Estimation of the minimum motor blocking potency ratio for intrathecal bupivacaine and lidocaine. Int J Obstet Anesth. 2008;17:223-227. [PMID: 18501583 DOI: 10.1016/j.ijoa.2007.05.015]

Safe Use of Epidural Corticosteroid Injections: Recommendations of the WIP Benelux Work Group

BACKGROUND

Epidural corticosteroid injections are used frequently worldwide in the treatment of radicular pain. Concerns have arisen involving rare major neurologic injuries after this treatment. Recommendations to prevent these complications have been published, but local implementation is not always feasible due to local circumstances, necessitating local recommendations based on literature review.

METHODS

A work group of 4 stakeholder pain societies in Belgium, The Netherlands, and Luxembourg (Benelux) has reviewed the literature involving neurological complications after epidural corticosteroid injections and possible safety measures to prevent these major neurologic injuries.

RESULTS

Twenty-six considerations and recommendations were selected by the work group. These involve the use of imaging, injection equipment particulate and nonparticulate corticosteroids, epidural approach, and maximal volume to be injected.

CONCLUSION

Raising awareness about possible neurological complications and adoption of safety measures recommended by the work group aim at reducing the risks for these devastating events.

Effect of Baricity of Bupivacaine on Median Effective Doses for Motor Block

Background

The median effective dose (ED₅₀) of a drug gives the amount or dose of drug needed to produce effective therapeutic response or desired effect in at least 50% of the population taking it. Our study focused on determining the ED₅₀ required for effective motor block using hyperbaric and plain bupivacaine, and evaluated the influence of baricity on the ED₅₀ required for motor block.

Material/Methods

A total of 38 patients were randomly assigned into 2 groups according to the baricity of bupivacaine: group P received plain bupivacaine and group H received hyperbaric bupivacaine. The patients were administered 0.5% plain or hyperbaric bupivacaine intrathecally. The dosage of anesthetics in each patient was calculated according to the standard up-down sequential allocation method of Dixon. The first patient in each group received a dose of 7.5 mg bupivacaine, and a dose of 1.0 mg was used as the testing interval. The dose was increased or decreased by 1.0 mg for each patient according to the estimated score of motor block.

Results

The ED₅₀ required for effective motor block in spinal anesthesia was 7.20 and 10.05 mg in groups H and P, respectively. Their relative motor blocking potency ratio was found to be 0.72.

Conclusions

The ED₅₀ for motor block was significantly decreased using hyperbaric bupivacaine intrathecally compared with plain bupivacaine, and the baricity of bupivacaine obviously affected the ED₅₀ for the motor block.

Determination of the median effective dose (ED50) of spinal plain ropivacaine for motor block in adults

BACKGROUND

The median effective dose (ED50) for motor blockade of spinal plain bupivacaine in adults was previously reported; however, that of ropivacaine is unknown. This study aimed to determine the ED50 for motor blockade of spinal plain ropivacaine in adults, evaluating the effect of age on this parameter.

METHODS

133 patients in need of combined spinal and epidural anesthesia were enrolled in this sequential allocation study. They were divided into 6 groups according to age: 20-30, 31-40, 41-50, 51-60, 61-70, and 71-80 years. Using the up-and-down method of Dixon, the ropivacaine dose was varied according to the preceding patient's reaction. The modified Bromage and hip motor function score was used to evaluate the degree of motor block after administration of ropivacaine. ED50 values were estimated by the method of Dixon and Massey. Other indexes, including the onset of motor block, the analgesia level, and the duration of motor block were also assessed.

RESULTS

the ED50 for motor block of intrathecal ropivacaine was 20.96 mg (95 % CI: 19.83-22.16 mg) in 20-30, 19.05 mg (95 % CI: 18.43-19.70 mg) in 31-40, 17.91 mg (95 % CI: 17.10-18.76 mg) in 41-50, 17.91 mg (95 % CI: 16.49-19.44 mg) in 51-60, 16.11 mg (95 % CI: 14.50-17.90 mg) in 61-70, and 15.75 mg (95 % CI: 13.98-17.73 mg) in 71-80 year-old patients. Maximum cephalic analgesic effects were obtained at the L4-T6 and L4-T2 levels, at 5 and 10 min, respectively, after intrathecal administration of ropivacaine in all groups.

CONCLUSION

the ED50 for motor block in spinal plain ropivacaine decreases with advancing age, indicating that age has an influence on the potency of spinal ropivacaine.

Effect of Concentration on Median Effective Dose (ED50) for Motor Block of Intrathecal Plain Bupivacaine in Elderly Patients

Background

The aim of the study was to determine the median effective dose (ED₅₀) for motor block of various concentrations of intrathecally administered plain bupivacaine.

Material/Methods

Between 2011 and 2013, 64 patients aged ≥70 years, undergoing transurethral, or lower limb surgery with combined spinal and epidural anesthesia in a single hospital were enrolled. The patients were randomized into 3 groups to receive intrathecal 0.75% bupivacaine (Group 1), 0.375% bupivacaine (Group 2) or 0.25% bupivacaine (Group 3). Spinal anesthesia was achieved using injections of up-and-down doses of 0.75%, 0.375%, or 0.25% plain bupivacaine. The first patient in each group received 7.5 mg bupivacaine, and the testing interval was set at 0.75 mg. The efficacy of motor block in both legs was determined using a modified Bromage and a hip motor function scale. The ED₅₀ for motor block was estimated according to the Dixon’s up-and-down method.

Results

The ED₅₀ for motor block of bupivacaine was 6.10 (95% CI 5.58–6.66) mg in Group 1, 6.04 (95% CI 5.82–6.28) mg in Group 2, and 5.43 (95% CI 5.19–5.67) mg in Group 3. There were significant differences in the ED₅₀ for motor block among the groups (P=0.008).

Conclusions

The ED₅₀ doses for motor block with 3 bupivacaine concentrations were significantly different in elderly patients; the ED₅₀ dose of 0.75% bupivacaine being significantly higher than that of 0.25% bupivacaine.

Pharmacokinetics and pharmacodynamics of lignocaine: A review

Lignocaine is an essential drug on World Health Organisation essential drug list, considered efficacious, safe and cost-effective for any health-care system. Despite its ubiquitous use in medicine and surgery, there are few detailed reviews of its pharmacokinetics and pharmacodynamics. Being an amide-type local anesthetic and Class 1b antiarrhythmic, lignocaine is most frequently used clinically for its anesthetic and antiarrhythmic benefits. However, lignocaine has important antinociceptive, immuno-modulating, and anti-inflammatory properties. Information pertaining to the pharmacokinetics and pharmacodynamics of lignocaine was examined by performing a literature search of PubMed, Embase and MEDLINE (via Ovid), pharmacology textbooks and online sources. We present a focused synopsis of lignocaine’s pharmacological composition, indications for use and mechanisms of action, focusing on its anti-inflammatory, immuno-modulating and analgesia effects. In addition we review the dosing regimes and infusion kinetics of lignocaine in the clinical setting. Finally, we review the evidence for ligocaine’s modulation of the inflammatory response during major surgery and its specific effects on cancer recurrence. These indirect effects of local anesthetics in tumor development may stem from the reduction of neuroendocrine responses to the stress response elicited by major surgery and tissue damage, enhanced preservation of immune-competence, in addition to opioid-sparing effects of modulating tumor growth.

Application of the Continual Reassessment Method to Dose-finding Studies in Regional Anesthesia

Background

Previously reported estimates of the ED95 doses for local anesthetics used in brachial plexus blocks vary. The authors used the continual reassessment method, already established in oncology trials, to determine the ED95 dose for 0.5% bupivacaine for the ultrasound-guided supraclavicular block.

Methods

A double-blind, prospective trial was scheduled for 40 patients of American Society of Anesthesiologists class I–III presenting for upper limb surgery and supraclavicular block. The study dose to be administered was arbitrarily divided into six dose levels (12, 15, 18, 21, 24, and 27 ml) with a priori probabilities of success of 0.5, 0.75, 0.90, 0.95, 0.98, and 0.99 respectively. A continual reassessment method statistical program created a dose–response curve, which would shift direction depending on the success or failure of the block. Our starting dose was 21 ml and the next allocated dose was reestimated by the program to be the dose level with the updated posterior response probability closest to 0.95.

Results

After recruitment of eight patients, our initial dose levels and associated probabilities were deemed too low to determine the ED95. Updated a prioris were calculated from the statistical program, and the study recommenced with a new starting dose of 30 ml. On completion, the ED95 dose was estimated to be 27 ml (95% CI, 24–28 ml).

Conclusions

The continual reassessment method trial design provided a credible estimate for the ED95 dose for 0.5% bupivacaine for our technique of supraclavicular block and may be of value as a statistically robust method for dose-finding studies in anesthesiology.

Optimal effective concentration of ropivacaine for postoperative analgesia by single-shot femoral–sciatic nerve block in outpatient knee arthroscopy

Objective

To compare analgesic and mobility effects of different ropivacaine concentrations in femoral–sciatic nerve block, for postoperative analgesia in knee arthroscopy.

Methods

Outpatients (American Society of Anesthesiologists physical classification status of I or II), scheduled for elective knee arthroscopy, were randomly allocated to one of seven groups, prospectively investigating different concentrations of ropivacaine (0.12%; 0.14%; 0.16%; 0.18%; 0.20%; 0.22% or 0.50%), for ultrasound-guided femoral–sciatic nerve block procedures for postoperative analgesia. Visual analogue scale (VAS) pain scores and motor block evaluation scales were observed at 4, 8, 16 and 24 h postsurgery.

Results

In total, 105 patients were enrolled; results were analysed for 103. VAS scores for the 0.12%, 0.14% and 0.16% groups were significantly different from the 0.50% group. There were no significant differences between the 0.18%, 0.20%, 0.22% and 0.50% groups: half maximal effective concentrations and 95% maximal effective concentrations of ropivacaine were 0.158 (95% confidence intervals [CI] 0.149, 0.167) and 0.198 (95% CI 0.186, 0.221), respectively. Rates of motor blockade (Bromage score or hip motor function scale > 0) were significantly different between the 0.50% group and all other ropivacaine doses.

Conclusion

The 0.20% ropivacaine dose for femoral–sciatic nerve block in knee arthroscopy provided satisfactory postoperative analgesia, while preserving ability of motion.

Injectable corticosteroid and local anesthetic preparations: a review for radiologists

Corticosteroids and local anesthetics are some of the most commonly administered medications in radiology departments. These medications have marked variability in their formulations, which may increase their adverse event profile for specific procedures. In particular, certain corticosteroid preparations are associated with adverse central nervous system (CNS) sequelae. This is most likely due to distal embolization by particulate formulations. Nonparticulate steroid formulations are not associated with such events. Local anesthetics have severe CNS and cardiac adverse effects if injected intravascularly and have recently been associated with intraarticular chondrolysis if used in large doses. This review discusses these medications with particular emphasis on their established and postulated adverse effects. The administering radiologist should be aware of these potential effects and how best to reduce their occurrence.

Current world literature

This bibliography is compiled by clinicians from the journals listed at the end of this publication. It is based on literature entered into our database between 1 February 2008 and 31 January 2009 (articles are generally added to the database about two and a half months after publication). In addition, the bibliography contains every paper annotated by reviewers; these references were obtained from a variety of bibliographic databases and published between the beginning of the review period and the time of going to press. The bibliography has been grouped into topics that relate to the reviews in this issue.