Background: Pre-procedure ultrasound scanscan indicate the midpoint of the puncture site of spinal injection. However, there are limitations of the technic.
Objectives: To compare the success rate of spinal anesthesia by preprocedural ultrasound scan to compare 2needle puncture technics between using Point-Assisted Spinal Sonography (PASS)and skin marking.
Methods: Forty-eight patients undergoing elective spinal anesthesia were randomized to receive preprocedural ultrasound scan with transverse interspinous view to locate the needle puncture, using either the 2nd prototype of   PASS (n=24) or    skin marking (conventional) (n=24). The conventional technic was done by making the intersection point of the two lines across the short and long edges of the transducer, whereas the other used PASS to guide the needle trajec-tory. The primary outcome was the success rate of   spinal tap at   the first attempt. The number of total attempts and spinal tap duration to obtain the CSF were recorded as secondary outcomes.
Results: The success rate of spinal tap at the first attempt was 9/24 (37.5%) patients in   PASS and 11/24 (45.8%) in   skin marking group (P=0.55).S pinal tap duration and the number of total attempts were not statistically different (P=0.55 and 0.49 respectively).
Conclusion: The 2nd prototype of PASS produces comparable successful spinal block with using skin marking technic in terms of success rate at the first attempt and procedure time. Needling without marks or gel in PASS technic might take less risk of intrathecal contamination.