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Relation between functional deficit and intraneural local anesthetic during peripheral nerve block. A study in the
F A Popitz-Bergez1, S Leeson, G R Strichartz
1Department of Anesthesia Research Laboratories, Brigham and Women's Hospital, Boston, Massachusetts 02115, USA.
Anesthesiology
|September 1, 1995
Summary
Local anesthetic (LA) concentration inside nerves correlates with nerve block depth. Only a small fraction of injected LA enters the nerve, with content decreasing as function returns.
Area of Science:
- Pharmacology
- Neuroscience
- Anesthesiology
Background:
- Local anesthetics (LA) block nerve impulses by penetrating nerves.
- Understanding the relationship between intraneural LA concentration and functional loss in vivo is limited.
Purpose of the Study:
- To investigate the relationship between functional changes and intraneural LA content during peripheral nerve block in vivo.
Main Methods:
- Rats underwent sciatic nerve block using radiolabeled lidocaine.
- Intraneural LA uptake and distribution were measured at various time points and functional block stages.
- In vivo concentrations were compared to in vitro equilibrium uptake.
Main Results:
- Intraneural lidocaine peaked around 3 minutes and decreased over 70 minutes.
- Intraneural LA content was 1.6% during full block, decreasing to 0.3% and 0.065% as function returned.
- Longitudinal LA distribution remained constant despite varying total content.
Conclusions:
- Only a small percentage of injected LA penetrates the nerve during peripheral nerve block.
- Intraneural LA concentration directly correlates with the depth and duration of the functional block.