Postoperative pain after mastectomy remains a significant clinical problem that may impair patient comfort and delay early rehabilitation, potentially affecting functional recovery. Various analgesic techniques are used to manage postoperative pain. This study aims to compare serratus posterior superior intercostal plane block and erector spinae plane block, which are routinely used in our clinic for postoperative analgesia in patients undergoing mastectomy, in terms of ease of application and patient comfort.

Postoperative pain following mastectomy is a common and clinically significant issue that not only reduces patient comfort but may also hinder early mobilization and rehabilitation, thereby negatively impacting overall functional outcomes. Effective postoperative analgesia is therefore a key component of perioperative care in breast surgery.

A variety of analgesic techniques, including systemic analgesics and regional anesthesia methods, are currently employed to manage postoperative pain. Among these, ultrasound-guided fascial plane blocks have gained increasing popularity due to their relative safety, simplicity, and effectiveness. The serratus posterior superior intercostal plane (SPSIP) block and the erector spinae plane (ESP) block are two such regional techniques used for thoracic analgesia.

In our clinical practice, both SPSIP and ESP blocks are routinely used for patients undergoing mastectomy. However, comparative data regarding their ease of application and impact on patient comfort are limited. Ease of application is an important consideration for anesthesiologists, particularly in busy clinical settings, while patient comfort during block placement is a critical but often underreported outcome.

The primary aim of this study is to compare SPSIP block and ESP block in patients undergoing mastectomy in terms of ease of application and patient comfort during the procedure. Secondary considerations may include block-related characteristics and their contribution to postoperative recovery.

Inclusion Criteria:

• Patients aged 25-65 years American Society of Anesthesiologists (ASA) physical status I-III Patients scheduled for mastectomy under general anesthesia Patients with no history of previous breast surgery Patients who provide written informed consent to participate in the study

Exclusion Criteria:

• ASA physical status IV and above History of alcohol or substance abuse Known allergy to local anesthetics or opioids Patients with severe psychiatric disorders Patients who refuse to participate or do not provide informed consent

This study is designed as a triple-blind trial. Participants, perioperative care providers, and outcome assessors will be blinded to group allocation. Randomization will be performed using a computer-generated sequence, and group assignments will be concealed in sealed, opaque envelopes. The anesthesiologist performing the block will not be involved in postoperative care or outcome assessment. To maintain blinding, block procedures will be performed under standardized conditions, and patients will not be informed about the specific block type administered. Outcome data will be collected by investigators who are unaware of the assigned intervention.