In Response.

Abstract

We thank Wardhan and Smith1 for their interest in our recent research article.2 First, we had clearly predefined the primary outcome—the number of needle passes as “the number of forward advancements of the needle required to achieve successful dural puncture.”2 The number of passes/attempts required for success has been the main outcome measure of many previous publications on this subject3 because it represents the technical difficulty of neuraxial procedures along with the procedural time. Moreover, we considered excessive needle passes and insertion attempts during spinal anesthesia would increase the chance of traumatic needle manipulations near the epidural/intrathecal structures, postdural puncture headache, and infection and patient pain, discomfort, and dissatisfaction. Hence, providing spinal anesthesia via a single needle pass was recommended by consensus guidelines on neuraxial anesthesia and anticoagulation.4,5 We agree that the optimal medial angle of needle insertion is important to the successful paramedian approach.1 Ultrasound-assisted spinal anesthesia could be more accurately executed if the angle of the ultrasound probe was measured. The angle might be different according to the depth of intrathecal space and the distance from the midline to the site of probe applied. However, we considered it to be too difficult to implement in real practice. We did not measure the accurate angle of ultrasound probe but relied on the memory of the anesthesiologist of the angle of the probe in our study. In the landmark group in our study, the paramedian approach was used in 80%, whereas the midline approach was used in 20% of subjects as noted in Table 3.2 In the landmark group, we allowed the anesthesiologists to use either midline or paramedian approach at their own discretion. Since our study enrolled patients with abnormal spine anatomy, the anesthesiologists seem to have chosen to use paramedian approach rather than midline approach in most cases. For each of the 3 performers in this study, anesthesiologists A and C used a midline approach in 2 subjects, respectively. We do not believe that the predominant selection of midline approach would have changed our results. It must be better if we can avoid walking off the lamina, which requires multiple needle passes, to reach the interlaminar space regardless of approaches. Ultrasound-assisted spinal anesthesia may decrease unnecessary needle manipulations to locate the interlaminar space. Sun-Kyung Park, MDJin-Tae Kim, MD, PhDDepartment of Anesthesiology and Pain MedicineSeoul National University HospitalSeoul National University College of MedicineSeoul, Republic of Korea[email protected]