Objective: To verify whether preprocedural ultrasound of the lumbar spine could improve first-attempt success rate (defined as a successful neuraxial anesthesia with only one skin puncture) of neuraxial block in elderly patients. Methods: From septemble 2015 to February 2016, 200 elderly patients undergoing lower-limb surgery with neuraxial block at the Peking Universty Third Hospital were enrolled in this study.RandA 1.0 software was used to randomize patients into two groups: conventional surface landmark-guided group (group LM) and ultrasound-assisted group (group US). Ultrasound scanning of the lumbar spine was performed to determine the suitable insertion point of US group, using a low-frequency (2-5 MHz) curved-array probe in both paramedian sagittal oblique plane and transverse median plane.Spinal anesthesia was done via the paramedian approach.The primary outcome was the rate of successful access to subarchnoid space on the first needle insertion attempt.Secondary outcomes included the following: number of needle insertion attempts, number of needle redirection times, actual epidural needle insertion depth, time taken to eastablish landmarks, time taken to perform the spinal anesthesia (the duration between local infiltration and bupivacaine injection), procedure time (the duration from sterilizing the back to converting into supine position), total time (the sum of the time to establish landmarks and the procedure time), adverse events during the procedure and anesthesia related complications. Results: A total of 191 patients successfully received combined spinal-epidural anesthesia by resident anesthesiologists, 9 patients (7 patients in group LM vs 2 patients in group US) failed.The first-attempt success rate in group LM was 37.6%, while the first-attempt success rate in group US was 68.4%, the difference between the two groups was significant (χ²=18.112, P<0.01). In group LM, the number of needle insertion attempts and needle redirection attempts were 2(1, 3) and 5(3, 10), respectively. In group US, the number of needle insertion attempts and needle redirection attempts were 1(1, 2) and 3(0, 5), respectively.The differences in the number of needle insertion attempts and needle redirection attempts between the two groups were significant (Z=-4.132, -4.077, all P<0.01). In group US, the time spent on determining the insertion point, on puncture, on finishing the procedure and the total time were as the following: 2.8(2.6, 3.1), 2.5(1.8, 4.1), 7.8(6.5, 8.9), 10.6(9.5, 11.9) min.In contrast, in group LM, those indices were as the following: 0.4(0.3, 0.4), 4.1(2.2, 6.3), 8.8(7.5, 11.4), 9.2(7.8, 11.9) min.There were significant differences in the above factors between the two groups (Z=-11.931, -4.025, -3.550, -3.290, all P<0.01). The paramedian sagittal oblique scanning image was superior to that of the transverse median plane. Conclusions: For elderly patients, ultrasound imaging before neuraxial block increases first-attempt success rate, decreases puncture time.The strengths of prepuncture ultrasound scanning outweighs its longer total time.

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