Does Interneural Local Anesthetic Spread at the Site of Sciatic Nerve Bifurcation Shorten Block Onset Time?

University Health Network, Toronto88 enrolled

Overview

Following foot and ankle surgery, ultrasound-guided sciatic nerve block (SNB) at the popliteal fossa decreases post-operative pain and opioid consumption. At the popliteal fossa, the sciatic nerve bifurcates to form the Common Peroneal Nerve (CPN) and Tibial Nerve (TN). Studies have shown that when both branches are blocked separately distal to the bifurcation site, block onset time is reduced by 30%. Through clinical observation, the investigators found that onset time is further shortened when ultrasound-guided SNB is performed at the site of bifurcation. This is because the local anesthetic spreads interneurally. The purpose of this study is to compare the block onset time of an ultrasound-guided sciatic nerve block at the site of nerve bifurcation with the blockade of each terminal nerve separately (TN and CPN) distal to sciatic nerve bifurcation.

Study Type

INTERVENTIONAL

Allocation

RANDOMIZED

Purpose

OTHER

Masking

DOUBLE

Enrollment

Conditions

Post Operative Analgesia Regional Anesthesia Sciatic Nerve Block

Eligibility

Sex: ALLMin age: 18 YearsMax age: 85 Years

Medical Language ↔ Plain English

Inclusion Criteria: * ASA physical status I-III * 18-85 years of age, inclusive * 50-120 kg, inclusive * 150 cm of height or greater Exclusion Criteria: * Contraindications to sciatic nerve block (e.g., allergy to local anesthetics, coagulopathy, malignancy or infection in the popliteal area) * Significant peripheral neuropathy or neurological disorder affecting the lower extremity * Pregnancy * History of alcohol or drug dependency/abuse * History of significant psychiatric conditions that may affect patient assessment

Outcomes

Primary Outcomes

Block onset Time

We aim to compare the block onset time of an ultrasound-guided sciatic nerve block at the site of nerve bifurcation resulting in interneural spread of local anesthetic with that of blockade of each terminal nerve separately (TN and CPN), distal to sciatic nerve bifurcation. We hypothesize that sciatic nerve blockade at the site of bifurcation with interneural local anesthetic spread within a common epineural sheath results in shorter onset time compared to blockade of each terminal nerve distal to sciatic nerve bifurcation.

Time frame: every 5 minutes up to 45 minutes of the block or until surgery starts

Secondary Outcomes

Extent of longitudinal local anesthetic solution spread

Time frame: starting at block administration till 5 minutes after complete injection

Nerve diameter prior to and following injection

Time frame: starting at block administration till 5 minutes after complete injection

Block procedure time

Time frame: starting at block administration till complete injection(up to 10 minutes)

Number of skin punctures required.

Time frame: starting at first attempt of block administration till complete injection(up to 10 minutes)

Block success rate

Time frame: starting after complete injection up to 45 minutes

Incidence of block-related complications

Incidence of block-related complications (vascular puncture, hematoma formation, intravascular injection and post-operative neurologic deficit) will be documented, but due to the very low incidence in all block-related complications, this study is not powered to show a difference in safety

Time frame: immediately , at 24 hours and Post operative day 7

Postoperative pain

Postoperative pain: Postoperative pain using a verbal rating score (0-10, where 0= no pain, 10=excruciating pain) at 0, 30, 60, 90 and 120 min upon admission to post-anesthetic care unit.

Time frame: starting at patient's arrival at post-anesthetic care unit till 120 minutes