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

Abstract

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.

Keywords: Analgesia; Cervical plexus; Entropy; Nerve block; Sevoflurane; Thyroidectomy.

Fig. 1.

CONSORT flow diagram. Group A: BSCPB with Bupivacaine (test group), Group B: BSCPB with saline (control group).

Fig. 2.

Comparison of the trends in end-tidal sevoflurane concentration between the two groups. *The end-tidal sevoflurane concentration was significantly lower in group A compared to group B at 15, 30, 45, and 50 min (P < 0.05). Group A: BSCPB with Bupivacaine (test group), Group B: BSCPB with saline (control group). Post: post-intubation.

Fig. 3.

Postoperative median visual analog scores. Median visual analog scale (VAS) scores (with interquartile ranges) for both groups. *The scores were significantly lower in group A compared to group B at 30 min, 1, 2, and 3 h (P < 0.001). Analgesia extended to 6 h in group A compared to 3 h in group B.

Fig. 4.

Hemodynamic parameters. Heart rate (HR) and mean arterial pressure (MAP) trends in both groups. Values were comparable at all points of time (P > 0.05). Group A: BSCPB with Bupivacaine (test group), Group B: BSCPB with saline (control group).

Fig. 5.

Trends in response entropy (RE) in both groups. RE was < 60 at all time points in both groups and comparable between the groups (P > 0.05). Group A: BSCPB with Bupivacaine (test group), Group B: BSCPB with saline (control group).