Popliteal SNB:Evaluation of Block Dynamics After Subparaneural Injection Below CPN & TN

The Chinese University of Hong Kong

Status: Completed

Conditions: Musculoskeletal Diseases or Conditions

Treatments: Procedure: Popliteal Sciatic nerve block

Study type: Interventional

Funder types: Other

Identifiers

NCT04506879

CREC.2020.314

Details and patient eligibility

About

This study aims to assess the effect of twin subparaneural injection into individual paraneural sheaths of Common Peroneal Nerve (CPN) and Tibial Nerve (TN) below their point of divergence from the sciatic nerve on the sensory motor blockade after Popliteal Sciatic Nerve Block (PSNB) at the popliteal fossa (back of the thigh) for patients requiring lower limb surgeries.

Full description

Ultrasound (US) guided Popliteal Sciatic Nerve Block (PSNB) has been routinely used to provide surgical anaesthesia for ankle and foot surgeries, and the introduction of ultrasound (US) guidance has improved the ease and accuracy of performing PSNB. However, the challenge of achieving the optimal 'readiness for surgery' time after the US guided PSNB continues to confront anaesthesiologists. Cumulative evidence indicates that a subparaneural PSNB improves sensory motor block outcome when compared to subepimyseal PSNB where the local anaesthetic is deposited outside the paraneural sheath.

While these are encouraging results, producing sensory motor blockade, i.e. surgical anaesthesia in the area innervated by the sciatic nerve within 30 minutes of local anaesthetic (LA) injection, after a subparaneural PSNB, remains a challenge with the success rate varying from 62-92%. Reasons for this shortcoming, despite LA being deposited in subparaneural space, close to the epineurium of the sciatic nerve, is probably multifactorial as the nerve size, surface area exposed to local anaesthetic, and internal architecture (the connective tissue component) of the sciatic nerve and its branches are all seems to influence block onset time and completeness. It was observed from our clinical practice that distal subparaneural injection (twin halo) into individual paraneural sheaths of common peroneal nerve (CPN) and tibial nerve (TN) below the point of divergence at the popliteal fossa demonstrated a faster sensory motor blockade after PSNB. Therefore, this study aims to assess the effect of twin subparaneural injection into individual paraneural sheaths of CPN and TN below their point of divergence from the sciatic nerve on the sensory motor blockade after PSNB at the popliteal fossa.

Enrollment: 20 patients

Sex: All

Ages: 18 to 75 years old

Volunteers: No Healthy Volunteers

Inclusion criteria

• American Society of Anesthesiologists (ASA) physical status I-III scheduled to undergo elective foot and/or ankle surgery under regional anesthesia.

Exclusion criteria

• Patient refusal, ASA physical status > Ⅲ, pregnancy, neuromuscular disorder, prior surgery in the popliteal fossa, coagulopathy, allergy to local anaesthetic drugs, and skin infection at the site of needle insertion.

Trial design

Primary purpose: Treatment

Allocation: N/A

Interventional model: Single Group Assignment

Masking: None (Open label)

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20 participants in 1 patient group

Popliteal Sciatic Nerve block

Other group

Description:

Patients will lie on their chest on the examination couch with both feet rested on the pillow to relax their lower extremity. Ultrasound scan of the nerves in popliteal fossa will be identified and then local anesthetic agents \[1.5% lidocaine with 1:200,000 adrenaline and 0.5ml of 8.4% sodium bicarbonate (total 30ml)\] will be injected close to the nerves (Common peroneal nerve and tibial nerve). The injections below the bifurcation near the two nerves are expected to produce quicker block than the injections above the bifurcation.

Treatment:

Procedure: Popliteal Sciatic nerve block