Cadaveric regional anaesthesia workshops – do we really need them?

Regional anaesthesia always works when you put the right dose of the right drug in the right place. When it doesn’t work, it is usually because the local anaesthetic has not been delivered to the right place. From the first brachial plexus block performed under direct vision, through percutaneous techniques using various anatomical landmarks, later paresthesia and nerve stimulation to real time ultrasound guidance, anatomy has been deemed of the utmost importance for correct needle tip location and injection of local anaesthetic. I am sure, everyone in the world of regional anaesthesia is aware of famous Alon Winnie’s quote ‘regional anaesthesia is simply an exercise in applied anatomy’.

Cadaveric workshops were traditionally connected to the core training of future regionalists. Whilst we would generally agree, that teaching anatomy is still extremely relevant, the question is, are the cadaveric workshops still necessary and fit for purpose in 2021 and for the years ahead? We will try to find out the answers for this and few other questions from the three experts with close connection to regional anaesthesia and anatomy.

from left to right:

Prof. Paul Kessler
ESRA Chair for cadaveric workshops,
Vice Chairman Anaesthesia & Intensive Care Medicine, Frankfurt, Germany

Prof. Graeme McLeod
Consultant Anaesthetist Dundee, Scotland
Co-Lead MSc Regional Anaesthesia, University of East Anglia, Norwich, England

Dr. Mario Fajardo-Perez
Director of ESRA Cadaveric Workshop, Madrid, Spain
Director of Ultradissection

Why do we need cadaveric workshops for regional anaesthesia?

Prof. Kessler

• The successful performance of an ultrasound-guided interfascial or peripheral nerve block is a highly complex process. These include to visualize nervous structures, to guide the needle to the target and to deposit local anaesthetic solution around the nerve. Since it is unethical to learn such a complex process on the patient, there are different phantom models for acquiring one’s skills in ultrasound-guided regional blocks.
• The most realistic and closest to the patient are cadavers. All components of nerve block such as nerve anatomy, needle movement, fascial penetration, perineural fluid injection and inadvertent intraneural injection can be shown and learned. Therefore, when properly prepared, the use of cadavers is second to none for proper ultrasound procedural training and learning. Cadavers provide an ideal tool for learning sono-anatomy and skills required for performing U/S-guided regional anaesthesia.

Prof. McLeod

• Regional anaesthesia can provide the best possible outcomes for patients. We should be aiming for complete anaesthesia without need for adjuvants or resort to general anaesthesia; and prolonged pain relief, based on the type and extent of the surgical procedure, while taking account of individual chronic pain and psychological make-up.
• Thus, the bar for clinical performance in regional anaesthesia is set high. Excellent practice, the repetitive, every-day provision of high-quality anaesthesia and analgesia outlined above is difficult to achieve. The learning curve for excellence is long and reflective of other interventional and surgical practice.
• Regional anaesthesia practice is a double-edged sword. Failure to provide adequate anaesthesia or premature postoperative resolution of block, can ruin the expectations of patients and surgeons, and limit enthusiasm for a block service. Indeed, failure to ensure the highest possible quality of regional anaesthesia is characteristic of many outcome trials.
• Thus, within current practice considerable variation occurs in the performance of block between and within anaesthetists; and between patients with regard to postoperative pain, pain trajectories, chronic pain and functional outcome.
• Traditional learning has been based on the accumulation of as much self-taught clinical experience as possible. Curricula have ordained a set number of supervised and non-supervised blocks, and a level of proficiency that reflects the minimum standard needed for a clinician to progress to the next stage of training. In fact, the number of blocks performed has little influence on individual performance and clinical outcomes.
• Simulation seeks to: reduce such variability; and accelerate learning, in order to translate higher skills to clinical practice.

Dr. Fajardo-Perez

• I think the anaesthesiologist needs to learn applied anatomy. We don’t have a good book on regional anaesthesia and applied anatomy. Anaesthesiologists are learning through youtube videos and anatomy based books. The entire college and curriculum must include basic science such as anatomy. All regional anaesthesia society need join to one university to send the residents to learn.

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Can we use other resources (book, atlas, videos … etc) for anatomy teaching?

Prof. Kessler

• The basic prerequisites for successful regional anaesthesia are, in addition to well-founded anatomy, knowledge of the physical and physicochemical properties of local anaesthetics and the associated pathophysiological changes in the organism.
• This knowledge can be acquired from books, atlases or videos, also on YouTube. Webinars, which are increasingly popular as e-learning methods, are also suitable. Nowadays, book-bound learning materials such as atlases deliver CDs or the videos can be viewed via barcode recognition. In the meantime there is a large number of excellent video animations on the internet about the implementation of almost all clinically used nerve blocks, from the anatomical basics to the complications, including the current literature. Videos are mostly more up-to-date than atlases, which is an advantage given the large number of new blocks.
• There are various Apps about regional anaesthesia for mobile phones, also from the anaesthesiology societies. Handling is usually easy, sometimes expensive. I don’t want to focus on names now, but in principle the Apps are better that not only explain the simple performance of the nerve block, but also go into things such as indication, contraindication, advantages and disadvantages, complications, i.e. illuminating a regional block from a to z.

Prof. McLeod

• Books and atlases provide detailed description of anatomy, but retention of knowledge is variable. Videos can provide good 3D rotating images and mnemonics to aid, for example the nerves of the brachial plexus.
• Are there any good virtual reality software or mobile apps for teaching anatomy? What are their strengths and weaknesses?
• Complete Anatomy from Elsevier provides 3D rotating images and plenty of detail

Dr. Fajardo-Perez

• I think the main source of anatomy learning is cadaver dissection and training with cadaver to improve your needling skills, prior to performing the blocks in real patients, and simulate the complicactions
• The residents should be evaluated in regional or international cadaver course practicing in cadaver.
• The residents should have an unrestricted access to the anatomy labs

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What kind of cadaveric specimens can we use and what are their advantages and disadvantages?

Prof. Kessler

• Cadavers differ in several aspects such as color, flexibility, quality of preserved tissue, cost, and storage on the basis of embalming method. Depending on the preservation technique used, there are three types of cadavers.
• Traditionally, formalin embalmed cadavers have been used for learning various surgical skills. Fresh frozen cadavers were developed by keeping the cadavers in deep freezing refrigerator at −20°C for 3–4 days after serologic testing for infectious diseases. Fresh, non-embalmed specimens begin to deteriorate within 1-2 days and are quite foul smelling. Formaldehyde is a known carcinogen, absorbed easily through skin and mucous membranes, and non-embalmed cadavers, such as fresh cadavers, increase the risk of exposure to infection.
• Cadavers prepared using Thiel’s embalming method overcome many of these problems. Thiel’s embalming mixture is a water-based mixture of salts for fixation, boric acid for disinfecting, glycol, chlorocresol and ethanol,morpholine as colour preservative, and a small amount of formaldehyde. Fully embalmed specimens last longer but do not have the texture, flexibility and tactile feedback from needling that is important for learning needle guided procedures such as nerve blocks. Formalin embalmed cadavers were rigid with stiff joints and had an unpleasant odor, fresh frozen cadavers were less rigid, and Thiel cadavers were the most flexible. Color, suppleness of skin, joint flexibility, and fascial integrity of the cadavers is retained. In Thiel cadavers, due to fluid in tissues echogenicity of muscles increases which enhances the sonographic contrast between muscles and nerves.
• One problem with cadavers is the absence of normal vascular anatomy. For all cadavers, vessels are usually collapsed, which makes it difficult to carry out some nerve blocks where the nerves run right next to the vessels. Many nerve structures are accompanied by, or adjacent to, blood vessels that are often better identifiable using ultrasound than the nerve. This is why using blood vessel landmarks for ultrasound-guided localization of neural structures is more difficult in the cadaver than in the real patient.
• A disadvantage of fresh frozen and Thiel’s embalmed cadavers is that they are more expensive than cadavers embalmed with formaldehyde. Furthermore, one has to consider that, for moral and ethical reasons, cadavers are not permitted in all countries. Under certain circumstances, individual body parts are permitted for study purposes, on which us-guided nerve blocks can also be carried out.

Prof. McLeod

Four cadaver preparations are available: formaldehyde-based; plastinated; fresh-frozen and soft embalmed.

• Formaldehyde is a traditional embalming fluid that denatures proteins and kills bacteria. It is highly toxic and carcinogenic. Cadavers are dry and stiff, and insonation is not possible.
• Plastination was invented by Gunther von Hagens in 1977. It involves: fixation with formaldehyde; dehydration in an acetone bath, vaporisation of acetone in a vacuum; cell replacement with liquid polymer and hardening. Tissues feel plastic but retain their size, shape, and 3D anatomical relationships
• Fresh frozen cadavers are unembalmed cadavers. They possess fine anatomical detail and provide good ultrasound images of needle-tissue interaction. However, they decompose quickly and accumulate injectate, distorting anatomy.
• Soft preparation or soft-fix methods preserve tissue elasticity, and thus enable limb movement, ventilation, and tissue expansion and relaxation following injection. Dispersion of fluid from the target area allows repeated injection with minimal tissue change.
• An example of soft embalming is the Thiel preservation method. Cadavers are soaked in large vats containing solutions of boric acid, propylene glycol and a very small amount of formaldehyde for up to 6 months. Thereafter, cadavers remain soft and flexible1. Histology is maintained for 12 months. The cadaver retains elasticity, has similar strain properties as patients during extraneural and intraneural injection. Injection fluid “opening” pressure has been validated at different flow rates against anaesthetized animal models and patients2. Although representing the best available UGRA simulator, the cost of preparation and storage is prohibitive.

Dr. Fajardo-Perez

• The best cadaver to ultrasound and needling its Thiel, for dissection formaldehyde.

What should be included in ideal cadaveric course for novices and what for advanced learners in your opinion?

Prof. Kessler

• In principle, whole-body cadavers and dissected cadavers should be made available for both beginners and advanced users. For cost reasons, half of the body could be dissected and the other half of the body kept intact. US-guided regional procedures can be performed on whole-body cadavers, while the topographical anatomy is demonstrated on the dissected cadavers. The so-called basic blocks are for novices, the more risky and deep blocks for advanced learners.
• Short, time-limited introductions in a lecture hall would be desirable.
• Monitors in the dissecting hall should first be used to demonstrate the individual steps of the various blocks, as well as the topographical anatomy.
• For better learning of needling, several stations with gel phantoms should also be available for novices.
• A sufficiently large number of high-resolution US machines, echogenic needles and catheters are a basic requirement.
• The ratio of participants per cadaver should ideally not be greater than 5: 1, as otherwise, from personal experience, there will not be enough time for the individual participants to practice. Such an implementation is becoming increasingly difficult due to the high cost of the cadaver.

Prof. McLeod

• Practical training for beginners consists of a short anatomy lecture; ultrasound training on a volunteer, scanning the neck and forearm; needle-ultrasound alignment training on a blue plastic phantom or pork belly with embedded tendon.
• We regard training as a continuum that regularly needs appraisal and testing.
• We use mastery learning3 as the basis of training, whereby trainees gain expertise irrespective of time, by repeating a specific task until a predefined standard has been achieved. Mastery learning is characterised by seven factors: (i) baseline testing; (ii) clear learning objectives; (iii) deliberate practice; (iv) a set minimum passing standard for each educational unit; (v) formative feedback; (vi) progress to the next educational level; and (vii) continued practice until a pre-defined standard is reached.
• The expert performance approach4 uses mastery learning as a baseline. In Dundee, we believe that clinical excellence can be taught using the expert-performance approach with deliberate practice on high fidelity soft-embalmed cadaver simulators. The expert-performance approach embraces reliable, objective real-time metrics, immediate feedback, and the assimilation of mental approach to excellence that drives self-reflection and learning that achieves the marginal gains necessary to improve patient outcomes. This approach is not dissimilar to that used to train elite athletes or within aerospace. Deliberate practice is intense. It entails 1:1 training on a simulator that emphasises repetition and successive refinement while undertaking effortful tasks demanding high concentration
• All participants, irrespective of experience, are trained on cadavers. Our recent pilot work showed that novice anaesthetists trained on the Thiel cadaver, rather than a piece of pork, showed better skills performing interscalene block on the Thiel cadaver after training. Moreover, they translated those skills to performance of interscalene block on patients three weeks after training. We believe that novices and expert should be trained on the same simulator. The expert performance approach enhances skills appropriate to the stage of training.

Dr. Fajardo-Perez

• I think the residents should go to the cadaver labs all month, to learn anatomy, ultrasounds, dissections, neurophysiology.

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What else can we incorporate into cadaveric anatomy teaching?

Prof. Kessler

• In the meantime, the requirements for cadaver course have increased. The purely descriptive anatomy is no longer sufficient; newer conservation techniques make it possible to imitate a complete us-guided nerve block.
• This means first of all searching for and recognizing the target structure, advancing the puncture needle and injecting and perineural spreading the local anaesthetic, another key component of successful block. Even an intraneural needle position and spread of the local anaesthetic as a sign of nerve damage can be demonstrated, a process that must be avoided at all times on the patient.
• Continuous procedures with catheter advancement and correct placement are also possible in cadavers. Often it is not possible to identify the position of the catheter tip even with US and injection of fluid. Cadavers allow targeted search for the catheter tip by means of tissue dissection.
• Various needling techniques, in-plane and out-of-plane, can be learned, alignment of needle and US beam as well as hand-eye coordination. For learning fascia blocks the feeling of the passage of fascia (pop sound) is important, which is felt very well with especially embalmed cadavers. Likewise, the correct spread of the local anaesthetic between two layers of fascia is shown in cadavers.
• While non-dissected cadavers are required for us-guided as well as for landmark-guided blocks, the topographical anatomy of the nerves and the surrounding tissue can be demonstrated particularly well on dissected cadavers.

Prof.McLeod

• The collection and use of digital metrics lies at the heart of the expert performance approach⁵.
• First and foremost, we use validated checklists of steps and errors – steps that should be performed and errors that should be avoided. Trainees are videoed under exam conditions and at least two trainers independently rate video performance. Our checklist has been refined to 15 steps and 6 errors. In addition, we provide summative assessment using a standard, validated global rating score. Our experience is that our checklists and global rating scores align well⁶.
• We use eye tracking, an acknowledged objective measure of visual attention in order to gain an insight into visual perception. We have demonstrated construct validity using eye tracking and good correlation with checklists and global rating scores. Our data shows that both checklists and eye tracking can discriminate between skill levels.
• Measurement of fine motor skills remains a research tool⁷, but should be investigated as a metric for use within skills courses.

Dr. Fajardo-Perez

• A lot of teachers of regional anaesthesia don’t practice any cadaver dissections. In my opinion there is definitely room for improvement.

What else can we incorporate into cadaveric anatomy teaching?

Prof.Kessler

• Possibly, which would be regrettable, we will have to forego cadaver workshops in 2035 because the costs are too high.
• One solution would be to switch to body parts.
• It would also be possible that by then there will be corresponding simulators with which everything that is possible on cadavers can be done.
• The bottom line is that whole body and especially Thiel-embalmed cadavers provides best conditions for anaesthetists to learn sonoanatomy and simulate regional anaesthetic block techniques using ultrasound.

Prof.McLeod

• Immersive technologies will be used in training rather than clinically. Formal time will be given to simulation training. Variation in the quality of clinical input/interventions and clinical outcomes will drive the need for simulation training.
• Formal simulation skills training will allow trainers to address technical and non-technical problems before patient exposure, identify individual traits and measure performance relative to peer groups.
• New technologies will embrace 3D Virtual Reality (VR), and Augmented/Mixed Reality (AR/MR), whereby anatomy is superimposed over a cadaver or patient. Immersion will allow interaction within computer-generated 3D environments.
• The role of VR and AR in training is not yet established. Application to training should be based on the learning needs of trainees and the desired outcomes on patients. Thus the make-up of technology will be reverse engineered from clinical need.
• Combination of AR/VR with traditional teaching needs to be established.
• In addition, the mechanisms underpinning the interaction of anaesthetists with real and virtual environments needs to be understood better, particularly when presented with a tricky or stressful scenario.
• There needs to be a deeper scientific understanding of the processes that underlie skill acquisition, perception, movement, decision making and machine interaction. That way application of eye-tracking, haptics and wearable sensors to training will be based on a mechanistic approach.
• This means a greater role for psychologists in skills training.

Dr. Fajardo-Perez

• I think we will combinate anatomy, ultrasound, neurophysiology, virtual reality and cadaver.

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References:

1. Munirama S, Eisma R, Columb M, Corner GA, McLeod GA. Physical properties and functional alignment of soft-embalmed Thiel human cadaver when used as a simulator for ultrasound-guided regional anaesthesia. Br J Anaesth 2016; 116: 699-707
2. McLeod G, Zhang S, Sadler A, et al. Validation of the Soft Embalmed Thiel Cadaver as a High Fidelity Simulator of Pressure during Targeted Nerve Injection Reg Anesth Pain Med 2021
3. Gallagher AG. Metric-based simulation training to proficiency in medical education:- what it is and how to do it. Ulster Med J 2012; 81: 107-13
4. Ericsson KA. Acquisition and maintenance of medical expertise: a perspective from the expert-performance approach with deliberate practice. Acad Med 2015; 90: 1471-86
5. McGaghie WC. Mastery learning: it is time for medical education to join the 21st century. Acad Med 2015; 90: 1438-41
6. McLeod G, McKendrick M, Taylor A, et al. Validity and reliability of metrics for translation of regional anaesthesia performance from cadavers to patients. Br J Anaesth 2019; 123: 368-77
7. Kasine T, Romundstad L, Rosseland LA, et al. Ultrasonographic needle tip tracking for in-plane infraclavicular brachialis plexus blocks: a randomized controlled volunteer study. Reg Anesth Pain Med 2020