Peripheral nerve stimulator guided pectoralis (PEC-I) block: A novel approach to the chest wall block
Authors: Roy Ritesh , Singh Shiv Kumar , Agarwal Gaurav , Pradhan Chandrasekhar 
Published: April 2023

Introduction: Thoracic epidural and paravertebral blocks, the gold standard for post-operative analgesia for chest wall surgeries have a high incidence of complications and adverse effects. The pectoralis (PEC) blocks, first described by Blanco et al., have been proven to provide good analgesia postoperatively for breast surgeries, wide pectoral dissections, upper chest injuries, pacemaker insertions, port-a-cath placements, and intercostal chest drains. To widen the scope of this simple and useful analgesia technique, which mandates the availability of ultrasound machine and indepth knowledge of the sonoanatomy of the area, we are describing the conduct of PEC-I block using peripheral nerve stimulator, which is easily available to most anesthetists. Description of the Technique: Medial and lateral pectoral nerves (LPNs) are motor nerves originating in the brachial plexus innervate the pectoral muscles. The LPN runs in between pectoralis major and pectoralis minor muscle alongside the pectoral branch of thoracoacromial artery and supplies the pectoralis major muscle. The LPN communicates with the medial pectoral nerve and is known to carry nociceptive and proprioceptive fibers. The patient lies in a supine position with ipsilateral arm slightly abducted. The injection point is the intersection of a line drawn from the angle of Louis (2nd rib) and the anterior axillary line. After local infiltration of the skin with 1% lignocaine, a 50 mm insulated nerve stimulator needle with syringe filled with local anesthetic attached to the extension tubing is inserted perpendicular to the skin. The peripheral nerve stimulators (PNS)are initially set at 1.0–1.5 mA current, 0.1ms duration, and frequency of 1Hz. The needle is slowly advanced till the pectoralis muscle contractions is noted, with a current threshold of 0.3–0.5 mA. Persistence of contraction of pectoralis muscle at this level confirms the needle placement at the target site. The LA is then slowly injected in increments with frequent negative aspirations. Discussion: An increasing numbers of breast surgeries warrant better post-operative analgesia techniques, with fewer complications.Thoracic epidural analgesia, thoracic paravertebral blocks (TPVB), and intercostal nerve blocks have all been very effective for such surgeries but, are associated with complications such as epidural hemat omas, nerve injuries, pneumothorax,and hypotension. Analgesia technique like TPVB was unreliable with a single injection, and pectoral nerves were still spared producing inadequate analgesia of the chest wall and needed post-operative monitoring. The pectoralis block (PEC block), a novel technique, was described by Blanco et al. in 2011 using ultrasound and was easy, reliable, and associated with fewer complications. Peripheral nerve stimulator for such an easy and superficial block increases the utilization and benefits wider population. We have described the use of PNS for PEC-I block that can be used as a sole analgesia technique for breast implant insertion, pacemaker implantation, porta-cath insertion, ICD insertions or removals, and pectoralis muscle flaps. The PEC-I block can be further combined with PNS guided serratus anterior plane block to achieve excellent analgesia of the chest wall for surgeries. Conclusion: The PEC-I block along with PEC-II or SA plane block has a high success rate and minimal incidence of complications and provides a consistent and reliable block for hemithorax analgesia. In this article, we describe PEC-I block using PNS which is easily available to most anesthetist,unlike US machines which are available only to very few. PNS guided PEC-I block will increase the scope of this superficial, easy, and reliable block. Keywords: Pectoralis blocks, chest wall blocks, pectoralis-I, pectoralis-II, peripheral nervous system, peripheral nervous system guided chest wall block.