Development and trends in nerve block
In 1885, American scientist Halsted presented the concept of nerve block by injecting cocaine into the region surrounding nerves in the field of oral surgery (8). By the 1950s, Pearson (9) and Sarnoff (10) located motor nerves by electrical stimulation with an insulated needle and pioneered the use of nerve stimulators for nerve blocks. With the further development of medical science, nerve blocks guided by nerve stimulators are gradually being replaced by ultrasound-guided nerve blocks. Ultrasound guidance can enhance the efficacy of local anaesthetics and reduce associated complications (11, 12). Furthermore, there is a wide range of drugs available, from a single local anaesthetic to a combination of multiple drugs for nerve block. The most commonly used drug for nerve block has been constantly updated from lidocaine in the past to ropivacaine now (13). Nerve blocks can reduce the use of analgesics and facilitate postoperative pain management (14). In recent years, the development of anaesthesia management with nerve block surgery includes prostate puncture (15) and surgical analgesia, including head, neck, and maxillofacial surgery analgesia (16), and postoperative analgesia for total hip and total knee replacement (17). The erector spinae plane block is an emerging regional anaesthetic technique with significant potential for clinical use, such as analgesia in breast surgery (18). Suprascapular nerve block is combined with axillary nerve block for arthroscopic shoulder surgery (19). Peripheral nerve block is also an ideal analgesic method during ambulatory surgery (20). Recently, nerve block not only is used in daytime surgery but also in analgesia in emergency surgery, such as the fascia iliaca compartment block relieving hip fracture pain (17). Adjuvant pharmaceutics have been shown to prolong the duration of local anaesthetic for PNB. Research findings provide evidence for the consideration of dexmedetomidine (13), dexamethasone (21), and clonidine (22) as adjuvants to prolong PNB duration. Reversible nerve block can be achieved within a non-destructive temperature range.
Currently, nerve block has become an alternative option for postoperative multi-modal analgesia and some forms of chronic pain treatment (2, 3, 23). Based on the current number of published nerve block articles, the overall research trend has been increasing from 1990 to the present. In 1997, there were only 73 publications worldwide, but between 2010 and 2015, the number increased from under 200 to 400. By 2020, the number of articles on nerve blocks has increased to nearly 800, and according to the prediction made using regression statistics, the number of articles on nerve block will exceed 1000 by 2023, indicating that nerve block remains an important area of anaesthesia and pain research.
The United States still has the most related publications among the developed countries, followed by China, India, and other developing countries. Other developed countries, such as Canada, Britain, France, Germany, and Japan, also have several research articles on nerve block. A large number of clinical and basic studies have an economic basis, which may be the reason why developed countries significantly contribute to nerve block research. However, the number of studies in China and other developing countries is also increasing due to their increasing population and clinical needs. Based on the VOS chart, there are stronger cooperative relations between neighbouring countries, such as France–Belguim-Netherlands. In addition, there are settlements associated with South Korea, Singapore, and Turkey; and India, Thailand, and Iran, among other countries.
The journals that published more than 100 articles are basically anaesthesiology journals, such as Regional Anesthesia & Pain Medicine, Anesthesia & Analgesia, British Journal of Anaesthesia, Anesthesiology, and Acta Anaesthesiologica Scandinavica. This indicates that nerve block is the main field of anaesthesiology research. Notably, among the journals with more than 100 articles published, the Journal of Endodontics is also included. Therefore, from the perspective of treatment, nerve block has been increasingly used in oral therapy for assisted analgesia in recent years. In addition, a number of articles have been published in the Journal of Arthroplasty, illustrating the increasing use of nerve blocks in perioperative analgesia for extremity surgery.
Regarding the organisations publishing the articles, the top 10 basic research institutes are located in the United States, in addition to the University of Toronto in Canada and the University of Copenhagen in Denmark. Among the top 11th to 20th institutions, Birmingham Women’s Hospital and the University of London in the UK focused on nerve block research. Research institutions representing developing countries, led by Egyptian think tanks, have also contributed to the field of nerve block. In terms of the top 20 authors publishing articles, the United States still has the majority of authors publishing articles, and other countries, such as Italy, Canada, Denmark, France, and Austria, also have a large number of authors publishing articles. Liu J from China has published 24 related papers. This provides a new impetus for the research and promotion of nerve block in developing countries.
Among the top 10 most cited articles, the first was the study of a new method for ultrasound-guided nerve block in the chest wall (24), and seven of the articles were related to nerve block for limb surgery or pain (three articles were related to knee or hip surgeries, two were related to lower limb nerve blocks, and three were related to brachial plexus block and ischaemic nerve block in the forearm). The other two articles were mainly about the improvement of B-ultrasound guidance technology and the exploration of abdominal plane block after cholecystectomy for postoperative analgesia. In summary, we believe that the current focus of researchers on nerve block is mainly on the postoperative analgesia for limb surgery and the treatment of pain caused by other factors. In addition, researchers are constantly attempting to apply nerve block techniques in various aspects of postoperative analgesia, and the effect has been confirmed.
As shown in Figures 6A and B, using VOSviewer settlement analysis and trend analysis of the keywords, the study of nerve block has the following five aspects: nerve block anaesthesia, nerve block, nerve block and ultrasonic technology, nerve block analgesia (especially limb surgery), and all types of surgery with oral and maxillofacial nerve block therapy and drugs. From the perspective of increasing trends in the current research on nerve block, the injection of dexmedetomidine around the nerve has recently become the focus of many studies. In other words, dexmedetomidine (13, 25, 26) has become a new target drug for nerve block in recent years. In terms of postoperative pain management, adductor canal block and local infiltration analgesia may be a good method for postoperative analgesia in lower extremity surgery.
By searching bibliometric articles, we found only two similar bibliometric articles, one describing regional anaesthesia (27) and the other describing epidural anaesthesia (28). The emphases and concerns of the two articles are different from those of ours. Through the quantitative analysis of nerve block literature, our study aims to understand the emphases and hotspots of current national and institutional studies on nerve block and their correlation. In addition, this study also focused on the development trend of nerve block in the future. The following areas require further research: the use of new auxiliary drugs for nerves containing dexmedetomide and local nerve blocks in oral therapy.
Our study had some limitations. First, only the WOS database was used in our study, therefore, the data retrieval may have been incomplete. Future studies should include the PubMed and Scopus databases as well. Second, regarding the definition of keywords, nerve block includes central nerve block and PNB. Although the literature on these two parts is included in our search results, it seems more reasonable to measure the literature of central nerve block separately in future studies.