Real-Time Ultrasound/MRI Fusion for Suprasacral Parallel Shift Approach to Lumbosacral Plexus Blockade and Analysis of Injectate Spread: An Exploratory Randomized Controlled Trial

Abstract

Fused real-time ultrasound and magnetic resonance imaging (MRI) may be used to improve the accuracy of advanced image guided procedures. However, its use in regional anesthesia is practically nonexistent. In this randomized controlled crossover trial, we aim to explore effectiveness, procedure-related outcomes, injectate spread analyzed by MRI, and safety of ultrasound/MRI fusion versus ultrasound guided Suprasacral Parallel Shift (SSPS) technique for lumbosacral plexus blockade. Twenty-six healthy subjects aged 21-36 years received two SSPS blocks (20 mL 2% lidocaine-epinephrine [1 : 200,000] added 1 mL diluted contrast) guided by ultrasound/MRI fusion versus ultrasound. Number (proportion) of subjects with motor blockade of the femoral and obturator nerves and the lumbosacral trunk was equal (ultrasound/MRI, 23/26 [88%]; ultrasound, 23/26 [88%]; p = 1.00). Median (interquartile range) preparation and procedure times (s) were longer for the ultrasound/MRI fusion guided technique (686 [552-1023] versus 196 [167-228], p < 0.001 and 333 [254-439] versus 216 [176-294], p = 0.001). Both techniques produced perineural spread and corresponding sensory analgesia from L2 to S1. Epidural spread and lidocaine pharmacokinetics were similar. Different compartmentalized patterns of injectate spread were observed. Ultrasound/MRI fusion guided SSPS was equally effective and safe but required prolonged time, compared to ultrasound guided SSPS. This trial is registered with EudraCT (2013-004013-41) and ClinicalTrials.gov (NCT02593370).

Conflict of interest statement

None of the authors have any potential conflicts of interests to declare.

Figures

Figure 1

The ultrasonographic (a) and MR (b) images are fused and displayed side-by-side. The blue line in the top is the projection of the block needle and the large green circle marks the anticipated intersection of the block needle tip and the ultrasound beam, here coinciding with the rami of spinal nerve L5 (yellow arrow) displayed on the MR image. The line of small blue and yellow dots marks the anticipated trajectory of the block needle prior to and after the intersection with the ultrasound beam, respectively. PMM, major psoas muscle; S, sacral ala; TP L4-5, transverse processes of the fourth and fifth lumbar vertebral bodies.

Figure 2

Modified CONSORT 2010 flow diagram of the study subjects receiving ultrasound (US)/magnetic resonance imaging (MRI) fusion versus US guided lumbosacral plexus blockade with the Suprasacral Parallel Shift (SSPS) technique.

Figure 3

MRI of one subject visualizing spread of lidocaine-epinephrine added diluted contrast (magenta arrow) primarily medial to the psoas major muscle (PMM), that is, in the parapsoas compartment. (a) Sagittal plane. (b) Axial plane. (c) Coronal plane. Line (blue), position of coronal plane; Line (orange), position of sagittal plane; Line (purple), position of axial plane; S, sacral ala; VB L5, fifth lumbar vertebral body.

Figure 4

MRI of one subject visualizing spread of lidocaine-epinephrine added diluted contrast (magenta arrow) primarily posterior to the psoas major muscle (PPM), that is, in the retropsoas subcompartment, with minor seeping into the fascial plane between the anterior and posterior (red arrow) lamina of the PMM that contains the lumbar plexus. (a) Sagittal plane. (b) Axial plane. (c) Coronal plane. L5, fifth lumbar vertebral body; Line (blue), position of coronal plane; Line (orange), position of sagittal plane; Line (purple), position of axial plane; S, sacral ala.

Figure 5

MRI of one subject visualizing spread of lidocaine-epinephrine added diluted contrast (magenta arrow) primarily lateral to the psoas major muscle (PMM), that is, in the retroperitoneal compartment, with minor seeping into the retropsoas subcompartment. (a) Sagittal plane. (b) Axial plane. (c) Coronal plane. Line (blue), position of coronal plane; Line (orange), position of sagittal plane; Line (purple), position of axial plane; S, sacral ala; VB L5, fifth lumbar vertebral body.

Figure 6

Plasma concentration of lidocaine 0 to 90 min after injection with the ultrasound/MRI fusion guided (US/MRI) versus the ultrasound guided (US) Suprasacral Parallel Shift technique for lumbosacral plexus blockade (n = 25). Values are presented as mean (SD).

Figure 7

Axial diffusion weighted MRI at the level of the cranial border of the sacral ala, demonstrating a possible anterior approach to the lumbosacral plexus in the supine position. A needle (white arrow) can be inserted close to the anterior superior iliac spine and advanced between the psoas major and iliacus muscles. A first injection of local anesthetic into the retropsoas subcompartment will spread to the femoral nerve (red arrow) and the lateral femoral cutaneous nerve (green arrow). A second injection of local anesthetic into the parapsoas compartment will spread to the anterior rami of spinal nerves L4 and L5, the lumbosacral trunk (yellow arrow) and the obturator nerve (pink arrow).

Figure 8

The anterior lumbosacral plexus approach guided by real-time ultrasound/MRI fusion in an anticipated experimental setting. (a) The probe is axially oriented, slightly rotated clock-wise, and medial to the anterior superior iliac spine where the phantom needle is oriented in-plane with the US/MR image planes. (b) Fused real-time ultrasound (b1) and MRI (b2) depicting the needle trajectory into the retropsoas subcompartment. (c) Fused real-time ultrasound (c1) and MRI (c2) depicting the needle trajectory through the psoas major muscle (PMM) into the parapsoas compartment. Guided by real-time ultrasound/MRI fusion and needle navigation, the “insertion point” and angulation of the phantom needle are adjusted until the anticipated intersection between the needle tip and the ultrasound beam (green circle) coincides with the target lumbosacral plexus nerves in the retropsoas compartment (b) and in the parapsoas subcompartment (c) anterior to the border of the sacral ala (S). The line of small blue and yellow dots marks the anticipated trajectory of the block needle prior to and after the intersection with the ultrasound beam, respectively.