Ultrasound imaging facilitates subarachnoid blockade in patients with difficult surface anatomic landmarks

Background Ultrasound imaging of the spine has recently been proposed to facilitate identification of the anatomic landmarks for subarachnoid blockade. This study assessed the accuracy and precision of the ultrasound-guided subarachnoid blockade over the conventional surface landmark-guided technique in patients with difficult surface anatomic landmarks undergoing elective orthopedic lower limb surgery. Patients and methods This prospective, randomized controlled study was conducted on 60 patients with difficult surface anatomic landmarks for subarachnoid block, scheduled for elective orthopedic lower limb surgery. These patients were randomly allocated into two equal groups: group LM in which subarachnoid block was performed using the conventional surface landmark-guided technique and group US in which subarachnoid block was performed using the ultrasound. The primary outcome was the rate of successful dural puncture on the first needle insertion attempt. The secondary outcomes included number of needle redirection, number of repeated needle insertion, number of failed attempts, time taken to establish landmarks, and time taken to perform the spinal anesthesia. Results Successful dural puncture on the first needle insertion attempt was achieved in 21 (70%) patients in group US and in eight (26.7%) patients in group LM (P < 0.001), whereas the number of patients requiring needle redirection in group US was seven (23.3%), which was significantly less than in group LM in which half of the patients required needle redirection after the first insertion of the needle. The number of patients requiring repeated needle insertions in group LM was three-fold the number of patients in group US [six (20%) vs. two (6.7%), respectively]. There was only one failed attempt in group LM. The mean time taken to establish anatomic landmarks was highly significantly longer in group US than in group LM (5.7 ± 0.93 vs. 2.27 ± 1.23 min, respectively; P < 0.001). There was a highly significant reduction in the time required to perform the spinal anesthesia in group US (5.01 ± 0.78 min) than in group LM (7.75 ± 0.96 min; P < 0.001). Conclusion Ultrasound-guided approach is a reliable and effective method in patients in whom technical difficulty is expected.