Guidelines for Regional Anesthesia Fellowship Training

What Is the Risk of Postoperative Neurologic Symptoms After Regional Anesthesia in Upper Extremity Surgery? A Systematic Review and Meta-analysis of Randomized Trials

BACKGROUND

The risk of neurologic symptoms after regional anesthesia in orthopaedic surgery is estimated to approach 3%, with long-term deficits affecting 2 to 4 per 10,000 patients. However, current estimates are derived from large retrospective or observational studies that are subject to important systemic biases. Therefore, to harness the highest quality data and overcome the challenge of small numbers of participants in individual randomized trials, we undertook this systematic review and meta-analysis of contemporary randomized trials.

QUESTIONS/PURPOSES

In this systematic review and meta-analysis of randomized trials we asked: (1) What is the aggregate pessimistic and optimistic risk of postoperative neurologic symptoms after regional anesthesia in upper extremity surgery? (2) What block locations have the highest and lowest risk of postoperative neurologic symptoms? (3) What is the timing of occurrence of postoperative neurologic symptoms (in days) after surgery?

METHODS

We searched Ovid MEDLINE, Embase, Cochrane Central Register of Controlled Trials and Cochrane Database of Systematic Reviews, Web of Science, Scopus, and PubMed for randomized controlled trials (RCTs) published between 2008 and 2019 that prospectively evaluated postoperative neurologic symptoms after peripheral nerve blocks in operative procedures. Based on the Grading of Recommendations, Assessment, Development, and Evaluation guidance for using the Risk of Bias in Non-Randomized Studies of Interventions tool, most trials registered a global rating of a low-to-intermediate risk of bias. A total of 12,532 participants in 143 trials were analyzed. Data were pooled and interpreted using two approaches to calculate the aggregate risk of postoperative neurologic symptoms: first according to the occurrence of each neurologic symptom, such that all reported symptoms were considered mutually exclusive (pessimistic estimate), and second according to the occurrence of any neurologic symptom for each participant, such that all reported symptoms were considered mutually inclusive (optimistic estimate).

RESULTS

At any time postoperatively, the aggregate pessimistic and optimistic risks of postoperative neurologic symptoms were 7% (915 of 12,532 [95% CI 7% to 8%]) and 6% (775 of 12,532 [95% CI 6% to 7%]), respectively. Interscalene block was associated with the highest risk (13% [661 of 5101] [95% CI 12% to 14%]) and axillary block the lowest (3% [88 of 3026] [95% CI 2% to 4%]). Of all symptom occurrences, 73% (724 of 998) were reported between 0 and 7 days, 24% (243 of 998) between 7 and 90 days, and 3% (30 of 998) between 90 and 180 days. Among the 31 occurrences reported at 90 days or beyond, all involved sensory deficits and four involved motor deficits, three of which ultimately resolved.

CONCLUSION

When assessed prospectively in randomized trials, the aggregate risk of postoperative neurologic symptoms associated with peripheral nerve block in upper extremity surgery was approximately 7%, which is greater than previous estimates described in large retrospective and observational trials. Most occurrences were reported within the first week and were associated with an interscalene block. Few occurrences were reported after 90 days, and they primarily involved sensory deficits. Although these findings cannot inform causation, they can help inform risk discussions and clinical decisions, as well as bolster our understanding of the evolution of postoperative neurologic symptoms after regional anesthesia in upper extremity surgery. Future prospective trials examining the risks of neurologic symptoms should aim to standardize descriptions of symptoms, timing of evaluation, classification of severity, and diagnostic methods.

LEVEL OF EVIDENCE

Level I, therapeutic study.

The ultrasound-guided proximal intercostal block: anatomical study and clinical correlation to analgesia for breast surgery

Background

The ultrasound-guided proximal intercostal block (PICB) is performed at the proximal intercostal space (ICS) between the internal intercostal membrane (IIM) and the endothoracic fascia/parietal pleura (EFPP) complex. Injectate spread may follow several routes and allow for multilevel trunk analgesia. The goal of this study was to examine the anatomical spread of large-volume PICB injections and its relevance to breast surgery analgesia.

Methods

Fifteen two-level PICBs were performed in ten soft-embalmed cadavers. Radiographic contrast mixed with methylene blue was injected at the 2nd(15 ml) and 4th(25 ml) ICS, respectively. Fluoroscopy and dissection were performed to examine the injectate spread. Additionally, the medical records of 12 patients who had PICB for breast surgery were reviewed for documented dermatomal levels of clinical hypoesthesia. The records of twelve matched patients who had the same operations without PICB were reviewed to compare analgesia and opioid consumption.

Results

Median contrast/dye spread was 4 (2–8) and 3 (2–5) vertebral segments by fluoroscopy and dissection respectively. Dissection revealed injectate spread to the adjacent paravertebral space, T3 (60%) and T5 (27%), and cranio-caudal spread along the endothoracic fascia (80%). Clinically, the median documented area of hypoesthesia was 5 (4–7) dermatomes with 100 and 92% of the injections covering adjacent T3 and T5 dermatomes, respectively. The patients with PICB had significantly lower perioperative opioid consumption and trend towards lower pain scores.

Conclusions

In this anatomical study, PICB at the 2nd and 4th ICS produced lateral spread along the corresponding intercostal space, medial spread to the adjacent paravertebral/epidural space and cranio-caudal spread along the endothoracic fascial plane. Clinically, combined PICBs at the same levels resulted in consistent segmental chest wall analgesia and reduction in perioperative opioid consumption after breast surgery. The incomplete overlap between paravertebral spread in the anatomical study and area of hypoesthesia in our clinical findings, suggests that additional non-paravertebral routes of injectate distribution, such as the endothoracic fascial plane, may play important clinical role in the multi-level coverage provided by this block technique.

Nerve blocks or no nerve blocks for pain control after elective hip replacement (arthroplasty) surgery in adults

BACKGROUND

It is estimated that over 300,000 total hip replacements are performed each year in the USA. For European countries, the number of hip replacement procedures per 100,000 people performed in 2007 varied from less than 50 to over 250. To facilitate postoperative rehabilitation, pain must be adequately treated. Peripheral nerve blocks and neuraxial blocks have been proposed to replace or supplement systemic analgesia.

OBJECTIVES

We aimed to compare the relative effects (benefits and harms) of the different nerve blocks that may be used to relieve pain after elective hip replacement in adults.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL, Issue 12, 2016), MEDLINE (Ovid SP) (1946 to December Week 49, 2016), Embase (Ovid SP) (1980 to December week 49, 2016), CINAHL (EBSCO host) (1982 to 6 December 2016), ISI Web of Science (1973 to 6 December 2016), Scopus (from inception to December 2016), trials registers, and relevant web sites.

SELECTION CRITERIA

We included all randomized controlled trials (RCTs) performed in adults undergoing elective primary hip replacement and comparing peripheral nerve blocks to any other pain treatment modality. We applied no language or publication status restrictions.

DATA COLLECTION AND ANALYSIS

Data were extracted independently by two review authors. We contacted study authors.

MAIN RESULTS

We included 51 RCTs with 2793 participants; of these 45 RCTs (2491 participants: peripheral nerve block = 1288; comparators = 1203) were included in meta-analyses. There are 11 ongoing studies and three awaiting classification.Compared to systemic analgesia alone, peripheral nerve blocks reduced: pain at rest on arrival in the postoperative care unit (SMD -1.12, 95% CI -1.67 to -0.56; 9 trials, 429 participants; equivalent to 3.2 on 0 to 10 scale; moderate-quality evidence); risk of acute confusional status: risk ratio (RR) 0.10 95% CI 0.02 to 0.54; 1 trial, 225 participants; number needed to treat for additional benefit (NNTB) 12, 95% CI 11 to 22; very low-quality evidence); pruritus (RR 0.16, 95% CI 0.04 to 0.70; 2 trials, 259 participants for continuous peripheral nerve blocks; NNTB 4 (95% CI 4 to 8); very low-quality evidence); hospital length of stay (SMD -0.75, 95% CI -1.02 to -0.48; very low-quality evidence; 2 trials, 249 participants; equivalent to 0.75 day). Participant satisfaction increased (SMD 0.67, 95% CI 0.45 to 0.89; low-quality evidence; 5 trials, 363 participants; equivalent to 2.4 on 0 to 10 scale). We did not find a difference for the number of participants walking on postoperative day one (very low-quality evidence). Two nerve block-related complications were reported: one local haematoma and one delayed persistent paresis.Compared to neuraxial blocks, peripheral nerve blocks reduced the risk of pruritus (RR 0.33, 95% CI 0.19 to 0.58; 6 trials, 299 participants; moderate-quality evidence; NNTB 6 (95% CI 5 to 9). We did not find a difference for pain at rest on arrival in the postoperative care unit (moderate-quality evidence); number of nerve block-related complications (low-quality evidence); acute confusional status (very low-quality evidence); hospital length of stay (low quality-evidence); time to first walk (low-quality evidence); or participant satisfaction (high-quality evidence).We found that peripheral nerve blocks provide better pain control compared to systemic analgesia with no major differences between peripheral nerve blocks and neuraxial blocks. We also found that peripheral nerve blocks may be associated with reduced risk of postoperative acute confusional state and a modest reduction in hospital length of stay that could be meaningful in terms of cost reduction considering the increasing numbers of procedures performed annually.

AUTHORS' CONCLUSIONS

Compared to systemic analgesia alone, there is moderate-quality evidence that peripheral nerve blocks reduce postoperative pain, low-quality evidence that patient satisfaction is increased and very low-quality evidence for reductions in acute confusional status, pruritus and hospital length of stay .We found moderate-quality evidence that peripheral nerve blocks reduce pruritus compared with neuraxial blocks.The 11 ongoing studies, once completed, and the three studies awaiting classification may alter the conclusions of the review once assessed.

Acute Pain Medicine in the United States: A Status Report

BACKGROUND

Consensus indicates that a comprehensive,multimodal, holistic approach is foundational to the practice of acute pain medicine (APM),but lack of uniform, evidence-based clinical pathways leads to undesirable variability throughout U. S. healthcare systems. Acute pain studies are inconsistently synthesized to guide educational programs. Advanced practice techniques involving regional anesthesia assume the presence of a physician-led, multidisciplinary acute pain service,which is often unavailable or inconsistently applied.This heterogeneity of educational and organizational standards may result in unnecessary patient pain and escalation of healthcare costs.

METHODS

A multidisciplinary panel was nominated through the APM Shared Interest Group of the American Academy of Pain Medicine. The panel met in Chicago, IL, in July 2014, to identify gaps and set priorities in APM research and education.

RESULTS

The panel identified three areas of critical need: 1) an open-source acute pain data registry and clinical support tool to inform clinical decision making and resource allocation and to enhance research efforts; 2) a strong professional APM identity as an accredited subspecialty; and 3) educational goals targeted toward third-party payers,hospital administrators, and other key stake holders to convey the importance of APM.

CONCLUSION

This report is the first step in a 3-year initiative aimed at creating conditions and incentives for the optimal provision of APM services to facilitate and enhance the quality of patient recovery after surgery, illness, or trauma. The ultimate goal is to reduce the conversion of acute pain to the debilitating disease of chronic pain.

Blockade of the mental nerve for lower lip surgery as a safe alternative to general anesthesia in two very old patients

Purpose

Regional anesthesia is gaining popularity with anesthesiologists as it offers superb postoperative analgesia. However, as the sole anesthetic technique in high-risk patients in whom general anesthesia is not preferred, some regional anesthetic possibilities may be easily overlooked. By presenting two cases of very old patients with considerable comorbidities, we would like to bring the mental nerve field block under renewed attention as a safe alternative to general anesthesia and to achieve broader application of this simple nerve block.

Patients and methods

Two very old male patients (84 and 91 years) both presented with an ulcerative lesion at the lower lip for which surgical removal was scheduled. Because of their considerable comorbidities and increased frailty, bilateral blockade of the mental nerve was considered superior to general anesthesia. As an additional advantage for the 84-year-old patient, who had a pneumonectomy in his medical history, the procedure could be safely performed in a beach-chair position to prevent atelectasis and optimize the ventilation/perfusion ratio of the single lung. The mental nerve blockades were performed intraorally in a blind fashion, after eversion of the lip and identifying the lower canine. A 5 mL syringe with a 23-gauge needle attached was passed into the buccal mucosa until it approximated the mental foramen, where 2 mL of lidocaine 2% with adrenaline 1:100.000 was injected. The other side was anesthetized in a similar fashion.

Results

Both patients underwent the surgical procedure uneventfully under a bilateral mental nerve block and were discharged from the hospital on the same day.

Conclusion

A mental nerve block is an easy-to-perform regional anesthetic technique for lower lip surgery. This technique might be especially advantageous in the very old, frail patient.

Regional anesthesia practice in Greece: A census report

Background and Aims:

Regional anesthesia (RA) techniques (central neuraxial and peripheral nerve blocks [CNBs and PNBs]) are well-established anesthesia/analgesia modalities. However, information on their nationwide use is sparse. The aim of the survey was to assess the utility of RA techniques in Greece, during 2011.

Materials and Methods:

A nationwide, cross-sectional descriptive survey was conducted (March to June, 2012), using a structured questionnaire that was sent to 128 Greek Anesthesia Departments.

Results:

Sixty-six completed questionnaires (response rate 51.56%) were analyzed. The data corresponded to 187,703 operations and represented all hospital categories and geographical regions of Greece. On the whole, RA was used in 45.5% of performed surgical procedures (85,386/187,703). Spinal anesthesia was the technique of choice (51.9% of all RA techniques), mostly preferred in orthopedics (44.8%). Epidural anesthesia/analgesia (application rate of 23.2%), was mostly used in obstetrics and gynecology (50.4%). Combined spinal-epidural and PNBs were less commonly instituted (11.24% and 13.64% of all RA techniques, respectively). Most PNBs (78.5%) were performed with a neurostimulator, while elicitation of paresthesia was used in 16% of the cases. Conversely, ultrasound guidance was quite limited (5%). The vast majority of consultant anesthesologists (94.49%) were familiar with CNBs, whereas only 46.4% were familiar with PNBs. The main reported limitations to RA application were lack of equipment (58.23%) and inadequate education/training (49.29%).

Conclusion:

Regional modalities were routinely used by Greek anesthesiologists during 2011. Neuraxial blocks, especially spinal anesthesia, were preferred over PNBs. The underutilization of certain RA techniques was attributed to lack of equipment and inadequate training.

Acute pain medicine in anesthesiology

The American Academy of Pain Medicine and the American Society for Regional Anesthesia have recently focused on the evolving practice of acute pain medicine. There is increasing recognition that the scope and practice of acute pain therapies must extend beyond the subacute pain phase to include pre-pain and pre-intervention risk stratification, resident and fellow education in regional anesthesia and multimodal analgesia, as well as a deeper understanding of the pathophysiologic mechanisms that are integral to the variability observed among individual responses to nociception. Acute pain medicine is also being established as a vital component of successful systems-level acute pain management programs, inpatient cost containment, and patient satisfaction scores. In this review, we discuss the evolution and practice of acute pain medicine and we aim to facilitate further discussion on the evolution and advancement of this field as a subspecialty of anesthesiology.

Survey of international regional anesthesia fellowship directors

Background

The scope of regional anesthesia fellowship programs has not been analyzed but may provide insights that could improve fellowship training and standards.

Methods

Regional anesthesia fellowship directors across the world were asked to complete a comprehensive survey that detailed the range of educational and practical experience and attitudes as well as assessment procedures offered in their programs.

Results

The survey response rate was 66% (45/68). Overall, the range of activities and the time and resources committed to education during fellowships is encouraging. A wide range of nerve block experience is reported with most programs also offering acute pain management, research, and teaching opportunities. Only two-thirds of fellowships provide formal feedback. This feedback is typically a formative assessment.

Conclusion

This is the first survey of regional anesthesia fellowship directors, and it illustrates the international scope and continuing expansion of education and training in the field. The results should be of interest to program directors seeking to benchmark and improve their educational programs and to faculty involved in further curriculum development.

Evaluation of education, attitude, and practice of the Turkish anesthesiologists in regional block techniques

BACKGROUND

The demand for regional blocks from both patients and surgeons has significantly increased in anesthesia practice during the last 30 years. Although the studies show that the complications are rare, regional blocks still have serious difficulties which can be prevented by training programs.

OBJECTIVES

The purpose of this study was to determine the factors affecting the educational methods, attitude and practice of the Turkish anesthesiologists in regional blocks during and following residency programs.

PATIENTS AND METHODS

Anesthesiologists were asked to answer a questionnaire. Educational proficiency was determined by at least 50 spinal, 50 epidural and 50 peripheral block applications during residency. Specialists were asked for the numbers of spinal, epidural and peripheral blocks (PBs) they applied in 2009. The mean and median values were calculated.

RESULTS

One hundred and eighty-eight anesthesiologists (84.3 %) agreed to participate in the study. While all participants had made their first attempts in neuraxial blocks (NBs) when they were residents, this ratio was detected as 96.8% for PBs. All participants learned neuraxial and PBs on patients in the operating theater. Education proficiency ratios for spinal, epidural and PBs were 98.1 %, 92.5 % and 62.3 %, respectively. Age, perception of adequate training, nerve block rotation, adequate application in education, following innovations were the factors which significantly affected the number of PBs in practice according to univariate analysis. The participants who consider their applications on NBs were adequate (P = 0.029) and the ones working in state or private hospitals (P = 0.017), applied NBs significantly above the median number.

CONCLUSIONS

Anesthesiologists had adequate education and practice of NB applications but a significant proportion of participants (51.8%) lacked both in PBs applications. We believe that NBs are more easily learned than PBs during residency training program.

The evolution and practice of acute pain medicine

BACKGROUND

In recent years, the field of acute pain medicine (APM) has witnessed a surge in its development, and pain has begun to be recognized not merely as a symptom, but as an actual disease process. This development warrants increased education of residents both in the performance of regional anesthesia as well as in the disease course of acute pain and the biopsychosocial mechanisms that define interindividual variability.

REVIEW SUMMARY

We reviewed the organization and function of the modern APM program. Following a discussion of the nomenclature of acute pain-related practices, we discuss the historical evolution and modern role of APM teams, including the use of traditional, as well as complementary and alternative, therapies for treating acute pain. Staffing and equipment requirements are also evaluated, in addition to the training requirements for achieving expertise in APM. Lastly, we briefly explore future considerations related to the essential role and development of APM.

CONCLUSION

The scope and practice of APM must be expanded to include pre-pain/pre-intervention risk stratification and extended through the phase of subacute pain.

Different Learning Curves for Axillary Brachial Plexus Block: Ultrasound Guidance versus Nerve Stimulation

Little is known about the learning of the skills needed to perform ultrasound- or nerve stimulator-guided peripheral nerve blocks. The aim of this study was to compare the learning curves of residents trained in ultrasound guidance versus residents trained in nerve stimulation for axillary brachial plexus block. Ten residents with no previous experience with using ultrasound received ultrasound training and another ten residents with no previous experience with using nerve stimulation received nerve stimulation training. The novices' learning curves were generated by retrospective data analysis out of our electronic anaesthesia database. Individual success rates were pooled, and the institutional learning curve was calculated using a bootstrapping technique in combination with a Monte Carlo simulation procedure. The skills required to perform successful ultrasound-guided axillary brachial plexus block can be learnt faster and lead to a higher final success rate compared to nerve stimulator-guided axillary brachial plexus block.

Upper extremity regional anesthesia: essentials of our current understanding, 2008

Brachial plexus blockade is the cornerstone of the peripheral nerve regional anesthesia practice of most anesthesiologists. As part of the American Society of Regional Anesthesia and Pain Medicine's commitment to providing intensive evidence-based education related to regional anesthesia and analgesia, this article is a complete update of our 2002 comprehensive review of upper extremity anesthesia. The text of the review focuses on (1) pertinent anatomy, (2) approaches to the brachial plexus and techniques that optimize block quality, (4) local anesthetic and adjuvant pharmacology, (5) complications, (6) perioperative issues, and (6) challenges for future research.

Ultrasound-Guided Regional Anesthesia: Current Concepts and Future Trends

The scope of ultrasound imaging guidance for regional anesthesia is growing rapidly. Preliminary data, although limited, suggest that ultrasound can improve block success rate and decrease complications. In this review, we describe the basic principles of ultrasound scanning and needling techniques for nerve blocks, highlight some of the data on clinical outcome, discuss specific limitations of ultrasound for regional anesthesia, and speculate on the future direction for physician training and competency assessment with this technology.

Neurological complications after regional anesthesia: contemporary estimates of risk

BACKGROUND

Regional anesthesia (RA) provides excellent anesthesia and analgesia for many surgical procedures. Anesthesiologists and patients must understand the risks in addition to the benefits of RA to make an informed choice of anesthetic technique. Many studies that have investigated neurological complications after RA are dated, and do not reflect the increasing indications and applications of RA nor the advances in training and techniques. In this brief narrative review we collate the contemporary investigations of neurological complications after the most common RA techniques.

METHODS

We reviewed all 32 studies published between January 1, 1995 and December 31, 2005 where the primary intent was to investigate neurological complications of RA.

RESULTS

The sample size of the studies that investigated neurological complications after central and peripheral (PNB) nerve blockade ranged from 4185 to 1,260,000 and 20 to 10,309 blocks, respectively. The rate of neuropathy after spinal and epidural anesthesia was 3.78:10,000 (95% CI: 1.06-13.50:10,000) and 2.19:10,000 (95% CI: 0.88-5.44:10,000), respectively. For common PNB techniques, the rate of neuropathy after interscalene brachial plexus block, axillary brachial plexus block, and femoral nerve block was 2.84:100 (95% CI 1.33-5.98:100), 1.48:100 (95% CI: 0.52-4.11:100), and 0.34:100 (95% CI: 0.04-2.81:100), respectively. The rate of permanent neurological injury after spinal and epidural anesthesia ranged from 0-4.2:10,000 and 0-7.6:10,000, respectively. Only one case of permanent neuropathy was reported among 16 studies of neurological complications after PNB.

CONCLUSIONS

Our review suggests that the rate of neurological complications after central nerve blockade is <4:10,000, or 0.04%. The rate of neuropathy after PNB is <3:100, or 3%. However, permanent neurological injury after RA is rare in contemporary anesthetic practice.

How to teach regional anesthesia

PURPOSE OF REVIEW

The demand for peripheral nerve blocks and neuroaxial blocks from both patients and surgeons has increased over the last few years. This change in attitude towards regional anesthesia is prompted by the insight that adequate perioperative pain management leads to earlier ambulation, shorter hospital stay, reduced cost and increased patient satisfaction. To avoid serious complications of these techniques structured residency programs need to be available.

RECENT FINDINGS

Until 2004, the Residency Review Committee for Anesthesiology in the United States required a minimum of 50 epidurals, 40 spinals and 40 peripheral nerve blocks during residency. Similarly, the German Society for Anesthesia and Intensive Care required 100 neuroaxial blocks and 50 peripheral nerve blocks. In 2004 the American Society of Regional Anesthesia and Pain Medicine endorsed standardized guidelines for regional anesthesia fellowships which regulate the administrative, equipment and educational demands.

SUMMARY

This review introduces the reader to the different teaching methods available, including cadaver workshops, three-dimensional videoclips, video filming, ultrasound guidance and acoustic assist devices as well as demonstrating their advantages and disadvantages. Moreover, an overview is given of future residency training programs, which integrate administrative, material and educative demands as well as the teaching means into the daily clinical routine.

Current practice in regional anaesthesia in Germany

BACKGROUND AND OBJECTIVE

Several new techniques and agents (e.g. ropivacaine) have been introduced in regional anaesthesia to improve patients outcome and safety. The beneficial effects on patient outcome are clear with these techniques, however, no information is available about their pattern and frequency of use in clinical practice. This study presents data concerning the current practice of regional anaesthesia in Germany.

METHODS

A questionnaire was sent to every German anaesthesia department (n = 1381). Questions focused on the frequency and range of regional anaesthetic procedures employed, with attention also to the organizational structural of the individual institution.

RESULTS

Six hundred and sixty-seven questionnaires were returned anonymously, representing a return rate of 48.3%. In hospitals with less than 200 beds, the number of regional anaesthetics was markedly higher compared to large hospitals with more than 400 beds. In contrast, small hospitals tended to provide only basic techniques of regional anaesthesia, whereas larger hospitals implemented more advanced techniques. Bupivacaine remains the most commonly used long-lasting local anaesthetic. Staff structure was also different in small departments - patient care was performed by board certified anaesthesiologists while residents were responsible for the patients in larger departments.

CONCLUSIONS

In small hospitals a majority of board certified anaesthesiologists rely on basic regional anaesthesia techniques. In large departments some consultants provide the entire spectrum of regional anaesthesia, with the majority of cases transferred to the residents responsibility. These results indicate the strong need to improve residency programs with regard to regional anaesthesia.