Minimum Effective Volume of Combined Lidocaine-Bupivacaine for Analgesic Subparaneural Popliteal Sciatic Nerve Block

Abstract

For ultrasound-guided subparaneural (analgesic) popliteal sciatic nerve block, the MEV90 of combined lidocaine 1.0%-bupivacaine 0.25% with epinephrine 5 μg/mL is 13.3 mL (95% confidence interval, 10.2-16.4 mL).

Dose-Finding Methodology for Peripheral Nerve Blocks

“…[36][37][38] In recent dose-finding studies, ED 90 and ED 95 have been most frequently investigated. [27][28][29][30][31][32][33][34] In theory, ED 99 would be more useful than ED 90/95 because it provides the dose required for a successful block in almost 100% of subjects. However, its measurement requires a larger number of patients than that of ED 90 or ED 95 .…”

“…Although this raises theoretical concerns pertaining to toxicity, published dose-finding studies show that the doses used remain within the clinical therapeutic (and not toxic) range. [27][28][29][30][31][32][33][34] Homogeneity of the study population is difficult to accomplish because biologic/genetic variability exists among patients and constitutes an inherent part of the practice of regional anesthesia.…”

“…[27][28][29][30][31] In 4 of the 5 studies, the isotonic regression dose estimator μ3 and a bootstrapping approach for the calculation of confidence intervals (CIs) were used to estimate the target dose at the specific quantile. 27,28,30,31 Following the notation of Stylianou et al, 46 the dose estimator μ3 was defined as the interpolated dose with an estimated toxicity exactly equal to 0.9. Isotonic regression represents a piece-wise, linear, nondecreasing function used in settings where monotonicity constitutes a rational assumption (ie, the success of a nerve block increases with LA dosing increases).…”

“…For example, surgical anesthesia may require different LA doses/volumes/concentrations than postoperative analgesia. 31 Because the combination of different LAs, additives, adjunctive modalities, techniques, and end points can yield an infinite number of variations, it would be futile (as well as impractical) to investigate all possible permutations. Instead, future studies should thrive for pragmatism: they should restrict themselves to combinations that maximize clinical relevance.…”

“…Whereas the Dixon-Mood up-and-down method remains most prevalent, [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] recent trials have advocated using a Biased Coin Design variant. [27][28][29][30][31] Alternately, 3 studies published in 2013 used Bayesian analysis and the Continual Reassessment Method. [32][33][34] Compared to conventional methods, the latter uses all available information (inside and outside of the trial) to determine the optimal dose for every subject enrolled in the trial: in theory, this minimizes the number of failed blocks.…”