Neuraxial Ultrasound and Spinal Anesthesia for Cesarean Delivery

This video provides a step-by-step demonstration of preprocedural neuraxial ultrasound for lumbar neuraxial procedures. The film shows probe selection and orientation, sonoanatomy landmarks (sagittal and transverse views), measurement of skin-to-posterior complex depth, and skin marking. Indications and evidence for improved procedural accuracy and reduced needle passes are discussed. The technique is applicable to routine obstetric neuraxial procedures and is especially useful in patients with challenging surface landmarks or a history of difficult neuraxial placement.

Neuraxial ultrasound; neuraxial anesthesia.

Neuraxial ultrasound has emerged as a noninvasive tool to reduce technical difficulties of neuraxial placement, improve success of lumbar epidural analgesia, and potentially increase the safety of spinal and epidural procedures. Neuraxial ultrasound provides preprocedural visualization of vertebral sonoanatomy, identifies the midline and optimal interspace, and estimates the depth to the epidural and intrathecal spaces. Preprocedural scanning improves accuracy of level identification and reduces failed attempts and needle redirections compared with landmark palpation alone.¹ Recent meta-analyses and systematic reviews support the use of ultrasound as an adjunct to improve efficacy and potentially reduce complications in neuraxial procedures.²

The patient is a 38-year-old female scheduled for a repeat cesarean delivery, with a high body mass index and poorly palpable lumbar spinous process, in whom traditional landmark palpation was assessed as unreliable. Because difficult surface anatomy is a known predictor of failed or traumatic neuraxial attempts, a preprocedural neuraxial ultrasound scan was performed to identify midline, help select the optimal interspace, and determine skin-to-epidural depth.

Difficulty with neuraxial procedures due to obesity, spine deformity, prior surgery, or poor landmarks is associated with multiple attempts, increased procedure times, patient discomfort, and a higher risk of complications. Using ultrasound to guide the procedure can mitigate these risks and improve first-pass success in many patients.² For routine cases with clear surface landmarks, landmark-based neuraxial techniques remain the most performed approach. For patients with difficult anatomy or prior failed attempts, options include preprocedural ultrasound to plan the optimal approach. Preprocedural ultrasound is the most evidence-support adjunct and balances accuracy with technical simplicity and workflow efficiency. Real-time ultrasound-guided needle insertion can be considered in select cases when difficulty is encountered despite preprocedural ultrasound markings.

The goals of neuraxial ultrasound assistance are to accurately identify midline and appropriate interspace and determine needle insertion depth and angle. This preprocedural information reduces needle passes and redirections, decreases procedure times, and ultimately may lower complication risk. Preprocedural ultrasound accomplished these aims by translating sonographic landmarks to precise skin markings and depth measurements,³ enabling a targeted, reproducible insertion path.

Limitations include ultrasound device and curvilinear probe availability and operator expertise. Anesthesiologists require supervised practice and focused training to reliably acquire and interpret lumbar sonoanatomy. Studies have shown that clinicians may need a few dozen supervised scans to reach high accuracy.⁴ Image quality and acoustic windows can be poor in some patients because bone produces acoustic shadowing and deep structures may be difficult to visualize in obese patients.

This video provides a comprehensive step-by-step demonstration of a neuraxial ultrasound examination. The procedure begins with positioning the patient in the sitting position typically used during neuraxial placement. The curvilinear transducer is initially placed in the longitudinal orientation at the paramedian sagittal oblique plane to identify the sacrum. Once the sacrum is identified, the interlaminar space is identified by visualization of the posterior and anterior complex. The interlaminar spaces are marked from L5 to L2, and the optimal interspace selected (e.g., L3/4 for labor analgesia). In this same orientation, the loss-of-resistance (LOR) depth can be estimated by measuring from the skin to the posterior complex. The posterior complex is a hyperechoic linear structure that represents the ligamentum flavum-dura complex. It is important to know that ultrasound may underestimate the LOR due to tissue compression in obese patients, and probe pressure needs to be released prior to depth measurements.³

The transducer is then placed into the transverse orientation to delineate the spinous process, a hyperechoic peak with acoustic shadowing. The spinous process is centered on the ultrasound screen, which confirms midline alignment. Once the midline is marked, the transducer is placed between the spinous processes to identify the interlaminar space. In the transverse orientation, the interlaminar space is identified by a characteristic “equal sign” or “bat’s ears” image. The equal sign represents two parallel hyperechoic lines (posterior line = ligamentum flavum-dura complex and anterior line = vertebral body) with a central acoustic window showing the spinal space between these lines.³ The interspaces are compared and confirmed from the identification in the paramedian sagittal oblique plane. This neuraxial ultrasound technique facilitates spinal anesthesia via a midline approach by confirming midline alignment, identifying the optimal interspace, and estimating LOR depth.

Neuraxial ultrasound is a practical, evidence-based adjunct that reduces technical difficulty, increases neuraxial success, and may reduce complications for lumbar neuraxial procedures. Integrating a brief preprocedural scan into either routine practice or in select patients is recommended, and is a skill worth acquiring to help with challenging neuraxial placements.

Nothing to disclose.

The patient referred to in this video article has given their informed consent to be filmed and is aware that information and images will be published online.