Efficacy of Superficial Cervical Plexus Block (SCPB) with Dexmedetomidine Adjuvant Compared to Without Adjuvant in Thyroid Surgery. This is a double-blinded, randomized controlled trial designed to evaluate the effectiveness of adding perineural dexmedetomidine to a Superficial Cervical Plexus Block (SCPB) for pain management in patients undergoing thyroid surgery. The study aims to prove that SCPB with dexmedetomidine adjuvant provides superior post-operative analgesia, lowers total opioid consumption, prolongs the time until the first analgesic request, and reduces the incidence of chronic pain three months post-surgery compared to SCPB without the adjuvant. The study will also evaluate the anti-inflammatory effect by measuring the reduction in Interleukin-6 (IL-6) levels post-operatively and compare the incidence of bradycardia as a side effect. The total required sample size is 58 subjects.

Thyroid surgery is a major procedure often associated with acute and chronic postoperative pain in the neck area. Chronic post-surgical pain can significantly affect the patient's long-term quality of life. Superficial Cervical Plexus Block (SCPB) is an effective regional anesthesia technique used to manage perioperative pain and reduce the need for postoperative opioids. However, achieving an optimal duration of analgesia remains a challenge. Dexmedetomidine, an alpha_2-adrenergic receptor agonist, is frequently used as an adjuvant to prolong the analgesic effect of nerve blocks. Studies have shown that combining dexmedetomidine with SCPB provides better and longer-lasting analgesia. Dexmedetomidine also possesses anti-inflammatory properties, potentially lowering the level of Interleukin-6 (IL-6), a biomarker of inflammation often elevated after surgery that can exacerbate pain. The effectiveness of SCPB with dexmedetomidine adjuvant, particularly in reducing inflammation and chronic pain incidence, has not been widely explored locally at RSUP Prof. Dr. I.G.N.G. Ngoerah.Study Objectives: The primary goal is to prove the effectiveness of dexmedetomidine as an SCPB adjuvant in thyroid surgery, assessed by acute and chronic pain outcomes. Acute Pain Outcomes: Measured by Visual Analogue Scale (VAS) scores at 6, 12, and 24 hours post-operation, time to first Patient-Controlled Analgesia (PCA) button press, total opioid consumption via PCA over 24 hours, and changes in the inflammatory biomarker Interleukin-6 (IL-6). Chronic Pain Outcomes: Measured by the incidence of chronic pain three months post-surgery using the Brief Pain Inventory Short Form (BPI-SF) questionnaire. Safety Outcome: Measured by the incidence of bradycardia. Correlations: To prove the correlation between the change in Interleukin-6 levels with 24-hour pain scores and the incidence of chronic pain.Study Design and Intervention: This is a true experimental study with a double-blinded randomized pre- and post-control group design. Group P1 (Intervention): Patients receive SCPB with 0.375% Bupivacaine plus 0.5 mcg/kgbw Dexmedetomidine (total volume 20 mL, injected 10 mL on each side). Group P2 (Control): Patients receive SCPB with 0.375% Bupivacaine only (total volume 20 mL, injected 10 mL on each side).All procedures are performed under general anesthesia with Ultrasound guidance. Analgesia management includes PCA Fentanyl and combination analgesics (Paracetamol and Ibuprofen). The minimum required sample size is 58 subjects.

Inclusion Criteria:

• Patients aged 30-59 years.
• Patients with ASA physical status classification I-III.
• Patients with Body Mass Index (BMI) between 18 and 25 kg/m

Exclusion Criteria:

• Patients with contraindications for regional anesthesia.
• Patients with a history of autoimmune disease.
• Presence of infection in the puncture area.
• Patients with allergies and contraindications to the use of dexmedetomidine.
• Patients on routine medication, including beta-blockers, anti-depressants, or anti-seizure medications.
• Prolonged opioid use.
• Patients unable to be assessed using the Visual Analogue Scale (VAS) or unable to operate the Patient-Controlled Analgesia (PCA) device.
• Patients who refuse to participate in the study.

This is a double-blinded study. The following measures ensure blinding:

Intervention Blinding: The preparation and mixing of the local anesthetic solution (with or without Dexmedetomidine adjuvant) are performed by a third party not involved in the execution of the block or patient follow-up. The final solutions are made to look identical.

Investigator/Assessor Blinding: The principal investigator and the Acute Pain Service (APS) team that performs post-operative assessments (VAS scores, opioid consumption, complications, and long-term follow-up) are blinded to the treatment group allocation (Dexmedetomidine or control).

Participant Blinding: Participants are informed that the difference lies only in the adjuvant given, thus they are blinded to the specific substance received.