Overview

Regional anaesthesia is an important component of modern perioperative care, providing effective analgesia while reducing opioid use and improving recovery. The use of ultrasound guidance has significantly improved the safety and accuracy of nerve blocks by allowing clinicians to visualise anatomical structures in real time. However, identifying nerves on ultrasound can still be challenging due to complex anatomy, variable image quality, and operator experience.

I have had the pleasure to experience new groundbreaking AI technologies that are emerging in the area of regional ultrasound guided anaesthesia. AI-assisted ultrasound systems analyse images in real time and highlight key anatomical structures such as nerves and vessels. Early research suggests these tools may improve anatomical recognition, support trainee learning, and enhance scanning performance.

Healthcare in Europe – “A breakthrough in real-time ultrasound guidance for regional anesthesia.”https://healthcare-in-europe.com/en/news/a-breakthrough-in-real-time-ultrasound-guidance-for-regional-anesthesia.html

Why Nerve Localisation Is Difficult

Ultrasound-guided regional anaesthesia has dramatically improved the safety and accuracy of nerve blocks. However, identifying nerves and anatomical landmarks on ultrasound remains challenging, particularly for inexperienced practitioners.

Several factors contribute to this difficulty. First, ultrasound images often provide limited contrast between nerves and surrounding tissues, making structures difficult to distinguish. Additionally, technical factors such as poor needle visibility, deep anatomical targets, or patient characteristics such as obesity can further complicate image interpretation.

Ultrasound-guided blocks require clinicians to simultaneously interpret sonographic anatomy, manipulate the probe, and guide the needle toward the target structure. This complex visuospatial task demands significant experience and pattern recognition. As a result, the learning curve for regional anaesthesia can be steep, and incorrect interpretation of anatomy may lead to complications such as vascular puncture, nerve injury, or block failure.

What Is AI-Assisted Ultrasound?

AI-assisted ultrasound refers to the use of machine learning algorithms to analyse ultrasound images and identify anatomical structures in real time.

Most systems rely on deep learning neural networks trained on large datasets of annotated ultrasound images. These algorithms learn to recognise visual patterns associated with nerves, vessels, muscles, and fascial planes. Once trained, the system can analyse live ultrasound images and overlay colour highlights on key anatomical structures, helping clinicians interpret the image more easily.

In regional anaesthesia, AI tools may assist clinicians by:

• Identifying nerves and surrounding anatomy
  

• Highlighting critical safety structures such as vessels or pleura
  

• Improving ultrasound image interpretation
  

• Assisting with needle localisation and trajectory planning.
  

AI-assisted systems function as decision-support tools, augmenting the clinician’s interpretation rather than replacing clinical judgement. Their goal is to enhance anatomical recognition and improve procedural accuracy during nerve blocks.

Br J Anaesth. 2022 Aug 18;130(2):217–225. doi: 10.1016/j.bja.2022.06.031

What Does the Evidence Show?

Emerging research suggests that AI-assisted ultrasound may improve ultrasound scanning performance, particularly among less experienced clinicians.

A prospective study evaluating an assistive AI ultrasound device found that non-expert anaesthetists were more likely to obtain the correct block view when using AI assistance. In this study, the correct block view was obtained in 90.3% of scans with AI compared with 75.1% without AI assistance.

Similarly, correct identification of sonographic anatomical structures was significantly higher when AI support was used (88.8% vs 77.4% without AI).

These findings suggest that AI may enhance both image acquisition and interpretation, two critical steps in ultrasound-guided nerve blocks.

Broader reviews of the literature have also identified several potential benefits of AI-assisted ultrasound. These include improved identification of anatomical landmarks, enhanced visualisation of needle advancement, and optimisation of ultrasound image interpretation. AI tools may therefore help reduce complications such as injury to surrounding structures or incorrect needle placement.

However, despite promising early results, the current body of evidence remains relatively limited, and further large-scale clinical trials are required to confirm whether these technologies improve patient outcomes.

Expert global rating score. Distribution of all expert global rating scores, showing a breakdown of scans performed with or without ScanNav Anatomy Peripheral Nerve Block. PNB, Peripheral Nerve Block.

How AI Could Transform Regional Anaesthesia Training

One of the most exciting potential applications of AI-assisted ultrasound is in education and training.

Learning regional anaesthesia requires the development of strong sono-anatomy recognition skills, which traditionally develop through repeated scanning and expert supervision. AI tools could accelerate this learning process by providing real-time anatomical guidance during ultrasound scanning.

For trainees, AI systems may:

• Help identify correct anatomical landmarks during scanning
  

• Reinforce recognition of normal sonographic anatomy
  

• Improve confidence during early learning stages
  

• Provide immediate visual feedback.
  

Studies have suggested that AI assistance may help non-expert clinicians improve their ability to acquire correct ultrasound views and recognise anatomical structures, which could shorten the learning curve for ultrasound-guided blocks.

More broadly, AI-assisted ultrasound could become an important component of technology-enhanced regional anaesthesia training, alongside simulation, augmented reality, and ultrasound-guided training platforms.

Limitations and Concerns of AI-Assisted Ultrasound

Despite the enthusiasm surrounding AI-assisted ultrasound, several limitations and concerns remain.

First, the current evidence base is still developing. Reviews of the literature highlight that many studies involve small sample sizes or experimental settings, and high-quality randomised controlled trials are still lacking.

Another important concern is over-reliance on AI systems. While AI can assist with image interpretation, clinicians must still possess a strong understanding of ultrasound anatomy. Incorrect AI identification of anatomical structures could potentially mislead inexperienced users if they rely too heavily on the technology.

Technical limitations also remain. AI systems may struggle in cases with unusual anatomy, poor image quality, or deep anatomical structures, and their performance may vary depending on the ultrasound machine or scanning conditions.

Finally, there are broader issues related to regulation and standardisation of AI devices. Different AI systems may be evaluated using different datasets and performance metrics, making it difficult for clinicians to compare their accuracy and clinical utility.

Addressing these challenges will require collaboration between clinicians, engineers, and regulatory bodies to ensure that AI technologies are implemented safely and effectively in clinical practice.

Conclusion

Artificial intelligence is beginning to reshape how clinicians interpret ultrasound during regional anaesthesia. Early studies suggest that AI-assisted systems can improve the identification of anatomical structures and help clinicians obtain optimal ultrasound views, particularly among less experienced users. By highlighting nerves, vessels, and surrounding anatomy in real time, these technologies have the potential to enhance procedural accuracy and support the learning process for trainees.

However, AI should be viewed as a clinical decision-support tool rather than a replacement for anatomical knowledge or ultrasound expertise. The current evidence base remains limited, and further research is needed to determine whether these systems translate into improved patient outcomes and reduced complications. As the technology continues to evolve, AI-assisted ultrasound may become an increasingly valuable adjunct in regional anaesthesia practice and education.

References

Bowness JS, Burckett-St Laurent D, Hernandez N, Keane PA, Lobo C, Margetts S, et al. Assistive artificial intelligence for ultrasound image interpretation in regional anaesthesia: an external validation study. Br J Anaesth. 2023;130(2):217-225. doi:10.1016/j.bja.2022.06.031.

Bowness JS, Burckett-St Laurent D, Margetts S, Pawa A, Noble JA, Higham H, et al. Evaluation of the impact of assistive artificial intelligence on ultrasound scanning for regional anaesthesia. Br J Anaesth. 2023;130(2):226-233.

Bowness JS, Lobo C, Burckett-St Laurent D, Noble JA, Pawa A, Higham H, et al. Variability between human experts and artificial intelligence in identification of anatomical structures by ultrasound in regional anaesthesia: a framework for evaluation of assistive artificial intelligence. Br J Anaesth. 2024;132(5):1063-1072.

Healthcare in Europe. A breakthrough in real-time ultrasound guidance for regional anesthesia [Internet]. Healthcare in Europe; [cited 2026 Mar 17]. Available from: A breakthrough in real-time ultrasound guidance for regional anesthesia

Article Reference: Whately, Y. and Stead, M. (2023) ‘Perioperative management of patients on naltrexone’, Australasian anaesthesia 2023. Edited by B. Cheung. doi:https://doi.org/10.60115/11055/1180.

Key Points

• Naltrexone is a long-acting opioid receptor antagonist, used commonly to manage alcohol use disorder.

• Due to its opioid receptor antagonism, naltrexone presents challenges for managing pain in the perioperative period – making patients both resistant to, and have increased sensitivity to the respiratory side effects of opioids.

• It is recommended to discontinue naltrexone 3 days before surgery to ensure effective and safe use of opioid analgesia.

• In emergency cases, additional post op monitoring may be needed, as higher doses of opioid are required to overcome the naltrexone blockade, making patients vulnerable to respiratory side effects.

• In all cases, an individualised and multi-disciplinary approach is recommended for optimal care.

Case

You are an anaesthetic trainee working in a pre-assessment clinic. You see a 45-year-old male patient scheduled for an elective laparoscopic cholecystectomy. The patient has no significant past medical history besides a history of alcohol use disorder, for which he has been on naltrexone 50mg daily for the past 6 months.

He reports good compliance with his medication and has maintained sobriety.

You remember learning that some extra planning and consideration is required with naltrexone but you can’t remember why.

What is Naltrexone

Naltrexone is a competitive opioid receptor antagonist most commonly used in the treatment of alcohol use disorder. It has high mu opioid receptor affinity but does not activate them and blocks opioids from attaching and mediating their effects.

In the treatment of alcohol use disorder, it works by blunting the opioid receptor-mediated reward pathway and blocking the pleasurable effects of endogenous opioids that are released with alcohol consumption. It is also used in opioid abstinence programmes. In other drug combinations and dose formulation, it can be used in weight loss, chronic pain, and severe constipation.

The most common formulation is the daily oral 50mg tablet, which is used in alcohol and opioid dependence. Other formulations of naltrexone include a long-acting surgical implant, monthly depo injection, a combination drug with bupropion, and a low-dose tablet form.

Relevance for the Anaesthetist

Patients taking naltrexone present a significant challenge in managing perioperative pain because of their competitive blockade of opioid analgesics. It reduces the effectiveness of opioids, often necessitating higher doses to achieve adequate pain relief. However, the increased opioid requirement in turn heightens the risk of opioid-related side effects, such as respiratory depression and sedation.

Due to the homeostatic upregulation of opioid receptors that can occur after long-term naltrexone use, patients who have stopped taking naltrexone pre-op remain at increased risk of opioid-induced adverse effects with conventional analgesic doses.

Careful consideration is needed for these cases and planning between the anaesthetist, surgical team, patient, and naltrexone prescriber is essential to ensure the best outcome. As such, timely detection and referral of these patients to multidisciplinary perioperative teams would allow streamlined optimisation, increase team preparedness, prevent unnecessary delays and improve patient outcomes.

Management of Patients for Elective Procedures

If the patient is presenting for a minor procedure with minimal expected postoperative pain, then it is reasonable to continue naltrexone and use non-opioid analgesia. Examples include minor plastics and general surgical cases where combination of local anaesthetic and simple analgesia may be sufficient.

In most cases, where there is an expected need for opioids, oral naltrexone should be stopped at least 24 hours, and ideally 72 hours, prior to surgery. A longer period may be required in renal or hepatic insufficiency and for long-acting formulations. While naltrexone therapy is temporarily discontinued, extra support is recommended as it is a vulnerable time for potential relapse.

Management in Acute or Emergency Cases

In emergency cases, where discontinuation is not feasible, careful planning and implementing an opioid-sparing strategy is essential.

These patients are prone to variability in their response to opioids and must be monitored in a space with a capacity for airway and ventilation support due to the high risk of respiratory depression. If the last dose of naltrexone was taken within 72 hours of surgery, higher doses of opioids will be required for effective pain management. Prioritising alternative pain management techniques through neuraxial or regional anaesthesia, and non-opioid analgesia is favoured in these cases to minimise unpredictable and harmful effects.

Post-operative planning

In the post-op period, the Acute Pain Service, in liaison with the Addiction Medicine service, should be involved to guide the analgesic regime . Determining the optimal time to resume naltrexone requires an individualised, multi-disciplinary approach. The decision must carefully balance the need for effective pain management with the potential risks of restarting naltrexone too soon, as well as the risks of delaying its use, which could hinder the therapeutic benefits it was initially prescribed for. Once the acute pain has resolved and opioids have been discontinued, it is recommended to have at least a 5 day opioid free interval before restarting naltrexone. If there are any doubts or concerns regarding opioid dependence, a naltrexone challenge can be performed to avoid any precipitated withdrawal.

Conclusion

You sit down with your supervisor to discuss the case. You correctly flag your patient with your institution’s Acute Pain service. They agree with your plan for the patient to discontinue naltrexone 3 days before surgery, and adopt an opioid-sparing anaesthetic and to minimise their use post-operatively. You coordinate with the patient, surgeon, and naltrexone prescriber who are all on board..

The case goes well. The Acute Pain Service are involved post-operatively and manage to avoid excess use of opioids following surgery. The patient experiences no opioid-induced sedation or ventilatory impairment.

The patient is safely restarted on his regular medication.

References

Beauchamp GA, Hanisak JL, Amaducci AM, Koons AL, Laskosky J, Maron BM, McLoughlin TM. Perioperative Management of Patients on Maintenance Medication for Addiction Treatment: The Development of an Institutional Guideline. AANA J. 2022;90(1):50-57. PMID: 35076384.

Lane O, Ambai V, Bakshi A, et al Alcohol use disorder in the perioperative period: a summary and recommendations for anesthesiologists and pain physicians. Regional Anesthesia & Pain Medicine 2024;49:621-627.

Whately, Y. and Stead, M. ‘Perioperative management of patients on naltrexone’, Australasian anaesthesia 2023. Edited by B. Cheung. doi:https://doi.org/10.60115/11055/1180.

Key reference:

Verret, P et al (2024). Intraoperative pharmacological opioid minimization strategies and patient-centred outcomes after surgery: A scoping review. British Journal of Anaesthesia, 132(4), 758-770. https://www.bjanaesthesia.org/article/S0007-0912(24)00009-6/fulltext

Quick summary:

• Intraoperative opioid minimisation forms part of the broader multidisciplinary effort to reduce opioid-related complications, misuse, and overuse at patient, community, and health system levels.

• Robust evidence supporting novel opioid-sparing “balanced” anaesthesia techniques in patient-centred outcomes remains lacking

• Based on the evidence available, the scoping review identified three promising analgesia methods for opioid minimisation:

  • dexmedetomidine,

  • systemic lidocaine

  • COX-2 inhibitors.

• Less promising opioid alternatives investigated included ketamine, paracetamol, and gabapentinoids.

• There is limited research into the impacts on high-risk population groups.

  • 3% of studies investigated geriatric surgical populations.

  • <1% of studies investigated patients with either a chronic pain history or preexisting long-term opioid use.

Preamble:

You are an anaesthesia trainee about to review Mr. LC for your morning list. He is a 60-year-old gentleman, BMI 27, here for his elective laparoscopic cholecystectomy. He has no significant past anaesthetic complications or postoperative nausea and vomiting. He is otherwise fit and well apart from a worsening chronic lower back pain which is currently managed with paracetamol and ibuprofen. .

“I’m scared that my back will kill me after the surgery. Any chance you can give me some strong painkillers to get me through the surgery and going home?

You consider Mr. LC’s request and raise this with your consultant, correctly highlighting the potential risks and benefits of utilising opioids intraoperatively for this patient. You ask if there are potential alternatives that can minimise Mr. LC’s opioid use.

Introduction

Opioid minimisation has gained increasing traction in light of the escalating health burden of problematic opioid misuse and overdose-related morbidity and mortality, stemming in part from the pervasive overuse of prescription opioids across our health service. As one of the most frequent prescribers, anaesthetists and pain clinicians hold key responsibilities in opioid stewardship and opioid-sparing practice. However, it would be remiss to ignore the therapeutic benefit opioids offer for acute surgical pain, its vital role in multimodal anaesthesia, and post-operative function and recovery. As such the move to reduce opioid usage is not simple.

Table 1. List of some of the potential risks and benefits of opioid use

Discussion

The decision to utilise perioperative opioids requires careful consideration of patient, surgical, and anaesthetic-related factors relevant to each case.

For Mr. LC, the surgical-related factors in this case of intra-abdominal surgery include the increased risk of postoperative ileus/ pseudo-obstruction making the side effects of nausea, vomiting, and constipation particularly detrimental.

From the anaesthetic and pain management perspective, Mr. LC’s postoperative abdominal pain as well as his preexisting chronic back pain may make deep breathing and mobilisation challenging, meaning that adequate opioid analgesia may be necessary to promote patient comfort, function, and post-operative recovery. Appropriate opioid management of acute post-surgical pain is also important in minimising development of postoperative chronic pain. However, this must be balanced against the short-term and long-term adverse effects of opioids as aforementioned, with a clear immediate plan for symptom management and post-operative monitoring, as well as a clear pathway for timely opioid de-escalation and community follow-up. Patient education and setting of expectations also form part of the biopsychosocial model of pain management, where patients must be counselled on the lack of evidence of opioids for chronic non-cancerous back pain to avert the risk of opioid dependence.

The ideal solution would be for an opioid-sparing alternative that would offer adequate pain relief. Although requiring more evidence, this scoping review by Verret et al. (2024) into the potential replacement therapies offered three promising substitutes; dexmedetomidine, systemic lidocaine, and COX-2 inhibitors. Interestingly, other modalities often reached for in the operating theatre including ketamine, paracetamol, and gabapentinoids offered less encouraging results (see Table 2). According to this paper, there is evidence of change within this field, however robust research is lacking due to, in part, significant inter-institutional heterogeneity in opioid-sparing practice and paucity of multicentre, high-quality trials.

Table 2. Summary of analgesics discussed in the scoping review

Ultimately, more research is required to determine an appropriate change to practice that would lead to improved patient outcomes. This would require holistic review of patient-centred outcomes along with more objective outcomes such as long-term analgesic requirements.

Notably, looking into short-term or long-term opioid use alone without patient-centred outcomes may be misleading. Opioid requirement may not be a consequence of opioid tolerance or dependence but rather the result of high analgesia requirements. Moreover, opioid use itself may not necessarily lead to poorer health outcomes when compared to alternative therapies. Thus, clinical context is likely required in conjunction with opioid use parameters in order to determine whether there are truly negative impacts of opioids compared to substitute analgesics.

There are indeed benefits of opioid use intraoperatively including haemodynamic stability during general anaesthetic as well as the increased rapid emergence through a reduced required sedative dose as there can be an additive effect of opioids with other hypnotic agents.

Conclusion

You come back to the anaesthetic bay and discuss your pain plan with Mr. LC. You explain that you will be giving him pain relief with opioids during and immediately after his operation as part of his anaesthesia, but also a range of other analgesics such as paracetamol and NSAIDs as part of a multimodal approach to limit the amount of strong opioids needed. You highlight some of the common side effects of opioids, which you hope to control with PRNs for his nausea and vomiting and constipation. You mention that although there are other non-opioid alternatives, they currently don’t have the evidence for you to confidently use safely with proven effectiveness. You set some expectations with Mr. LC, that the aim is not to get Mr. LC pain-free, but to a level that will allow him to do simple tasks and aid his post-op recovery.

Regarding his discharge, you reiterate that opioids, although effective in the short-term for his surgical pain, have no evidence that it would be useful for his chronic back pain, and that long-term use may cause more harm. You recommend that Mr. LC has a discussion with his GP and explore other strategies such as physiotherapy.

Mr. LC is understanding of your explanation and is thankful for your careful consideration of his situation.

…..

More research with subjective outcomes is required to ascertain suitable substitutes to opioids which optimise patient recovery.

Dexmedetomidine, systemic lidocaine, and COX-2 inhibitors were identified as likely promising analgesic candidates.

There is a potential benefit to reducing opioid use given their associated significant adverse effects. However, opioids do offer many desirable properties including haemodynamic stability intraoperatively as well as strong analgesia intraoperatively making this balance difficult.

References:

Australian Medicines Handbook Pty Ltd. (2024). Australian Medical Handbook.

Carley, M. et al. (2021). Pharmacotherapy of the prevention of chronic pain after surgery in adults: An updated systematic review and meta-analysis. Anesthesiology, 135 (2), 304-325 https://pubmed.ncbi.nlm.nih.gov/34237128/

DrugBank (2005). Acetaminophen. Retrieved from https://go.drugban k.com/drugs/DB00316

Foo, A et al. (2020). The use of intravenous lidocaine for postoperative pain and recovery: International consensus statement on efficacy and safety. Anaethesia, 76(2), 238-250. https://associationofanaesthetists-publications.onlinelibrary.wiley.com/doi/10.1111/anae.15270

The Lancet (2019). Global patterns of opioid use and dependence: Harms to populations, interventions, and future action. The Lancet, 394(10208), 1560-1579. https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(19)32229-9/abstract

Verret, P et al (2024). Intraoperative pharmacological opioid minimization strategies and patient-centred outcomes after surgery: A scoping review. British Journal of Anaesthesia, 132(4), 758-770. https://www.bjanaesthesia.org/article/S0007-0912(24)00009-6/fulltext

Verret, P et al (2020). Perioperative use of gabapentinoids for the management of postoperative acute pain: A systematic review and meta-analysis. Anesthesiology, 133, 265-279. https://pubs.asahq.org/anesthesiology/article/133/2/265/109137/Perioperative-Use-of-Gabapentinoids-for-the