Breast surgeries are usually associated with significant postoperative pain. Suitability of analgesic technique after breast surgery is always questionable. The aim of this study is to compare US guided Pecs II block versus thoracic paravertebral block performed by US guidance as regards to potential complications and analgesic efficacy of both techniques in the first 24 h after modified radical mastectomy.

Various modalities have been used for perioperative pain management in relevance to breast surgery. Thoracic epidural and paravertebral blocks (PVB) became the gold standard techniques to achieve this goal. However, both techniques may be associated with devastating complications such as spinal cord injury, total spinal anesthesia, inadvertent intravascular injection and pneumothorax.

On the other hand, the advancement of ultrasound (US) technology and our ability to visualize the pleura and other structures in and around the paravertebral space has increased interest in performing thoracic paravertebral blocks guided by US.

"Pecs" block is a less invasive procedure involving US guided interfascial injections has been suggested as potential alternative analgesic technique. The Pecs I block was initially described by Blanco for minor breast surgery. A year later, on 2012, he described a Pecs II block or "modified Pecs block" for breast surgery involving the axilla.

The Pecs I block targets the medial pectoral nerve (MPN) from C8 and T1 and the lateral pectoral nerve (LPN) from C5, C6, and C7. These nerves arise from the medial and lateral cords of the brachial plexus, respectively, and innervate the pectoralis muscles.

The Pecs II block targets the T2-6 intercostal nerves, the long thoracic nerve which supplies the serratus anterior, and the thoracodorsal nerve which supplies the latissimus dorsi. Potential complications include accidental intravascular injection and pneumothorax.

The easily identifiable landmarks allow this block to provide a simple alternative to paravertebral and neuraxial blocks for breast surgery. The block produces excellent analgesia and can be used as a rescue block in cases with patchy or ineffective paravertebral or epidural block.

Inclusion Criteria:

• American Association for Anesthesiologists physical status I or II
• Body mass index > 40 kg/m2

Exclusion Criteria:

• Patient refusal
• Severe or uncompensated cardiovascular disease.
• Significant renal disease.
• Significant hepatic disease.
• Significant endocrinal disease.
• Pregnancy.
• Postpartum period.
• Lactating females.
• Allergy to any of the study medication.
• Coagulation disorders.
• Infection at the site of needle insertion.