Using ultrasound for nerve blocks and neuraxial anaesthesia

This Invited Commentary accompanies the following original article: Boselli E, Hopkins P, Lamperti M, et al. European Society of Anaesthesiology and Intensive Care Guidelines on peri-operative use of ultrasound for regional anaesthesia (PERSEUS regional anesthesia): peripheral nerves blocks and neuraxial anaesthesia. Eur J Anaesthesiol 2021; 38:219–250. The Consensus Guidelines on the Use of Ultrasound for Regional Anaesthesia, drawn up by an expert panel from the European Society of Anaesthesiology and Intensive Care, comes at a time when the use of ultrasound has spread into virtually every facet of modern medicine.1 The guidelines seek to define whether this widespread use is grounded in evidence, and what are the gaps in knowledge that need to be filled to advance the practice of regional anaesthesia. The PERSEUS authors followed a methodologically rigorous process, seeking to add to our knowledge in three ways: first, investigate the evidence for efficacy of ultrasound guidance in regional anaesthesia; second, propose a general framework for teaching and education in regional anaesthesia; and third, suggest procedure-specific quality control parameters to measure maintenance of competency. In this Editorial, we will highlight the key elements that must be considered moving forward in regional anaesthesia, and how the PERSEUS guidelines provide a platform for this progress. In evaluating the usefulness of ultrasound in performing nerve blocks and neuraxial anaesthesia, the PERSEUS authors have used a composite outcome between patient-related variables ranging from technical factors to block success rates; patient-reported outcomes such as satisfaction; and complication rates. In doing so, they deliver a comprehensive and balanced overview of the current state of the evidence. The main conclusions are, unfortunately, that the quality of evidence on which to base recommendations for the use of ultrasound is generally weak for the indications investigated here. Does the limited evidence-base supporting the use of ultrasound in performing regional anaesthesia matter? And if it does, do we need to focus our energies on proving the efficacy and safety of ultrasound over nerve stimulation or landmark-based techniques? The use of peri-operative ultrasound for performing peripheral nerve blocks is now virtually ubiquitous, with a wide range of devices including Food and Drug Administration-approved and CE-certified ultrasound probes that can be connected to commercially available handheld tablets costing less than €1000. Training programmes that are not centred on a foundational understanding of ultrasound technology, including its physics, practical use and needling skills, are now unheard of, whereas complications of regional anaesthesia performed without the use of ultrasound are likely to place practitioners at high litigation risk. In addition, point-of-care ultrasound is now used to improve patient care virtually anywhere in the continuum of peri-operative care, from the emergency room to the operating room to postoperative ICUs. This means that ultrasound skills obtained while learning nerve blocks can be used for more than just regional anaesthesia, they will be synergistic with competencies gained when using ultrasound for other indications, such as central venous or arterial line placements, and diagnostic scans. For these reasons, the use of ultrasound for peripheral nerve blocks has become the defacto gold standard and, in this regard, it is unclear what benefit there would be to develop the evidence further. However, one avenue that may merit increased focus is the use of ultrasound to enhance the quality and success rate of neuraxial anaesthesia. Here, at least in adults, landmark-based techniques remain the gold standard. Despite an ever-increasing evidence-base, there remain unanswered questions about ultrasound-assisted neuraxial anaesthesia. The PERSEUS guidelines do encourage the use of ultrasound to safely select the correct intervertebral space for neuraxial access. For classical neuraxial techniques, one interspace too high or too low would likely not translate to a fundamentally different clinical outcome, yet it is clear that our subjective estimation of intervertebral spaces lacks accuracy. A further question is whether the routine use of ultrasound would improve the success rate for placement of epidural catheters. There is substantial heterogeneity in the success rates using the landmark technique in clinical practice and training programmes,2 with failure rates as low as 0.8%3 and as high as 15%4,5 for labour analgesia, and up to 30% for thoracic epidurals.6 However, the majority of failures of this technique do not seem to occur due to inability to locate the epidural space, but rather fall under the heading secondary failures, for example misplacement or migration of epidural catheters.7 Other problems that limit the usefulness of epidurals include hypotension, urinary retention and pruritus, and are independent of the localisation method. Improving epidural space localisation, unfortunately, is only a small part of optimising epidural anaesthesia, and probably not the most important one in the grand scheme of things. Use of ultrasound therefore still might not improve overall clinical outcomes, even though proficiency in neuraxial ultrasound may certainly help facilitate placement in select patients with challenging anatomy. We propose that increased efforts should be directed at demonstrating benefits of regional anaesthesia and refining our knowledge on how best to tailor our regional technique to the patient and surgery. As the American Society of Regional Anesthesia and Pain Medicine puts it, we have to make a strong ‘value proposition’ for our work, to showcase and prove using high-quality evidence the benefit we will bring to the table in shaping the peri-operative pathway of the future. Regional anaesthesia must improve outcomes for patients (patient-centred outcomes), healthcare services (resource-utilisation outcomes), in training (workforce outcomes) and for society as a whole (including ecological outcomes). This is especially important since, unfortunately, hopes of improving long-term outcomes such as mortality, cancer recurrence and chronic pain have either not been fulfilled,8 or fulfilled only for defined patient cohorts.9 Small as the intervention may be, we need to demonstrate improvements beyond the immediate term, or at least demonstrate superior pain relief and improved patient-centred outcomes with as few drawbacks (e.g. rebound pain after the block wears off) and risks as possible. Whether these benefits are achieved using ultrasound or other modalities such as nerve stimulation may not matter at first sight and may even be irrelevant to other healthcare workers. However, the bigger picture is that ultrasound allows us to offer the full spectrum of regional anaesthesia. While many ‘classical’ nerve blocks, such as interscalene block, have a very high success rate even with a nerve stimulator in expert hands,10 other blocks that have been adopted widely such as transverse abdominis plane block, rectus sheath block, erector spinae plane blocks and pectoral nerves blocks cannot be performed without ultrasound guidance without accepting abysmal failure rates, or high degrees of risk. As another example, the supraclavicular brachial plexus block could only be reintroduced because ultrasound allows us to avoid the very high risk of pneumothorax. Therefore, the use of ultrasound opens doors for improvements in patient care with possible benefits that extend beyond the individual. The guidelines presented here1 take an important step towards standardisation of teaching novices, and training trainers in ultrasound-guided regional anaesthesia. The recommendations put forward are an important start to the discussions on how to properly implement training, certification and continuing education frameworks that will assure standards in regional anaesthesia are harmonised as much as possible across Europe. While it may seem challenging and even unattainable to implement formal year-long fellowships in regional anaesthesia, as they are offered in the United States and Canada, the European Society of Regional Anaesthesia and Pain Therapy has been certifying providers for more than a decade, and there are prominent structured educational efforts, such as the University Diploma in Regional Anaesthesia (Sorbonne University, Paris, France), and the Master of Science in Regional Anaesthesia (University of East Anglia, Norwich, United Kingdom). The PERSEUS guidelines now formulate that a period of observation and ‘dry scanning’ should precede every ultrasound-guided procedure done for the first time, and that trainees should maintain a block logbook to demonstrate education and training, and achievement of criteria that define successful outcome, including block success rate, rate of conversion to general anaesthesia, procedural time, incidence of complications and patients satisfaction. The guidelines thereby challenge us to find ways to systematically assess the success of our interventions on a daily basis, and use that data to identify strengths and weaknesses in our practice. The guidelines also define requirements for expert trainers, including performance logs and evidence of continued professional development, but refrain from mandating absolute numbers of blocks that need to be performed to maintain competency. This touches on an important subject, as there is no agreement of how many blocks the provider is supposed to perform per year. Is it 50 blocks per year? If so, then theoretically, 10 blocks could be done five times each, or five blocks could be done 10 times each. This distinction is important because maintenance of competency necessitates a certain level of practice, the exact extent of which has not been universally agreed upon. The PERSEUS guidelines find a middle way by focusing on the quality indicators for nerve blocks rather than block numbers. Nevertheless, for the majority of providers, it seems prudent to limit the number of blocks performed, and to become expert at those blocks. At workshops for beginners, we should be teaching five or six important blocks, not 20. This focus on the essential blocks will increase the availability of regional anaesthesia, with potential benefits beyond the individual patient. The focus should be quality in the few select blocks we do, not the quantity of blocks offered. This leads us to the question ‘what should we be teaching our residents using ultrasound’? The number of blocks described in literature is high, but the evidence for most of them is low. At one end of the spectrum are techniques such as interscalene, supraclavicular, axillary, femoral, sciatic and saphenous nerve blocks. Literature searches for technique and indication list hundreds of scientific articles. A simple, unrestricted, cursory literature search on the topic of ‘interscalene block’ yields more than a thousand articles. At the other end of the spectrum are a large number of blocks that have been described but have gained neither clinical nor academic traction. Tran et al.11 rightfully pointed to this problem in their editorial entitled ‘Beyond Ultrasound Guidance for Regional Anesthesiology’, where they made the important argument that, after years of introducing new blocks and new block descriptions virtually every month, we as a specialty need to take a deep breath, take a step back and assess which blocks we really need to provide the greatest value to the greatest number of patients. The concept of a basic blocks list, previously referred to as the ‘Big Five’ and more recently updated to the ‘Plan A blocks’ has been proposed to increase the use of regional anaesthesia by more clinicians (Table 1).12 These blocks should be suitable to treat severe postoperative pain in most relevant regions of the body, to serve as primary anaesthetic blocks, or postoperative rescue blocks. Simply put, this is a set of nerve blocks with a very high likelihood of successful patient outcomes that will get you through a busy on-call shift. The aim is not to be able to anaesthetise every part of the body, but rather to cover those regions most often responsible for severe postoperative pain which may be very hard to treat using intravenous medications (e.g. foot and ankle surgery, knee surgery, amputations, thoracic and abdominal surgery, rib fractures, upper extremity fractures), to provide the highest quality anaesthetic care for elective and acute surgical patients. This should serve as a foundation for all anaesthetists, while the array of alternative block techniques available for very specific indications should be provided by subspecialty trained regional anaesthetists. The selection of the appropriate blocks to be included in the basic armamentarium remains unclear, but the process may be guided by a Commonwealth Fund grading system of increasing access, enhancing efficiency, decreasing disparities and improving outcomes.13 There remains much work to be done in this important field. Table 1 - Two contrasting yet similar proposals for basic regional anaesthetic techniques that should be taught to all trainees ‘Big five’ blocks Plan A blocks Supraclavicular brachial plexus block Interscalene brachial plexus block Femoral nerve block (alternative: saphenous/adductor canal) Axillary brachial plexus block Popliteal sciatic nerve block Erector spinae plane block Paravertebral block Rectus sheath block TAP block Femoral nerve block Popliteal sciatic nerve block TAP, transverse abdominis plane. A ‘big five’ suggestion and plan A blocks from Turbitt et al.12 The PERSEUS guidelines highlight our current understanding of the additional value ultrasound brings to the practice of regional anaesthesia. Although gaps are identified in demonstrating whether assistance from ultrasound is unequivocally better than other techniques when performing nerve blocks, future research should focus on the clinical efficacy of the specific blocks performed using state-of-the-art imaging, rather than the potential superiority of any individual guidance. Using the PERSEUS guidelines as platform, our top priorities going forward should be embedding regional anaesthesia in training for all anaesthetists, selecting the appropriate techniques that bring the greatest value to the greatest number of patients, and demonstrating the wider role regional anaesthesia plays in the peri-operative pathway of the future.