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
  • Safety net
    • Helps the teacher
    • Novice practitioner loses view of needle tip, PNS allows some confirmation that needle tip is not contacting nerve

Useful Links

The role of peripheral nerve stimulation, Anaesthesia 2021