Does Bilateral Superficial Cervical Plexus Block Decrease Analgesic Requirement After Thyroid Surgery?

Abstract

In this randomized, double-blind and controlled study we evaluated and compared the analgesic efficacy of bilateral superficial cervical plexus block and local anesthetic wound infiltration after thyroid surgery. Forty-five patients were assigned to 3 groups. After general anesthesia induction, bilateral superficial cervical plexus block with 0.25% bupivacaine 15 mL in each side was performed in Group I, and local anesthetic wound infiltration with 0.25% bupivacaine 20 mL was performed in Group II. In Group III (control) no regional block was administered. Intravenous patient-controlled analgesia was used to evaluate postoperative analgesic requirement. Neither visual analog scale scores nor total patient-controlled analgesia doses were different among groups. We concluded that bilateral superficial cervical plexus block or local anesthetic wound infiltration with 0.25% bupivacaine did not decrease analgesic requirement after thyroid surgery.

In Brief

IMPLICATIONS: We evaluated and compared the analgesic efficacy of bilateral superficial cervical plexus block and local anesthetic wound infiltration after thyroid surgery in this randomized, double-blind and controlled study and concluded that neither of the regional techniques decreased postoperative opioid requirement.

Although thyroid surgery is a short-stay procedure, most patients require effective postoperative analgesia. It has been reported that the mean postoperative pain score was 6.9 on a visual analog scale (VAS) from 0 to 10 and 90% of the patients required morphine during the first postoperative day (¹). However, nausea and vomiting are the most frequent side effects of opioids and in one study the incidence of postthyroidectomy nausea-vomiting was reported to be 54% (²). Therefore the most recent studies concerning postthyroidectomy analgesia are focused on the efficacy of regional techniques. Local anesthetic wound infiltration (LWI), bilateral superficial cervical plexus block (BSCPB), and bilateral combined superficial and deep cervical plexus block were reported to reduce postoperative opioid requirements (^1,3–5). However the risk-benefit ratio of these regional blocks differs and the analgesic efficacy of these techniques after thyroid surgery has not been compared.

The aim of this double-blind, randomized and controlled study was to evaluate and compare the effects of LWI and BSCPB on postoperative opioid requirements and side effects after thyroid surgery.

Methods

After Institutional Ethics Committee approval and patients' written consent, 45 patients ASA physical status I-II, aged 20–70 yr and scheduled for elective thyroid surgery under general anesthesia were enrolled in the study. Thyroid surgery was performed by the same surgeon with a similar surgical technique and surgical drains were used in a consistent fashion. All patients were euthyroid at the time of surgery. Patients were randomized by using sealed envelopes into 3 groups (15 patients in each group).

Patients were premedicated with midazolam 0.07 mg/kg IM. The surgeon routinely marked the intended cervical incisional line before the patients are delivered to the operation room. General anesthesia was induced with 5 mg/kg thiopental and 0.1 mg/kg vecuronium IV. After endotracheal intubation, in Group I, BSCPB with 0.25% bupivacaine 15 mL in each site and in Group II, LWI with 20 mL 0.25% bupivacaine were performed by the same anesthesiologist. In Group III (control) no regional block was administered. BSCPB was performed with a 22-gauge needle inserted at the midpoint of the lateral border of the sternocleidomastoid muscle. Ten mL of solution was injected in both cranial and caudal directions along the lateral border of the muscle and 5 mL was injected horizontally above the muscle in each site. LWI was performed with a 22-gauge needle inserted along the preoperatively marked incision line and 20 mL of solution was injected in subcutaneous layers of the incision line. The patients, surgeon, and the anesthesiologist responsible for follow-up of patients in the postoperative period were blinded as to group allocation. General anesthesia was maintained with oxygen in 70% nitrous oxide and 1.5%–2% sevoflurane. No opioids were administered intraoperatively.

In the postanesthesia care unit, the first analgesic requirement time (VAS > 30) was recorded and IV patient-controlled analgesia (PCA) with meperidine (10 mg/mL, bolus dose 1.5 mL and lockout time 8 min) was started after a bolus dose of meperidine sufficient to obtain a VAS score of 30. On the ward, VAS scores were recorded at 1, 2, 4, 8, 12, 16, 20, and 24 h postoperatively. The incidence of nausea and vomiting and total meperidine dose during the 24-h postoperative period were also recorded.

The main outcome measure of this study was a 30% decrease in postoperative opioid requirement. Group size was selected by using proportions sample size estimates (α = 0.05, β = 0.085). Values are reported as mean ± sd. VAS scores were compared with two-way repeated measures of analysis of variance, and post hoc statistical testing was performed according to Tukey Kramer test. Student's t-test for unpaired data and Fisher's exact test for the incidence of nausea and vomiting were performed.

Results

Demographic characteristics and the duration of surgery were not different among the groups (P > 0.05) (Table 1).

Table 1: Demographic Characteristics and Duration of Surgery

There were no differences in VAS scores among the groups at all time intervals (P > 0.05) (Table 2). The total amount of PCA consumption (10 mg/mL meperidine) was not different among the groups (P > 0.05) (Table 3). The first analgesic requirement time in Group I was significantly longer than for the control group (P < 0.05) (Table 3).

Table 2: Visual Analog Scale (VAS) Scores of Patients

Table 3: Total Patient-Controlled Analgesia Consumption, First Analgesic Requirement Time, Incidence of Nausea and Vomiting

The incidence of nausea and vomiting was similar in all groups (P > 0.05) (Table 3).

Discussion

In this study, neither LWI nor BSCPB decreased opioid requirements or pain scores after thyroid surgery. LWI is a simple technique used for postoperative analgesia. However, the literature is confusing, with numerous reports supporting the value of this approach and a similar number disputing the beneficial effect (^1,3,6,7). LWI has been used in different types of surgery with different doses of local anesthetics and the opioid requirement was assessed with different methods, such as on-demand administration or PCA. For postthyroidectomy analgesia, Gozal et al. (¹) infiltrated the wound with 10 mL 0.5% bupivacaine at the end of surgery and found that the 24-h morphine requirement and the mean pain scores were significantly less in the treatment group. We could not demonstrate any difference in pain scores, or the 24-h meperidine consumption, of patients whose wounds were infiltrated with bupivacaine, when compared with those of the control group. The possible explanation for our contradictory result could be the differences in study design and pain management. The study of Gozal et al. (¹) was not double-blind and their postoperative pain medication included morphine IV or IM as needed. We used IV-PCA, which is a more objective and sensitive method for assessing the postoperative opioid demand. However, we cannot exclude the possibility of obtaining better results with a larger concentration of bupivacaine (0.5%) because a significant dose-response relationship was reported when a larger concentration of local anesthetic caused the most pronounced effect (^7,8). There is also the possibility of a longer duration with 0.25% bupivacaine with epinephrine. Further studies are needed to evaluate the ideal volume and drug concentration for LWI.

BSCPB was found to reduce pain intensity scores and the amount of cumulative morphine doses after thyroidectomy in the study of Dieudonne et al. (⁴). They performed BSCPB with 20 mL bupivacaine 0.25% with 1:200,000 epinephrine at the end of surgery and found lower pain intensity scores in the early postoperative period in the treatment group. However, we used 30 mL bupivacaine 0.25% for BSCPB and could not demonstrate any beneficial effect on postoperative opioid demand or pain scores. The main difference in their study was in pain assessment intervals and the manner in which a nurse evaluated the patient's numeric rating scale (NRS)-11 score every 4 h; 5 mg morphine was administered subcutaneously if the pain score was 4 or higher. In our study we evaluated the 24-h opioid demand with IV PCA and pain scores in 2-h intervals during the first 8 h. Dieudonne et al. (⁴) concluded that BSCPB did not provide optimal pain relief because 65% of patients needed additional analgesics and the reduced opioid consumption was less clinically relevant, as it did not result in reduced side effects. It seems that the decrease in morphine consumption was not enough to have an impact on the morphine-related side effects and this would weaken the clinical relevance of opioid-sparing.

Bilateral deep cervical plexus block (⁹) or combined superficial and deep cervical plexus block (⁵) were also found to be effective for decreasing postoperative thyroidectomy pain. However, deep cervical plexus block has been reported to cause hemidiaphragmatic dysfunction in 61% of patients (¹⁰). We suggest that bilateral deep cervical block can produce significant respiratory dysfunction and should not be encouraged for postoperative pain management.

In our study, the only beneficial effect of BSCPB was the prolonged first analgesic requirement time, which was about 15 min. This result was statistically significant but of no clinical significance.

A likely explanation for the lack of beneficial effects of BSCPB or LWI on postthyroidectomy analgesia is that pain arising from areas that cannot be blocked by a superficial approach is of greater significance than that from cutaneous, subcutaneous, and muscular layers after thyroid surgery. Intraoperative neck position and wound drainage are also important components of postthyroidectomy pain.

In conclusion, BSCPB or LWI with 0.25% bupivacaine did not decrease opioid requirement or pain scores after thyroid surgery.