Serratus Anterior Plane Block for Modified Radical Mastectomy: Double-point VS Single-point

Nowadays, the incidence of breast cancer is the first number of malignant tumors, and the primary treatment method is surgery. As is known to all, less postoperative complications and enhanced recovery are closely related to effective analgesia. However, postoperative patients often experience moderate pain, while associated with axillary discomfort. Serratus Anterior Plane Block (SAPB) relieves postoperative pain, but traditional single point block method has no effect on axillary discomfort. Therefore, it is necessary to try double point blocks to explore their impact on postoperative analgesia and axillary comfort. This RCT will recruit patients proposed to undergo Modified Radical Mastectomy (MRM) and be randomized to single point or double point groups to evaluate their postoperative pain score and axillary comfort in order to provide clinical guidance.

The conventional SAPB, which often performs single point block from the level of the fifth rib, does not completely relieve postoperative pain in patients with axillary lymph node dissection, probably due to insufficient range of local anesthetic diffusion.Anatomical study indicated that with a double point SAPB at the third and fifth rib levels, respectively, the local anesthetic diffusion range can reach the axillary level and may provide better analgesic effects. However, the support of clinical data is lacking.Therefore, the hypothesis of this study is that double point SAPB will provide better postoperative analgesia compared with conventional single point SAPB in patients undergoing modified radical mastectomy.This study will include 60 patients proposed to undergo modified radical mastectomy, allocated to the Double-point or Single-point group in a 1:1 ratio, randomly.The Double-point group will perform a double point SAPB, which is a combined block at the third and fifth rib levels, respectively.The Single-point group will undergo a single point SAPB, traditionally performed at the level of the fifth rib.Observation outcomes included changes in blood pressure and heart rate during dissection of skin and dissection of axillary lymph nodes, postoperative pain scores, axillary comfort, recovery quality, and related complications and postoperative hospital stay.Therefore, the objective is to investigate whether this simple technical modification can better reduce postoperative pain and promote rehabilitation in patients with modified radical mastectomy.

Eligibility Criteria:
Inclusion Criteria:

* Patients are proposed to undergo Modified Radical Mastectomy
* Patients with American Society of Anesthesiologists (ASA) physical status I\~III
* aged 18-70 years
* BMI ≤ 35 kg/m2

Exclusion Criteria:

* Patients with a pre-existing neuropathy or sensory deficit affecting the operative region
* Pregnancy
* Chronic pain or opioid dependence (at least 30 mg of oxycodone or equivalent per day)
* Allergy to local anaesthesia or any component of the proposed multimodal analgesia regimen
* Local or systemic contra-indications to peripheral nerve blocks (local infection at the puncture site, coagulopathy, platelets less than 80\*10\^9/L and prothrombin time more than 15 s)