Minimum effective volume of ropivacaine for ultrasound-guided adductor canal + IPACK block in total knee arthroplasty: A double-blind, randomized dose-finding trial.

BACKGROUND: Our previous study reported that when a respective 20 mL of ropivacaine was used for adductor canal block (ACB) combined with infiltration between the popliteal artery and capsule of the posterior knee (IPACK) block for patients undergoing total knee arthroplasty (TKA), the minimum concentration of 0.275% could provide successful block in almost all patients. Based on the results, the primary objective of this study was to investigate the minimum effective volume (MEV90, defined as the volume which can provide successful block in 90% of patients) of ACB + IPACK block. METHODS: This double-blind, randomized dose-finding trial was based on a biased coin up-and-down sequential design, where the volume of ropivacaine administered to a given patient depended on the previous patient's response. The first patient received 15 mL of 0.275% ropivacaine for ACB and again for IPACK. If the block failed, the next subject received a 1 mL higher volume for ACB and IPACK, respectively; otherwise, the next subject received either a 1 mL lower volume (probability of 0.11) or the same volume (probability of 0.89). The primary outcome was whether the block was successful. Block success was defined as the patient did not suffer significant pain and did not receive rescue analgesia within 6 h after surgery. Then the MEV90 was estimated by isotonic regression. RESULTS: Based on analysis of 53 patients, the MEV90 was 17.99 mL (95% CI 17.47-18.61 mL), MEV95 was 18.48 mL (95% CI 17.45-18.98 mL) and MEV99 was 18.90 mL (95% CI 17.38-19.07 mL). Patients whose blocks succeeded had significantly lower NRS pain scores, lower morphine consumption, and shorter hospitalization. CONCLUSION: 0.275% ropivacaine in 17.99 mL respectively can provide successful ACB + IPACK block in 90% of patients undergoing TKA. The minimum effective volume (MEV90) of ACB + IPACK block was 17.99 mL.

Study on MEV90 of 0.5% ropivacaine for US-guided caudal epidural block in anorectal surgery.

Background: Choosing the appropriate concentration and volume of anesthetics is critical for a successful nerve block. The current study aimed to determine the minimum effective volume (MEV) of 0.5% ropivacaine for US-guided CEB in 90% of patients (MEV90) undergoing anorectal surgery. The aims were to reduce the occurrence of complications associated with a sacral blockade in anorectal surgery, broaden the indications for surgical procedures and treatment, and improve patient satisfaction. This study presents the groundwork for the development of individualized anesthetic programs. We believe that the study would serve as a reference for the use of caudal epidural block (CEB) in lower abdominal surgery for intraoperative and postoperative analgesia. Methods: This study used a biased coin design (BCD) up-and-down method (UDM). We divided the participants into two groups based on gender, and each group independently performed the biased coin design up-and-down method. We used 0.5% ropivacaine for the first patient in each group; however, the volume was 10 ml for men and 8 ml for women. Therefore, the dose of anesthetics given to each patient was determined by the response of the previous patient. If the block of the previous patient failed, the volume was increased by 2 ml in the following patient. Otherwise, the next subject had an 11% chance of receiving a volume of 2 ml less or an 89% chance of receiving no volume change. We defined a successful block as painless surgery with anal sphincter relaxation 15 min after the drug injection. Enrollment was completed after 45 successful caudal blocks for each group. Results: Caudal epidural block was successfully performed on 50 men and 49 women. The MEV90 of ropivacaine for CEB was calculated to be 12.88 ml (95% CI: 10.8-14 ml) for men and 10.73 ml (95% CI: 9.67-12 ml) for women. Men had a MEV99 of 13.88 ml (95% CI: 12.97-14 ml), and women had a MEV99 of 11.87 ml (95% CI: 11.72-12 ml). Conclusion: With operability and general applicability, it is possible to increase the success rate of CEB for anorectal surgery to 99% as well as decrease the incidence of anesthesia-related complications. CEB can meet the needs of patients for rapid postoperative rehabilitation, improve patient satisfaction, and lay a solid foundation for postoperative analgesia.

Minimum effective volume of local anesthetic in peribulbar block: does it differ with the eyeball axial length?

BACKGROUND: Peribulbar Anesthesia (PBA) is a relatively safe method for cataract surgery. The anesthetic volume should be adjusted according to the axial eyeball length. Thus, using Minimum Effective Volume (MEV) of local anesthetic helps avoiding unnecessary volumes, preventing increases in intra-ocular pressure, and producing satisfactory conditions for cataract surgery. This study aims to determine the MEV90 of local anesthetics in relation to eye globe axial length in peribulbar blocks for cataract surgery. METHODS: Patients scheduled for cataract extraction under local anesthesia were divided according to their axial eyeball length; Group 1 included those with axial length from 22 to 24 mm, Group 2 included patients with axial length from 24.1 to 26 mm. The initial volume used was 7 mL of a solution of bupivacaine 0.5% (3 mL) + lidocaine 2% (3 mL) + hyaluronidase 150 IU (1 mL). The subsequent volumes were dependent on the response of the previous patient, by using a Bias Coin Design (BCD) and Up and Down Method (UDM) for MEV-90 determination. RESULTS: The study was concluded with 119 patients. Sixteen patients needed supplemental volume of local anesthetic in Group 1 and thirteen in Group 2. The MEV90 for Group 1 was approximately 5.82 mL (95% CI 5.6 to 5.87 mL) and 5.45 mL for Group 2 (95% CI 5.38 to 5.91 mL). No major complications were noted. There was a negative correlation between the effective volume of LA and eye globe axial length in both groups (p = 0.001). CONCLUSION: The MEV90 of local anesthetics for peribulbar block show a strong and inverse correlation with eye globe axial length. This may help achieving an effective block with minimum complications.

Truncal injection brachial plexus block: A Description of a novel injection technique and dose finding study.

BACKGROUND AND AIMS: Brachial plexus (BP) blocks continue to be described with reference to anatomical landmarks (Interscalene and Supraclavicular), even after the introduction of ultrasound which enables us to directly identify the roots, trunks and divisions of the BP. The aim of this study was to describe a novel injection technique targeting trunks of BP and to determine the minimum effective local anaesthetic volume (MELAV) required to produce BP block with this approach. METHODS: Twenty-one male patients in the age group 20-40 years, undergoing elective forearm bony procedures received an ultrasound-guided truncal injection BP block. MELAV50 was determined using the Dixon and Mood up-and-down method. Initial volume of local anaesthetic (LA; 50:50 mixture of bupivacaine 0.5% and lignocaine 2% with 5 µg/ml epinephrine) injected was 6 ml in each trunk, which was varied by 1 ml/trunk for each consecutive patient according to the response of the previous patient. The MELAV50, MELAV95 and MELAV99 were calculated using Probit transformation and logistic regression. RESULTS: Out of the 21 patients, 13 patients had a successful block. The MELAV50, MELAV95 and MELAV99 were 7.41, 10.47 and 12 ml, respectively. Eight patients in whom block failed had sparing in the ulnar and median nerve territories. CONCLUSION: Trunks of the brachial plexus can be identified and targeted for the injection of local anaesthetics. The MELAV50 and MELAV95 required for ultrasound-guided truncal injection brachial plexus block were 7.4 and 10.4 ml, respectively.

Mean effective volume of local anesthetics by nerve conduction technique.

BACKGROUND: This study aimed to investigate whether nerve conduction could be used to objectively evaluate mean effective volume of 1.5% lidocaine after subparaneural or extraparaneural injection. METHODS: Twenty patients undergoing unilateral foot or ankle surgery were randomized into either subparaneural or extraparaneural injection group, and ultrasound-guided continuous popliteal sciatic nerve block was performed. The action potential amplitude of the distal gastrocnemius muscle was monitored. The time of anesthesia onset and dosage of lidocaine were recorded when amplitude declined to 0.5 mV. The operative analgesic effect, score of numeric rating scales, patient's satisfaction, and movement or sensation were recorded during or after surgery. RESULTS: Preoperative dose of local anesthetics (10.7±1.6 vs. 16.2±1.2 mL) and the time of onset (19.4±3.3 vs. 30.4±2.5 min) reduced significantly in the subparaneural group (P<0.05). The intra-operative analgesic effect (1.2±0.422 vs. 1.3±0.483) and the score of resting numeric rating scales (0.6±1.0 vs. 1.9±2.1 and 0.4±0.7 vs. 1.2±1.1) 24 and 48 h after surgery were comparable between groups, but the subparaneural group had markedly lower scores of activity numeric rating scales (0.3±0.6 vs. 2.1±2.0, 0.7±1.2 vs. 2.2±1.9 and 0.5±0.8 vs. 1.5±1.2) at 6, 24 and 48 h, and significantly higher satisfaction (9.7±0.5 vs. 8.8±0.8) (P<0.05). There were no obvious symptoms of movement or sensation within 3 days in two groups. CONCLUSIONS: The nerve conduction can be used to objectively evaluate the mean effective volume of 1.5% lidocaine in different injection groups, and subparaneural injection has more advantages as compared to extraparaneural injection for continuous popliteal sciatic nerve block.

Minimum Effective Volume of 0.75% Ropivacaine for Ultrasound-Guided Axillary Brachial Plexus Block.

Background Ultrasound-guided peripheral nerve block provides direct visualization of nerve and reduces the complications associated with classical landmark guided technique, by reducing the dosage of local anesthetic drugs. This study aims to determine the minimum effective volume (MEAV) of 0.75% ropivacaine for ultrasound-guided axillary brachial plexus block. Methodology A total of 23 patients of age group 18-75 years belonging to ASA grade 1, 2, and 3 were selected based on inclusion criteria. The MEAV was determined by using Dixons & Massey Step-up and Step-down method. The initial volume was selected as 15 mL based on previous studies. Depending on block success or failure, 1 mL of the drug was decreased or increased. Block was assessed in terms of motor and sensory components. The study was aborted after attaining five cases of block failure, followed by five cases of a successful block. Results The MEAV to be given for a successful block in 50% of patients (MEAV50) was 8.62 mL (95%CI 3.54-9.89). The MEAV to be given for a successful block in 90% of patients (MEAV 90) was 11.82 mL (95% CI 9.9-75.7). Conclusion  Ultrasound guidance reduces the dosage of local anesthetic drugs to be used and provides surgical anesthesia without any complications or adverse effects.

Minimum effective volume of bupivacaine 0. 5% for ultrasound-guided retroclavicular approach to infraclavicular brachial plexus block / Volume mínimo efetivo de bupivacaína a 0, 5% para abordagem retroclavicular guiada por ultrassom no bloqueio do plexo braquial por via infraclavicular

Abstract Background and objectives: The current study aimed to determine the minimum effective volume (MEV) of bupivacaine 0.5% in 50% of patients for an ultrasound-guided retroclavicular approach to infraclavicular brachial plexus block. Methods: A total of 25 adult patients who were scheduled for upper limb surgery received an ultrasound-guided retroclavicular approach to infraclavicular brachial plexus block with bupivacaine 0.5%. The needle insertion point was posterior to the clavicle and the needle was advanced from cephalad to caudal. Block success was defined as a composite score of 14 at 30 min after local anesthetic (LA) injection. The minimum effective volume in 50% of patients was determined using the Dixon-Massey up-and-down staircase method. Minimum effective volume for a successful block in 95% of the patients was also calculated using logistic regression and probit transformation. Results: The minimum effective volume of bupivacaine 0.5% resulting in successful block in 50% of patients (MEV50) according to the up-and-down staircase method was found to be 9.6 mL (95% confidence interval (CI), 5.7-13.4). The calculated minimum effective volume required for a successful block in 95% of patients (MEV95) using the probit transformation and logistic regression analysis was 23.2 mL (95% CI, 18.8-36.7). Conclusions: The MEV50 of bupivacaine 0.5% for US-guided retroclavicular approach to infraclavicular brachial plexus block was 9.6 mL and the calculated MEV95 was 23.2 mL. Future studies are required for infraclavicular brachial plexus block with different approaches, other LA agents and different concentrations of bupivacaine.

Resumo Justificativa e objetivos: Determinar o volume mínimo efetivo (VE) de bupivacaína a 0,5% em 50% dos pacientes para uma abordagem retroclavicular guiada por ultrassom no bloqueio do plexo braquial por via infraclavicular. Métodos: Um total de 25 pacientes adultos agendados para cirurgia do membro superior receberam abordagem retroclavicular guiada por ultrassom para o bloqueio do plexo braquial por via infraclavicular com bupivacaína a 0,5%. O ponto de inserção da agulha foi posterior à clavícula e a agulha foi avançada de cefálica para caudal. O sucesso do bloqueio foi definido como um escore composto de 14 aos 30 min após a injeção do anestésico local. O VE em 50% dos pacientes foi determinado com o método de escalonamento progressivo-regressivo de Dixon-Massey. O VE para um bloqueio bem-sucedido em 95% dos pacientes também foi calculado com regressão logística e transformação probit. Resultados: O volume mínimo efetivo (VE50) de bupivacaína a 0,5% que resultou em bloqueio bem-sucedido em 50% dos pacientes, de acordo com o método de escalonamento progressivo-regressivo, foi de 9,6 ml (intervalo de confiança de 95%, IC 5,7-13,4). O cálculo do volume mínimo efetivo necessário para um bloqueio bem-sucedido em 95% dos pacientes (VE95) com a análise de transformação probit e regressão logística foi de 23,2 ml (IC 95%, 18,8-36,7). Conclusões: O VE50 de bupivacaína a 0,5% para abordagem retroclavicular guiada por US para o bloqueio do plexo braquial por via infraclavicular foi de 9,6 ml e o VE95 calculado foi de 23,2 ml. Estudos futuros são necessários para o bloqueio do plexo braquial por via infraclavicular com diferentes abordagens, outros anestésicos locais e diferentes concentrações de bupivacaína.

[Minimum effective volume of bupivacaine 0.5% for ultrasound-guided retroclavicular approach to infraclavicular brachial plexus block]. / Volume mínimo efetivo de bupivacaína a 0,5% para abordagem retroclavicular guiada por ultrassom no bloqueio do plexo braquial por via infraclavicular.

BACKGROUND AND OBJECTIVES: The current study aimed to determine the minimum effective volume (MEV) of bupivacaine 0.5% in 50% of patients for an ultrasound-guided retroclavicular approach to infraclavicular brachial plexus block. METHODS: A total of 25 adult patients who were scheduled for upper limb surgery received an ultrasound-guided retroclavicular approach to infraclavicular brachial plexus block with bupivacaine 0.5%. The needle insertion point was posterior to the clavicle and the needle was advanced from cephalad to caudal. Block success was defined as a composite score of 14 at 30min after local anesthetic (LA) injection. The minimum effective volume in 50% of patients was determined using the Dixon-Massey up-and-down staircase method. Minimum effective volume for a successful block in 95% of the patients was also calculated using logistic regression and probit transformation. RESULTS: The minimum effective volume of bupivacaine 0.5% resulting in successful block in 50% of patients (MEV50) according to the up-and-down staircase method was found to be 9.6mL (95% confidence interval (CI), 5.7-13.4). The calculated minimum effective volume required for a successful block in 95% of patients (MEV95) using the probit transformation and logistic regression analysis was 23.2mL (95% CI, 18.8-36.7). CONCLUSIONS: The MEV50 of bupivacaine 0.5% for US-guided retroclavicular approach to infraclavicular brachial plexus block was 9.6mL and the calculated MEV95 was 23.2mL. Future studies are required for infraclavicular brachial plexus block with different approaches, other LA agents and different concentrations of bupivacaine.

Minimum effective volume of normal saline for epidural volume extension.

BACKGROUND: Rescue strategies like changes in tilt of table are used to raise the level of an inadequate sensory block following intrathecal injection. Epidural volume extension (EVE) refers to an injection of normal saline through epidural catheter following an intrathecal block. It results in a rapid increase in the sensory level of subarachnoid block. Thus, it has been postulated that EVE may be used as a rescue strategy for an inadequate post-spinal sensory block. However, the minimum effective volume (MEV) of normal saline for EVE induced increase in level of spinal block has not been researched till date. We proposed to determine the MEV of normal saline required for EVE induced increase in post-spinal block sensory level. MATERIALS AND METHODS: This prospective sequential allocation study was conducted in consenting adult males after institutional ethical committee approval scheduled for lower limb surgery under combined spinal epidural (CSE) anesthesia, who had an inadequate level of sensory block. Herein, an inadequate level was defined as lower than T10 at 10 min after the intrathecal injection, with no ascent for two consecutive readings taken 2 min apart. The EVE was performed with normal saline injected through epidural catheter, and was considered successful if the level of sensory block increased by two or more dermatomal segments within 5 min of the injection. The volume of normal saline for EVE was decided by using the up-and-down method, with the first patient receiving 10 mL and a dosing interval of 1 mL in subsequent patients. The analysis was done using the formula of Dixon and Massey, which enabled calculation of the MEV with 95% CI. Quantitative parametric data is represented as mean ± SD and nonparametric data as median (range). RESULTS AND CONCLUSION: The MEV of normal saline to raise the level of sensory block by two or more dermatomal segments within 5 min of EVE is 7.4 mL (95% CI: 5.5-9.9 mL).

Minimum effective volume of mepivacaine for ultrasound-guided supraclavicular block.

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.

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.