Evaluate the effect of addition of morphine, dexmedetomidine to bupivacaine in PVB could improve the analgesic effect and thus reduce postoperative morphine consumption and development of chronic neuropathic pain, compared to PVB with bupivacaine , in patients undergoing major breast cancer surgery, i.e., modified radical mastectomy (MRM) and breast conservation surgery with axillary lymph node dissection.

Breast cancer is the most commonly diagnosed malignancy and a leading cause of cancer-related deaths among women. Surgery followed by chemotherapy and/or radiotherapy are the mainstay of current management. Chronic pain, or persistent postsurgical pain, which until recently was considered infrequent after breast cancer surgery (BCS), affects 60% to 80% of breast cancer survivors. The exact cause of chronic pain after BCS is not clear, but there is an association between acute postoperative pain and chronic pain generation after BCS. Postoperative pain intensity and analgesic consumption are significantly higher in patients who develop chronic pain after BCS, and it is suggested that optimizing postoperative pain management may reduce chronic pain. preoperative paravertebral block (PVB) administration in additional to general anesthesia, which has consistently been demonstrated to improve acute postoperative pain control and decrease length of hospital stay. The role of TPVB in preventing chronic pain is still evolving. Karmakar et al. shed more light on the impact of TPVBs in preventing and reducing the severity of chronic pain after breast surgery.

The discovery of peripheral opioid receptors led to the clinical application of adding opioids to local anesthetics for peripheral nerve blocks. Studies from the 1990s showed mixed results from the addition of morphine to peripheral nerve blocks, with two suggesting enhancement of analgesia duration and several showing no benefit at all.

Dexmedetomidine is a highly selective alpha-2 adrenoreceptor agonist that has been shown to have both sedative and analgesic effects. Although it is approved only for intravenous (IV) sedation, it has been extensively used for off-label indications, including neuraxial and peripheral nerve blocks, with good results. A significant prolongation of duration of analgesia has been reported when dexmedetomidine was added to LA for epidural analgesia, caudal block, subarachnoid block, PVB, brachial plexus block, ulnar nerve block and greater palatine nerve block.

Inclusion Criteria:

• physical status classes I to III ( weight 50 - 85 kg), will be scheduled for unilateral modified radical mastectomy (MRM) with axillary evacuation will be consecutively enrolled.

Exclusion Criteria:

• patient refusal,
• patients with a known allergy to investigated drugs,
• bleeding disorders,
• anatomical abnormalities,
• infection in the paravertebral region,
• pregnancy, breast feeding,
• a history of drug or alcohol abuse, and patients with chronic pain or regularly receiving analgesics.
• patients subjected for bilateral mastectomy or any unilateral breast surgery other than MRM with axillary evacuation.