Minimum Local Anesthetic Dose Research Articles

Ultrasound guided pediatric caudal dose: a two-center randomized controlled trial

BackgroundThe drug volume to be used in caudal in pediatric patients has remained an unmet issue since long. We determined the minimum drug volume required to reach T10 level in pediatric patients using ultrasonography and compared it with the already established volume by Armitage formula.AimTo determine the minimum effective caudal local anesthetic dose using ultrasound guidance.MethodsStudy was performed at two centres and at each centre, 50 pediatric patients (Total 100 patients), aged 1 to 3 years, undergoing below umbilical surgeries were included and randomised into two groups of 25 each (Total 50) to receive ultrasound guided drug volume vs. Armitage formula based volume. The volume required to reach T10 level was assessed with ultrasound in one group. Also, maximum height achieved, cutaneous level achieved after 15 min, FLACC scores 30 min post extubation and parental satisfaction scores were noted.ResultsThe mean drug volume required to reach T10 level in Group U was 0.755 ± 0.053 ml/kg with a P value < 0.001. (Compared to the drug volume of 1 ml/kg using one sample t test). The highest level achieved in both groups were calculated as the mode value of T8 and T7 in Group U and Group A respectively. The highest cutaneous level achieved after 15 min was also calculated as the mode value of T4 in both groups. FLACC scores at 30 min were also comparable. Satisfaction scores were comparable in both groups.ConclusionA volume of 0.7 ml/kg of local anaesthetic in pediatric caudal block is sufficient to achieve a target of T10 level for infraumblical surgeries.

Minimum Local Anesthetic Dose of Ropivacaine in Cesarean Section for Real-Time Ultrasound-Guided Spinal Anesthesia Using 24-Gauge versus 26-Gauge Needles Based on Fluid Simulation Technology: A Randomized Controlled Trial.

Previous research has demonstrated that real-time ultrasound-guided (UG) spinal anesthesia requires a higher minimum local anesthetic dose (MLAD) compared to traditional methods. However, the precise MLAD of ropivacaine for UG cesarean sections remains undetermined. In this study, we ascertained the MLAD of ropivacaine for cesarean section. We also investigated the mechanism underlying the diffusion of ropivacaine within the spinal canal using fluid simulation technology. We randomly placed 60healthy parturients undergoing elective cesarean section with real-time UG spinal anesthesia into Groups I (26-gauge spinal needle) and II (24-gauge spinal needle). For the first parturient in both groups, 15 mg of ropivacaine was administered intrathecally. Based on the effective or ineffective response of the previous parturient, the dose for the subsequent parturient was increased or decreased by 1 mg. Spinal anesthesia characteristics and side effects were recorded. A computer-generated spinal canal model was developed. Leveraging fluid dynamics simulation technology, we documented the diffusion of ropivacaine in the spinal canal using 26-and 24-gauge spinal needles. The MLADs in Groups I and II were 12.728 mg (12.339-13.130 mg) and 9.795 mg (9.491-10.110 mg), respectively. No significant difference was observed in the onset times and durations of sensory or motor blocks, incidence of complications, or neonatal Apgar scores between both groups. Fluid simulation modeling indicated that the 26-gauge spinal needle achieved a higher distribution level more quickly; however, its peak drug concentration was lower compared to the 24-gauge spinal needle. For cesarean section anesthetization, the required MLAD of ropivacaine when using a real-time UG 26-gauge spinal needle is significantly greater than that with a 24-gauge needle. The spinal needle diameter influences ropivacaine's MLAD by markedly affecting its diffusion rate within the spinal canal.

Comparing the minimum local anesthetic dose of ropivacaine in real-time ultrasound-guided spinal anesthesia and traditional landmark-guided spinal anesthesia: a randomized controlled trial of knee surgery patients.

BackgroundThrough previous studies and clinical practice, we have found that real-time ultrasound-guided (UG) spinal anesthesia (SA) and traditional landmark-guided (LG) SA each require a different minimum local anesthetic dose (MLAD) of ropivacaine. For this study, we used Dixon’s up-and-down sequential method to analyze and compare the MLAD of different ropivacaine concentrations required for the UG and LG SA methods.MethodsA total of 120 patients undergoing knee surgery were consecutively recruited and randomly divided into four groups (30 patients per group). These groups were categorized as follows: Group I: high ropivacaine ultrasound-guided (HRUG), Group II: low ropivacaine ultrasound-guided (LRUG), Group III: high ropivacaine landmark-guided (HRLG), and Group IV: low ropivacaine landmark-guided (LRLG). SA was established by a bolus administration of up-and-down doses of 0.75% or 0.5% plain ropivacaine. Initial doses of 16, 18, 12, and 14 mg were administered to groups I–IV, and after that, increased or decreased by 1.5 mg according to dose effectiveness. Upon identifying the intervertebral puncture level, a lumbar X-ray was performed with metal markers, and actual radiographic findings were identified and compared to the initial markings.ResultsFor UG groups, the MLAD in the LRUG group was significantly higher than in the HRUG group [20.192 mg (95% CI, 19.256–21.174) versus 17.176 mg (95% CI, 16.276–18.124), respectively; P<0.001]. For LG groups, the MLAD in the LRLG group was significantly higher than in the HLRG group [14.478 mg (95% CI, 13.364–15.500) versus 13.201 mg (95% CI, 11.959–14.571), respectively; P=0.047]. When comparing both high ropivacaine groups (HRGs: I/III) to the low ropivacaine groups (LRGs: II/IV), we found that both UG subgroups (I/II) had a significantly higher MLAD than LG subgroups (III/IV) (P<0.001). US identified L4–5 in up to 90% of cases. Comparatively, palpation was successful in only 33.3% of patients. The rates of cephalad localization by US and palpation were 6.67% vs. 66.67%, respectively (P=0.002).ConclusionsWe found a higher MLAD of ropivacaine was required for UG SA at the L4–5 level due to the method providing a more accurate (less cephalad) localization than traditional LG SA.Trial RegistrationChinese Clinical Trial Registry ChiCTR2000033158.

Determination of the initial minimum effective dose of 0.5% bupivacaine with 20 μg of fentanyl for an operative fixation of fractured neck of femur: a prospective, observational trial.

Fractured neck of femur (FNF) is a common cause of morbidity and mortality in elderly. Spinal catheter allows fractionation of local anesthetic dose which combined with intrathecal opioid leads to a dose reduction and better hemodynamic stability. The primary objective of this paper was to investigate the initial minimum local anesthetic dose (iMLAD) of 0.5% isobaric bupivacaine with 20 μg of fentanyl administered via spinal catheter in order to commence the operative fixation of FNF. A prospective, single-blinded, adaptive clinical trial with patients undergoing dynamic hip screw implantation (DHS) or hemiarthroplasty (HEMI) due to FNF. The Dixon and Massey's up and down method was used to determine the ED50 of intrathecal bupivacaine. This figure was confirmed with Probit analysis, in addition to the ED95. Using the Dixon and Massey's approach, the iMLADED50 for DHS was 0.29 mL (1.45 mg) and the iMLADED50 for HEMI was 0.33 mL (1.65 mg) of 0.5% isobaric bupivacaine. The Probit analyses demonstrated that the iMLADED95 for DHS and HEMI were 0.32 mL (1.6 mg) and 0.34 mL (1.7 mg) respectively. The mean cumulative dose of 0.5% bupivacaine for the whole surgery was 0.67 mL (3.35 mg) and 0.87 mL (4.35 mg) in the DHS and HEMI groups, respectively. This study demonstrates that the placement of a spinal catheter allows for careful titration of local anesthetic, enabling a reduction of the initial intrathecal dose of 0.5% isobaric bupivacaine below 0.4 mL (2 mg) and leading to a significant reduction of a dose required for the whole surgery when combined with an intrathecal opioid.

Minimum local anesthetic dose of ropivacaine in real-time ultrasound-guided intraspinal anesthesia for lower extremity surgery: a randomized controlled trial.

Despite the many advantages real-time ultrasound-guided lumbar anesthesia has over traditional lumbar anesthesia, it seemingly involves a much higher dose of ropivacaine. This study aimed to determine the minimum local anesthetic dose (MLAD) and the 95% confidence interval of ropivacaine at different concentrations in real-time ultrasound-guided lumbar anesthesia for lower extremity surgery. A total of 60 patients who were consecutively scheduled for selective lower extremity surgery were enrolled. The patients were randomly divided into two groups, which each received different concentrations of ropivacaine at different initial dosages when Dixon's up-and-down sequential method was applied. The high ropivacaine group and the low ropivacaine group received 0.75% and 0.5% ropivacaine, respectively. The patients' baseline characteristics, the MLAD, and the 95% confidence interval were assessed. The highest level of sensory block, time to reach the T10 sensory block, duration for sensory blocks higher than T10, highest plane for sensory block, and onset time and duration for motor block were recorded. Comparisons were also made between the patients' vital signs and adverse reactions. The minimum local anaesthetic dose (MLAD) and 95% confidence interval in the high ropivacaine group and the low ropivacaine group were 17.176 (16.276 to 18.124) and 20.192 (19.256 to 21.174) mg, respectively. Moreover, motor block maintenance was greatly reduced in the 0.5% ropivacaine compared to the 0.75% ropivacaine group (P=0.0309). In real-time ultrasound-guided intraspinal anesthesia for lower extremity surgery, both 0.75% and 0.5% ropivacaine provide satisfactory anesthesia. Our results suggest that shortened motor block duration can hold benefits for patients including earlier mobilization and a quicker rehabilitation process.

Minimal Local Analgesic Dose of Intrathecal Bupivacaine and Ropivacaine in Patients Undergoing Cesarean Section: A Comparative Study

Introduction: Spinal anesthesia is a reasonable option for cesarean section. Bupivacaine and ropivacaine have been used as intrathecal drugs alone or in combination with various opiods. Ropivacaine is considered a valid and safe alternative to bupivacaine for intrathecal anesthesia. This study aims to determine the median effective dose (ED50) of intrathecal bupivacaine and ropivacaine for cesarean section and defines this as the minimum local anesthetic dose (MLAD). Methods: Forty pregnant women undergoing elective cesarean section were allocated and randomized into two groups. The initial dose was 13mg for both ropivacaine and bupivacaine groups and was increased or decreased of 0.3mg, using the up-down sequential allocation technique. Efficacy was accepted if adequate sensory dermatomal anesthesia to pinprick to T6 was attained within 20 minutes after intrathecal injection and required no supplemental epidural injection for procedure until at least 50 minutes after the intrathecal injection of test drugs. The MLAD for both bupivacaine and ropivacaine was calculated with 95% confidence interval using the formula of Dixon and Massey. Comparison of different variables between the groups was done using t-test with significant p value at &lt; 0.05. Results: The two groups were comparable in terms of demographic profile and clinical characteristics. The MLAD of ropivacaine and bupivacaine were 11.63 mg (95% CI, 11.5-12.92) and 10.459 mg (95% CI, 10.12-10.87) respectively. The potency ratio between spinal ropivacaine and bupivacaine was 0.89. Conclusion: Ropivacaine provided clinically surgical anaesthesia of shorter duration without compromising neonatal outcome and can be used as a safe alternative to bupivacaine.

Pharmacodynamics and Pharmacokinetics of Lidocaine in a Rodent Model of Diabetic Neuropathy.

Clinical and experimental data show that peripheral nerve blocks last longer in the presence of diabetic neuropathy. This may occur because diabetic nerve fibers are more sensitive to local anesthetics or because the local anesthetic concentration decreases more slowly in the diabetic nerve. The aim of this study was to investigate both hypotheses in a rodent model of neuropathy secondary to type 2 diabetes. We performed a series of sciatic nerve block experiments in 25 Zucker Diabetic Fatty rats aged 20 weeks with a neuropathy component confirmed by neurophysiology and control rats. We determined in vivo the minimum local anesthetic dose of lidocaine for sciatic nerve block. To investigate the pharmacokinetic hypothesis, we determined concentrations of radiolabeled (C) lidocaine up to 90 min after administration. Last, dorsal root ganglia were excised for patch clamp measurements of sodium channel activity. First, in vivo minimum local anesthetic dose of lidocaine for sciatic nerve motor block was significantly lower in diabetic (0.9%) as compared to control rats (1.4%). Second, at 60 min after nerve block, intraneural lidocaine was higher in the diabetic animals. Third, single cell measurements showed a lower inhibitory concentration of lidocaine for blocking sodium currents in neuropathic as compared to control neurons. We demonstrate increased sensitivity of the diabetic neuropathic nerve toward local anesthetics, and prolonged residence time of local anesthetics in the diabetic neuropathic nerve. In this rodent model of neuropathy, both pharmacodynamic and pharmacokinetic mechanisms contribute to prolonged nerve block duration.

Adding sufentanil to levobupivacaine or ropivacaine intrathecal anaesthesia affects the minimum local anaesthetic dose required

We carried out this prospective, randomized, double-blind study in order to evaluate whether the intrathecal addition of sufentanil 3.3 mcg affects both the minimum local anaesthetic dose (MLAD) of spinal levobupivacaine and ropivacaine for a caesarean section and enhances the spinal block characteristics. One hundred and eighty women were randomly allocated into four groups: levobupivacaine (Group L), levobupivacaine plus sufentanil (Group L+S), ropivacaine (Group R) and ropivacaine plus sufentanil (Group R+S). Each received 3 ml of the study solution intrathecally as part of a combined spinal/epidural technique. The initial dose was 12 mg for Groups L and L+S, and 15 mg for Groups R and R+S. The test solution was required to achieve a visual analogue pain score (VAPS) of 30 mm or less to be considered effective at skin incision, uterine incision, birth, peritoneal closure and at the conclusion of surgery. Effective or ineffective responses determined a 0.5 mg decrease or increase of the same drug, respectively, for the next patient in the same group, using an up-down sequential allocation. Using the Dixon and Massey formula, the MLAD was 10.65 mg [confidence interval (CI) 95%: 10.14-11.56] in Group L, 4.73 mg (CI 95%: 4.39-5.07) in Group L+S, 14.12 mg (CI 95%: 13.50-14.60) in Group R and 6.44 mg (CI 95%: 5.86-7.02) in Group R+S. The addition of sufentanil reduced the MLAD of both the local anaesthetics. It did not affect their potency ratio significantly and resulted in enhanced spinal anaesthesia.

490. The Effect of Different Volumes of Intrathecal Ropivacaine on the Minimum Local Anesthetic Dose (MLAD) in Women Undergoing Cesarean Section

490. The Effect of Different Volumes of Intrathecal Ropivacaine on the Minimum Local Anesthetic Dose (MLAD) in Women Undergoing Cesarean Section

490: The Effect of Different Volumes of Intrathecal Ropivacaine on the Minimum Local Anesthetic Dose (MLAD) in Women Undergoing Cesarean Section

490: The Effect of Different Volumes of Intrathecal Ropivacaine on the Minimum Local Anesthetic Dose (MLAD) in Women Undergoing Cesarean Section

The Effect of Different Volumes of Intrathecal Ropivacaine on the Minimum Local Anesthetic Dose (MLAD) in Women Undergoing Cesarean Section

The Effect of Different Volumes of Intrathecal Ropivacaine on the Minimum Local Anesthetic Dose (MLAD) in Women Undergoing Cesarean Section

678. Intratechal Ropivacaine in Cesarean Section: Determination of the “minimum Local Anaesthetic Dose (MLAD)”

678. Intratechal Ropivacaine in Cesarean Section: Determination of the “minimum Local Anaesthetic Dose (MLAD)”

678: Intratechal Ropivacaine in Cesarean Section: Determination of the “minimum Local Anaesthetic Dose (MLAD)”

678: Intratechal Ropivacaine in Cesarean Section: Determination of the “minimum Local Anaesthetic Dose (MLAD)”

494: Effect of Intrathecal Sufentanil Addition on the Minimum Local Anesthetic Dose (MLAD) of Intrathecal Levobupivacaine and Ropivacaine for Cesarean Section

494: Effect of Intrathecal Sufentanil Addition on the Minimum Local Anesthetic Dose (MLAD) of Intrathecal Levobupivacaine and Ropivacaine for Cesarean Section

Intratechal Ropivacaine in Cesarean Section: Determination of the “minimum Local Anaesthetic Dose (MLAD)”

Intratechal Ropivacaine in Cesarean Section: Determination of the “minimum Local Anaesthetic Dose (MLAD)”

494. Effect of Intrathecal Sufentanil Addition on the Minimum Local Anesthetic Dose (MLAD) of Intrathecal Levobupivacaine and Ropivacaine for Cesarean Section

494. Effect of Intrathecal Sufentanil Addition on the Minimum Local Anesthetic Dose (MLAD) of Intrathecal Levobupivacaine and Ropivacaine for Cesarean Section

Effect of Intrathecal Sufentanil Addition on the Minimum Local Anesthetic Dose (MLAD) of Intrathecal Levobupivacaine and Ropivacaine for Cesarean Section

Effect of Intrathecal Sufentanil Addition on the Minimum Local Anesthetic Dose (MLAD) of Intrathecal Levobupivacaine and Ropivacaine for Cesarean Section

Ropivacaine spinal anesthesia in neonates: a dose range finding study

Our primary aim was to determine the minimum local anaesthetic dose (MLAD) defined as the median effective local anesthetic dose for spinal anesthesia in neonates. Secondary aims were to determine the dose-response curve for spinal anesthesia including the clinically relevant ED95 dose and to describe the duration of motor block following ropivacaine spinal anesthesia. Fifty neonates less than 55 weeks postmenstrual age (PMA) having inguinal hernia repair were enrolled. The study was performed in two stages. The MLAD dose of ropivacaine was determined by up-down sequential allocation. An expanded dose ranging study was then performed with dose escalation to doses predicted to fall in the ED50-95 range dose. Probit and logit analysis on all patients was used to compare ED50 with the value described by the Dixon-Massey method and to determine doses up to the ED95. Fifty neonates with a mean PMA of 43 weeks and mean weight of 3.7 kg were enrolled. The motor block MLAD (95% confidence interval) determined by the Dixon-Massey method was 0.51 (0.38-0.64) mg x kg(-1). A logistic regression analysis of the results of all 50 patients confirmed the Dixon-Massey result. The ED50 (95% CI) was 0.50 (0.39-0.63) mg x kg(-1) with an estimated ED95 was 1.08 (0.70-1.67) mg x kg(-1). These values were confirmed by probit analysis. Overall the mean duration (95% confidence interval) of lower limb motor blockade was 60.0 min (51.5-68.5 min). The duration of anesthesia far exceeded surgical duration in all successful cases. Ropivacaine is an effective agent for spinal anesthesia in neonates at a recommended dose of 1.08 mg.kg(-1). The motor block duration, however, is significantly shorter than equivalent agents and highly variable in duration.

Minimum local anaesthetic dose (MLAD) of intrathecal levobupivacaine and ropivacaine for Caesarean section*

We determined the minimum local anaesthetic dose (MLAD) of spinal levobupivacaine and ropivacaine for Caesarean section. Ninety women were randomly allocated to two groups and received 3 ml of study solution by a combined spinal/epidural technique. The initial dose was 12 mg for levobupivacaine and 17 mg for ropivacaine groups. To be considered effective, a test solution had to achieve a visual analogue pain score (VAPS) of 30 mm or less at skin incision, uterine incision, birth, peritoneal closure, and at the end of surgery. Effective or ineffective responses determined, respectively, a 0.3 mg decrease or increase of the same drug for the next patient in the same group, using up-down sequential allocation. The MLAD of levobupivacaine was 10.58 mg (CI 95%: 10.08-11.09) and the MLAD of ropivacaine 14.22 mg (CI 95%: 13.67-14.77), using the Dixon and Massey formula. The potency ratio between spinal levobupivacaine and spinal ropivacaine was 1.34.

Minimum effective local anaesthetic dose of isobaric levobupivacaine and ropivacaine administered via a spinal catheter for hip replacement surgery

Continuous spinal anaesthesia with spinal catheters allows incremental dosing of local anaesthetic and, consequently, less haemodynamic changes. However, little is known about the required doses. Therefore, we designed a study to assess the minimum effective local anaesthetic dose (MLAD) of levobupivacaine and ropivacaine in this context. Forty-one patients undergoing hip replacement surgery were randomly allocated to one of the two local anaesthetic groups in a double-blind manner. The initial dose of local anaesthetic was determined by the response of the previous patient: the effective dose resulted in a 1 mg decrease in the dose of levobupivacaine or ropivacaine, and an ineffective dose resulted in a 1 mg increase. The MLAD was calculated by the Dixon up-and-down method. The MLAD of levobupivacaine was 11.7 mg (95% CI, 11.1-12.4) and that of ropivacaine 12.8 mg (95% CI, 12.2-13.4). These doses are significantly smaller than doses reported before for single-shot spinal anaesthesia. Continuous spinal anaesthesia allows the use of relatively small doses of local anaesthetic.