This prospective, randomized, double-blind, placebo-controlled clinical trial aims to evaluate the analgesic efficacy of ultrasound-guided intermediate cervical plexus block (ICB) in patients undergoing vagus nerve stimulation (VNS) implantation surgery under general anesthesia. Participants are randomly assigned to receive either an ultrasound-guided ICB with 10 mL of 0.25% bupivacaine or a placebo injection with 10 mL of normal saline following induction of general anesthesia. The primary outcome is total postoperative morphine consumption during the first 24 hours after surgery. Secondary outcomes include intraoperative remifentanil consumption, postoperative pain intensity assessed using the Numeric Rating Scale (NRS), time to first analgesic request, length of hospital stay, and postoperative seizure incidence.

Postoperative pain following vagus nerve stimulation (VNS) implantation surgery originates from both cervical and infraclavicular surgical incisions. Although opioid analgesics are commonly used for postoperative pain control, minimizing opioid exposure is particularly desirable in patients with drug-resistant epilepsy because opioid-related adverse effects may delay recovery and potentially influence neurological assessment.

The intermediate cervical plexus block (ICB) is an ultrasound-guided regional anesthesia technique that provides sensory blockade of the superficial branches of the cervical plexus while allowing accurate deposition of local anesthetic between the investing and prevertebral layers of the deep cervical fascia. Previous studies have demonstrated the effectiveness of cervical plexus blocks in various cervical surgical procedures; however, evidence regarding their use during VNS implantation surgery remains limited.

This prospective, randomized, double-blind, placebo-controlled study compares ultrasound-guided ICB using 10 mL of 0.25% bupivacaine with a placebo injection of 10 mL normal saline administered after induction of general anesthesia. The primary objective is to determine whether ICB reduces postoperative opioid requirements during the first 24 hours after surgery. Secondary objectives include evaluation of intraoperative remifentanil consumption, postoperative pain scores, time to first rescue analgesic, length of hospital stay, and postoperative seizure incidence. The findings are expected to provide evidence regarding the effectiveness and safety of ultrasound-guided intermediate cervical plexus block as part of multimodal analgesia for patients undergoing VNS implantation surgery.

Inclusion Criteria:

• Adults aged 18-60 years
• American Society of Anesthesiologists (ASA) physical status II-III
• Drug-resistant epilepsy
• Scheduled for elective vagus nerve stimulation implantation surgery under general anesthesia
• Written informed consent obtained

Exclusion Criteria:

• Allergy or contraindication to local anesthetics
• Coagulopathy or current anticoagulant therapy
• Infection at the injection site
• Pregnancy or breastfeeding
• Severe pulmonary disease
• Inability to understand or use the Numeric Rating Scale (NRS)
• Refusal to participate

De-identified individual participant data underlying the results reported in this study will be made available upon reasonable request to the corresponding author, following publication, subject to institutional approval and applicable ethical and legal requirements.

Participants, postoperative care providers, and outcome assessors were blinded to treatment allocation. Study solutions were prepared in identical syringes by an independent anesthesiologist not involved in postoperative assessments or data analysis. The anesthesiologist performing the block was aware of the assigned intervention but did not participate in postoperative outcome assessment.