Cadaveric training – the solution for ultrasound‐guided regional anaesthesia?

For the many anaesthetists that practice regional anaesthesia techniques, the benefits of being able to directly visualise relevant nerve structures are well recognised. Despite LeGrange and colleagues first describing the use of ultrasound to perform a brachial plexus block as early as the 1970s 1, regional anaesthesia continued to be performed throughout the 80s and 90s by using more basic techniques such as anatomical landmarks, identifying ‘clicks’ or loss of resistance as the needle goes through fascia or sheath, and latterly by the use of nerve stimulators in an attempt to more accurately identify the relevant nerve. Although the adoption of nerve stimulators was regarded as the ‘gold standard’ in the practice of regional anaesthesia, there was still a significant rate of failed block and risk of neural damage 2. Indeed, an analysis of claims against the NHS related to regional anaesthesia between 1995 and 2007 revealed that £7.3 million was paid out in non-obstetric related claims 3. It is only in the last two decades that the use of ultrasound-guided regional anaesthesia (UGRA) has gained wider acceptance, in part due to the wealth of related publications that have been generated over this period. Initially used for peripheral nerve blocks, improvements in ultrasound technologies helped investigators experiment with deeper blocks and perineural catheter placement. In 2010, an expert panel charged by the American Society of Regional Anesthesia and Pain Management to review the evidence base of UGRA concluded that it represented ‘a significant advance in the practice of regional anaesthesia and pain management’ 4. In 2005, Marhofer et al. described the principles that needed to be learned by anaesthetists to obtain the required level of competence to practice ultrasound-guided regional techniques. These included a need to develop a thorough understanding of the anatomical structures involved, acquire a solid grounding in ultrasound technology and the practical skills to visualise nerve structures 2. From an ethical point of view, the use of simulation or phantoms offers the opportunity for candidates to learn these skills in safe environments, which are low-risk to both candidate and patient, whilst not being seen to ‘practice on patients’. The study by Chuan and colleagues published in this edition of Anaesthesia reports a blinded, randomised controlled study to compare novices’ acquisition of the technical skills of ultrasound-guided regional anaesthesia using either a meat phantom model or fresh frozen human cadavers 5. Their hypothesis was that training on a fresh frozen cadaver would enable candidates to learn the technique of needle localisation and injection of saline around the nerve more quickly compared with training on a porcine meat model. Seven types of error in the conduct of the block were recorded by assessors as secondary outcome measures. Their main findings were that training of novices improved performance, but there was no significant difference in both primary and secondary outcome measures within groups and between groups, leading the authors to conclude that there was no advantage in training novices in ultrasound-guided techniques using fresh frozen cadavers. Their finding that there is an improvement in performance after training is not surprising. It is interesting to note, however, that the trend of the change in the time taken to do the procedure does show a greater proportionate decrease in the cadaveric group. The lack of statistical significance may be a reflection of the small number of volunteers in each group. The study raises a number of questions of how best to train clinicians in ultrasound-guided regional anaesthesia: what type of phantoms and simulators should be used? Should there be different methods employed at different stages of training? Is training using meat models good enough and human cadavers an unnecessary luxury? As a result of improvements in technology, the use of simulators has become an integral part of many facets of medical training and procedural skills acquisition; a development recognised by Sir Liam Donaldson, the Chief Medical Officer in his 2008 annual report 6. In the section on safer medical practice entitled ‘Machines, manikins and polo mints’, he advocated developing leading-edge methods to help improve outcomes and patient safety which should be fully integrated into the health service. He went on to summarise that “simulation in all its forms will be a vital part of building a safer healthcare system”. Whilst these comments were aimed at high-fidelity simulators, the implication was that ‘all forms of simulator’ would include other technologies as well as tissue phantoms. So, was the Chief Medical Officer correct in promoting this? The criticism of simulation training in anaesthetic practice has been the lack of evidence that this type of training is beneficial to long-term skills acquisition and retention or patient outcome. Simulation, of course, encompasses both the acquisition of technical as well as non-technical skills, and has been shown to be effective at reducing errors both within the anaesthetic community and other medical disciplines 7-9. Although it is recognised that the anaesthetic community is often at the forefront of innovation in training and patient safety, there are lessons to be learned from simulation in other specialties and industries. When reporting simulation in the healthcare literature, the inevitable parallel is drawn between the successful integration of simulation in aviation and potential benefits in medicine. If we also look at evidence from our surgical colleagues, there is good data to suggest that simulation training for junior surgeons may enable them to perform a specific surgical task significantly quicker, more efficiently and with reduced number of errors 10. In 2009, the American Society of Regional Anesthesia and Pain Management joint committee published recommendations for education and training of ultrasound-guided regional anaesthesia 11. As part of the curriculum, they recommended that trainees should ‘practice procedural techniques on available organic and inorganic simulators’. However, there was no specific recommendation on the type of simulator or phantom. A wide variety of phantoms are described, ranging from water, tofu, gravy, rubber, animal tissue (turkey, beef, pork) and human cadaveric material (embalmed and unembalmed). A review of the benefits and pitfalls of different types of phantom for training ultrasound-guided regional anaesthesia concluded that, as non-meat phantoms enhanced needle visibility due to low background echogenicity, they were good for practicing needle placement. Meat-based phantoms however, provide more realistic tissue feedback, permit local anesthetic injection, and have a background echogenicity that is closer to that of human tissue. Their main problem is the tissue has a short shelf-life, even with various methods to preserve and prepare them 12. The authors of this review also concluded that human cadaveric tissue provides a more realistic environment for ultrasound-guided regional anaesthesia practice, but availability of such tissue is limited. In determining how we align training needs with the correct simulation or phantom methods, one needs to consider the procedure being taught. When training to perform ultrasound-guided regional anaesthesia, three key techniques have been described: correct image acquisition; accurate needle guidance; and appropriate spread of anesthesic 13. Chuan et al. acknowledge that needle visibility is falsely superior in their model but that spread of the injectate is similar. Is the falsely superior simulation in needle visibility necessarily a bad thing for complete novices? As long as this is highlighted during a training course, this may in fact enhance learning for those new to the technique. Accurate needle guidance and appropriate spread of injectate seem to be appropriately simulated with their porcine model, which probably represents the early learning-curve for ultrasound-guided regional anaesthesia. Obtaining the correct image acquisition requires identification of surrounding structures as well as the target organ (such as the sciatic nerve). This may not have been simulated well with the current model, and certainly, for more complex procedures, would probably have resulted in poor tissue fidelity, for example if trying to simulate brachial plexus blocks. However, these observations come back to the principle of aligning educational goals with the education tool. Thus, for the basic skills acquisition of ultrasound-guided regional anaesthesia, the porcine model may well achieve the appropriate educational goals/needs for novices, thereby obviating the need for more expensive cadaveric models. Aviation, of course, has long used simulation as a method for training, although some within aviation have also questioned if the benefits of equivalent high-fidelity simulators are really needed to achieve the expected educational goals 14. Pilots certainly don't start on full-motion, high-fidelity simulators in the early stages of their careers, and will initially use static simulation platforms as an adjunct to skills acquisition, before adding in the additional complexity of more high-fidelity simulation platforms, when costs of practice in the real world starts to become prohibitive. With this is mind, this article by Chuan et al. reflects what is already happening in aviation, with a demonstration that for complete novices, the initial part of the learning curve can certainly be achieved on less expensive ‘simulations’. The findings of this article are thus probably more a reflection of where the benefits of differing simulation models lie on the learning curves for specific procedures. Further studies will be needed to determine if cadaveric simulation for more advanced trainees is more of benefit for obtaining accurate needle placement, and then there is the question of translation into ‘real-world practice’ to see if the complication rates and errors in clinical practice are reduced. Cadaveric simulation has high validity and is generally very well received by both candidates and faculty, but is expensive. For many surgical programs, it is now considered to be the ‘gold standard’ for simulation 15. However, it comes at a price: in one surgical program, it accounted for almost two-thirds of their annual budget for training 16. It would therefore seem sensible that a valuable resource such as cadaveric material should be used only in the appropriate setting. Much is made of the cost of cadaveric training, which is primarily met by the candidates themselves, outside of funded research studies. Should training institutions and/or employers be asked to help with ongoing training programs, as is the case for those in aviation? It has been shown that training juniors adds time onto operating lists, which as for the aviation industry, is not always a cost-effective way of training 17. There is thus a cost incentive for institutions to move some of the learning curve away from time-expensive and pressured environments such as the operating theatre to simulated ones. Complications from procedures have also been shown to increase health care expenditure by as much as 600% 18. Simulation has been shown to reduce procedural error and with that complication rates 19. There are therefore several aspects of simulation that should make the funding of such educational programs attractive to employers. This reduction in risk has also started to have an effect on indemnity insurance for individuals and institutions. In Harvard Medical School Hospitals in the early 2000s, through their indemnity insurer, anesthetists were able to reduce their premiums by 6% with an introduction of a simulation program for crisis resource management. By 2007, the program was such a success that the premium reduction was increased to 19% and a new program in Obstetrics and Gynaecology was started, with an initial reduction of 10% in premiums 20. In 2011, a ‘Framework for Technology-Enhanced Learning’ was published by the Department of Health, in which six principles for delivery of technology-enhanced learning were suggested 21. Training should: be patient-centred and service driven; be educationally coherent; be innovative and evidence-based; deliver high educational outcome; deliver value for money; and ensure equity of access and quality of provision. Cadaveric training would easily satisfy the first four principles for most training programs. Value for money is likely to be satisfied for surgical procedures if time saved in theatre and reductions in complications are taken into account, although definitive evidence is still lacking. In the UK, there are relatively few cadaveric centres which have facilities for fresh frozen material specifically available for postgraduate training, thereby limiting equity of access to such material. Inclusion of anatomy laboratories which have embalmed cadavers, will, however, help widen access. How do we reconcile the conclusions of Chuan et al. with the perceived advantages of training for ultrasound-guided regional anaesthesia on cadavers in the UK in the context of the technology-enhanced learning framework? Currently, the curriculum set out for Advanced training by the Royal College of Anaesthetists requires the demonstration of ‘a high level of skill’ in performing ultrasound-guided regional anaesthesia, but does not stipulate how these skills should be attained. However, those wishing to obtain the European Diploma of Regional Anaesthesia and Pain Management are required to have undertaken at least one cadaveric workshop as a pre-requisite for entering the Part 2 examination. Should the Royal College of Anaesthetists therefore follow the lead of Europe? The conclusions of Chuan et al. imply that novices can learn the basic principles of ultrasound-guided regional anaesthesia on meat models or embalmed cadavers. Common sense would dictate that acquisition of skills for the more challenging procedures and higher technical skills are best acquired on a simulation that is as ‘real life as possible’, which fresh frozen cadaveric material will deliver. What is required is evidence, similar to that from our surgical colleagues, that cadaveric training improves patient outcomes. In the case of ultrasound-guided regional anaesthesia, these should include quality of block and a reduction in complication rates in patients. It is conceivable that with time and further evidence, procedural training for ultrasound-guided regional anaesthesia will follow a tiered approach, with cadaveric phantoms used as a training module for ‘advanced skills’. These advanced skills would need to be determined by the College, but, if accepted, would then move cadaveric training for ultrasound-guided regional anaesthesia from an ‘expensive luxury’ into mainstream training. No external funding or conflicts of interest declared.