The Study Of Ultrasound In The Epidural Space Puncture

Objective In recent years, ultrasound technology has been widely used in Peripheral nerve blocks and vascular punctures. Compared with traditional methods, ultrasonography in the lumbar epidural puncture already has been viewed as the foreword from its unique clinical advantages. We used ultrasound equipment with a 5-MHz transducer to assess the anatomy of the ES and the posterior parts of the lumbar spinal column. Our idea was to assess the ultrasound localization of the epidural space by defining the optimum puncture point, puncture angle, and puncture depth.Methods Part one: ultrasonography was adopted to study the anatomy of the lumbar spine and identify the position of the L_3-4 intervertebral space and the Tuffier's line. 113 consecutive patients were recruited. We gained the optimum ultrasound image of the lumbar spine through a portable ultrasound system with a convex array 3～7 MHz curved ultrasound probe. Using the top of the buttock crease as a starting point, the probe was moved in a cephalad direction to identify the cephalic or upper end of the sacrum, and the spinous process of each lumbar vertebra. If the interspaces could not be conclusively identified, the probe was moved in a caudal direction from the 12th vertebral body. We assessed the changes in the relationship between the iliac crests and lumbar spinal levels on two different positions .Ultrasound scanning of the lumbar spine was performed at the L_3-4 and L5S1 vertebral interspaces. Three ultrasound planes were employed: the transverse, median, and paramedian longitudinal approaches. The visibility of the ligamentum flavum and the dura mater on ultrasound were rated as"none,""sufficient,"or"good."And,at the same time,the spinal region between the L_2-3 intervertebral space and L5 spinous process was divided into nine different regions. We recorded the position of the different iliac crest connection. Part two: the usefulness of ultrasonography in facilitating successful localization of the epidural space .Eighty patients scheduled for elective surgery were randomized into 2 matched groups; 40 patients underwent CSE without ultrasound imaging and 40 patients underwent CSE after ultrasound imaging. In the UC-CSE group, ultrasound scans of the appropriate lumbar segments were taken before ES puncture. Scanning was performed in the midline overlying the L_3-4 interspaces in transverse and longitudinal planes. Using the ultrasound images, the optimal level, angle, and depth of ES cannulation were identified. We measured the time elapsed for the ultrasound scanning, the number of puncture attempt, the ES depth on ultrasound images (i.e., the distance from the skin to the ligamentum flavum) and by the LOR method (i.e., needle depth from the skin at the time of LOR) respectively. The visibility of the ligamentum flavum and the dura mater on ultrasound were rated as"none,""sufficient,"or"good."The criteria for the classification was same with the first part .The ES depth seen on ultrasound images were measured with ultrasound workstation (V1.3).Results Part one: A series of clips of the transducer probe could be seen in a transverse orientation moving from the L3 spinous process to the interspaces below it. The ES could be positively identified in almost all cases. Both guiding structures (ligamentum flavum and dura mater) could be identified in 92% and 100% of cases. Paramedian longitudinal imaging allowed greatest visibility of the dura mater. Dura mater appears thin, highly liner, and bright. The ligamentum flavum is the first echogenic structure encountered beyond which lies the dura mater. Epidural space is located beyond the relatively hyperechoic dura mater. Palpation, using anatomical landmarks, has been shown to be inaccurate at identifying lumbar vertebrae. There was poor agreement between palpation and ultrasound estimation of the specific lumbar interspaces. There was a trend for the iliac crest to shift cephalad from 90°to 135°positioning. The position of the Tuffier's was correlation with gender, its low in women. We haven't found correlation with age. Part two: The ultrasound scanning time was 1.9±2.1min; The ES depth (i.e., the distance from the skin to the ligamentum flavum) seen on ultrasound images was 5.21±0.92cm; The ES depth measured by the LOR method (i.e., needle depth from the skin at the time of LOR) was 5.27±0.93cm in the ultrasound group and 5.30±1.02cm in the control group . The Pearson correlation coefficient was 0.964 between the two depth in the ultrasound group(P<0.01). The number of punctured before the ES successfully accessed was significantly lower in the UC-CSE-group(P<0.05).It was 1.4±0.6 in the ultrasound and 2.1±0.8 in the control group. Ligamentum flavum and dura mater could be identified in 88% and 95% of cases in the paramedian longitudinal imaging of the ultrasound groupConclusion Low-frequency ultrasound can clearly show the structures of the lumbar epidural space regional and neighboring anatomical structures。The correct L_3-4 intervertebral spaces can be identified used ultrasonography. It's useful to localize the epidural space by defining the optimum puncture point, puncture angle, and puncture depth. Ultrasonography significantly improved operating conditions for epidural anesthesia. The depth of the epidural space measured by ultrasound and the needle is highly consistent. These procedures require multiple still images in different planes to capture accurate measurement with the ultrasound device.