Ultrasound-guided lumbar plexus block using a transverse scan through the lumbar intertransverse space: a prospective case series.

BACKGROUND AND OBJECTIVES: A paramedian transverse scan (PMTS) can be used to delineate the anatomy relevant for ultrasound-guided lumbar plexus block (LPB) through the lumbar intertransverse space. This case series evaluated the feasibility of using the PMTS to guide LPBs for anesthesia. METHODS: After research ethics committee approval and written informed consent, 15 American Society of Anesthesiologists physical status 1 to III patients with body mass index of less than 35 kg/m scheduled for lower-extremity surgery received an ultrasound-guided LPB and a sciatic nerve block for anesthesia. The blocks were performed using the PMTS and in-plane needle insertion. Localization of the lumbar plexus was confirmed by obtaining quadriceps muscle twitch. Successful blocks were defined as adequate anesthesia for lower-extremity surgery in the sensory territory of the lumbar plexus. RESULTS: The articular process and psoas muscle were visualized on ultrasound in all 15 patients (mean age, 46.3 ± 20.4 years; body mass index, 22.2 ± 2.4 kg/m), but the lumbar plexus was identified in two-thirds of the patients. Blocks were successfully performed in 14 (93%) of the 15 patients. Poor visibility in 1 patient (7%) precluded the use of ultrasound guidance. The needle was visualized in the psoas muscle in 14 patients (93%), whereas proper needle location was confirmed in all patients by nerve stimulation. Needle to lumbar plexus contact was delineated on ultrasound in 8 (53%) and 14 patients (93%), before and after injection of local anesthetic, respectively. Adequate anesthesia was accomplished in all patients within 30 minutes of injection. CONCLUSION: Ultrasound-guided LPBs can be reliably accomplished using the PMTS.

Sonoanatomy relevant for lumbar plexus block in volunteers correlated with cross-sectional anatomic and magnetic resonance images.

BACKGROUND: Ultrasound imaging of the anatomy relevant for lumbar plexus block (LPB) is challenging because of its deep anatomic location and the "acoustic shadow" of the overlying transverse processes. 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. This study assessed the feasibility of using PMTS-ITS for imaging the anatomy relevant for LPB in healthy volunteers. METHODS: Thirty young volunteers underwent a PMTS-ITS of the right lumbar paravertebral region. The sonoanatomy was defined in corresponding cadaver anatomic sections and magnetic resonance images. Visibility of the paravertebral structures in the sonograms was assessed by 4 independent observers using a 4-point Likert scale (0, not visible; 1, hardly visible; 2, well visible; 3, very well visible), and the mean total ultrasound visibility score (UVS; maximum score possible, 30) was determined. Overall ultrasound visibility was judged as good if the total UVS was greater than 20, average if it was 10 to 20, and poor if it was less than 10. RESULTS: Ultrasound imaging of the right lumbar paravertebral region at the L3-L4-L5 vertebral level was successfully performed through the PMTS-ITS scan window in all volunteers studied. The lumbar nerve root, lumbar paravertebral space, lumbar plexus, and the psoas compartment were delineated in 57%, 27%, 57%, and 87% of volunteers, respectively. Overall ultrasound visibility of the lumbar paravertebral structures was judged as "good" (mean [SD] total UVS, 20.4 [3]). CONCLUSIONS: A PMTS-ITS can be used to image the sonoanatomy relevant for LPB including the lumbar nerve root, lumbar paravertebral space, lumbar plexus, and the psoas compartment.

Regional hemodynamic changes after an axillary brachial plexus block: a pulsed-wave Doppler ultrasound study.

BACKGROUND: Brachial plexus block (BPB) causes vasodilatation and an increase in blood flow to the ipsilateral upper limb. However, no reports have comprehensively evaluated the regional hemodynamic changes after a BPB. METHODS: Eight healthy adult patients who were scheduled for elective hand surgery had an ultrasound-guided axillary BPB for anesthesia. Regional hemodynamic parameters were measured in the ipsilateral brachial artery, using pulsed-wave Doppler (PWD) ultrasound before the block (0 minute) and at regular intervals for 30 minutes after the block. Skin temperature on the dorsum of the ipsilateral hand was also recorded at the same time intervals. Regional hemodynamic parameters that were measured in the brachial artery included peak systolic velocity (PSV, cm/s), end-diastolic velocity (EDV, cm/s), mean velocity (Vmean) and time-averaged mean velocity (TAVM, cm/s), ratio of PSV and EDV (S/D), diameter (d, cm), resistance index (RI), and pulsatility index (PI). Brachial artery blood flow (Q) was calculated as the product of TAVM and cross-sectional area. RESULTS: The ultrasound-guided axillary BPB was successful in all the patients studied. The earliest change after the BPB was a change in the morphology of the PWD spectral waveform from a triphasic to a monophasic waveform and an elevation in the diastolic blood flow velocity. Over time, there was also a significant increase in PSV, EDV, Vmean, TAVM, d, brachial artery blood flow, and skin temperature and a decrease in S/D ratio, RI, and PI. Most of these changes were seen as early as 5 minutes after the block. The increase in EDV (3.7-fold) was the most notable change, and it was greater (P < 0.05) than the increase in PSV (1.5-fold) and Vmean (2.8-fold). CONCLUSIONS: Regional hemodynamic changes that occur after an axillary BPB include a change in the morphology of the PWD spectral waveform, arterial vasodilatation, an increase in blood flow velocity, and an increase in blood flow through the ipsilateral brachial artery.

Gelatin-agar lumbosacral spine phantom: a simple model for learning the basic skills required to perform real-time sonographically guided central neuraxial blocks.

This report describes the preparation of a gelatin-agar spine phantom that was used for spinal sonography and to practice the hand-eye coordination skills required to perform sonographically guided central neuraxial blocks. The phantom was prepared by embedding a lumbosacral spine model into a mixture of gelatin and agar in a plastic box. Cellulose powder and chlorhexidine were also added to the mixture, after which it was allowed to solidify. Sonography of the osseous elements of the lumbosacral spine in the phantom was then performed, and their sonographic appearances were compared to those in volunteers. Simulated real-time sonographically guided paramedian spinal needle insertions were also performed in the phantom. The texture and echogenicity of the phantom were subjectively comparable to those of tissue in vivo. The osseous elements of the spine in the phantom were clearly delineated, and their sonographic appearances were comparable to those seen in vivo in the volunteers. During the simulated sonographically guided spinal injections, the needle could be clearly visualized, but the phantom provided little tactile feedback. In conclusion, the gelatin-agar spine phantom is a simple and inexpensive sonographic spine model that has a tissuelike texture and echogenicity. It can be used to study the osseous anatomy of the lumbar spine and practice the skills required to perform sonographically guided central neuraxial blocks.