Locating the epidural space in obstetric patients-ultrasound a useful tool: continuing professional development.

PURPOSE: The objective of this continuing professional development module is to describe the role of ultrasound for spine demarcation before placement of neuraxial blocks and to provide a comprehensive systematic approach towards ultrasound scanning in obstetric patients.

PRINCIPAL FINDINGS: Ultrasound imaging of the lumbar spine has been shown to be effective in improving the success rate of neuraxial blocks in obstetric patients. The success rate of ultrasound-guided epidural insertions at first attempt was found to be 30-60% greater when compared with the traditional epidural method. Pre-puncture ultrasound scanning can provide reliable and accurate information on several critical aspects needed for successful epidural placement, such as the interspace level, the midline of the spine, the optimal puncture point, the optimal angle for needle insertion, and the depth to the epidural space. Ultrasound scanning of the lumbar spine can generate images in two distinct patterns - one in the transverse plane represented by a "flying bat" and the other in the paramedian longitudinal plane represented by a "saw-tooth" configuration. Both approaches allow the visualization of the ligamentum flavum and the dura mater in addition to other adjacent bony landmarks. A stepwise scanning approach can serve as a useful guide to facilitate the successful placement of epidural needles in patients with both normal and abnormal spinal anatomy.

CONCLUSIONS: Incorporating the use of lumbar spine ultrasound scanning into day-to-day clinical practice may improve the ease of performing epidurals as well as add to patient safety and comfort.