The traditional intra-fascial interscalene brachial plexus block (ISB) is already one of the routine anesthesia methods for pediatric upper limb surgeries in clinical practice. This study aims to clarify the effect of the extra-fascial interscalene brachial plexus block on the diaphragm function of school-age children, as well as its analgesic effect, and to compare it with the traditional intra-fascial ISB. It intends to explore a more effective and safer ISB method for children. With the aim of optimizing techniques and accurately evaluating, to balance the benefits of analgesia and safety, and thereby promoting the development of precise pediatric anesthesia.

Inclusion Criteria:

• Age range: School-aged children (6-12 years old).
• Type of surgery: Upper limb surgery.
• ASA classification: Grades I-II.

Exclusion Criteria:

• Infection, anatomical deformity, or tumor at the puncture site.
• Coagulation disorders (INR > 1.4, platelet count < 100 × 10⁹/L).
• History of allergy to local anesthetics (ropivacaine).
• Severe cardiopulmonary or neurological diseases (e.g., epilepsy, myopathy).
• Pre-existing ipsilateral phrenic nerve paralysis or Horner syndrome.
• Preoperative long-term use of analgesics (which may affect efficacy assessment).
• Parent or child refusal to participate in the study.
• Emergency surgery or inability to cooperate with assessments (e.g., severe developmental delay).