Exploring cocktails, remixes and innovations in regional nerve blocks: The clinical research journey continues

Abstract

Ever since Halsted and Hall's sensory block of peripheral nerves using cocaine injection stunned the world in 1880, the journey of regional anaesthesia has been remarkable and today, nerve blocks are commonly performed all over the world. A major concern in the past was a higher failure rate of the nerve blocks. Several factors are responsible for the success or failure of a peripheral nerve block- the operator's thorough knowledge of the descriptive and topoanatomy of the nerve to be blocked, his technical skills, experience, location of the needle tip in the proper plane, proper nerve location, proper needle size and correct volume and concentration of drugs. Even in the best of the hands, failures were still not uncommon and resulted in the form of total failure, an incomplete block, a patchy block, a wear-off block or a misdirected block.[1] In due course of time, it was realised that proper nerve location was the key to success in regional anaesthesia. Morgan had stated that “Regional anaesthesia always works – provided you put the right dose of the right drug in the right place.” Different techniques of nerve localisation gradually evolved to assist the landmark technique. It took 100 years after the introduction of the concept of nerve block, for the adoption of electro-localisation during peripheral nerve blockade in the 1990s, with Perthes developing the electrical nerve stimulator in 1912 and Pearson introducing the concept of insulated needles for nerve localisation in 1955. Ansbro first described the continuous peripheral nerve block technique in the supraclavicular area in 1946. It was the team of Ting and Sivagnanaratnam in 1989 who first used ultrasonography (USG) to confirm needle location and visualise the spread of a local anaesthetic in the axillary sheath while performing an axillary brachial plexus block. Peripheral nerve stimulation and ultrasound guided techniques to locate nerves soon became popular in clinical practice. Novel approaches to block peripheral nerves using advances in ultrasound technique, introduction of long acting local anaesthetics and extended release local anaesthetics have now come up. Research on automated nerve recognition and automated nerve block performance without human intervention culminated in the design of the Magellan system in 2013-the first robotic system designed specifically to perform nerve blocks.[2] No medical stream can advance further without the assistance of research activities. Clinical research is going on since 2015 on nanocarriers like liposomes, polymersomes in extended release for local anaesthetic drug delivery and combinations of nanocarriers and hybrid-nanocarriers. Extended release local anaesthetics continuously release a safe dose of drug with single administration. Recently, there have been positive results seen in research conducted on nano-structured extended release local anaesthetics; liposomal and polymeric are prominent mainstream systems amongst these.[3] EXPAREL (Pacira Pharmaceuticals, New Jersey, USA) is the first extended release liposomal local anaesthetic loaded with bupivacaine and approved by the American Food and Drug Administration (FDA). It was allowed legally initially in limited clinical situations like wound infiltration in 2011 and in interscalene brachial plexus block in 2018. It can achieve prolonged release and analgesic efficacy up to 72 hours. Positive results using EXPAREL have been demonstrated in interscalene block for shoulder arthroplasty, posterior intercostals (IC) nerve block in lung resection, multilevel IC block in open thoracotomy, IC nerve rib blocks in video-assisted thoracoscopic pulmonary resection, transversus abdominis plane (TAP) block in major lower abdominal and laparoscopic hand-assisted donor nephrectomy.[3] The wide spectrum of regional anaesthesia provides numerous choices for achieving the desired results. Regional nerve blocks for chest wall surgery like in modified radical mastectomy (MRM) inclu