Breast cancer is the most common cancer among women, with surgery being a primary treatment option. A modified radical mastectomy is a standard procedure. Postoperative pain can significantly impact quality of life and may lead to chronic pain syndrome. Various nerve blocks, such as thoracic paravertebral, thoracic epidural, intercostal nerve, and interscalene brachial plexus blocks, have been utilised for anaesthesia and pain relief during modified radical mastectomy. However, their use is often limited due to the complexity of the procedures and the risk of severe complications.

Recently, there has been growing interest in a new, less invasive approach known as the pectoral nerve (PECS) block. The PECS block is an increasingly used regional anaesthetic technique for postoperative pain management in patients undergoing breast surgeries, including modified radical mastectomy. It offers a promising alternative to traditional methods, aiming to reduce post-op pain and improve patient satisfaction.

The PECS I block is performed between the pectoralis major and minor muscles, while the PECS II block adds an injection above the serratus anterior muscle at the third rib. Studies indicate that administering the PECS block before general anaesthesia can spread local anaesthetics along fascial planes and limit electrocautery use, leading to surgical clarity issues. To mitigate these problems, some surgeons now perform pectoral nerve blocks under direct vision just before closure to enhance postoperative analgesia in breast surgeries.