Peripheral Nerve Stimulator guided serratus anterior plane block : A novel approach to the chest wall block

Journal of Anaesthesia and Critical Care Case Reports 2017 Sep-Dec;3(3):24-26 Consultant Anesthesiologist, CARE Hospitals, Bhubaneswar, Odisha, India, Consultant Anaesthesiologist, Royal Liverpool University Hospitals, Prescot Streets, Liverpool, UK L7 8XP Address of Correspondence Dr. GauravAgarwal, 1510/B, Sector 6, CDA , Cuttack– 753014, Odisha, India. E-mail: Dr.agarwalgaurav@gmail.com © 2017 by Journal of Anaesthesia and Critical Care Case Reports| Available on www.jaccr.com | This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. Journal of Anaesthesia and Critical Care Case Reports Volume 3 Issue 3 Sep-Dec 2017 Page 24-26 24 | | | | | Dr. Ritesh Roy Dr.Shiv Kumar Singh Dr. Chandrasekhar Pradhan Dr. Gaurav Agarwal tubing is used for performing the block. Following preparing the area with antiseptic solution, sterile drapes are applied,and the area around the landmark is infiltrated with LA solution. The nerve stimulator is set to an initial current of 1mA of 0.1ms duration and 1Hz frequency. Once the LA has taken effect, the block needle is inserted at the above point and slowly advanced till the SA muscle contraction is noted, stimulation of long thoracic nerve that supplies the muscle. The needle is kept at this depth and current is reduced to 0.3mA. Persistence of contraction of SA at this level confirms the needle placement at target site, i.e.above the SA muscle plane. The LA drug (20mls of 0.2% ropivacaine) is slowly injected in increments with frequent negative aspirations at 5.0mls aliquots.Our target is to block the lateral and posterior cutaneous branches of the intercostal nerves that lie in the same plane as the long thoracic nerve. (Fig 4) Discussion In 2013, Blanco et al. first described a new block of the thoracic wall, the serratus plane block under US guidance. LA was deposited in the SA Plane. The lateral cutaneous branches of the intercostal nerves, before dividing into anterior and posterior branches are blocked as they pass through this plane to supply sensation to most of the chest wall. The authors observed that an injection superficial to the SA muscle spreads wider and lasts longer than an injection deep to it [3]. Varghese et al. have done anatomical studies to describe widespread of LA in SAP block using US guidance techniques as described by Blanco et al.[10]. The risk of LA toxicity remains low in this technique as lower volume of anesthetic, as compared to other fascial plane blocks, is required for a higher spread and the absorption is lower as the plane is avascular [11].This can be considered an advantage over alternative technique such as intercostal nerve block. Dermatomal block after a single thoracic paravertebral injection is unpredictable and varies widely[12,13]. Wide dermatomal spread with paravertebral block and intercostal blocks need multiple injections, which are time-consuming, and associated with increased incidence of pneumothorax[14,15,16,17]. If the specialist is skilled with US and has a good understanding of the sonoanatomy of the lateral thoracic wall, serratus plane block is a superficial and easy to perform, with a high success rate and minimal incidence of complications. In situations where US machine is not available, it will not be possible for the block to be administeredand, if the specialist is not skilled in the use of US, failure and/or pneumothorax could easily result [11]. SAP block has been studied by various researchers as a consistent and reliable block for hemithorax analgesia, particularly for breast surgeries [18], post-thoracotomy pain[6], multiple rib fractures, and other chest wall procedures [5]. The limitation of the novel technique being, availability of US machine. This limitation can be offset by the PNS guided technique as described above. It is comparatively reliable technique for the SAP block. Our experience The authors have used this technique in more than 100 cases until now and documented the drug spread using US of the blocked area in patients after PNS guided injection of the drug and noticed good spread of the LA in the plane above SA muscle described as SA plane block as well as good post-operative pain relief (Fig.5a and b). Most of the patients were managed with simple oral analgesics in the postoperative period, and of the cases receiving this block, only 5 patients needed analgesia supplementation with opioids. Limitations SAP block is a relatively safe and superficial block that can be done by even those who are new to regional anesthesia, but concerns relating to deep puncture and pneumothorax remains. This area is a Roy R et al www.jaccr.com Journal of Anaesthesia and Critical Care Case Reports Volume 3 Issue 3 Sep-Dec 2017 Page 24-26 25 | | | | | Figure 2: Landmarks of serratus anterior plane block. Figure 3:Schematic description of the landmarks and the injection point. Figure 1: Anatomy relevant to the serratus anteriorplane block. Figure 4:Anatomical depiction of the drug spread. Figure 5: (a, b) Drug spread in serratus anterior plane with aperipheral nerve stimulator (PNS) A B