In-depth knowledge of anatomy is a prerequisite for performing UGRA. Identification of key anatomical landmarks (e.g., muscles, fascias, bones, and blood vessels) is the first task outlined in the joint ASRA-ESRA recommendations for UGRA [9], and detailed knowledge of relevant anatomy is essential to identify sonoanatomy [29]. Without an understanding of relevant anatomy, novice learners cannot progress into “advanced sonoanatomy” (i.e., using ultrasound to identify anatomical landmarks surrounding target nerve) but instead can fall into a habit of “pattern recognition” (i.e., scanning until the ultrasound image closely resembles sonoanatomy they have seen previously) [8,30]. Furthermore, without knowledge of anatomy and correct interpretation of sonoanatomy, novices can fail to recognize abnormal anatomy and may endanger patients with inadvertent needle puncture of tissues or vessels [31].

Simulation-based education can be a time-efficient modality to learn UGRA-related anatomy. Ramlogan et al. [32] enrolled anesthesia residents and fellows in a training session using an online virtual-reality simulator that presented interactive 3-dimensional images and allowed virtual scanning. After a 1-hour self-study session, participants scored higher than their baseline on a multiple-choice exam and reported that the simulator tool was easy to use and beneficial to their learning. In a study by Woodworth et al. [33], a 25-minute video about anatomy complemented by a 5-minute interactive simulation module employing a virtual transducer (i.e., scanning produced both ultrasound and corresponding magnetic resonance images) led to improved scores on a written exam compared to a control group that only watched a sham video. However, the intervention group did not show improvement in image acquisition while scanning on live models, implying that virtual reality scanning may have limited clinical applications.

A few studies endorse the inclusion of real-time ultrasound images to learn anatomy and sonoanatomy. In a study by VanderWielen et al. [34], participants who viewed a brief instructional video (viewing session did not exceed ten minutes) that partly reviewed basic anatomy and demonstrated ultrasound scanning techniques improved their ability to acquire ultrasound images and identify anatomical landmarks on a live model. However, a group randomized to a hands-on training session with an anatomy-based gel phantom (scanning session did not exceed ten minutes) was more successful than the video group in identifying anatomical landmarks when both were compared to a control group, reinforcing the value of hands-on experience and dynamic image interpretation to learn sonoanatomy. During a 4-week regional anesthesia rotation, Orebaugh et al. [31] introduced a UGRA training curriculum to residents prior to performing nerve block procedures. Didactics covered numerous UGRA-related topics, including anatomy, and teaching of sonoanatomy involved focused scanning of patients under supervision. Compared to their pre-rotation standardized exam scores, residents at the end of the rotation demonstrated improvement in acquiring ultrasound images and identifying anatomical and neural structures at four different block sites (interscalene, supraclavicular, femoral, popliteal fossa). Likewise, Barrington et al. [35] demonstrated that a combination of standardized didactics followed by supervised hands-on scanning sessions on live models allowed residents to become proficient in acquiring ultrasound images and identifying relevant anatomical landmarks. This group specifically focused on axillary brachial plexus blocks and determined residents needed eight to ten training sessions with feedback from expert faculty to achieve proficiency. For residents who may not have access to experienced trainers but seek additional knowledge of sonoanatomy, scanning live models or patients with the aid of an electronic tutorial may enhance learning. In a study by Wegener et al. [29], novice clinicians who practiced with an ultrasound machine that simultaneously displayed anatomical tutorials alongside real-time images identified correctly more anatomical structures on a live model exam than the control group that practiced without the tutorial.

Ultrasound knowledge is a core competency outlined by the joint ASRA-ESRA committee and includes skills like understanding basic ultrasound physics (e.g., frequency, attenuation, refraction), equipment functions (e.g., depth, gain), and artifacts (e.g., reverberations, acoustic shadowing) [9]. Prior to performing simulated UGRA, it is recommended that through didactics residents become familiarized with concepts like appropriate transducer selection, transducer orientation to target (transverse vs. longitudinal), scanning techniques (rotation, alignment, tilt, pressure), needle visualization (in- vs. out-of-plane), and correct local anesthetic spread around the nerve [9]. Appropriate preparatory teaching can help residents understand the technical skills required to successfully perform UGRA and deconstruct procedures into individual tasks to facilitate learning [7]. Then, residents can proceed to hands-on practice to acquire proficiency in those individual UGRA tasks until sufficient skills are obtained to perform a UGRA procedure in its entirety [7].

For practice of UGRA technical skills, numerous simulated models have been introduced, including self-assembled phantoms (gelatin, meat, tofu) [34,36,37], commercially available trainers [25,38], hybrid simulators [39,40], and cadavers [6,41,42]. Simulation-based training in needle visualization has been shown to improve hand-eye coordination [43], decrease technical errors [44], and reduce number of needle passes [45]. A group of residents that underwent a 1-hour hands-on training session on a simulation model, focusing on needle visualization and hand-eye coordination, had higher clinical success rate of UGRA compared to a control group that did not receive simulation training [25].

Although recommendations cannot be made on the ideal simulation modality for learning UGRA-related technical skills, comparative studies suggest that low-fidelity phantom models can be cost-effective and accessible [46,47]. Chuan et al. [46] randomized novices to practice on either a porcine meat model with embedded bovine tendon (low-fidelity) or a fresh-frozen cadaveric upper limb (high-fidelity). Each participant underwent a deliberate practice session of 45 minutes during which time 30 practice trials were allowed with individualized feedback. The post-training examination consisted of identifying the sciatic nerve on a cadaver and injecting saline around the nerve. Between the low- and high-fidelity groups, there were no differences in time to complete the simulated sciatic nerve block, errors committed, and ultrasound image quality of the nerve. In another study, Friedman et al. [47] investigated the effects of a high- versus low-fidelity simulator on performance of epidural catheter placement in actual patients. In the high-fidelity group, anesthesiology residents practiced epidural needle insertion on a mannequin simulator with a “virtual-reality display of needle progression,” while the low-fidelity group practiced inserting needles into a banana (“greengrocer’s” model) to simulate loss of resistance. Each group was allowed sixty minutes of supervised training followed by live procedural observations. Throughout a six-month period, the two groups did not show a difference in skill acquisition when assessed by a checklist and global rating scale (GRS). For educators, the selection of a simulation modality will depend on availability of financial resources and time commitment; however, when devising a simulated environment, the priority should rest in supporting resident skill acquisition and assessment rather than simulation fidelity [8,48]. Practice sessions should have defined objectives that provide exposure to different types of transducers, superficial and deep targets, inand out-of-plane needle visualization, and short- and long-axis target views. Residents should also become familiarized with ultrasound artifacts, which may not be replicated on simulated models, but can confuse novices during UGRA procedures on actual patients [49,50].

When initially learning UGRA, it is common for residents to focus primarily on the hands-on aspects of UGRA [13]; however, technical competency alone does not result in UGRA proficiency [51]. Table 1 outlines examples of non-technical knowledge and skills necessary to progress toward independent practice. Specific topics like clinical pharmacology and risks and contraindications of regional anesthesia can be covered through didactics. Other tasks and skills, like aseptic technique, monitoring of vital signs and patient comfort, management of complex patients or complications, and coordination of care with other health care providers, can be learned through clinical experience. Although simulation training has not been studied extensively for non-technical UGRA skills, residents can practice providing informed consent, explaining post-procedural care, and discussing management of complications as part of a simulated UGRA procedure [52]. Additionally, simulation can be used to teach certain skills like situational awareness, multi-tasking, and teamwork during crisis management [21,24], and standardized simulated scenarios can allow residents to develop an approach to managing UGRA-related complications [53]. For example, during simulation-based training for local anesthetic systemic toxicity (LAST), trainees who used a checklist of therapeutic interventions demonstrated superior management of LAST events and exhibited better decision-making skills compared to trainees who relied on their memory [53]. Other scenarios for simulation that have been described include high spinal anesthesia and postoperative nerve injury [54].

There is a well-known adage about performance assessment: “When performance is measured, performance improves. When performance is measured and reported, the rate of improvement accelerates.”¹⁾ The principle of performance measurement is equally applicable to learning UGRA. Objective assessments and feedback are critical components of simulation training that can reduce learning curves [4] and enhance UGRA education [3,8,14]. For UGRA, a few validated assessment tools can be considered during training. Woodworth et al. [55] demonstrated reliability, content validity, and construct validity of a multiple-choice exam that specifically assesses knowledge of sonoanatomy. The strengths of this exam include accessibility (online format), applicability to residents at various levels of UGRA experience, and immediate feedback that is not dependent on an evaluator. However, this exam was designed to assess knowledge of UGRA and does not necessarily correlate with technical skills. Other assessment tools that have been used for regional anesthesia include checklists and GRS [47,56]. A checklist and GRS specifically for UGRA was first published in 2012 [57] and since has been validated through assessment of residents performing nerve block procedures on patients [58] and modified to allow evaluation of regional anesthesia performance irrespective of regional anesthesia type (neuraxial or peripheral) and nerve localization technique (ultrasound, nerve stimulation, or combined) [59]. Checklists can deconstruct a procedure into a discrete series of steps and allow educators to provide objective and specific feedback to residents at various stages of learning [59].

For competency-based models of training, a standardized assessment tool has been introduced. In the United States, the ACGME and the American Board of Anesthesiology jointly released the Regional Anesthesiology and Acute Pain Medicine Milestone Project to assess UGRA competencies [60]. Although this assessment was created for accredited regional anesthesiology fellowship programs, the milestones can be potentially modified and implemented as part of a UGRA curriculum to evaluate residents’ knowledge, interactions with patients and other health care providers, technical skills, and professionalism. Proficiency in each competency is measured by achievement of milestones that are categorized into five levels. Level 1 indicates performance expected of a fellow (or resident) at the beginning of their training and level 5 denotes performance of a clinician who has been in independent practice for several years. For technical skills, the primary measure of milestone achievement is the level of supervision required to successfully perform a procedure in a clinical setting. To standardize attainment of technical skill milestones (i.e., progression from one level to the next), educators can consider incorporating checklists and/or GRS to provide consistent and objective requirements for advancement.

Feedback is a critical learning tool for residents during all stages of UGRA skill acquisition [7]. With feedback, novice learners can improve performance time of UGRA tasks, decrease number of needle passes, and reduce errors [19]. Simulation-based training that combines deliberate practice with feedback has been shown to improve residents’ block performance and success rate in a clinical setting [25,61]. It also has been observed that learning of advanced or complex UGRA procedures requires feedback from experienced instructors [50]. The quality of feedback by educators may be even more effective than the fidelity of the simulation training in improving novice performance [46]. Conversely, simulation training can provide an optimal environment for residents who require time to assimilate new knowledge and learn from internal feedback [7] and self-reflection [51] (i.e., independent deliberate practice). Residents who underwent self-guided practice of UGRA in a hybrid simulator performed equally well when assessed by a checklist and GRS compared to residents who received coaching during simulation training [62]. This finding supports a prior observation that excessive feedback during task training or procedural performance can result in dependence on external feedback and decrease in skill retention [7,19].

The various types and timing of feedback and their application to UGRA have been previously described by Slater et al. [7]. Although further studies are needed to elucidate the optimal feedback model for resident learning of UGRA [3,19], educators should take an individualized approach since each resident will have different aptitudes, experiences, and learning preferences. Prior to training sessions, learning objectives should be clearly delineated and feedback should focus on specific tasks with emphasis placed on “constructive criticism, identification of weaknesses, problem-solving, and positive reinforcement of the resident’s technique” [7].

In novices, skill attrition can occur rapidly after gaining initial proficiency in UGRA tasks [19,34], and frequent exposure has been identified as an essential element for learning UGRA [11]. For acquisition and retention of technical skills, two educational models have been investigated: massed practice in which residents participate in a consolidated training session and a distributed model that spaces training sessions over a period of time [73]. Although the effects of massed versus distributed practice can vary on the type and complexity of the UGRA task [7,35] and need to be further delineated in anesthesiology residents, these training models have been studied more extensively in surgery residents who also experience technical skill decay in a short period of time without continued practice [74,75]. Simulation-based training was adopted early by the surgery community to facilitate learning of laparoscopic skills [76] and continues to be used widely across surgical specialties [22]. In a recent systematic review comparing massed versus distributed practice for retention of surgery-related technical skills, novice learners who participated in spaced practice sessions performed better on retention tests than novices who underwent massed practice [77]. However, the effects of distributed learning on skill maintenance for novices can also be influenced by the quality of the practice sessions [78]. Simulation-based UGRA education has been shown to result in greater retention of knowledge compared to non-simulation teaching [25]; however, extrapolating from the surgical literature, anesthesiology residents will likely require periodic retraining through simulated practice to maintain technical proficiency. The ideal time interval between training sessions remains unknown at this time for UGRA and will likely vary for each resident and skill set. According to the surgery literature, however, technical skills may decline noticeably after three to six months [74,79].

Motivating residents to participate in regularly scheduled training can be challenging due to demands of residency and time constraints. Gamification of a UGRA curriculum can be an innovative modality to encourage residents to seek independent learning and simulated practice outside of required didactics and clinical rotations. A medical knowledge competition using a Web-based question-bank [64] or Twitter [69] to assign daily multiple-choice or open-ended questions resulted in increased academic reading, retention of knowledge, and standardized in-training exam scores. Similar gamification strategies can be considered to engage anesthesiology residents in UGRA-related knowledge questions even when they are not on a dedicated regional anesthesia rotation. Likewise, incentives offered by gamification can also compel residents to take advantage of available simulation equipment to engage in deliberate practice in their own time after completion of clinical responsibilities [80]. As part of resident training in point-of-care ultrasound, the Society for Academic Emergency Medicine hosts an annual, four-hour, interactive competition called the “SonoGames” [81] that has been shown to increase competency, enthusiasm, and clinical use of ultrasound in participating residents [70]. For cardiothoracic surgery residents, the implementation of an annual, national competition for technical and cognitive skills assessment motivated residents to engage in simulation training and increased their utilization of a standardized educational curriculum to prepare for the live contest [82]. Gamification of simulation training has yet to be explored for UGRA, but successful integration of game design elements can likely offer anesthesiology residents an interactive learning environment that can promote self-initiated learning and retention of skills.

Residency programs with limited resources can consider alternative learning opportunities for residents. Remote simulation teaching in collaboration with other institutions has been described and consists of tele-simulation workshops incorporating live and simulation model scanning, didactics, and self-directed practice sessions [52]. Additionally, residency programs can support resident participation in programs like the UGRA Education and Clinical Training Portfolio offered by ASRA and American Society of Anesthesiology (http://www.asahq.org) or the European Diploma for Regional Anesthesia and Acute Pain Management endorsed by ESRA (http://academy.esraeurope.org), both of which require completion of didactics and workshops, a minimum number of clinical procedures, and standardized examinations as part of their certification process.