Ultrasound-guided Spinal Anesthesia Research Articles

Methodological considerations of ultrasound-guided spinal anesthesia using the Ultrasonix GPS™ needle tracking system

To the Editor, We read with interest the recent case report on ultrasound-guided spinal anesthesia with the Ultrasonix GPS needle tracking system. Based on our recent experience with this technique, we suggest that this report merits further discussion on certain methodological considerations. We recently described our preliminary experience with this system on spinal anesthesia in two cadavers in the prone position, and we have subsequently used the technique in several patients in the sitting position. In our cadaver study, a 2-5 MHz convex transducer was used in a parasagittal oblique plane. A 19G SonixGPS needle was inserted out-of-plane using the needle guidance technology and coloured dye was injected. The spinal needles were left in situ, and 16 injections between T2/3 and L4/5 were completed. All 16 attempts required only a single skin puncture. An anatomist carried out a post-procedural dissection, revealing successful needle and dye placement in the neuraxial space in 100% of attempts. In the case report by Wong et al., it is unclear which needle trajectory was employed relative to the ultrasound plane. Based on their Fig. 2, it appears that they utilized an in-plane approach directed cephalad. The position of the needle relative to the probe is indicated at the bottom right of the screen shot. For our cadaver study, we used both in-plane and out-of-plane approaches with the SonixGPS system. We found that the in-plane approach was technically difficult because of the size of the transducer head, the acute angle required, and the narrow interlaminar space. This approach also increased the skin-to-target distance travelled by the needle. The approach facilitating easiest access to the neuraxial space without encountering the lamina was the medially angled paramedian view with the needle entering out-of-plane at the medial aspect of the transducer (Figure). Needle tracking using the SonixGPS system with an in-plane approach helps to align the needle with the transducer and to identify the position of the needle shaft and tip. Nevertheless, the needle entry point is confined to the midline on either the caudal or cephalad edge of the transducer. Due to the length of the curvilinear probe, an in-plane approach greatly increases the required needle length to reach the subarachnoid space. An out-of-plane approach, however, maximizes the benefit of a needle tracking system. The system extrapolates where the needle tip will intersect the ultrasound plane based on the needle trajectory. This allows for unlimited needle entry starting points along the long edge of the transducer with a shorter distance to the dura and, in the case of neuraxial blocks, helps avoid laminae. The needle trajectory does not need to line up with the plane of the ultrasound beam and, therefore, this constraint is eliminated. Based on our experience with real-time ultrasoundguided neuraxial techniques using the SonixGPS in the prone and sitting positions, we also consider the sitting position to be more familiar and more ergonomic for the anesthesiologist. We agree with the authors that the SonixGPS system is a technological advance that may be helpful with difficult spinal anesthetics and needs further evaluation in the clinical setting. Editor’s Note: The authors of the article: Can J Anesth 2012; DOI: 10.1007/s12630-012-9809-2 respectfully declined an invitation to submit a reply to the above Letter to the Editor.

Erratum to: Real-time ultrasound-guided spinal anesthesia using the SonixGPS® needle tracking system: a case report

Erratum to: Real-time ultrasound-guided spinal anesthesia using the SonixGPS® needle tracking system: a case report

Real-time ultrasound-guided spinal anesthesia using the SonixGPS® needle tracking system: a case report

The SonixGPS® is an electromagnetic needle tracking system for ultrasound-guided needle intervention. Both current and predicted needle tip position are displayed on the ultrasound screen in real-time, facilitating needle-beam alignment and guidance to the target. This case report illustrates the use of the SonixGPS system for successful performance of real-time ultrasound-guided spinal anesthesia in a patient with difficult spinal anatomy. A 67-yr-old male was admitted to our hospital to undergo revision of total right hip arthroplasty. His four previous arthroplasties for hip revision were performed under general anesthesia because he had undergone L3-L5 instrumentation for spinal stenosis. The L4-L5 interspace was viewed with the patient in the left lateral decubitus position. A 19G 80-mm proprietary needle (Ultrasonix Medical Corp, Richmond, BC, Canada) was inserted and directed through the paraspinal muscles to the ligamentum flavum in plane to the ultrasound beam. A 120-mm 25G Whitacre spinal needle was then inserted through the introducer needle in a conventional fashion. Successful dural puncture was achieved on the second attempt, as indicated by a flow of clear cerebrospinal fluid. The patient tolerated the procedure well, and the spinal anesthetic was adequate for the duration of the surgery. The SonixGPS is a novel technology that can reduce the technical difficulty of real-time ultrasound-guided neuraxial blockade. It may also have applications in other advanced ultrasound-guided regional anesthesia techniques where needle-beam alignment is critical.

Real-Time Ultrasound-Guided Spinal Anesthesia Using Taylor's Approach

The role of ultrasound scanning in spinal anesthesia is principally limited to preprocedure imaging and identification of anatomical structures. We describe our experience with a real-time ultrasound technique for visualization and performance of spinal anesthesia. An initial cadaver study was performed in 5 unembalmed cadavers to develop a technique for real-time performance of ultrasound-guided spinal anesthesia via Taylor's approach (paramedian approach to the L5-S1 interspace). Subsequently, 10 patients scheduled for joint arthroplasty underwent real-time ultrasound-guided spinal anesthesia in the prone position. The relevant anatomy and the needletip were visualized easily and all spinals were effective for joint arthroplasty.

Real‐time ultrasound‐guided spinal anesthesia in patients with a challenging spinal anatomy: two case reports

Spinal anesthesia may be challenging in patients with poorly palpable surface landmarks or abnormal spinal anatomy. Pre-procedural ultrasound imaging of the lumbar spine can help by providing additional anatomical information, thus permitting a more accurate estimation of the appropriate needle insertion site and trajectory. However, actual needle insertion in the pre-puncture ultrasound-assisted technique remains a 'blind' procedure. We describe two patients with an abnormal spinal anatomy in whom ultrasound-assisted spinal anesthesia was unsuccessful. Successful dural puncture was subsequently achieved using a technique of real-time ultrasound-guided spinal anesthesia. This may be a useful option in patients in whom landmark-guided and ultrasound-assisted techniques have failed.

Cesarean delivery under ultrasound-guided spinal anesthesia, in a parturient with poliomyelitis and Harrington instumentation

Purpose: To describe the anesthetic implications, and management of a medically complex parturient, who presented for Cesarean delivery (CD). The patient had poliomyelitis complicated with severe kyphoscoliosis, which had been treated with extensive spinal surgery. We used ultrasound guidance to facilitate successful spinal analgesia and anesthesia. Clinical features: A 27-yr-old woman, with a history of poliomyelitis and moderate restrictive lung disease secondary to kyphoscoliosis, presented at 38 weeks gestation for elective CD because of cephalopelvic disproportion. The woman had Harrington rodsin situ from the level of the second thoracic vertebra, to the level of the fourth lumbar vertebra. Ultrasound guidance enabled one intervertebral space to be visualized (L5-S1), 3 cm from the expected spinal midline, and spinal anesthesia was performed at this interspace without any complications. A healthy infant was delivered, and the mother recovered uneventfully. Conclusions: Spinal anesthesia can be effectively performed in patients with poliomyelitis and severe kyphoscoliosis, that has been treated with extensive Harrington instrumentation. To facilitate regional techniques in such patients, bedside ultrasound may be greatly beneficial in identifying the correct spinal interspace.