Many patients require acute pain control during the first day after thyroid surgery, especially during the first hours after surgery. In one study, the mean reported pain score after thyroidectomy was 6.9 on a visual analogue scale from 0 to 10, and 90% of the patients required morphine . Thyroidectomy pain has a large superficial component  and preincision injection of lidocaine in an experimental incision model delayed development of primary hyperalgesia up to 4 h . If we can control early postoperative pain and avoid the nausea and vomiting that are induced by opioids, patients can achieve a good quality of analgesia after thyroidectomy.
Many studies have reported that incision pain after thyroidectomy may be controlled by wound infiltration or superficial cervical plexus block (SCPB) or combined superficial and deep cervical plexus block (COCPB) with local anaesthetics [1,3–7]. Although COCPB can evoke serious complications, it may provide better analgesia than SCPB. However, there has been no study that compared the analgesic effect between SCPB and COCPB. Moreover, patients also experience headache and posterior neck pain after thyroidectomy, but this has been rarely studied.
Therefore, the goal of this study was to compare the analgesic efficacy between bilateral SCPB and COCPB for controlling the incision pain, headache and posterior neck pain after thyroidectomy.
The Ethics Committee of Saint's Vincent Hospital for human investigations approved this study. Ninety ASA physical status I or II adult patients who were scheduled for elective thyroid lobectomy under general anaesthesia were included in this study. All patients were euthyroid before surgery, and the same surgeon performed all the procedures.
The noninclusion criteria included previous headache and posterior neck pain, diabetes, hypertension and an inability to understand the study protocol or the pain scale. The day before surgery, all patients were instructed about the study protocol, the numeric rating scale (NRS) and the complications. Written, informed consent was obtained from each patient. The patients were premedicated with zolpidem tartrate 10 mg.
Using a random number sequence, the patients were allocated to a control group (group C, n = 30), an SCPB group (group S, n = 30) and a COCPB group (group CO, n = 30). After arrival in the operating room, the patients were checked for bispectral index (BIS), blood pressure and heart rate. Group C patients did not receive any regional block, the group S patients received bilateral SCPB and the group CO patients received bilateral COCPB with 0.25% bupivacaine 18 ml.
The patient was placed in a supine position with the head turned away from the side to be blocked, and then the sternocleidomastoid muscle (SCM) was identified by slight head elevation. SCPB was performed with a 26-gauge needle that was inserted at the midpoint of the posterior border of the SCM muscle and the needle was advanced just past the SCM muscle. Some solution was slowly injected transversely (6 ml in group S and 4 ml in group CO). The needle was then redirected and the remaining solution was injected up (2 ml) and downward (1 ml). Deep cervical plexus block was carried out as follows: a line was drawn between the mastoid process and the posterior aspect of the insertion of the SCM muscle at the clavicle, and a point approximately 5 cm below the mastoid process was then identified. A needle was inserted at approximately 1 cm in front of the previously identified point on the line and the needle was advanced to a depth of approximately 2.5 cm in a slightly anterior and caudal direction. After gentle aspiration, 2 ml solution was injected (Fig. 1). The block was assessed by numbness at bilateral C2, C3 and C4 dermatomes.
General anaesthesia was induced by using a target-controlled infusor (Orchestra, Fresenius Kabi, Bad Homburg, Germany) with propofol 4 μg ml−1 until loss of consciousness, and then rocuronium 0.6–0.8 mg kg−1 and remifentanil 4 ng ml−1 were administered. Orotracheal intubation was done after 90 s, and the propofol and remifentanil were reduced to 3 μg ml−1 and 0.8 ng ml−1, respectively. N2O 60% and O2 40% were then used. Propofol was controlled to maintain a BIS of 40–60, and remifentanil was given to maintain blood pressure within 20% of that on the ward. We increased or decreased propofol 0.2 μg ml−1 and remifentanil 0.2 ng ml−1 by degrees. The propofol and remifentanil were stopped at the start of skin closure.
After the operation, the total amount and the average concentration of propofol and remifentanil, the duration of the operation and anaesthesia were recorded. The postoperative incision pain, headache and posterior neck pain were evaluated at the time of admission to the recovery room (0 h), and at 2, 4, 6, 12 and 24 h postoperatively by a nurse who was trained to assess pain. The surgeon and the pain assessment nurse did not know which group any of the patients were in. The type of analgesic and the dose used in the recovery room and ward, the side effects and the patients' satisfaction were evaluated at postoperative 24 h. For postoperative pain management, diclofenac sodium 75 mg was given when the pain score was 4–6 at rest. Pethidine 25 mg was given as needed when the pain score was more than 6 at rest. The pain score was assessed using a NRS that ranged from 0 to 10.
Assuming that bilateral SCPB and COCPB would reduce the dose of intraoperative opioid and postoperative analgesics by 30%, the size of the groups was selected by using estimates of the sample size proportions (α = 0.05, β = 0.1). Continuous parametric variables are reported as mean ± SD. The differences between groups were examined by using the Kruskal–Wallis test. Sheff's test was used for post-hoc comparison. Categorical variables were analysed with χ2 tests. A value of P less than 0.05 was considered statistically significant.
All the 90 enrolled patients completed the study protocol. The surgeon's opinion of the surgical conditions was very good and the surgeon did not experience any problems. Patients' characteristics were similar between the three groups. The average concentration of remifentanil was significantly reduced in group S as compared with group C and group CO (1.1 ± 0.3, 1.8 ± 0.4, and 1.8 ± 0.7 ng ml−1, respectively; P < 0.05; Table 1). The incision pain at rest and on swallowing were significantly reduced at 0, 2 and 4 h in group S as compared with group C (P < 0.05). There was a reduced tendency for headache in group S and group CO, but this was not significant as compared with group C. Posterior neck pain was not different among the three groups (Fig. 2a–d). Seven patients in group S and six patients in group CO did not need analgesics for 24 h. The requirement for opioid analgesics in the recovery room was significantly reduced in group S as compared with groups C and CO (P < 0.05), and the requirement for nonopioid analgesics on the day of surgery was significantly reduced in groups S and CO as compared with group C (P < 0.05; Table 2). The incidence of postoperative nausea and vomiting (PONV) was significantly reduced in group S as compared with the two other groups (P < 0.05). In addition, group C patients required significantly more antiemetics than did those in groups S and CO (P < 0.05; Table 3). The patients' satisfaction was higher in group S than in groups C and CO (Table 4).
Our results show that preoperative bilateral SCPB reduced the intraoperative average remifentanil requirement and reduced the incision pain during the first hours after surgery and the need for rescue analgesics. Preoperative bilateral SCPB induced fewer side effects and higher patients' satisfaction than control and COCPB.
We expected that nerve block could reduce the required average dose of intraoperative remifentanil and propofol because of the analgesic, anti-inflammatory and sedative effects of local anaesthetics. Aunac et al.  reported that the SCPB with 0.75% ropivacaine group (with or without clonidine) required significantly less intraoperative propofol and sufentanil than the saline group. However, our study showed that the required average concentration of propofol was not different among the three groups and the required average concentration of intraoperative remifentanil was reduced in only group S. The difference between the two studies was that, in Aunac's study , the authors increased the propofol concentration first and then increased the sufentanil concentration when the heart rate or the systolic arterial blood pressure increased more than 20% as compared with the baseline value. In our study, we increased the remifentanil dose when the systolic arterial blood pressure increased more than 20% as compared with the baseline value.
Our results are comparable to those of another study that reported that bilateral SCPB after skin closure using 0.25% bupivacaine 20 ml with 1: 200 000 epinephrine significantly reduced the pain intensity in the early postoperative stage . Our study showed similar results. Nevertheless, one previous study reported that bilateral SCPB using 0.75% ropivacaine administered before or after surgery did not improve postoperative tanalgesia after thyroidectomy . This may be explained by the fact that those authors subcutaneously injected ropivacaine 10 ml and then only ropivacaine 4 ml was injected up and downward for SCPB. As was pointed out by those authors, the extension of the block to the transcervical branches is mandatory to achieve a successful SCPB . Pandit et al.  reported that methylene blue dye did not spread beyond the subcutaneous tissue after subcutaneous injection in the cervical area. This may explain the efficacy of our blocks because our bupivacaine injections targeted the transversal cervical branches and bupivacaine was not injected subcutaneously. The difference of methods might have produced different results. When we consider the reduced intraoperative average remifentanil concentration in only group S and not group CO in our study, this supports that postthyroidectomy pain has a large ‘superficial component’ . Although the duration of action of the local anaesthetics stopped after 6 h, groups S and CO showed a reduced incision pain score as compared with group C. This prolonged effect could be related to the suppression of primary hyperalgesia and the prevention of secondary hyperalgesia .
Sixty-one perc ent (24 in group C, 18 in group S and 13 in group CO) of the patients complained of headache and 9% (two in group C, two in group S and one in group CO) of the patients with headache complained more of headache than of incision pain. Fifty-four per cent (eight in group C, 16 in group S and 15 in group CO) of the patients complained of posterior neck pain. Han et al.  explained that mechanical injury or entrapment of the greater occipital nerve during hyperextension of the neck can occur and they reported that preoperatively the greater occipital nerve block during total thyroidectomy could reduce postoperative headache and posterior neck pain. We found that 35% (19 patients) of patients who complained of headache mentioned either ipsilateral headache, occasionally toothache, otalgia or ocular pain. It is known that the thyroid is mainly supplied by the superficial cervical plexus, and surgery stimulates the sternothyroid and sternohyoid muscle receptors, which transmit these stimuli to the lesser occipital nerve, the greater auricular nerve and the deep cervical plexus. Therefore, the muscles supplied by these nerves can evoke headache, posterior neck pain, ocular pain, ear pain or toothache. We expected SCPB and COCPB could reduce many components of these referred pain symptoms. However, only headache showed a tendency to be reduced in group CO as compared with group C.
In our study, the pain score was higher than that in other previous studies [3–7]. Upon reflection, the first reason for this was that we did not give regular analgesics such as paracetamol, which was used in other studies [3,5,6]. The second reason was that the original study protocol allowed rescue analgesics to be given when the pain at rest was 4–6, but rescue analgesics were mostly prescribed when the pain score at rest was more than 6. Therefore, more analgesics might be required for good pain control after thyroidectomy in the three groups. The third reason was that control group patients might think they did not have any advantage by block. This might have had an influence on the greater number of requests for rescue drugs and the higher pain scores in the control group.
Sonner et al.  reported that the rates for PONV were 44 and 64%, respectively, when propofol vs. isoflurane was used for maintenance of anaesthesia during thyroidectomy. In our study, 45% of group C was similar to Sonner's propofol group. Reduced headache, less opioid use and the use of intraoperative propofol might have influenced the lower PONV rate (0%) in group S compared with 28% in group CO.
In conclusion, SCPB is a safe, simple and effective technique to reduce the intraoperative opioid requirement during thyroidectomy. In addition, when compared with a COCPB, the SCPB reduces the intensity of the incision pain that occurs immediately after the operation.
The authors thank Kyeong Hee Kim, registered nurse, Department of General Surgery, Saint Vincent Hospital, for her help with this research.
1 Gozal Y, Shapira SC, Gozal D, Magora F. Bupivacaine wound infiltration in thyroid surgery reduces postoperative pain and opioid demand. Acta Anaesthesiol Scand 1994; 38:813–815.
2 Dieudonne N, Gomola A, Bonnichon P, Ozier YM. Prevention of postoperative pain after thyroid surgery: a double-blind randomized study of bilateral superficial cervical plexus blocks. Anesth Analg 2001; 92:1538–1542.
3 Kawamata M, Watanabe H, Nishikawa K, et al
. Different mechanisms of development and maintenance of experimental incision-induced hyperalgesia in human skin. Anesthesiology 2002; 97:550–559.
4 Herbland A, Cantini O, Reynier P, et al
. The bilateral superficial cervical plexus block
with 0.75% ropivacaine administered before or after surgery does not prevent postoperative pain after total thyroidectomy. Reg Anesth Pain Med 2006; 31:34–39.
5 Aunac S, Carlier M, Singelyn F, DeKock M. The analgesic efficacy of bilateral combined superficial and deep cervical plexus block
administered before thyroid surgery under general anesthesia. Anesth Analg 2002; 95:746–750.
6 Andrieu G, Amrouni H, Robin E, et al
. Analgesic efficacy of bilateral superficial cervical plexus block
administered before thyroid surgery under general anaesthesia. Br J Anaesth 2007; 99:561–566.
7 Eti Z, Irmak P, Gulluoglu BM, et al
. Does bilateral superficial cervical plexus block
decrease analgesic requirement after thyroid surgery? Anesth Analg 2006; 102:1174–1176.
8 Pandit JJ, Dutta D, Morris JF. Spread of injectate with superficial cervical plexus block
in human: an anatomical study. Br J Anaesth 2003; 91:733–735.
9 Han DW, Koo BN, Chung WY, et al
. Preoperative greater occipital nerve block in total thyroidectomy patients can reduce postoperative occipital headache
and posterior neck pain
. Thyroid 2006; 16:599–603.
10 Sonner JM, Hynson JM, Clari O, Katz JA. Nausea and vomiting following thyroid and parathyroid surgery. J Clin Anesth 1997; 9:398–402.