A randomized comparison between classical landmark-based and ultrasound-guided right superficial cervical plexus block in attenuating postlaparoscopic shoulder pain under subarachnoid anesthesia

Background: Postlaparoscopic shoulder pain is believed to be due to phrenic nerve involvement, with an incidence of 35%–80%. Classical landmark-based right superficial cervical plexus block (SCPB) has been utilized to alleviate postlaparoscopic shoulder pain. However, there is no possibility of phrenic nerve blockade with subcutaneously deposited injectate in landmark-based SCPB. Therefore, we hypothesized that the local anesthetic injectate in the sternocleidomastoid-scalene intermuscular fascial plane under ultrasound guidance is paramount in achieving phrenic nerve blockade. The main objective was to evaluate the effect of ultrasound-guided right SCPB in decreasing postlaparoscopic shoulder pain compared to conventional landmark-guided SCPB. Methods: In this prospective randomized trial, 79 adult patients reported for laparoscopic surgeries under spinal anesthesia were randomly divided into groups; A and B. Group A patients received intermediate approach to SCPB with 10 ml of 0.5% bupivacaine under ultrasound guidance. Group B patients received SCPB using a classical landmark-based approach. The incidence of intraoperative and postoperative shoulder pain and other adverse effects were noted. Results: Intraoperative shoulder pain was significantly less in Group A than in Group B (5% vs. 43.5%, P < 0.001). The postoperative shoulder pain was also significantly reduced in Group A than in Group B (5% vs. 28.2%, P = 0.013). There were no instances of major adverse effects. Conclusion: We conclude that the ultrasound-guided injectate in the sternocleidomastoid-scalene intermuscular space deeper to investing layer but superficial to the prevertebral layer of the deep cervical fascia is central to providing superior shoulder pain relief in patients undergoing laparoscopic surgery under spinal anesthesia than the classical landmark-based SCPB.