This study aims to assess the effectiveness of the Serratus Posterior Superior Intercostal Plane Block (SPSIP Block) for postoperative pain control, reducing opioid analgesic consumption, minimizing postoperative respiratory complications, and enhancing patient satisfaction (measured using the QoR-15 index) in patients undergoing robotic thymectomy, compared to patients who do not receive the block.

All patients enrolled in the study will receive the SPSIP Block under ultrasound guidance 15 minutes before entering the operating room. The SPSIP Block will be performed by the attending anesthetist (investigator 1), who will use a syringe pre-filled with 30 ml of a solution prepared in advance by another investigator (investigator 2). According to the randomization scheme, the solution in the syringe used for the SPSIP Block will contain either 0.25% bupivacaine for 50% of the cases (SPSIP group) or sterile saline solution (0.9% NaCl) for the remaining 50% of the cases (control group). Postoperatively, data collection will be managed by a third investigator (investigator 3). Neither the investigator 1, the patient, nor the investigator 3 will be informed of the syringe's contents, ensuring the study is conducted blind.

All patients enrolled in the study will receive 1000 mg of paracetamol and 30 mg of ketorolac at the end of the surgery, during skin closure. Additionally, upon arrival in the recovery room, all patients will be connected to a PCA (Patient Controlled Analgesia) pump filled with a solution containing opioids. Patients who have NPRS scores greater than 4 during postoperative pain reassessments, despite PCA use, will be given a rescue analgesic dose of 1000 mg of paracetamol (which can be repeated after 8 hours, up to a maximum of 3000 mg in 24 hours).

Postoperative pain intensity will be assessed by investigator 3 at 0, 2, 6, 12, and 24 hours after the end of surgery using the Numeric Pain Rating Scale (NPRS). Assessments will be conducted both at rest and during coughing. Total opioid and rescue analgesic consumption, incidence of postoperative complications, and length of hospital stay will also be recorded. Twenty-four hours after the surgery, investigator 3 will administer the Quality of Recovery 15 (QoR-15) questionnaire to all patients enrolled in the study. The responses will be used by investigator 3 to calculate the QoR-15 Index, which summarizes the degree of patient satisfaction.

Inclusion Criteria:

• Patients affected by thymoma, thymic hyperplasia, or thymic pathologies (cysts, teratomas) who have given informed consent to the study.

Exclusion Criteria:

• Patients who refuse to participate in the study by not signing the informed consent;
• Patients with myasthenia gravis, severe obesity (BMI > 35), history of OSAS with or without CPAP;
• Patients belonging to ASA classes > 3, according to the system developed by the American Society of Anesthesiologists;
• Patients unable to understand the functioning of the NPR Scale or the PCA device that will be used for postoperative analgesia;
• Patients with allergies to analgesic and/or anesthetic drugs;
• Patients on anticoagulant therapy;
• Patients with a history of chronic pain;
• Patients with an infection at the site where SPSIPB will be performed;
• Patients who have had previous thoracic surgery and/or thoracic trauma with rib fractures on the side of the surgery;
• Patients with chest deformities and/or neuromuscular diseases that interfere with normal ventilatory function.

Additionally, patients whose surgery is intraoperatively converted to sternotomy thymectomy will be excluded post-hoc from the study.