Circumferential Spread of Anesthetic and Success in Sciatic Nerve Blockade

Does Ensuring Circumferential Local Anesthetic Spread Improve the Success of Ultrasound Guided Sciatic Nerve Block at the Popliteal Fossa?

Current practices when performing any peripheral nerve block may or may not involve ensuring circumferential spread of local anesthetic around the nerve. Ensuring circumferential spread can involve several redirections of the needle above and below the nerve, and potentially could result in either more discomfort for the patient or an increased chance of inadvertent direct trauma to the nerve. Not ensuring spread around the nerve may result in a slower and less complete blockade. The investigators suspect that by ensuring complete spread around the nerve, the speed of block onset would be quicker because it avoids the loss due to diffusion time.

Inclusion Criteria:

1. English-speaking
2. ASA physical status I-III
3. 18-85 years of age, inclusive
4. 50-110 kg, inclusive
5. 150 cm of height or grater
6. Scheduled for elective foot or ankle surgery

Exclusion Criteria:

1. Contraindications to sciatic nerve block (e.g., allergy to local anesthetics, coagulopathy, malignancy or infection in the popliteal area)
2. Significant peripheral neuropathy or neurologic disorder affecting the lower extremity
3. Pregnancy
4. Contraindications to, allergies to, and/or past adverse reactions to study medications (local anesthetics, opioid analgesics)
5. History of alcohol or drug dependency/abuse
6. History of long term opioid intake
7. History of significant psychiatric conditions that may affect patient assessment