Standardizing nomenclature in regional anesthesia: an ASRA-ESRA Delphi consensus study of upper and lower limb nerve blocks

BACKGROUND

Inconsistent nomenclature and anatomical descriptions of regional anesthetic techniques hinder scientific communication and engender confusion; this in turn has implications for research, education and clinical implementation of regional anesthesia. Having produced standardized nomenclature for abdominal wall, paraspinal and chest wall regional anesthetic techniques, we aimed to similarly do so for upper and lower limb peripheral nerve blocks.

METHODS

We performed a three-round Delphi international consensus study to generate standardized names and anatomical descriptions of upper and lower limb regional anesthetic techniques. A long list of names and anatomical description of blocks of upper and lower extremities was produced by the members of the steering committee. Subsequently, two rounds of anonymized voting and commenting were followed by a third virtual round table to secure consensus for items that remained outstanding after the first and second rounds. As with previous methodology, strong consensus was defined as ≥75% agreement and weak consensus as 50%-74% agreement.

RESULTS

A total of 94, 91 and 65 collaborators participated in the first, second and third rounds, respectively. We achieved strong consensus for 38 names and 33 anatomical descriptions, and weak consensus for five anatomical descriptions. We agreed on a template for naming peripheral nerve blocks based on the name of the nerve and the anatomical location of the blockade and identified several areas for future research.

CONCLUSIONS

We achieved consensus on nomenclature and anatomical descriptions of regional anesthetic techniques for upper and lower limb nerve blocks, and recommend using this framework in clinical and academic practice. This should improve research, teaching and learning of regional anesthesia to eventually improve patient care.

Pilot Study Exploring if an Augmented Reality NeedleTrainer Device Improves Novice Performance of a Simulated Central Venous Catheter Insertion on a Phantom

Introduction Needle insertion and visualisation skills needed for ultrasound (US)-guided procedures can be challenging to acquire. The novel NeedleTrainer device superimposes a digital holographic needle on a real-time US image display without puncturing a surface. The aim of this randomised control study was to compare the success of trainees performing a simulated central venous catheter insertion on a phantom either with or without prior NeedleTrainer device practice. Methods West of Scotland junior trainees who had not performed insertion of a central venous catheter were randomised into two groups (n=20). Participants undertook standardized online training through a pre-recorded video and training on how to handle a US probe. Group 1 had 10 minutes of supervised training with the NeedleTrainer device. Group 2 were a control group. Participants were assessed on needle insertion to a pre-defined target vein in a phantom. The outcome measures were the time taken for needle placement (secs), number of needle passes (n), operator confidence (0-10), assessor confidence (0-10), and NASA task load index score. Results The mean mental demand score in the control group was 7.65 (SD 3.5) compared to 12.8 (SD 2.2, p=0.005) in the NeedleTrainer group. There was no statistical difference between the groups in any of the other outcome measures. Discussion This was a small pilot study, and small participant numbers may have impacted the statistical significance. There is natural variation of skill within participants that could not have been controlled for. The difference in pressure needed using the NeedleTrainer compared to a real needle may impact the outcome measures.

Recommendations for anatomical structures to identify on ultrasound for the performance of intermediate and advanced blocks in ultrasound-guided regional anesthesia

Recent recommendations describe a set of core anatomical structures to identify on ultrasound for the performance of basic blocks in ultrasound-guided regional anesthesia (UGRA). This project aimed to generate consensus recommendations for core structures to identify during the performance of intermediate and advanced blocks. An initial longlist of structures was refined by an international panel of key opinion leaders in UGRA over a three-round Delphi process. All rounds were conducted virtually and anonymously. Blocks were considered twice in each round: for “orientation scanning” (the dynamic process of acquiring the final view) and for “block view” (which visualizes the block site and is maintained for needle insertion/injection). A “strong recommendation” was made if ≥75% of participants rated any structure as “definitely include” in any round. A “weak recommendation” was made if >50% of participants rated it as “definitely include” or “probably include” for all rounds, but the criterion for strong recommendation was never met. Structures which did not meet either criterion were excluded. Forty-one participants were invited and 40 accepted; 38 completed all three rounds. Participants considered the ultrasound scanning for 19 peripheral nerve blocks across all three rounds. Two hundred and seventy-four structures were reviewed for both orientation scanning and block view; a “strong recommendation” was made for 60 structures on orientation scanning and 44 on the block view. A “weak recommendation” was made for 107 and 62 structures, respectively. These recommendations are intended to help standardize teaching and research in UGRA and support widespread and consistent practice.

Identifying anatomical structures on ultrasound: assistive artificial intelligence in ultrasound-guided regional anesthesia

Ultrasound-guided regional anesthesia involves visualizing sono-anatomy to guide needle insertion and the perineural injection of local anesthetic. Anatomical knowledge and recognition of anatomical structures on ultrasound are known to be imperfect amongst anesthesiologists. This investigation evaluates the performance of an assistive artificial intelligence (AI) system in aiding the identification of anatomical structures on ultrasound. Three independent experts in regional anesthesia reviewed 40 ultrasound scans of seven body regions. Unmodified ultrasound videos were presented side-by-side with AI-highlighted ultrasound videos. Experts rated the overall system performance, ascertained whether highlighting helped identify specific anatomical structures, and provided opinion on whether it would help confirm the correct ultrasound view to a less experienced practitioner. Two hundred and seventy-five assessments were performed (five videos contained inadequate views); mean highlighting scores ranged from 7.87 to 8.69 (out of 10). The Kruskal-Wallis H-test showed a statistically significant difference in the overall performance rating (χ² [6] = 36.719, asymptotic p < 0.001); regions containing a prominent vascular landmark ranked most highly. AI-highlighting was helpful in identifying specific anatomical structures in 1330/1334 cases (99.7%) and for confirming the correct ultrasound view in 273/275 scans (99.3%). These data demonstrate the clinical utility of an assistive AI system in aiding the identification of anatomical structures on ultrasound during ultrasound-guided regional anesthesia. Whilst further evaluation must follow, such technology may present an opportunity to enhance clinical practice and energize the important field of clinical anatomy amongst clinicians.

A marking of the cricothyroid membrane with extended neck returns to correct position after neck manipulation and repositioning

BACKGROUND

Emergency front of neck airway access by anaesthetists carries a high failure rate and it is recommended to identify the cricothyroid membrane before induction of anaesthesia in patients with a predicted difficult airway. We have investigated whether a marking of the cricothyroid membrane done in the extended neck position remains correct after the patient's neck has been manipulated and subsequently repositioned.

METHODS

The subject was first placed in the extended head and neck position and had the cricothyroid membrane identified and marked with 3 methods, palpation, 'laryngeal handshake' and ultrasonography and the distance from the suprasternal notch to the cricothyroid membrane was measured. The subject then moved off the table and sat on a chair and subsequently returned to the extended neck position and examinations were repeated.

RESULTS

Skin markings of all 11 subjects lay within the boundaries of the cricothyroid membrane when the subject was repositioned back to the extended neck position and the median difference between the two measurements of the distance from the suprasternal notch was 0 mm (range 0-2 mm).

CONCLUSION

The cricothyroid membrane can be identified and marked with the subject in the extended neck position. Then the patient's position can be changed as needed, for example to the 'sniffing' neck position for conventional intubation. If a front of neck airway access is required during subsequent airway management, the patient can be returned expediently to the extended-neck position, and the marking of the centre of the membrane will still be in the correct place.

Arterial anatomy of the anterior abdominal wall: Ultrasound evaluation as a real-time guide to percutaneous instrumentation

INTRODUCTION

Instrumenting the anterior abdominal wall carries a potential for vascular trauma. We previously assessed the presence, position, and size of the anterior abdominal wall superior and inferior (deep) epigastric arteries with computed tomography (CT). We now present a study using ultrasound (US) assessment of these arteries, to evaluate its use for real time guidance of percutaneous procedures involving the rectus sheath.

MATERIALS AND METHODS

Twenty-four participants (mean age 67.9 ± 9 years, 15 M:9 F [62:38%]) were assessed with US at three axial planes on the anterior abdominal wall: transpyloric plane (TPP), umbilicus, and anterior superior iliac spine (ASIS).

RESULTS

An artery was visible least frequently at the TPP (62.5 - 45.8%), compared with the umbilicus (95.8-100%) and ASIS (100%), on the left, χ² (2) = 20.571; p < .001, and right, χ² (2) = 27.842; p < .001, with a moderate strength association (Cramer's V = 0.535 [left] and 0.622 [right]). Arteries were most commonly observed within the rectus abdominis muscle at the level of the TPP and umbilicus, but posterior to the muscle at the level of the ASIS (95.8-100%). As with the CT study, the inferior epigastric artery was observed to be larger in diameter, start more laterally, and move medially as it coursed superiorly.

CONCLUSIONS

These data corroborate our previous results and suggest that the safest level to instrument the rectus sheath (with respect to vascular anatomy) is at the TPP. Such information may be particularly relevant to anesthetists performing rectus sheath block and surgeons during laparoscopic port insertion.

Ultrasound-Guided Regional Anaesthesia: Visualising the Nerve and Needle

Regional anaesthesia involves targeting specific peripheral nerves with local anaesthetic. It facilitates the delivery of anaesthesia and analgesia to an increasingly complex, elderly and co-morbid patient population. Regional anaesthesia practice has been transformed by the use of ultrasound, which confers advantages such as accuracy of needle placement, visualisation of local anaesthetic spread, avoidance of intraneural injection and the ability to accommodate for anatomical variation.An US beam is generated by the application of electrical current to an array of piezoelectric crystals, causing vibration and consequential production of high-frequency sound waves. The sound energy is reflected at tissue interfaces, detected by the piezoelectric crystals in the ultrasound probe, and most frequently displayed as a 2D image.Optimising image acquisition involves selection of the appropriate US frequency: this represents a trade-off between image resolution (better with high frequency) and tissue penetration/beam attenuation (better with low frequency). Altering alignment, rotation and tilt of the probe is often required to optimise the view as nerves are best visualised when the ultrasound beam is directly perpendicular to their fibres. Adjusting the focus, depth, and gain (brightness) of the image display can also help in this matter.Three key challenges exist in regional anaesthesia; image optimisation, image interpretation (nerve visualisation) and needle visualisation. There are characteristic sonographic appearances of the nerve structures for peripheral nerve blocks, as discussed in this chapter, and the above techniques can be used to enhance their appearance. Much research has been done, and is ongoing, with the aim of improving needle visualisation; this is also reviewed. Image interpretation requires the application of anatomical knowledge and understanding of the typical sonographic appearance of different tissues (as well as the needle). Years of practice are required to attain expertise, although it is hoped that continuing advances in nerve and needle visualisation, as described in this chapter, will expedite that process.

Arterial Anatomy of the Anterior Abdominal Wall: Evidence-Based Safe Sites for Instrumentation Based on Radiological Analysis of 100 Patients

Multiple medical interventions require percutaneous instrumentation of the anterior abdominal wall, all of which carry a potential for vascular trauma. We assessed the presence, position, and size of the anterior abdominal wall superior and inferior (deep) epigastric arteries to determine the safest site with respect to vascular anatomy of the rectus sheath. In a review of 100 arterial phase, contrast-enhanced abdominal computed tomography scans, anterior abdominal wall arteries were assessed bilaterally at three axial planes: transpyloric, umbilicus, and anterior superior iliac spine (ASIS). The mean age of patients was 69.2 years (SD ± 15), with 62 male and 38 female. An artery was visible least frequently at the transpyloric plane (5%), compared with the umbilicus (72-79%) and ASIS (93-96%), on the left (χ² (4) = 207.272; P < 0.001) and right (χ² (4) = 198.553; P < 0.001), with a moderate strength association (Cramer's V = 0.588 (left) and 0.575 (right)). The arteries were most commonly observed within the rectus abdominis muscle at the level of the umbilicus and ASIS on both sides (62-68%). The inferior epigastric artery was observed to be larger in diameter, start more laterally, and move medially as it travelled superiorly. These data suggest that the safest site to instrument the rectus sheath, with respect to vascular anatomy, is at the transpyloric plane. This information on anatomical variation of the anterior abdominal wall vasculature may be of particular interest to anesthetists performing rectus sheath block and surgeons during laparoscopic port insertion. Clin. Anat. 33:350-354, 2020. © 2019 Wiley Periodicals, Inc.