Pain after breast surgery can be quite severe and can significantly affect quality of life. By successfully treating acute pain, it is aimed to prevent the formation of pain memory and to ensure that chronic pain never occurs. It is known that by using regional techniques, the use of general anesthetics and opioids can be reduced and their harmful effects can be limited. In this study, it will be compared the analgesic effectiveness of superficial and deep serratus plane blocks in the postoperative acute and chronic periods.

Acute and chronic pain is a serious problem in patients undergoing breast surgery. Apart from the feeling of pain, it also causes psychological difficulties, increased hospital stays, delays or difficulties in mobilization, and so on. Due to all these reasons, postoperative pain control is very important.

Although opioids are the gold standard in the treatment of pain, their side effect profiles (sedation, respiratory depression, constipation, tolerance development, etc.) limit their use and different searches are on the agenda. There are studies showing that superficial and deep serratus plane blocks are effective in mastectomy operations. In this study, patients who underwent mastectomy these two blocks will be compared to see which one is superior and to investigate the differences that may occur in the acute and chronic periods.

After general anesthesia induction, a superficial serratus plane block will be performed on the first group of patients undergoing surgery by applying local anesthetic to the fascia between the serratus anterior and latissimus dorsi muscles at the level of the 4th and 5th ribs under ultrasound. then the patient will undergo surgical procedure. Likewise, for the second group of patients, after general anesthesia induction, a deep serratus plane block will be performed by applying local anesthetic between the rib and the serratus anterior muscle at the level of the 4th and 5th ribs, under ultrasound guidance, and the patient will be taken into surgery. Both groups of patients will be monitored for 24 hours after the operation with a patient-controlled analgesia device. Patients' pain scores, satisfaction scores, nausea and vomiting scores, and additional analgesic needs will be recorded 24 hours postoperatively.

Inclusion Criteria:

• patients who will undergo mastectomy surgery
• patients who agreed to participate in the study
• ASA I-II patients

Exclusion Criteria:

• Patients planned for bilateral breast surgery
• Patients who have had previous breast surgery
• Patients with existing neuropathic pain or receiving treatment for neuropathic pain
• Patients with psychiatric disorders
• Patients with opioid addiction
• Patients allergic to local anesthetics

Since breast cancer is much more common in women than men and to ensure homogenization in the study, only female patients will be included.