Low volume and high concentration of local anesthetic seems more efficient than high volume and low concentration with Labatʼs sciatic nerve block: a prospective, randomized comparison

Abstract What We Already Know about This Topic What This Article Tells Us That Is New Background Both extra- and intraneural sciatic injection resulted in significant axonal nerve damage. This study aimed to establish the minimum effective volume of intraneural ropivacaine 1% for complete sensory-motor sciatic nerve block in 90% of patients, and related electrophysiologic variations. Methods Forty-seven consecutive American Society of Anesthesiologists physical status I-II patients received an ultrasound-guided popliteal intraneural nerve block following the up-and-down biased coin design. The starting volume was 15 ml. Baseline, 5-week, and 6-month electrophysiologic tests were performed. Amplitude, latency, and velocity were evaluated. A follow-up telephone call at 6 months was also performed. Results The minimum effective volume of ropivacaine 1% in 90% of patients for complete sensory-motor sciatic nerve block resulted in 6.6 ml (95% CI, 6.4 to 6.7) with an onset time of 19 ± 12 min. Success rate was 98%. Baseline amplitude of action potential (mV) at ankle, fibula, malleolus, and popliteus were 8.4 ± 2.3, 7.1 ± 2.0, 15.4 ± 6.5, and 11.7 ± 5.1 respectively. They were significantly reduced at the fifth week (4.3 ± 2.1, 3.5 ± 1.8, 6.9 ± 3.7, and 5.2 ± 3.0) and at the sixth month (5.9 ± 2.3, 5.1 ± 2.1, 10.3 ± 4.0, and 7.5 ± 2.7) (P < 0.001 in all cases). Latency and velocity did not change from the baseline. No patient reported neurologic symptoms at 6-month follow-up. Conclusions The intraneural ultrasound-guided popliteal local anesthetic injection significantly reduces the local anesthetic dose to achieve an effective sensory-motor block, decreasing the risk of systemic toxicity. Persistent electrophysiologic changes suggest possible axonal damage that will require further investigation.

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Effect of Local Anesthetic Dilution on the Onset Time and Duration of Double-Injection Sciatic Nerve Block

Survey of Anesthesiology ◽

10.1097/sa.0000000000000186 ◽

2015 ◽

Vol 59 (6) ◽

pp. 287-288

Author(s):

Gianluca Cappelleri ◽

Andrea Luigi Ambrosoli ◽

Stefania Turconi ◽

Marco Gemma ◽

Erika Basso Ricci ◽

...

Keyword(s):

Sciatic Nerve ◽

Nerve Block ◽

Local Anesthetic ◽

Onset Time ◽

Sciatic Nerve Block ◽

Double Injection

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Ultralong Peripheral Nerve Block by Lidocaine:Prilocaine 1:1 Mixture in a Lipid Depot Formulation

Anesthesiology ◽

10.1097/00000542-200601000-00017 ◽

2006 ◽

Vol 104 (1) ◽

pp. 110-121 ◽

Cited By ~ 23

Author(s):

Lars Söderberg ◽

Henrik Dyhre ◽

Bodil Roth ◽

Sven Björkman

Keyword(s):

Sciatic Nerve ◽

Nerve Block ◽

Local Anesthetic ◽

In Vitro Release ◽

Sciatic Nerve Block ◽

Depot Formulation ◽

Duration Of Action ◽

Depot Preparations

Background The aim of this study was to develop stable and easily injectable lipid depot preparations of local anesthetics in which the drug concentration can be varied according to desired duration of action. Methods The formulations contained a 2.0, 5.0, 10, 20, 40, 60, 80, or 100% eutectic mixture of lidocaine and prilocaine base in medium-chain triglyceride. Duration of sciatic nerve block and local neurotoxicity was investigated in rats with 2.0% lidocaine:prilocaine HCl solution and 99.5% ethanol as controls. The rate of release of local anesthetic from the site of administration and the possibility to predict in vivo depot characteristics from in vitro release data were investigated for the 20 and 60% formulations. Results The duration of sensory sciatic block was prolonged 3 times with the 20% formulation and approximately 180 times with the 60% formulation, in comparison with the 2% aqueous solution. With the 80 and 100% formulations, all animals still showed nerve block after 2 weeks. The in vivo release of local anesthetic could be approximately predicted from in vitro data for the 20% but not for the 60% formulation. The formulations of 60% or greater and ethanol showed neurotoxic effects. Conclusions The pharmaceutical properties of these formulations compare favorably with those of other depot preparations. The high-percentage ones showed the longest duration of action yet reported for sciatic nerve block in rats. The possibility of using a high-concentration local anesthetic depot formulation as an alternative to ethanol or phenol for long-term nerve blocks in chronic pain merits further investigation.

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N-Butyl Tetracaine as a Neurolytic Agent for Ultralong Sciatic Nerve Block

Anesthesiology ◽

10.1097/00000542-199612000-00020 ◽

1996 ◽

Vol 85 (6) ◽

pp. 1386-1394. ◽

Cited By ~ 13

Author(s):

G. K. Wang ◽

M. Vladimirov ◽

C. Quan ◽

W. M. Mok ◽

J. G. Thalhammer ◽

...

Keyword(s):

Sciatic Nerve ◽

Nerve Block ◽

Local Anesthetic ◽

Single Injection ◽

Nerve Fibers ◽

Sciatic Nerve Block ◽

Na Currents ◽

Dependent Inhibition ◽

Withdrawal Response

Background Neurolytic agents such as phenol (5% to 10%) and absolute alcohol have long been used clinically to destroy the pathogenic nerve regions that manifest pain. Both phenol and alcohol are highly destructive to nerve fibers. However, these agents exert only weak local anesthetic effects and therefore are difficult to administer to alert patients without pain. This report describes a tetracaine derivative that displays both local anesthetic and neurolytic properties. Studies with such a compound may lead to the design of neurolytic agents that are more effective and more easily administered than phenol and alcohol. Methods A tetracaine derivative, N-butyl tetracaine quaternary ammonium bromide, was synthesized, and its ability to elicit sciatic nerve block of sensory and motor functions in vivo was tested in rats. A single dose of 0.1 ml N-butyl tetracaine at 37 mM was injected into the sciatic notch. Transverse sections of treated sciatic nerves were subsequently examined to determine the neurolytic effect of this drug. Finally, the local anesthetic properties of N-butyl tetracaine were studied in vitro; both tonic inhibition and use-dependent inhibition of Na+ currents in neuronal GH3 cells were characterized under whole-cell voltage-clamp conditions. Results N-butyl tetracaine at 37 mM (equivalent to 1.11% tetracaine-hydrochloric acid concentration) elicited prolonged sciatic nerve block of the withdrawal response to noxious pinch in rats for more than 2 weeks. The withdrawal response was fully restored after 9 weeks. Parallel to sensory block, motor functions of the hind legs were similarly blocked by this drug. Morphologic examinations 3 and 5 weeks after a single injection of drug revealed degeneration of many sciatic nerve fibers, consistent with the results of functional tests. Finally, N-butyl tetracaine was found to be a potent Na+ channel blocker in vitro. It produced strong tonic and use-dependent inhibition of Na+ currents with a potency comparable to that of tetracaine. Conclusions A single injection of N-butyl tetracaine produces ultralong sciatic nerve block in rats. This compound possesses both local anesthetic and neurolytic properties and may prove useful as a neurolytic agent in pain management.

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