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.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
TREATMENT
Masking
DOUBLE
Enrollment
48
An insulated nerve block needle connected to a nerve stimulator that was delivering a current of 1.5 mA at a frequency of 2 Hz was then inserted in the long axis (in- plane) of the ultrasound transducer towards the the hypoechoic psoas compartment. If the quadriceps contraction which produces patella twitching was elicited with an initial current of 1.5mA,then the current should be reduced until contraction is still present between 0.3 to 0.5 mA .Afterward, the lumbar plexus nerve block was performed by using 30mL of 0.5% ropivacaine. Contraction should stop below a current of 0.3mA, otherwise intraneural needle position should be suspected.
The block was conducted following traditional Winnie approach. The accepted end point for the lumbar plexus is stimulation of the femoral nerve component, observed by contraction of the quadriceps muscle. Quadriceps contraction which produces patella twitching should be sought with an initial current of 1.5mA, and once elicited the current should be reduced until contraction is still present between 0.3 to 0.5 mA. Afterward, the lumbar plexus nerve block was performed by using 30mL of 0.5% ropivacaine. Contraction should stop below a current of 0.3mA, otherwise intraneural needle position should be suspected.
Tongji Hospital
Wuhan, Hubei, China
Onset time of sensory block to cold and pinprick
Onset time of sensory block (cold/pinprick), defined as time interval from completion of local anesthetic injection to the achievement of complete sensory block (defined as no sensation in three major branches including the femoral nerve, the lateral femoral cutaneous nerve and the obturator nerve) .
Time frame: up to 40 min after ropivacaine injection
Total ultrasound visibility score (UVS)
The independent observer attempted to visualize 10 paravertebral structures in images of the ultrasound scans from the patients
Time frame: 30 min before and 5 min after lumbar plexus block
Performance time of block
Performance time of block is the preparing time and procedure time. Preparing time (defined as the time from the beginning of the sterile preparation right before the first needle contact with the skin). Procedure time (time between the insertion of the needle and the end of local anesthetic injection)
Time frame: up to 20 min after needle insertion
Number of needle passes during block
Number of needle passes during block
Time frame: up to 20min after needle insertion
Minimal stimulating current of the needle
All peripheral nerve blocks were performed by the same anesthesiologist with an 100-mm insulated stimulating needle attached to a nerve stimulator. The intensity of the stimulating current, initially set to deliver 1 to 1.5 mA (0.1ms, 2Hz), was gradually decreased to \<0.5 mA while the appropriate motor response was maintained. For sciatic block, the targeted evoked motor response was plantar flexion of the foot. For lumbar plexus block, quadriceps muscle motor response was targeted.Contraction should stop below a current of 0.2mA, otherwise intraneural needle position should be suspected and the needle should be withdraw and readjusted. The Minimal stimulating current ( intensity of the current when the needle was considered to be adequately positioned) finally demonstrated on nerve stimulator was recorded, then ropivacaine was injected slowly after careful intermittent aspirations.
Time frame: up to 20min after needle insertion
Onset time of motor block
onset time of motor block, defined as time interval from completion of local anesthetic injection to the achievement of satisfied motor block (defined as a Modified Bromage scale equal to 3).
Time frame: up to 40min after ropivacaine injection
Incidence of paresthesia during block
Incidence of paresthesia during block reported by patients
Time frame: up to 20min after needle insertion
Incidence of accidental vascular puncture
Incidence of accidental vascular puncture, defined as blood by aspiration.
Time frame: up to 20min after needle insertion
Changes of muscle strength of quadriceps femoris and adductors
Muscle strength of quadriceps femoris and adductors was measured with hand-held dynamometer (HHD, Hogan Health Industries, MicroFET3) during knee extension and hip adduction.
Time frame: up to 40min after ropivacaine injection
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