Abstract: Objective To explore whether the application of high frequency linear array ultrasound assisted localization before puncture can improve the success rate of subarachnoid anesthesia in patients with difficulty in locating anatomical landmarks. Methods A randomized controlled trial was used to localize the anatomic landmarks.110 cases of patients who could not be touched the spinous process clearly were divided into two groups:the traditional anatomical positioning group(Group J) and the ultrasound assisted group(Group C),each group were 55 cases.The main outcome include the success rate of one-time puncture.Secondary outcome include the distance,puncture angle and puncture times between anatomical and ultrasound localization of L2-3 and L3-4. Results The success rate of one-time puncture was 26.53% in anatomy group and 61.11% in ultrasound group,the  difference was statistically significant(P<0.05). Conclusion The application of high-frequency linear array probe ultrasound assisted localization in patients with difficulty in anatomic localization of subarachnoid anesthesia can effectively improve the success rate of one-time puncture and reduce the times of puncture.

Key words: high frequency linear array probe, ultrasound assisted, subarachnoid anesthesia, spinal anesthesia