Ultrasound Plus Nerve Stimulator Versus Nerve Stimulator Guided Lumbar Plexus Block

A Randomized Comparison of Ultrasound Plus Nerve Stimulator Guided Lumbar Plexus Block to Conventional Nerve Stimulator Guided Technique Using Winnie Approach

Ultrasound imaging, an effective tool to localize peripheral nerves, may facilitate block performance. It allows direct visualization of nerve structures, needle guidance in real-time to the target, and observation of local anesthetic diffusion. Some case series have demonstrated significantly faster onset time for interscalene blocks, supraclavicular blocks and axillary brachial plexus blocks under ultrasound than with conventional techniques. Ultrasound guidance also enhances the quality of popliteal sciatic nerve block at the popliteal fossa compared with single injection, nerve stimulator-guided block using either a tibial or peroneal endpoint. Despite this impressive profile, the application of the ultrasound for lumbar plexus blocks has not been studied extensively. It is likely that lumbar plexus block (LPB) combined with either a sciatic nerve block or sedation or both is equivalent to general anesthesia and neuraxial anesthesia for knee arthroscopy. The lumbar plexus block is traditionally performed using surface anatomical landmarks and nerve stimulation. Ultrasound imaging of the anatomy relevant for LPB is challenging because of its deep anatomic location and the "acoustic shadow" of the overlying transverse processes. Recently, Karmakar M.K. etc. has demonstrated that a paramedian transverse scan (PMTS) of the lumbar paravertebral region with the ultrasound beam being insonated through the intertransverse space (ITS) and directed medially toward the intervertebral foramen (PMTS-ITS) may overcome the problem of the "acoustic shadow" and allow clear visualization of the anatomy relevant for LPB. However, the application of a PMTS-ITS used for lumbar plexus blocks has not been studied extensively and its advantages are not validated in a clinical study. Thus, we designed this prospective, randomized, subject and assessor blinded, parallel-group, active-controlled study to compare a PMTS ultrasound-guided lumbar plexus block combined with nerve stimulation and a conventional technique on time required to readiness for surgery in patients undergo knee arthroscopy surgery.

Inclusion Criteria:

• Informed consent
• Age 18-70yr
• American Society of Anesthesiologists physical status I-II
• Patients scheduled to undergo knee arthroscopy surgery
• Ultrasound visibility score equal or great than 10

Exclusion Criteria:

• Body mass index more than 35 kg/m²
• Pregnant or lactating women
• Allergy to local anesthetics
• Coagulopathy, on anticoagulants
• Malignancy or infection at puncture site
• Significant peripheral neuropathy or diabetic peripheral neuropathy
• Language barrier
• Neuropsychiatric disorder
• Severe cardiac or respiratory diseases
• Pathology or previous surgery or trauma to the lower limb
• Analgesics intake, history of substance abuse
• History of spinal surgery or deformity
• Ultrasound visibility score less than 10
• Participating in the investigation of another experimental agent