A 3-dimensional ultrasound study of local anesthetic spread during lateral popliteal nerve block: What is the ideal end point for needle tip position?

Andres Missair, Robyn Stacey Weisman, Maria Rene Suarez, Relin Yang, Ralf E. Gebhard

Research output: Contribution to journalArticlepeer-review

47 Scopus citations

Abstract

BACKGROUND AND OBJECTIVES: Recent clinical trials suggest that subfascial (sometimes termed subepineural) injections result in faster block onset and success compared with conventional techniques. This prospective, randomized, observer-blinded study measured and compared the 3-dimensional spread pattern and volume of perineural local anesthetic (LA) in contact with the sciatic nerve after subfascial versus extrafascial lateral popliteal injections. METHODS: Sixty patients were randomly assigned to either the subfascial or the extrafascial injection group. All patients received a single-injection, US-guided lateral popliteal sciatic nerve block for postoperative pain. Depending on group assignment, the needle tip was placed outside or beneath the sciatic fascial sheath for a single injection of 30 mL of ropivacaine 0.5%. Using 3-dimensional ultrasound imaging, postblock scans were acquired to quantify the volume and spread pattern of perineural LA around the sciatic nerve in each group. RESULTS: The mean LA perineural volume for the extrafascial group was 1.48 (SD, 0.50) mL versus a mean of 5.57 (SD, 1.68) mL for the subfascial group, P < 0.05. The mean distance of longitudinal perineural LA spread (along the length of the nerve) for the subfascial group was 66% greater than that observed using the conventional technique (9.3 vs 5.6 cm, P < 0.01). Complete sensory block to pinprick for the extrafascial group was 63% versus 90% (P < 0.05) for the subfascial group. CONCLUSIONS: Placement of the needle tip beneath the complex fascial sheath of the sciatic nerve resulted in significantly greater perineural local anesthetic volume following a single-injection lateral popliteal approach at the nerve bifurcation and was associated with greater sensory blockade and a characteristic laminar LA spread pattern.

Original languageEnglish (US)
Pages (from-to)627-632
Number of pages6
JournalRegional anesthesia and pain medicine
Volume37
Issue number6
DOIs
StatePublished - Nov 1 2012

ASJC Scopus subject areas

  • Anesthesiology and Pain Medicine

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