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Local anesthesia enhanced with increasing high-frequency ultrasound intensity
Kathleen Cullion1,2, Laura C Petishnok1,2, Tao Sun3
1Laboratory for Biomaterials and Drug Delivery, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA.
Drug Delivery and Translational Research
|April 21, 2020
Summary
Acoustic ultrasound at intensities over 0.5 W/cm² enhanced nerve blockade by tetrodotoxin (TTX), a hydrophilic anesthetic. This ultrasound method improved TTX effectiveness and duration without microbubbles or tissue damage, but did not affect bupivacaine.
Area of Science:
- Pharmacology
- Biophysics
- Anesthesiology
Background:
- Hydrophilic local anesthetics like tetrodotoxin (TTX) face tissue barriers limiting nerve cell access.
- Conventional methods to enhance TTX penetration include chemical enhancers, nanoencapsulation, and ultrasound with microbubbles.
Purpose of the Study:
- To investigate the effect of acoustic intensity on nerve blockade by TTX.
- To compare ultrasound's effect on TTX with its effect on the hydrophobic anesthetic bupivacaine.
Main Methods:
- Peripheral nerve blockade was induced in Sprague-Dawley rats using TTX and bupivacaine.
- Insonation with 1-MHz ultrasound at varying acoustic intensities was applied.
- Nerve block effectiveness, reliability, and duration were assessed, with and without microbubbles.
Main Results:
- Ultrasound at acoustic intensities >0.5 W/cm² significantly improved nerve block by TTX, enhancing effectiveness and prolonging sensory and motor blockade.
- Microbubbles did not augment the ultrasound-mediated enhancement of TTX nerve blockade.
- Ultrasound treatment at the tested intensities caused minimal to no tissue injury.
- Insonation did not enhance nerve blockade by bupivacaine.
Conclusions:
- Acoustic intensity above 0.5 W/cm² is a key factor in ultrasound-mediated enhancement of hydrophilic local anesthetic delivery.
- Ultrasound alone, without microbubbles, can effectively enhance TTX nerve blockade.
- This ultrasound-based approach offers a promising method for improving the delivery and efficacy of hydrophilic local anesthetics.
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