Arthroscopic shoulder surgery is associated with moderate to severe postoperative pain that may delay recovery and rehabilitation. Interscalene brachial plexus block (ISB) is widely used for postoperative analgesia in shoulder surgery; however, it may be associated with complications such as phrenic nerve paralysis. The serratus posterior superior intercostal plane (SPSIP) block is a recently described fascial plane block that may provide effective analgesia while avoiding some of the limitations of ISB.

This prospective, randomized, double-blind controlled trial aims to compare the analgesic efficacy of ISB and SPSIP block in patients undergoing elective arthroscopic shoulder surgery under general anesthesia. The primary outcome is total postoperative opioid consumption during the first 24 hours after surgery. Secondary outcomes include postoperative pain scores, quality of recovery, time to first rescue analgesia, rescue analgesic requirements, intraoperative opioid consumption, sensory block distribution, motor block characteristics, and block-related complications.

Postoperative pain following arthroscopic shoulder surgery can adversely affect patient comfort, early mobilization, rehabilitation, and overall recovery. Although the interscalene brachial plexus block is considered the reference regional anesthesia technique for shoulder surgery, its use may be limited by adverse effects such as hemidiaphragmatic paresis, phrenic nerve involvement, and upper extremity motor weakness.

The serratus posterior superior intercostal plane block is a novel ultrasound-guided fascial plane block targeting the posterior thoracic region. Preliminary evidence suggests that it may provide analgesia extending to the shoulder area through spread to cervical and upper thoracic dermatomes. However, comparative clinical evidence between SPSIP block and ISB for arthroscopic shoulder surgery remains limited.

In this prospective, randomized, double-blind controlled trial, eligible adult patients scheduled for elective arthroscopic shoulder surgery under general anesthesia will be randomly assigned to receive either an ultrasound-guided ISB or SPSIP block. All patients will receive standardized general anesthesia and postoperative multimodal analgesia.

The primary endpoint will be total opioid consumption during the first 24 postoperative hours. Secondary endpoints will include postoperative Numeric Rating Scale (NRS) pain scores at predefined time points, quality of recovery assessed with the QoR-15 questionnaire, intraoperative opioid consumption, time to first rescue analgesic requirement, total rescue analgesic consumption, sensory block distribution, motor block assessment, and block-related adverse events.

The study aims to determine whether SPSIP block can provide postoperative analgesia comparable to ISB while potentially reducing complications associated with brachial plexus blockade.

Inclusion Criteria:

• Age between 18 and 75 years
• ASA physical status I, II, or III
• Scheduled for elective arthroscopic shoulder surgery under general anesthesia
• Provision of written informed consent

Exclusion Criteria:

• Refusal to participate in the study
• Coagulopathy
• Current anticoagulant therapy
• Infection at the block site
• Previous surgery involving the planned block site
• Known allergy or history of toxicity to local anesthetics
• Hepatic failure
• Renal failure
• Uncontrolled diabetes mellitus
• Cognitive impairment or mental disability preventing reliable assessment
• Chronic opioid use or ongoing chronic pain treatment
• Pregnancy, suspected pregnancy, or breastfeeding
• Chronic pulmonary disease (e.g., COPD or asthma)
• Failed block

Double (Participant, Outcomes Assessor)