The main objective is to complete a double-blinded randomized controlled crossover trial of lumbar plexus block with the Shamrock technique guided by ultrasound (US)/magnetic resonance imaging (MRI) image fusion vs. the Shamrock technique guided by ultrasound in healthy volunteers. The investigators will assess block procedure-related parameters, anatomical spread of local anesthetic, and motor and sensory effects.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
TREATMENT
Masking
DOUBLE
Enrollment
22
Perineural injection of 20 ml 2% lidocaine with 0.0005% epinephrine added 1 ml of gadoterate meglumine (0.13 ml) and sodium chloride (NaCl, 0.87 ml). The 1 ml of gadoterate meglumine-NaCl is added to the local anesthetic prior to the perineural injection in order to enhance visualization of the local anesthetic on MRI scanning after the intervention.
Number of participants with a successful block of the femoral and obturator nerves (reduced muscle force compared to baseline assessed with handheld dynamometer), and of the lateral femoral cutaneous nerve (assessed with cold and pinprick test)
Block success is defined as the number of volunteers with a successful motor block of the femoral nerve and the obturator nerve, and with a successful sensory block of the lateral femoral cutaneous nerve. Motor block is a proxy marker of sensory block. A participant with a successful motor block has reduced muscle force after block compared to baseline muscle force assessed with handheld dynamometer, and a participant with a successful sensory block has decreased/absent sensation for cold and/or pinprick.
Time frame: Assessed 60 minutes after intervention. Data will be presented 10 months after study completion.
Time for preparation of block procedure (seconds)
Time for block preparation is defined as the time period from the time point when the volunteer is placed on the block bed to the time point when the pre-ultrasound scanning before intervention is complete.
Time frame: Assessed 3 minutes prior to intervention. Data will be presented 10 months after study completion.
Time for block procedure (seconds)
Time for block procedure is defined as the time period from the time point when the ultrasound probe is placed on the skin after completed preparation to the time point when the block needle is pulled out after injection of local anesthetics (end of intervention).
Time frame: Assessed 0 minutes after intervention. Data will be presented 10 months after study completion.
Electrical nerve stimulation strength (mA)
Minimal electrical nerve stimulation (mA) required to trigger neuromuscular response and confirm correct placement of block needle prior to injection of local anesthetics.
Time frame: Assessed 1 minute before injection of injectate. Data will be presented 10 months after study completion.
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Electrical nerve stimulation response (quadriceps, sartorius, other muscular, paresthesia, none)
Type of neuromuscular response on electrical nerve stimulation.
Time frame: Assessed 1 minute before injection of injectate. Data will be presented 10 months after study completion.
Needle advancements
Number of needle advancements during intervention.
Time frame: Assessed 0 minutes after intervention. Data will be presented 10 months after study completion.
Injection site
Time frame: Assessed 0 minutes after intervention. Data will be presented 10 months after study completion.
Block needle depth
Time frame: Assessed 0 minutes after intervention. Data will be presented 10 months after study completion.
Discomfort
Estimated on numeric rating scale 0-10
Time frame: Assessed 0 minutes after intervention. Data will be presented 10 months after study completion.
Mean arterial pressure change
Time frame: Mean arterial pressure is measured prior to intervention and 5 min after intervention. Data will be presented 10 months after study completion.
Number of participants with visual confirmed contact between the injectate and the spinal nerves L2-S1, the femoral, the obturator, and the lateral femoral cutaneous nerves, and the lumbosacral trunk assessed on MRI
Time frame: Assessed on MRI sampled 10-40 minutes after intervention. Data will be presented 10 months after study completion.
Number of participants with visually confirmed epidural spread of the injectate assessed on MRI.
Time frame: Assessed on MRI sampled 10-40 minutes after intervention. Data will be presented 10 months after study completion.
Number of participants with motor block
Muscle strength of the femoral, obturator, superior gluteal, and sciatic nerves are estimated with handheld dynamometer during knee extension, hip adduction, hip abduction, and knee flexion. Motor block is assessed as reduced muscle strength compared to baseline.
Time frame: Baseline muscle strength is estimated prior to first intervention. Post-block muscle strength is estimated 60 minutes after intervention. Data will be presented 10 months after study completion.
Number of participants with sensory block
Sensory block is defined as decreased or absent sensation for cold, warmth, touch, and pinprick are assessed for the dermatomes T8-S3 and the lateral femoral cutaneous nerve.
Time frame: Estimated 70 minutes after intervention. Data will be presented 10 months after study completion.
Cost-effectiveness (ICER)
ICER is estimated as the difference in mean marginal cost of the blocks.
Time frame: Calculated 1 month after study completion. Data will be presented 10 months after study completion.
Quantitative diffusion weighted MRI reproducibility
Time frame: Assessed on MRI sampled 40-55 minutes after intervention. Data will be presented 10 months after study completion.
Image evaluation of diffusion weighted MRI reproducibility
Time frame: Assessed on MRI sampled 40-55 minutes after intervention. Data will be presented 10 months after study completion.