Cancer breast is one of the most common tumors among women and surgery is still the key for its management and cure. Post-mastectomy pain control is crucial as acute postoperative pain is a significant factor in the development of persistent chronic pain in the form of post-mastectomy pain syndrome.

Post-mastectomy pain syndrome (PMPS) is a common complication after breast cancer surgery and is often challenging to manage. It is estimated that PMPS occurs in 20%-44% of patients after breast surgery.

Adequate pain control for PMPS has become one of the most important goals and recently can achieve by multiple tools including multimodal analgesia and regional techniques.

Erector spinae block (ESB) is one of the new described regional techniques. Although its mechanism is not clear, the published data agree that it is promising block for chronic and acute pain and its simplicity and safety compared with thoracic epidural or bilateral paravertebral blocks.

ESB can be performed using a superficial approach between the large rhomboid muscle and the erector spinae muscle or the deep method beneath the erector spinae.

The use of the ESPB for chronic pain has recently expanded for various neuropathic pain conditions. Also, it reported with several volumes range from 10 to 30 ml of total volume.

This prospective randomized open comparative study will be conducted in pain clinic, Mansoura University Hospitals. The study will be approved by the Ethics Research Committee of the Faculty of Medicine, Mansoura University and will be carried out in compliance with the Helsinki Declaration. Informed written consent will be signed from every patient participating in this study after full description of all details of every aspect in this study.

Patients more than 18 years old of both genders with PMPS not responding to medical treatments, and numeric rating scale (NRS) ≥ 4 that ranged from 0 (no pain) to 10 (extreme pain)., American society of Anesthesiology Physical Status class I and II, and Body mass index ˂ 30 were included in this study.

The exclusion criteria are patient refusal, local or systemic sepsis, coagulopathy, unstable cardiovascular and respiratory diseases, previous neurological deficits, history of psychiatric disorders, history of drug abuse, distorted local anatomy, and those who were allergic to the used medications were excluded from the study.

All the patients will inform about the numerical rating score (NRS) from zero to 10 (where 0 no pain, 10 the worst pain) to describe their pain.

Random selection of patients:

The study participants were randomly grouped on a scale of 1:1, using a computer-generated list of random numbers. The distribution results were sealed in an opaque envelope and kept by the study administrator. On the day of block, the study manager handed the envelope to the anesthesiologist who will perform the block.

Grouping:

Group A: receive ESR with 1mL of methylprednisolone 40mg/mL with 10 mL of 0.5% bupivacaine and 2mL of nonionic contrast in 7 ml saline 0.9% (total 20 ml with bupivacaine 0.25%).

Group B: receive ESR with 1mL of methylprednisolone 40mg/mL with 15 mL of 0.5% bupivacaine and 2mL of nonionic contrast in 12 ml saline 0.9% (total 30 ml with bupivacaine 0.25%).

Inclusion Criteria:

• Patients more than 18 years old of both genders
• with post-mastectomy pain syndrome not responding to medical treatments,
• and numeric rating scale (NRS) ≥ 4 that ranged from 0 (no pain) to 10 (extreme pain).,
• American society of Anesthesiology Physical Status class I and II,
• and Body mass index ˂ 30 were included in this study

Exclusion Criteria:

• patient refusal,
• local or systemic sepsis,
• coagulopathy,
• unstable cardiovascular
• and respiratory diseases,
• previous neurological deficits,
• history of psychiatric disorders,
• history of drug abuse,
• distorted local anatomy,
• and those who were allergic to the used medications