Comparing the ease of identifying the subarachnoid space at midline of L3 -L4 interspace by preprocedural ultrasound versus landmark technique - A randomized control study

Introduction: The role of ultrasound in central neuraxial blockade has been underappreciated, partly because of the relative ease of the landmark-guided technique and falsely perceived difficulty in imaging through the narrow acoustic windows. This study was designed to compare conventional landmark technique with preprocedural ultrasonography for identification of the subarachnoid space in patients for elective surgeries under spinal anaesthesia. Materials and Methods: Total 120 patients who were scheduled for elective surgery under spinal anaesthesia were included in this prospective randomised control trial and divided into 2 group, Group L (n = 60) (landmark guided technique) and Group U (n = 60) (ultrasound guided technique). Parameters such as time taken for the identification of the interspace, number of insertion attempts (the primary outcome), number of passes and time taken were recorded in both the groups. Result: The time taken for identification of interspinous space was significantly more in Group U (4.7 ± 2.1 mins) as compared to Group L (1.17 ± 0.52 min) but the number of attempts for needle insertion (1.12 ± 0.41 vs. 1.86 ± 0.91), number of passes in the same interspinous space (3.32 ± 1.44 vs. 6.98 ± 2.51) and the total time for successful lumbar puncture (38.72 ± 12.30 vs. 56.65 ± 11.32 s) were significantly less in Group U as compared to Group L. Conclusion: The ultrasound guided identification of subarachanoid space was time consuming, but resulted in fewer attempts to enter the subarachnoid space when compared to the conventional landmark-based approach. Keywords: Neuraxis, Subarachnoid space, Ultrasonography.