USG GUIDED NERVE BLOCKS PEC 1 PEC 2 BLOCK

Usg guided nerve blocks of thoracic region . Each blocks have been discussed with positions, anatomy and confirmation points

1. USG GUIDED NERVE BLOCKS DR Arjun Ganesan FINAL YEAR POSTGRADUATE

2. PEC 1 & PEC 2 NERVE BLOCK ANATOMY: Medial pectoral nerve The medial pectoral nerve originates from the medial cord of the brachial plexus, containing fibres from C8 and T1. It arises posterior to the first part of the axillary artery, before passing medially to the second part of the artery. It then runs anteriorly between the axillary artery and vein, where it commonly receives a branch of the lateral pectoral nerve to form a nerve loop ( ansa pectoralis). From here, it penetrates the pectoralis minor muscle, providing motor innervation. Some fibres continue through the muscle to supply the lower portion of the sternocostal head of the pectoralis major. Lateral Pectoral Nerve The lateral pectoral nerve originates from the lateral cord of the brachial plexus, containing fibres from C5-7. It first passes anterior to the axillary artery. Here, it commonly gives rise to a communicating branch which joins the medial pectoral nerve – forming the ansa pectoralis. It then pieces the costocoracoid membrane, before terminating at the deep surface of the pectoralis major muscle.

3. Nerves/Muscle involved Dermatome/Myotome/Osteotome   Medial pectoral Nerve The medial pectoral nerve supplies motor innervation to both: Pectoralis minor and Pectoralis major (sternocostal head) Nerve root involved: C8-T1 Lateral Pectoral Nerve The lateral pectoral nerve provides motor innervation to the pectoralis major. It also contributes to the innervation of the pectoralis minor muscle via the ansa pectoralis. Nerve root involved: C5-C7

4. PEC 1 Block: Pecs I nerve block was devised to anesthetize the medial and lateral pectoral nerves, which innervate the pectoralis muscles. This is accomplished by an injection of local anesthetic in the fascial plane between the pectoralis major and minor muscles. *PTA: Pectoral branch of thoracoacromial artery

5. PEC 2 Block: The Pecs II nerve block (which also includes the Pecs I nerve block) is an extension that involves a second injection lateral to the Pecs I injection point in the plane between the pectoralis minor and serratus anterior muscles with the intention of providing block of the upper intercostal nerves.

6. Indications of PEC blocks: These interfascial injections were developed as alternatives to thoracic epidural, paravertebral, intercostal, and intrapleural nerve blocks, primarily for analgesia after surgery on the hemithorax. Initially, Pecs nerve blocks were intended for analgesia after breast surgery; however, case reports have also described the use of Pecs and serratus plane nerve blocks for analgesia following thoracotomy and rib fracture.

7. ANATOMY: SERRATUS ANTERIOR PLANE NERVE BLOCK At the axillary fossa, the intercostobrachial nerve, lateral cutaneous branches of the intercostal nerves (T3–T9), long thoracic nerve, and thoracodorsal nerve are located in a compartment between the serratus anterior and the latissimus dorsi muscles, between the posterior and midaxillary lines. The two main anatomical landmarks are the latissimus dorsi and the serratus anterior muscles. The thoracodorsal artery runs in the fascial plane between the two. The ribs, pleura, and intercostal muscles can also be seen during the procedure. Lying on the side or supine with the arm brought forward is the preferable patient position.

8. Nerves/Muscle involved Dermatome/Myotome/Osteotome The intercostobrachial nerve is a lateral cutaneous branch of the second intercostal nerve that supplies sensation to the skin of the axilla. It leaves the second intercostal space at the midaxillary line and subsequently pierces the serratus anterior muscle to enter the subcutaneous tissues of the axilla. The lateral cutaneous branch (T2 – T6) pierces the external intercostal muscle at the midaxillary line and divides into anterior and posterior branches to supply the lateral side of the chest. The long thoracic nerve arises from the upper portion of the superior trunk of the brachial plexus and typically receives contributions from cervical nerve roots (C5, C6, and C7 ). It is responsible for the innervation of the serratus anterior muscle; the long thoracic nerve descends posteriorly to the roots of the brachial plexus and anteriorly to the scalenus posterior muscle, and courses along the chest wall in the mid-axillary line to lie on the superficial surface of the serratus anterior muscle. The thoracodorsal nerve (C6,C7,C8) originates from the posterior cord of the brachial plexus in the apex of the axilla.It typically lies between the upper and lower subscapular nerves, posterior to the subscapular artery. The nerve descends along the posterior wall of the axilla, before passing anterior to the artery – which now becomes the thoracodorsal artery. Together, this neurovascular bundle crosses the inferior border of teres major, before piercing the latissimus dorsi muscle.

9. There are two main methods for identifying the plane for the serratus nerve block. The first method requires counting the ribs from the clavicle while moving the transducer laterally and distally until the fourth and fifth ribs are identified. The transducer is orientated in the coronal plane and then tilted posteriorly until the latissimus dorsi (a superficial thick muscle) is identified . The serratus muscle, a thick, hypoechoic muscle deep to the latissimus dorsi is imaged over the ribs. Translating the transducer posteriorly facilitates the identification of the plane between the serratus anterior and latissimus dorsi muscles. An alternative method is to place the transducer across the axilla, where the latissimus dorsi will appear more prominent. The location of the thoracodorsal artery is easier to identify this way.

10. Indications B reast surgery C hronic pain after mastectomy R ib fractures T horacoscopy T horacotomy  

11. INTERCOSTAL NERVE BLOCK Anatomy of the spinal nerve. T1 and T2 send nerve fibers to the upper limbs and the upper thorax, T3 through T6 supply the thorax, T7 through T11 supply the lower thorax and abdomen, and T12 innervates the abdominal wall and the skin of the front part of the gluteal region.

12. Course Carrying both sensory and motor fibers, the ICN pierces the posterior intercostal membrane about 3 cm (in adults) distal to the intervertebral foramen to enter the subcostal grove where it, for the most part, continues to run parallel to the rib, although branches may often be found anywhere between adjacent ribs. Its course within the thorax is sandwiched between the parietal pleura and innermost intercostal ( intercostalis intimus ) muscles and the external and internal intercostal muscles (Figures 3 and 4). Just anterior to the midaxillary line, it gives off the lateral cutaneous branch. As the ICN approaches the midline, it turns anteriorly and pierces the overlying muscles and skin to terminate as the anterior cutaneous branch.

13. 1. The ICN can be blocked anywhere proximal to the midaxillary line, where the lateral cutaneous branch takes off. 2. In children, the block is commonly carried out at the posterior axillary line or, alternatively, just lateral to the paraspinal muscles, at the angle of the rib. 3. In adults, the most common site for ICNB is at the angle of the rib (6–8 cm from the spinous processes. At the angle of the rib, the rib is relatively superficial and easy to palpate, and the subcostal groove is the widest. 4. The nerve is inferior to the posterior intercostal artery, which is inferior to the intercostal vein.

14. Indications: 1. ICNB provides excellent analgesia in patients with rib fractures and for postsurgical pain after chest and upper abdominal surgery such as thoracotomy, thoracostomy, mastectomy, gastrostomy, and cholecystectomy. 2. Respiratory parameters typically show impressive improvements on relief of pain. block of the two dermatomes above and the two below the level of surgical incision is required. 3. ICNB does not block visceral abdominal pain, for which a celiac plexus block is required. 4. Neurolytic ICNB is used to manage chronic pain conditions such as postmastectomy pain (T2) and postthoracotomy pain.

15. INTRAPLEURAL NERVE BLOCK The intercostal spaces contain 3 muscle layers. The external intercostal muscles form the most superficial muscular layer of the intercostal space. The internal intercostal muscles form the next muscular layer. The innermost intercostal muscles form the deepest muscle layer of the intercostal space. A neurovascular bundle, containing an intercostal vein, artery, and nerve, is also located in the intercostal space. The intercostal nerve is derived from the anterior rami of the thoracic spinal nerve. These rami of the thoracic spinal nerves exit the intervertebral foramina and are typically initially located in the endothoracic fascia, just superficial to the parietal pleura. However, as these nerves course more distally from the neuraxis , they begin to pass superficially at the angle of the ribs. At this point, the nerves will continue their distal course between the internal and innermost intercostal muscles. As these nerves pass through the intercostal space, they tend to be located just under the rib along with the other components.