia with lidocaine. Mepivacaine which has a silimar duration of action and rare incidence of TNS may be an alternative to lidocaine for spinal anesthesia. This study was designed to compare the efficacy of hyperbaric 1.5% lidocaine and 1.5% mepivacaine for spinal anesthesia. METHODS: Sixty patients, ASA physical status I or II, scheduled for lower abdominal or lower extremity procedures under spinal anesthesia were randomly allocated into two groups. Lidocaine group received 2% lidocaine 75 mg with 10% dextrose 1.25 ml. Mepivacaine group received 2% mepivacaine 75 mg with 10% dextrose 1.25 ml. After intrathecal injection of the anesthetics, sensorimotor block and recovery, cardiovascular effect and quality of surgical anesthesia were evaluated. TNS was evaluated 1 day after the operation. RESULTS: Both groups were similar with regard to demographic data and surgical procedures. The onset of sensory and motor blocks was similar in both groups. Time to regression to L5 sensory level and complete resolution of motor blockade were significantly prolonged in mepivacaine group than in lidocaine group (p<0.05). The effect of cardiovascular system was similar in both groups. Fentanyl was required for 4 cases only in the lidocaine group. None of both groups developed TNS. CONCLUSIONS: Hyperbaric 1.5% mepivacaine produced longer duration of action than hyperbaric 1.5% lidocaine in spinal anesthesia. This study didn't prove what drug develops a higher incidence of TNS.

Serum Lidocaine and Mepivacaine Level during Axillary Brachial Plexus Block / 대한마취과학회지

BACKGROUND: The maximum recommened dose for lidocaine and mepivacaine with epinephrine is about 500 mg regardless of the injection site. But this dose is insufficient for brachial plexus block and it is known that mepivacaine is safer than lidocaine. So the purpose of this study was to determine whether the serum concentrations of 1.5% lidocaine 600 mg with epinephrine and 1.5% mepivacaine 600 mg with epinephrine are within a safe range and to know any differences between them during axillary brachial plexus block. METHODS: Fifteen ASA physical status class I-II patients were selected. They were randomly divided into two groups. Group L patients (n=8) were anesthetized with 40 ml 1.5% lidocaine (600 mg) with epinephrine and group M patients (n=7) with 40 ml 1.5% mepivacaine (600 mg) with epinephrine. The serum concentrations were measured at the 5, 15 and 30 minutes after injection. RESULTS: The serum concentrations were 1.99 +/- 1.47, 2.66 +/- 1.03 and 2.41 +/- 1.41 microgram/ml in group L, and 3.03 +/- 0.64, 4.07 +/- 0.93 and 3.99 +/- 1.02 microgram/ml in group M at the 5, 15 and 30 minutes after injection. There were no symptoms or signs of local anesthetic toxicity, and serum levels of lidocaine and mepivacaine remained below the level that usually caused toxic symptoms. CONCLUSIONS: Although the serum concentration of mepivacaine group was higher than that of lidocaine group at each time, 1.5% lidocaine 600 mg with epinephrine and 1.5% mepivacaine 600 mg with epinephrine can be safely administered into the axillary sheath because the serum concentrations are within a safe range.

Caudal Epidural Morphine for Postoperative Analgesia in Children / 대한마취과학회지

BACKGROUND: The use of caudal morphine for postoperative analgesia has been increased in popularity since 1981. The purpose of this study was to compare the effect of analgesia and incidence of side effects of a mepivacaine-morphine mixture with mepivacaine alone. METHODS: Forty patients were randomly divided into two groups. In group 1, caudal block was performed with 1% mepivacaine 1 ml/kg alone. In group 2, caudal block was performed with 1% mepivacaine 1ml/kg-morphine 0.03 mg/kg mixture. Postoperative five-point pain scores and side effects were measured. RESULTS: There were no significant differences in sedation dose, incidence of side effects and supplemental analgesics. Pain scores were significantly lower at postoperative 2 and 3 hours in mepivacaine-morphine mixture group. CONCLUSIONS: Caudal epidural mepivacaine-morphine (0.03 mg/kg) mixture is effective in children for control of postoperative pain without significant side effects.

Mechanical and Electrophysiological Effects of Mepivacaine on the Direct Myocardial Depression on the 1solated Ventricular Myocardium / 대한마취과학회지

BACKGROUND: The effects of various concentration (20, 50, 100? M) of mepivacaine were studied in isolated guinea pig and rat right ventricular papillary muscles by measuring the effects on myocardial contractility and electrophysiological parameters. METHODS: Isometric force of isolated guinea pig ventricular papillary muscle was studied in modified normal and 26 mM K+ Tyrode's solution. Rat papillary muscle was used to evaluate the effect on Ca2+ release from the sarcoplasmic reticulum (SR) at low stimulation rates. Normal and slow action potentials (APs) were evaluated by using conventional microelectrode technique. Rapid cooling contractures (RCCs), an index of SR Ca2+ content, which are known to be activated by Ca2+ released from the SR were performed. RESULTS: Mepivacaine caused dose-dependent depression of peak force from 0.5 to 3 Hz stimulation rates in guinea pig papillary muscles. Conduction block was frequently noted especially at higher stimulation rates (2 and 3 Hz) at all concentration ranges. In rat, ~20% depression of peak force was shown at rested state contraction. Shortening of AP duration and rate-dependent depression of dV/dt max could be observed at 100 M mepivacaine. In 26 mM K+ Tyrode's solution, 50 and 100 M mepivacaine caused dose-dependent depression of early and late force development. In slow APs, neither shortening of AP duration nor changes of dV/dtmax were not shown at 100 M mepivacaine. ~30% depression of RCC after 2 Hz stimulation rate was shown at 100 M mepivacaine. CONCLUSION: It may be concluded that the direct myocardial depressant effects of mepivacaine may partly be related to inhibition of Ca2+ release from the SR. Shortening of AP duration in normal APs seems to be partly related by blockade of TTX-sensitive ""window"" Na+ current.