Minimum Local Anesthetic Concentration Research Articles

Effect of caudal ketamine on minimum local anesthetic concentration of ropivacaine in children: a prospective randomized trial

BackgroundCaudal ketamine has been shown to provide an effective and prolonged post-operative analgesia with few adverse effects. However, the effect of caudal ketamine on the minimum local anesthetic concentration (MLAC) of ropivacaine for intra-operative analgesia is unclear.MethodsOne hundred and sixty-nine children were randomized to five groups: Group C (caudal ropivacaine only), Group K0.25 (caudal ropivacaine plus 0.25 mg/kg ketamine), Group K0.5 (caudal ropivacaine plus 0.5 mg/kg ketamine), Group K0.75 (caudal ropivacaine plus 0.75 mg/kg ketamine), and Group K1.0 (caudal ropivacaine plus 1.0 mg/kg ketamine). The primary outcome was the MLAC values of ropivacaine with/without ketamine for caudal block.ResultsThe MLAC values of ropivacaine were 0.128% (0.028%) in the control group, 0.112% (0.021%) in Group K0.25, 0.112% (0.018%) in Group K0.5, 0.110% (0.019%) in Group K0.75, and 0.110% (0.020%) in Group K1.0. There were no significant differences among the five groups for the MLAC values (p = 0.11). During the post-operative period the mean durations of analgesia were 270, 381, 430, 494, and 591 min in the control, K0.25, K0. 5, K0.75, and K1.0 groups respectively, which shown that control group is significantly different from all ketamine groups. Also there were significant differences between K0.25 and K0.75 groups, and between K1.0 groups and the other ketamine groups.ConclusionsAdding caudal ketamine to ropivacaine prolong the duration of post-operative analgesia; however, it does not decrease the MLAC of caudal ropivacaine for intra-operative analgesia in children.Clinical trial registrationChiCTR-TRC-13003492. Registered on 13 August 2013.

The minimum local anesthetic concentration of ropivacalne for ultrasound-guided phrenic nerve block in the treatments of central hiccup

Objective To determine the minimum local anesthetic concentration of ropivacalne for ultrasound-guided phrenic nerve block in the treatments of central hiccup. Methods In this experiment, sequential experimental method was used to select patients with hiccup after the operation of cerebral hemorrhage. The starting concentration of ropivacaine was 0.25%. The ratio between adjacent concentrations was 1.3. The superficial phrenic nerve on the left anterior scalene muscle of all patients were located by ultrasound. The predetermined concentration of ropiacaine 4 ml was injected. After twenty minutes, whether the injection works or not was judged by observing the symptom of all patients. If the first one is effective, the next injection dose will be decreased one concentration gradient. If the block was not effective, then 4 ml of 1.5% lidocaine will be injected at the same lateral phrenic nerve. If the block is still not effective, the next injection will be ropivacaine with increased one concentration gradient. If the hiccups still did not end, the routine drug treatment will be used. At the same time, with the approval of the patients′ family, after eight hours, we will take the right phrenic nerve block. Then this case will not be included in the data statistic. The next patient continues to use the same initial concentration ropivacaine. The effective cases were included in effective group(group A) while the cases with lidocaine supplement were divided into invalid group (group B). The drug concentration, blocking effect, median effective dose(ED50) and 95% confidence intervals (CI) were calculated according to Dixon and Brownlee methods. Results Ultrasound-guided application of ropivacaine for phrenic nerve block for central hiccup is safe, effective and requires little medication. 95%CI of ultrasound-guided phrenic nerve block for central hiccup is 0.267%-0.335%. Conclusions The minimum effective concentration of ropivacaine in the treatment of central hiccup was 0.299%. Key words: Phrenic nerve; Nerve blocking anesthesia; Hiccup; Ultrasound-guided; Ropivacaine

059 Local anaesthesia eluting property of Coloplast Titan penile prosthesis hydrophilic coating: An in-vitro drug elution profile and a randomised double-blind clinical outcome study

Local anaesthesia eluting property of Coloplast Titan penile prosthesis hydrophilic coating: An in-vitro drug elution profile and a randomised double-blind clinical outcome study. A two-part study to provide proof-of-concept with in-vitro analysis of drug elution property, and to evaluate the clinical outcome with Titan penile prosthesis hydrophilic coating dipped in local anaesthesia agent. An in-vitro analysis of local anaesthesia eluting property of hydrophilic coating to determine the amount and duration of local anaesthesia elution, and examine if the addition of local anaesthesia agent will dilute anti-microbial property of hydrophilic coating. Following internal ethics approval, a pilot study was conducted with 40 men randomised to receive Titan’s penile prosthesis dipped with or without 0.75% Ropivacaine and 0.5% Marcaine. An independent third-party survey with objective measurement of pain score (visual analog scale, VAS), analgesia requirement (opioid dose equivalence) and time to penile prosthesis recycling. In vitro-release kinetics confirmed passive drug elution above the minimum inhibitory concentration. The minimum local anaesthetic concentration (MLAC) of 0.75% Ropivacaine and 0.5% Marcaine was sustained over the 14 days of in-vitro drug elution test. The hydrophilic coating with combination local anesthesia and antimicrobial drugs showed sustained elution and zone of microbial inhibition at day 1, 3, 7 and 14 (p<0.05). In the clinical study, patients with Titan penile prosthesis dipped in local anaesthesia reported lower VAS score (p<0.05), less analgesia requirement (p<0.05) and shorter time to penile prosthesis recycling (p=0.08).

Dexmedetomidine decreases the required amount of bupivacaine for ultrasound-guided transversus abdominis plane block in pediatrics patients: a randomized study

BackgroundThe effect of dexmedetomidine on the potency of bupivacaine for transversus abdominis plane (TAP) block in pediatric patients has not been investigated. Study objectiveThe primary objective of this study was to assess the effectiveness of dexmedetomidine to decrease the concentration of bupivacaine needed for analgesia for ultrasound-guided TAP block in a pediatric patient undergoing hernia repair or hydrocelectomy. DesignThis is a randomized, double-blind, up-down, dose-finding study. SettingOperating room. PatientsSixty American Society of Anesthesiologists I and II patients aged 1-4 years scheduled for elective unilateral herniorrhaphy or hydrocelectomy. InterventionsPatients were randomly assigned to 1 of the 2 groups: group B (0.125% bupivacaine, 1mL/kg) TAP block or group BD (0.125% bupivacaine plus 2μg/kg dexmedetomidine, 1mL/kg) TAP block. MeasurementsThe response of each child was observed for 60 seconds after skin incision and evaluated as ‘unsuccessful’ when skin incision caused a change in hemodynamic parameters (heart rate and mean blood pressure) 20% more than the preincision values. If the response was determined to be unsuccessful, the concentration of bupivacaine administrated to the next patient was increased by 0.02%. If it was successful, the concentration of bupivacaine administrated to the next patient was decreased by 0.02%. ResultsThe minimum local anesthetic concentration of bupivacaine was 0.0839% (0.0137) in the B group and 0.0550% (0.0169) in the BD group. The difference was statistically significant (t=7.165, P=.0001). The total postoperative analgesic dosage of morphine was significantly higher in the B group (0.17±0.04 mg/kg) than the BD group (0.11±0.02 mg/kg, P=.001). ConclusionsThe addition of 2μg/kg of dexmedetomidine reduced the minimum local anesthetic concentration of bupivacaine used for a TAP block and improved postoperative analgesia in children undergoing surgery for inguinal hernia repair or hydrocelectomy.

Strategies to Optimize the Efficacy of Regional Anesthesia

The mode of delivery of epidural solutions has progressed from clinician-delivered boluses, to automated continuous epidural infusions and the addition of patient-controlled epidural analgesia (PCEA), and now to programmed intermittent epidural boluses (PIEBs) in addition to PCEA. Currently, there is promising evidence for the use of combination PIEB and PCEA to minimize additional bolus requirements and reduce the amount of local anesthetic consumed, as well as improved patient satisfaction. There are few data regarding this mode of delivery in peripheral nerve catheters. The existing data in the peripheral nerve catheters do not show a clear advantage for the use of the programmed intermittent bolus (PIB) method. More studies are needed in various peripheral nerve/fascia plane blocks to answer this question. Studies looking at the median effective dose in 50% of patients of local anesthetics for labor epidurals (minimum local anesthetic concentration [MLAC]) have allowed the comparison of the relative potency of different local anesthetics. Even though the absolute numbers are not useful, we know that ropivacaine is only 60% as potent as bupivacaine for its analgesic potency and development of motor block, so it provides no advantage over bupivacaine for the labor epidural setting. MLAC studies have also allowed the study of adjuvants and their effect on labor analgesia. Fentanyl, epinephrine, and clonidine have been studied, showing significant local anesthetic–sparing effects. The risks and benefits of each adjuvant should be weighed for each patient, but fentanyl and epinephrine have an excellent benefit-to-risk ratio.

Retrobulbar dexmedetomidine decreases the MLAC of ropivacaine in vitreoretinal surgery in children.

Dexmedetomidine can prolong the duration of local anesthetics, but the effect of retrobulbar dexmedetomidine on the potency of ropivacaine for retrobulbar block has not been investigated. Our study was designed to determine the effect of retrobulbar dexmedetomidine on ropivacaine for retrobulbar block in children. A group of 90 children aged 10-16 years scheduled for vitreoretinal surgery who received retrobulbar block were randomly assigned to 1 of 3 groups: group L (retrobulbar ropivacaine), group LD1 (ropivacaine plus 0.5 µg.kg-1 dexmedetomidine), or group LD2 (ropivacaine plus 1 µg.kg-1 dexmedetomidine). The minimum local anesthetic concentration (MLAC) was determined according to a Dixon-Massey protocol. The primary endpoint of the study was MLAC. Secondary outcomes were duration of postoperative analgesia, postoperative pain scores, dexmedetomidine side effects, and time to hospital discharge. The MLAC values of retrobulbar ropivacaine were 0.314%, 0.259%, and 0.246% in groups L, LD1, and LD2, respectively. The median (interquartile range) durations of analgesia in the postoperative period were 66 (54-117), 89 (40-157), and 168 (120-194) minutes in groups L, LD1, and LD2, respectively (L vs LD1 or LD2, p&lt;0.05). Wake-up time was significantly increased in groups LD1 and LD2. Retrobulbar dexmedetomidine reduces the MLAC values of ropivacaine and improves postoperative analgesia in children without any neurologic side effects.

Caudal dexmedetomidine decreases the required concentration of levobupivacaine for caudal block in pediatric patients: a randomized trial

Dexmedetomidine (D) can prolong the duration of local anesthetics, but the effect of caudal dexmedetomidine on the potency of levobupivacaine (L) for caudal block has not been investigated. This study was designed to determine the effect of caudal dexmedetomidine on levobupivacaine for caudal block in pediatric patients. Eighty-nine children scheduled for elective inguinal hernia repair or hydrocele were randomly assigned to one of the three groups: Group L (caudal levobupivacaine), Group LD1 (levobupivacaine plus 1μg·kg(-1) dexmedetomidine), or Group LD2 (levobupivacaine plus 2μg·kg(-1) dexmedetomidine). The primary endpoint was the minimum local anesthetic concentration (MLAC), which was determined using the Dixon up-and-down method. The secondary endpoints were the duration of analgesia and sedation. The MLAC values (sd) of caudal levobupivacaine were 0.103 (0.01)%, 0.068 (0.02)%, and 0.055 (0.03)% in Groups L, LD1, and LD2, respectively. The values of EC50 and EC95 (95% CI) of caudal levobupivacaine from logistic regression analysis were 0.094 (0.083-0.105)% and 0.129 (0.1-0.159)%, 0.058 (0.044-0.072)% and 0.106 (0.067-0.144)%, and 0.046 (0.033-0.059)% and 0.091 (0.055-0.127)% in Groups L, LD1, and LD2, respectively. The mean durations of analgesia in the postoperative period were 141, 378, and 412min in Groups L, LD1, and LD2, respectively (L vs LD1 or LD2, P<0.001). The mean durations of sedation in both Groups LD1 and LD2 also were significantly prolonged, compared with Group L (P<0.01). Caudal dexmedetomidine reduces the MLAC values of levobupivacaine and improves postoperative analgesia in children without any neurological side effects.

Ropivacaine: A review of its pharmacology and clinical use

Ropivacaine is a long-acting amide local anaesthetic agent and first produced as a pure enantiomer. It produces effects similar to other local anaesthetics via reversible inhibition of sodium ion influx in nerve fibres. Ropivacaine is less lipophilic than bupivacaine and is less likely to penetrate large myelinated motor fibres, resulting in a relatively reduced motor blockade. Thus, ropivacaine has a greater degree of motor sensory differentiation, which could be useful when motor blockade is undesirable. The reduced lipophilicity is also associated with decreased potential for central nervous system toxicity and cardiotoxicity. The drug displays linear and dose proportional pharmacokinetics (up to 80 mg administered intravenously). It is metabolised extensively in the liver and excreted in urine. The present article details the clinical applications of ropivacaine and its current place as a local anaesthetic in the group.

Effect of epidural clonidine on minimum local anesthetic concentration (ED50) of levobupivacaine for caudal block in children

Clonidine has the potential to significantly prolong the duration of caudal epidural anesthesia. We investigated the effect of the addition of clonidine to the MLAC of levobupivacaine in a randomized controlled dose-response trial. A group of 120 children aged <6 years of age received caudal anesthesia with levobupivacaine and 1, 2, or 3 μg·kg(-1) of clonidine. The MLAC was determined according to a Dixon-Massey protocol. The primary outcome was effective surgical anesthesia. Secondary outcomes were the duration of postoperative analgesia, postoperative pain scores, clonidine side effects, and time to hospital discharge. The MLAC of caudal levobupivacaine was 0.106%, 0.077%, and 0.035% with 1, 2, and 3 μg·kg(-1) of clonidine, respectively. There were significant dose-dependent increases in median duration of analgesia. The incidence of delayed discharge, somnolence, and PONV was significantly increased in the 3 μg·kg(-1) of clonidine group. Clonidine produces a local anesthetic sparing effect with a dose-dependent decrease in levobupivacaine MLAC for caudal anesthesia. In addition, there is a dose-dependent prolongation of postoperative analgesia following lower abdominal surgery in children. A dose of 2 μg·kg(-1) of clonidine provides the optimum balance between improved analgesia and minimal side effects.

The Effect of Sex on the Minimum Local Analgesic Concentration of Ropivacaine for Caudal Anesthesia in Anorectal Surgery

Caudal anesthesia is routinely used in our hospital for most of ambulatory anorectal surgery; patients need to recover as quickly as possible. The dose of local anesthetic may be different for male and female patients. We designed this study to investigate the effect of sex on the minimum local anesthetic concentration (MLAC) of ropivacaine for caudal anesthesia. In this double-blind, prospective study, we enrolled 70 ASA physical status I patients (35 male and 35 female) who were scheduled for anorectal surgery under caudal anesthesia, and allocated them to 2 study groups according to their gender. Each participant received a single injection of 20 mL ropivacaine through a caudal catheter. Using Dixon's up-and-down sequential allocation, the first participant received 0.2% and subsequent concentrations were determined by the analgesic response of the previous patients to the initial skin incision and laxity of the anal sphincter. The concentration change was 0.025%. The up-and-down sequences were analyzed using the Dixon and Massey method to quantify the caudal analgesic block effective concentrations in 50% of patients. The MLAC of ropivacaine for caudal analgesia was 0.296% (95% confidence interval, 0.286%-0.307%) in male patients and 0.389% (95% confidence interval, 0.372%-0.407%) in female patients (P < 0.01). We conclude that the ropivacaine MLAC for caudal anesthesia in female patients is 31% larger than in male patients.

Side effects of the addition of clonidine 75 μg or sufentanil 5 μg to 0.2% ropivacaine for labour epidural analgesia

Background Sufentanil 5 μg and clonidine 75 μg produce a similar reduction in minimum local anaesthetic concentration of ropivacaine. The aim of the present study was to compare the side effects of two equianalgesic solutions by combining 0.2% ropivacaine with either sufentanil 5 μg or clonidine 75 μg for labour epidural analgesia. Methods In a prospective double-blind study, 60 women at ⩽5 cm cervical dilatation were randomly allocated to receive 0.2% ropivacaine with either sufentanil 5 μg or clonidine 75 μg to initiate labour analgesia. The analgesic efficacy and side effects of the two mixtures were compared. Results Onset, duration and quality of analgesia and subsequent ropivacaine consumption were similar in the two groups. Hypotension was significantly more frequent and severe with clonidine than with sufentanil (systolic blood pressure <100 mmHg: 17/26 vs. 6/24, P <0.05; systolic blood pressure <90 mmHg: 5/26 vs. 0/24, P <0.05) resulting in more frequent ephedrine administration (11/26 vs. 2/24, P <0.05) and larger fluid requirements (1696 ± 583 mL vs. 1264 ± 407 mL, P < 0.05). Conversely, pruritus was more frequent with sufentanil than with clonidine (6/26 vs. 1/24, P <0.05). Conclusions Hypotension occurs more frequently when clonidine is added to epidural ropivacaine instead of an equianalgesic dose of sufentanil. Therefore, clonidine cannot be recommended for routine administration for labour epidural analgesia.

Minimum effective local anesthetic concentration of intrathecal ropivacaine for hip surgery in the elderly patients

目的 研究罗哌卡因用于老年人髋关节手术患者腰麻的最低有效浓度(MLAC).方法 择期行下肢手术老年患者20例,ASAⅡ～Ⅲ级,年龄65～88岁,选择L3-4间隙穿刺,第1例蛛网膜下腔注入0.40%罗哌卡因,其后各患者所用浓度按序贯法调整,浓度变化梯度为0.02%.观察感觉阻滞起效时间、感觉阻滞达到的最高平面、感觉阻滞持续时间、下肢运动阻滞的Bromage分级、辅助药的应用和麻醉相关并发症.根据Dixon-Massey法计算罗哌卡因MLAC.结果 罗哌卡因MLAC为0.29%(95%CI0.26%～0.31%).结论 连续腰麻应用于老年人下肢手术,可使用低浓度罗哌卡因,更有利于血流动力学的稳定。

Current status and clinical relevance of studies of minimum local-anaesthetic concentration (MLAC)

Studies comparing the effects of epidural local anaesthetics have been limited by the lack of knowledge of their relative potencies. In 1995 the concept of the minimum local-anaesthetic concentration (MLAC) was introduced, this has been defined primarily as the median effective analgesic concentration in the first stage of labour. Pharmacologically, this model aims to determine equipotent analgesic concentrations of local anaesthetics, to compare motor effects and to evaluate the relative toxicity during labour. However, results of recent MLAC studies are not uniform and rather confusing, and thus, the basic validity of the MLAC concept for determining local-anaesthetic potency is increasingly discussed. MLAC studies have postulated that ropivacaine is up to 40% less potent than bupivacaine, but as potent as levo-bupivacaine. Intriguingly, bupivacaine has been shown to be as effective as levo-bupivacaine in identical experimental protocols. Modified MLAC studies resulted additionally in local anaesthetic-sparing effects of epidural/intrathecal opioids, clonidine and epinephrine. MLAC studies have also been applied to compare the relative analgesic as well as relative motor-blocking potency of local anaesthetics. Relative differences in local anaesthetics' potencies derived from MLAC examinations are meaningful and correct from the pharmacological point of view, but they cannot simply be transferred to daily clinical practice. Thus, MLAC values should not be misinterpreted as these data are not suggested to be suitable to define and quantify the pharmacodynamics of local anaesthetics, nor to unequivocally predict their toxicological profile in clinically relevant concentrations.

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The Minimum Local Anesthetic Concentration of Ropivacaine for Caudal Analgesia in Children

The Minimum Local Anesthetic Concentration of Ropivacaine for Caudal Analgesia in Children