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Axonal sensitivity and block dynamics

delete2024-11-14
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PRE
AI
J
J.A.W. Wildsmith *
DOI:10.1136/rapm-2024-105950delete
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Abstract

Abstract

En 中文
The role of differential nerve block in the development of analgesia after erector spinae plane block has been questioned. While highly myelinated nerves are more sensitive to local anesthetics than unmyelinated ones in vitro, factors influencing drug diffusion, particularly pKa, are more relevant in the clinical setting. Bupivacaine (the drug most used for an 'analgesic' effect) has a relatively high pKa (8.1), and only 15% of it is present in the lipid permeant, unionized form at pH 7.4 so it will penetrate unmyelinated C fibers relatively easily, but the myelin sheaths around other fiber types are a significant barrier to drug diffusion. The greater sensitivity of myelinated axons to local anesthetic action will only be apparent if the drug can reach their membranes in significant concentrations. In the very dynamic situation pertaining to a local anesthetic injection (no matter the site), diffusion factors mean that the concentration of the drug around the axons is likely to be very low and may result in an effect on unmyelinated fibers only.
Keywords:
Analgesia
Anesthesia, Regional
Animal Experimentation

Journal

R
Regional Anesthesia and Pain Medicine
IF:
3.5
Papers:
4.6K
Citations:
7.7K

Organization

U
University of Dundee
Scholars:
1.3W
Papers: 1.1W
Citations: 1.6W
Cited Papers

Cited Papers

DIFFERENTIAL NERVE BLOCKADE - ESTERS V AMIDES AND THE INFLUENCE OF PKA
err1987-03-01
err32
errOAAI
errWILDSMITH, JAW; GISSEN, AJ; TAKMAN, B; COVINO, BG
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DIFFERENTIAL NERVE BLOCKING ACTIVITY OF AMINO-ESTER LOCAL-ANESTHETICS
err1985-06-01
err34
errOAAI
errWILDSMITH, JAW; GISSEN, AJ; GREGUS, J; COVINO, BG
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PLASMA CONCENTRATIONS OF LOCAL-ANESTHETICS AFTER INTERSCALENE BRACHIAL-PLEXUS BLOCK
err1977-05-01
err76
errOAAI
errWILDSMITH, JAW; TUCKER, GT; COOPER, S; SCOTT, DB; COVINO, BG
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