Intraneural injection during nerve stimulator-guided sciatic nerve block at the popliteal fossa

Area of Science:

• Anesthesiology
• Regional Anesthesia
• Ultrasound-Guided Procedures

Background:

• The precise needle tip location during nerve stimulation-guided peripheral nerve blocks remains uncertain.
• This study investigated the frequency of intraneural injection during nerve stimulator-guided sciatic nerve blocks in the popliteal fossa using high-frequency ultrasound.

Purpose of the Study:

• To test the hypothesis that intraneural injection is a frequent event during nerve stimulator-guided sciatic nerve blocks in the popliteal fossa.
• To assess the incidence of intraneural injection and its association with neurological outcomes.

Main Methods:

• Forty-two patients undergoing hallux valgus repair received a sciatic nerve block guided by nerve stimulation.
• Ultrasound imaging was used to measure sciatic nerve area before and after local anesthetic injection, assessing for nerve swelling and local anesthetic spread.
• Intraneural injection was defined by a significant increase in nerve area (>15%) and additional ultrasonographic markers.

Main Results:

• A nerve area increase of ≥15% was observed in 76% of patients post-injection.
• Nerve swelling with fascicular separation occurred in 88% of patients, and local anesthetic spread was noted proximally (14%) and distally (38%).
• Intraneural injection criteria were met in 66% of patients, with greater nerve area increase associated with faster block onset.

Conclusions:

• Intraneural injection is a common occurrence during nerve stimulator-guided sciatic nerve blocks in the popliteal fossa.
• Despite the high incidence of intraneural injection, no neurological complications were observed in the study cohort.
• These findings suggest that intraneural injection may not invariably result in adverse neurological outcomes.