Originally presented by Dr Alex Goswell
In the era of regional anaesthesia dominated by ultrasound-guidance, is there any need to continue using peripheral nerve stimulators (PNS)?
Nerve Localisation
Peripheral nerve stimulator (PNS) = INSENSITIVE
- False negative
- Current follows the path of least resistance
- Water and fascia can direct current away from nerve
- False positives
- Acceptable motor response even if needle tip is away from nerve
Ultrasound (US) = KING
- Higher block success
- Faster onset
- Longer duration
- Less vascular puncture
- Decreased need for rescue analgesia
PNS + US for difficult to see nerves
- Obturator nerve
- Subgluteal sciatic nerve
- Posterior lumbar plexus
Safety
- Peripheral nerve injury (PNI) rates are consistent despite US
- 2-4 per 10,000 blocks
“Dual guidance” – Motor response at 0.2mA = highly SPECIFIC for intra-neural needle placement
Combined Process
- Set PNS @ 0.5mA
- US-guided needle approach
- Motor response = pull back!
- Probably safer but evidence doesn’t exist
- Eg: adductor canal block
- Allows monitoring for proximity to nerve
Education
- Functional confirmation of anatomy
- Eg axillary brachial plexus block
- Variable location of nerves around axillary artery
- Motor responses with proximity to nerves – confirm what nerve is what
- Eg axillary brachial plexus block
- Safety net
- Helps the teacher
- Novice practitioner loses view of needle tip, PNS allows some confirmation that needle tip is not contacting nerve
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