We found statistically significant reduction in mean NRS–11 scores at all end-points in the block group. Time to first analgesic requirement was nearly by doubled in the block group (132.3 ± 71.5 min vs 71.4 ± 60.0 min, p = 0.009). Multiple studies have investigated the effectiveness of BSCPB in thyroid surgery and reported that it was effective in minimizing pain scores, opioid and total analgesic consumption and prolonging analgesia duration [12, 13, 21, 22]. A meta-analysis of 14 studies incorporated 1154 patients revealed BSCPB significantly reduced analgesic requirement, VAS scores and lengthen time to first analgesic request [14]. BSCPB was found significantly associated with nearly half shorter postoperative hospital staying days (2.4 ± 0.6 vs 4.7 ± 1.6; p < 0.05) [12].
In-contrast, some studies denied the effectiveness of BSCPB. The block had failed to demonstrate reduction in pain scores and opioid consumption. But longer time for first analgesic request was observed. They explained the result by pain arising from deeper and muscular structures, pain from positioning and wound drainages [17]. Despite these, pain after thyroidectomy was known to have large superficial component [23]. Different drug regimens, volumes, techniques of injections and duration of postoperative follow-up (36 hours) might be possible causes for these contradictory conclusions [18]. Another study has concluded equi-vocal as BSCPB reduced pain intensity and analgesic requirement but could not provide optimal pain relief alone since 65% of patients need additional analgesia [10]. Performing the block after the surgery might have effect on this equi-vocal outcome. In another study, hospital stay and postoperative analgesic consumption were comparable even if patients in the block group had lesser VAS scores. These differences might be due to 4 days follow-up [24].
In this study, all blocks were done by landmark technique by subcutaneous deposition of local anesthetic along the posterior border of sternocleidomastoid. In A recent Egyptian study that compared landmark and ultrasound-guided techniques found no difference in effectiveness and safety [25]. However, another study has concluded that an ultrasound-guided technique had superiority and explained by direct visualization of the nerves, adjacent structures and needle movement that results in faster, denser and longer block [26].
Performing regional nerve blocks and administration of multi-modal analgesics prior to surgical incision are helpful in reducing intra- and postoperative opioid consumption, primary hyperalgesia, central sensitization and chronic pain [14, 23, 27]. In combination with gabapentin, BSCPB has prevented delayed neuropathic pain at 6th postoperative month [28]. Thyroidectomy without BSCPB was three-times likely associated with neuropathic pain compared to thyroidectomy with BSCPB [29]. In our study, all BSCPBs were done in the preoperative time, immediately before induction as a part of multi-modal analgesia. This might provide the benefits of preemptive analgesia and minimized anesthetic duration. Some surgeons complained for disruption of the surgical anatomy by the block. In another study, according to surgeon’s opinions, the surgical conditions were very good and had encountered no problem [23]. An ultrasound-guided study suggested that performing BSCPB in the pre- or postoperative time were equally effective. Landmark technique was also found effective whether performed in the pre- or postsurgical time to reduce the VAS scores [24]. Furthermore, presurgical block is technically easier unless in very large thyroid mass. After surgery anatomical planes may be changed and facilitate leakage through incision and facial layers [13]. However, Herbland and colleagues reported that irrespective of time of injection (pre or postsurgical), BSCPB is not effective analgesic option for thyroidectomy. They explained it by incomplete sensory block because of limited spread of solution through the investing fascia and high vascularity of the area [18].
Wound infiltration is effective choice of analgesia after thyroid surgery. But compared to BSCPB, the later was found more effective. Time to first analgesia were 162 ± 124 min vs 544 ± 320 min vs 860 ± 59 min in control, wound infiltration and BSCPB groups respectively; p < 0.001 [30]. This analgesic duration was very long compared to our finding. This difference might be due to drug regimen as they used 15 ml of 0.5% bupivacaine and in the current study 10 ml of 0.25% bupivacaine. Two recent RCTs have declared that wound infiltration lacks effectiveness for treating pain after thyroidectomy; even in addition of adrenaline [31, 32].
The incidences of postoperative nausea and vomiting (PONV) after thyroidectomy ranges from 21.7% up to 84% [12, 33]. We have assessed PONV with simplified PONV impact scale and the incidence of clinically important PONV was 27% in block group and 35.1% in non-block group and no statistically significant difference was observed. These results were lower compared to other studies. The reason might be predominant use of propofol for induction of anesthesia in the current study [18]. Despite lower incidences of PONV, we found that comparable between the groups. This phenomenon might be explained by tramadol consumption. Even though, there was statistically significant reduction in tramadol consumption, patients in the block group might have consume clinically significant amount of tramadol. No clinically significant complication occurred in association with BSCPB.
We have concluded that BSCPB has significantly reduced pain scores, opioid and total analgesic consumption and prolong the time to first analgesic requirement. We recommend that BSCPB is simple and can be used effectively and safely for pain management after thyroid surgery as a part of multi-modal analgesia in the first 24 postoperative hours.
