Dexmedetomidine in Serratus Plane Block for Mastectomy

Overview

The serratus plane block (SPB) described by Blanco et al, 2013 is a progression from the work with the Pecs I and II blocks. The serratus muscle is a superficial and easily identified muscle and considered a true landmark to perform thoracic wall blocks because lateral cutaneous branches of the intercostal nerves pierce it in the mid-axillary line. A local anesthetic (LA) is injected under ultrasound (US) guidance either superficial or deep to serratus anterior muscle providing predictable and relatively long-lasting regional anesthesia, which would be suitable for surgical procedures performed on the chest wall. The linear US probe of frequency (6-13 MHz) is placed over the mid-clavicular region in a sagittal plane.The ribs are counted inferiorly and laterally until the fifth rib in the midaxillary line is identified.The latissimus dorsi, teres major, and serratus muscles are identified.

Possible regional techniques for breast surgery include selective intercostal nerve blockade, thoracic paravertebral blockade, thoracic epidural, intrapleural, local wound infiltration. Each of these techniques has advantages and disadvantages. In general, local or wound infiltration is safe but limited in terms of duration of action, depending on the local anesthetic (LA) used. More invasive techniques such as selective intercostal nerve blocks and thoracic paravertebral blockade may be complicated by pneumothorax or transient Horner's syndrome These techniques are also may be associated with higher risk of local anesthetic toxicity. Besides the neurological side-effects associated with thoracic epidural and paravertebral blocks such as post-sympathectomy hypotension and bradycardia, total spinal block, paraplegia, epidural hematoma, unpredictable spread, intravascular injection also requires special skill precluding their routine use in the setting of day-case surgery. With the use of ultrasound (US) devices in anesthetic practice, newer regional techniques based on detailed knowledge of innervations of the breast are developed as the pectoral nerve (Pecs) block I and II.The breast innervations briefly include lateral and medial pectoral nerves that arise from the brachial plexus innervating the pectoral muscles.The anterior divisions of the thoracic intercostal nerves from T2 to T6. They give off lateral and anterior branches. The Lateral branches pierce the external intercostalis and the serratus anterior muscles at the mid-axillary line to give off anterior and posterior terminal cutaneous branches. The lateral cutaneous branch of the second intercostal nerve does not divide and it is called the intercostobrachial nerve.The Anterior branches pierce the internal intercostalis muscle, the intercostal membranes, and pectoralis major to supply the breast in its medial aspect.The long thoracic nerve passes on the serratus anterior muscle supplying it. The thoracodorsal nerve innervates the latissimus dorsi muscle.