Effects of bilateral superficial cervical plexus block on sevoflurane consumption during thyroid surgery under entropy-guided general anesthesia: a prospective randomized study

BACKGROUND: Bilateral superficial cervical plexus block (BSCPB) provides good postoperative analgesia, but its effect on anesthetic consumption is unknown. This study evaluated the effects of BSCPB on sevoflurane consumption during thyroid surgery. METHODS: Fifty patients were randomly allocated into groups A and B of 25 each in this prospective double-blind study. Group A received BSCPB with 20 ml 0.25% bupivacaine, whereas group B received 20 ml saline immediately before entropy-guided general anesthesia. Intraoperative hemodynamic parameters, end-tidal sevoflurane concentration, minimum alveolar concentration, and sevoflurane consumption were recorded. Postoperative pain was assessed using a visual analog scale, and the time of the first request for analgesia was noted. All side effects were recorded. RESULTS: Demographics were comparable. Mean sevoflurane consumption [for 30 min: group A = 7.2 (1.1) ml, group B = 8.8 (2.0) ml, P = 0.001; for 60 min: group A = 13.5 (1.7) ml, group B = 16.5 (3.9) ml, P = 0.002] and mean end-tidal sevoflurane concentration [for 30 min: group A = 1.2% (0.2%), group B = 1.4% (0.2%), P = 0.008; for 60 min: group A = 1.2% (0.1%), group B = 1.4% (0.2%), P = 0.010] were significantly lower in group A. Patients in group A had a longer duration of analgesia [361.6 (79.5) min vs. 151.0 (60.2) min, P < 0.001] compared to those in group B. CONCLUSIONS: Preinduction BSCPB during thyroid surgery significantly reduced sevoflurane consumption and increased the duration of postoperative analgesia.