Superficial Cervical Plexus Block With Dexmedetomidine Versus Without Adjuvant in Thyroid Surgery

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.

• Dexmedetomidine & Bupivacaine. (Drug), also known as Dexmedetomidine, Bupivacaine, BPSS: Superficial Cervical Plexus Block (SCPB) performed under ultrasound guidance (in-plane technique). The regimen consists of Bupivacaine 0.375% with the adjuvant Dexmedetomidine at a dose of 0.5 mcg/kgbw. The total volume injected is 20 mL (10 mL on each side) into the fascial space between the sternocleidomastoid muscle and the prevertebral fascia. The block is performed after induction of general anesthesia
• Bupivacain (Drug), also known as Bupivacaine, BPSS: Superficial Cervical Plexus Block (SCPB) performed under ultrasound guidance (in-plane technique). The regimen consists of Bupivacaine 0.375% only. The total volume injected is 20 mL (10 mL on each side) \[cite_start\], supplemented with Saline/Placebo to match the volume and appearance of the active drug. The block is performed after induction of general anesthesia.

Primary outcomes

• Time to First Request for Opioid Analgesia (PCA Button Press) [up to 24 hours post-operation ( 1440 minutes )]: From the time of PCA activation in the Post-Anesthesia Care Unit (PACU) until the completion of the first 24 hours post-operation. The cumulative consumption of Fentanyl (in micrograms) is recorded from the PCA device's counter, with the assessment period duration calculated precisely in minutes

Secondary outcomes

• Visual Analogue Scale (VAS) Pain Score at 6, 12, and 24 Hours Post-Operation [6 hours, 12 hours, and 24 hours post-operation.]: Assessment of acute pain intensity using the Visual Analogue Scale (VAS) (0-100 mm, where 0 is no pain and 100 is the worst pain imaginable).
• Total Fentanyl Opioid Consumption in the First 24 Hours Post-Operation [24 hours post-operation]: The total amount of fentanyl (in mcg) consumed by the patient via the Patient-Controlled Analgesia (PCA) device.
• Change in Interleukin-6 (IL-6) Level Post-Operation [Measured as the difference between 24 hours post-operation and pre-general anesthesia.]: The delta change ($\\Delta$) in plasma Interleukin-6 (IL-6) concentration (in pg/mL) comparing the pre-operative baseline to the 24-hour post-operative measurement.
• Incidence of Chronic Pain at 3 Months Post-Operation [3 months post-operation (90 days)]: Incidence of Chronic Post-Surgical Pain (CPSP) defined by the Brief Pain Inventory Short Form (BPI-SF) score (any score > 0) lasting longer than three months.

Sex: All, ages: 30 Years to 59 Years

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.

• Lya Lusyana, dr., Study chair, Universitas Udayana
• Pontisomaya Parami, Sp.An, Study director, Universitas Udayana
• I Gusti Ngurah Mahaalit Arimbawa, Sp.An, Study director, Universitas Udayana