Regional Anaesthesia for Breast Surgery

Abstract

Innervation of the breast:nd thThe breast receives innervation mainly from the 2 to 6 thoracic (T2-6) spinal nerves. The thoracic spinal nerves after emerging from the intervertebral foramina divide into dorsal and ventral ramii [1]. The dorsal ramii provide innervation to the skin and the muscles of the medial back. Each ventral ramus continues anteriorly as an intercostal nerve, accompanied by an intercostal artery and vein lying between the innermost and the internal intercostal muscle along the inferior borders of the respective ribs.Near the midpoint of the hemithorax corresponding to the midaxillary line, each intercostal nerve gives a lateral cutaneous branch that further divides into an anterior and posterior branch. Sensory supply of lateral aspect of breast is provided by the anterior divisions of the lateral cutaneous branches of T2-T6 intercostal nerves with contributions from T1 and T7 nerves. The intercostal nerves interconnect providing overlapping nerve supply to the breast. The main intercostalnerve continues anteriorly and terminates as an anterior cutaneous branch that further divides into a medial and lateral divisions which provide cutaneous innervation over the sternum and medial part of the breast respectively [2-4] (Figure 1) [5].The intercostobrachial nerve (T2) mainly provides cutaneous innervation to the axillary tail of the breast, the axilla, and the medial upper arm. The medial cutaneous nerve of the arm (branch of the brachial plexus) may also supply the roof of the axilla and may receive contributions from T1 and T3 nerves. The supraclavicular nerves of the cervical plexus provide sensory supply to the infraclavicular or supramammary area [6, 7], (Figure 1). The muscles of chest wall underlying the breast, the pectoralis major (PMM) and pectoralis minor (PmM) are innervated by mixed motor and sensory nerves, the lateral pectoral nerves (LPN) (C5-7, lateral cord) and the medial pectoral nerves (MPN) (C7-T1, medial cord), branches of the brachial plexus. These nerves also possess proprioceptive and nociceptive fibres and thus traction, stretching or muscle spasm of these muscles can lead to dull, aching perioperative pain. In addition, the long thoracic nerve (LTN) (C5-7) and the thoracodorsal nerve (TDN) (C6-8, posterior cord) branches of the brachial plexus innervate the serratus anterior (SAM) and the latissimus dorsi (LD) muscles, that form part of the axilla [8]. Therefore, the breast, axilla and the surrounding tissues are supplied by interconnected network of T2-T6 intercostal nerves, branches of the brachial plexus and the lower branches of the cervical plexus (Figure 1) [5].Regional anaesthesia blocks used for Breast surgery: These blocks will be decribed starting from the older, posteriorly performed blocks to the newer, superficial antero-lateral chest wall blocks for breast surgery. Thoracic Epidural Anaesthesia (TEA)Thoracic epidural block performed at T4 has been used to provide segmental anaesthesia and analgesia extending from C8-T6 for breast surgery.Advantages of TE...