Minimum Effective Volume of Lidocaine for Ultrasound-Guided Infraclavicular Block

Abstract

For single-injection ultrasound-guided ICB, the MEV(90) of lidocaine 1.5% with epinephrine 5 μg/mL is 35 mL. Further dose-finding studies are required for other concentrations of lidocaine, other local anesthetic agents as well as techniques involving multiple injections, a more medial approach to ICB, or precise location of all 3 cords of the brachial plexus.

Ropivacaine in ultrasound-guided femoral nerve block: what is the minimal effective anaesthetic concentration (EC90)?

“…To minimise the required local anaesthetic dose, many studies have been performed to estimate the minimal effective concentration or minimal effective volume [9][10][11][12][13][14]. The up-down sequential method is commonly used to estimate the EC 50 and effective volume for 50% success (EV 50 ) [10], but both are of little clinical importance as by definition they have a 50% failure rate.…”

“…Furthermore, multiple nerve blocks may be required for lower limb surgery [12] leading to the frequent use of maximum recommended total doses. Clinical investigations have therefore been performed to address whether it is possible to reduce local anaesthetic doses but still reliably achieve successful nerve block [9][10][11][12][13][14]. The objective of this study was to estimate the minimal effective anaesthetic concentration of ropivacaine required to produce ultrasound-guided femoral nerve block in 90% of patients (EC 90 ).…”

“…Ropivacaine is a long-acting local anaesthetic that is widely used including for femoral nerve block [4][5][6][7][8]. The success rate of a nerve block relies on multiple interacting variables [9][10][11][12][13][14]; increasing the local anaesthetic volume or concentration generally improves block success rate, but at the expense of an increase in the local anaesthetic dose [9][10][11][12][13][14]. Furthermore, multiple nerve blocks may be required for lower limb surgery [12] leading to the frequent use of maximum recommended total doses.…”

“…Based on the biased-coin design up-down sequential method, ropivacaine concentration given to a patient depended on the response of the previous patient [13]. When a patient had a failed block, the ropivacaine concentration was increased by 0.02% w/v in the next patient.…”

“…A minimum of 45 successful blocks (the smallest multiple of 9 that is > 40) were needed to calculate the EC 90 [13]. Isotonic regression with bias corrected 95% confidence interval (CI) derived by bootstrapping was used to estimate the EC 90 [20].…”