Ultrasound guidance of peripheral nerve blocks is now widely used for hand, wrist and forearm surgery. The use of ultrasound when performing peripheral nerve blocks allows visualisation of the needle in movement and may reduce the incidence of vascular puncture. When compared with neurostimulation, ultrasound guidance has been shown to improve efficacy,1 reduce performance time2 and reduce local anaesthetic doses.3 Ultrasound guidance might also be expected to reduce the incidences of systemic toxicity of local anaesthetic and nerve injuries,4 but in recent studies, this has proved difficult to confirm.5,6
The incidence of seizures due to intravenous local anaesthetic injection varies between 1 per 800 and 1 per 1500 when nerve stimulation is used.7,8 Peripheral neurological complications not involving haematoma or infection are rare,9 with the incidence of permanent nerve injury being approximately 2 per 10 000 axillary brachial plexus blocks performed with nerve stimulation, reported in the last survey of the SOS French Regional Anaesthesia Hotline.10
Despite the fact that the axillary brachial plexus block is one of the most commonly performed peripheral nerve blocks, the number of patients required to compare ultrasound guidance with nerve stimulation is prohibitively large. A randomised controlled trial testing permanent nerve injury as the primary outcome would be almost impossible. In any case, because of the rapid spread of ultrasound-guided regional anaesthesia, a comparison involving a neurostimulation group has become unfeasible.
The objective of this study was to prospectively estimate the incidence of immediate complications related to ultrasound-guided axillary brachial plexus blocks in a multicentre observational cohort.
Materials and methods
The Ethics Committee approved the study and waived informed consent for the first step, as it was non-interventional (provided by the Ethical Committee, Rennes Hospital, France, number 09/17-729. The Institutional Review Board approved this project as a quality-assurance activity 07/01/2009). Written informed consent was obtained for the second step of the study.
French anaesthesiologists were invited to participate in this multicentre observational survey by mail. A letter was sent to the departments of anaesthesiology and intensive care at French public and private hospitals performing orthopaedic hand, wrist and forearm surgery. Additional information sessions took place, in Rennes during a conference in November 2009, and at other meetings of the French Society of Anaesthesia and Intensive Care. A letter was also posted on a dedicated website. Only procedures performed using ultrasonography alone or combined with nerve stimulation were included. Informed consent for anaesthesia and surgical procedures was routinely obtained.
Background data included the number of beds in the medical centre and whether the type of practice was private or public. The personal data of the anaesthesiologists included age, sex, year of graduation, starting year of regional anaesthesia practice, experience with ultrasound-guided regional anaesthesia (number of years) and type(s) of device(s) used for ultrasonography.
The study objective (to record the incidence of immediate complications related to ultrasound-guided axillary brachial plexus blocks) was based on data collected by anaesthesiologists through a web-based case report form (CRF). The CRF was used to report the number of axillary brachial plexus blocks for hand, wrist or forearm surgery performed on a weekly basis per participating institution. Reports of three immediately encountered serious adverse events related to the regional anaesthesia were collated: cardiac arrhythmia, cardiac arrest requiring cardiac compression and/or epinephrine; seizures; and peripheral nerve injury, defined as a sensory and/or motor deficit at hospital discharge. Pain (especially in the nerve block distribution), sensory and motor deficits were checked before discharge from the ambulatory unit by the anaesthesiologist or the surgeon in charge of the patient. Analgesics were given if necessary, and their administration required a longer stay in the ambulatory unit to ensure that there are no residual problems. Patients in whom a peripheral nerve injury was suspected were investigated to attribute the cause to anaesthesia or surgery. When anaesthesia-related nerve injury was suspected, the patient was managed through normal clinical channels that were not part of the study. The complications reported on a predefined web-based CRF were further validated during a telephone call between the principal investigator and the anaesthesiologist who reported the case. Specific details of patients and axillary brachial plexus blocks were not recorded.
In a second step, we studied the frequency of neurological complications related to ultrasound-guided axillary brachial plexus blocks. Patients were invited to participate in this second step only if their regional anaesthesia took place within predefined weeks called ‘active weeks’. For practical reasons, only 1 week per month during a consecutive 6-month period was ‘active’. After hospital discharge, neurological complications were identified only during ‘active weeks’. Data were collected by anaesthesiologists performing the blocks and from telephone interviews with the patients conducted by trained research assistants. Patients were called between day 7 and day 10 after regional anaesthesia; up to four calls were made within this period until contact was established. The questionnaire for the telephone interview included questions about neurological symptoms related to regional anaesthesia: numbness (paraesthesia), tingling, abnormal sensation, pain and/or weakness. Surgeons also reported anything suspicious during the postoperative visit within 30 days. When a non-surgical problem was suspected, the anaesthesiologist was informed. He or she then reviewed the file and contacted the patient to establish whether the symptoms were attributable to anaesthesia or surgery.
Data audits and accuracy
Data audits were performed in each of the centres. The first audit was to confirm that data for every block performed were collected for entry into the database and to ensure the accuracy of the denominator. The second audit was to detect transcription errors and to confirm and ensure the accuracy of the data in the database. At each site, an observer examined the entries in the database and compared those data with the original source data.
For the study objective, we estimated a frequency with 95% confidence intervals (CIs). Taking into account the survey design, we used PROC SURVEYFREQ (SAS 9.2; SAS Institute, Cary, North Carolina, USA) to compute variance estimates. The total number of primary sampling units (32 University Hospitals, approximately 1000 Public non-University Hospitals, and around 1000 Private Hospitals) was taken into account. We specified the following values: 0.0004 for intravascular complications and 0.0002 for neurological symptoms, as null hypotheses to be tested by one-way χ2 test. P < 0.05 indicates that the observed frequency is significantly lower than the chosen value.
Normally distributed data are presented as mean ± SD, whereas data that are widely skewed are presented as median with 25th and 75th percentiles.
Thirty-six centres took part in this study between 30 November 2009 and 29 July 2012.
The personal details of the 66 participating anaesthesiologists are shown in Table 1. All used ultrasound-guided axillary brachial plexus blocks, either as the sole technique (n = 41, 62%) or combined with nerve stimulation (n = 25, 38%). Seven of the 66 anaesthesiologists began using ultrasound-guided techniques exclusively during the 2-year study period. All anaesthesiologists identified the four nerves (median, ulnar, radial and musculocutaneous). The most common ultrasound equipment used was General Electric Logic e (44%), Sonosite-S-nerve (30%) and others from General Electric and Sonosite.
During the study period, 27 031 regional anaesthesia procedures were recorded with a mean of 4 per week per centre (minimum 1, maximum 38). There were 2823 investigator-weeks with at least one procedure and a mean of 9.6 procedures per week. Four local anaesthetic systemic toxicity reactions were recorded during the procedure (Table 2); the estimated frequency was 1.48 per 10 000 (95% exact confidence limits for binomial proportion: 0.0 to 4.0 per 10 000). Taking into account the survey design, the 95% confidence limits were 0.00 to 2.96 (F-test P value 0.0016), indicating that the observed proportion was significantly lower than 4 per 10 000. There was no systemic toxicity from local anaesthetic due to delayed absorption from the tissues. One instance of postoperative neurological symptoms at hospital discharge was noted. This was a 70-year-old patient scheduled for hand surgery, who experienced paraesthesia in the territory of the median nerve on the forearm, starting at 5 h and lasting 5 days after the block, which was performed solely with ultrasound guidance. It was managed conservatively. The estimated frequency was 0.37 per 10 000 (95% confidence limits 0.00 to 1.15; F-test P value 0.0002, indicating that the observed proportion was significantly lower than 2 per 10 000).
Of the 821 patients enrolled in the second step of the study, 699 (85%) answered the telephone interview, conducted by 30 researchers from 20 centres. There were no reports of serious neurological complications. Of the 699 patients interviewed, 307 (43.9%; 95% CI 40.2 to 47.7%) reported at least one symptom from tingling (n = 54), numbness (paraesthesia) (n = 138), abnormal sensation (n = 54), pain (n = 118) and weakness (n = 122). When pain was reported, it was in the area of the scar. Other symptoms were related to carpal tunnel syndrome present prior to surgery. None were considered to be related to regional anaesthesia after telephone interview and/or examination by an anaesthesiologist
This prospective survey contributes further information about the current risks associated with ultrasound-guided peripheral regional anaesthesia. The two main findings of this analysis are that the incidence of immediate systemic toxicity of local anaesthetic was very low, 1.5 per 10 000, and that the overall incidence of postoperative neurologic symptoms was 0.37 per 10 000. To our knowledge, this study, which includes 27 031 axillary brachial plexus blocks, is the largest published so far.
The most devastating complication of regional blockade is massive intravascular injection of local anaesthetic. Recommendations intended to prevent this clearly specify slow injection with fractionation of local anaesthetic dose, and frequent aspiration through the needle.11 The use of ultrasound guidance per se may further lower the risk,12 as it offers the anaesthesiologist a real-time view of the local anaesthetic injection, which nerve stimulation does not. As a result, an intravascular injection may be detected before a toxic dose is injected.6 Our results confirmed the low incidence of local anaesthetic systemic toxicity and are in agreement with the low incidence reported by Barrington et al.,13,14 Orebaugh et al.12 and the meta-analysis of Abraham et al.1 In their first study, Barrington et al. reported three major local anaesthetic systemic toxicity events in 8189 blocks, whereas Orebaugh et al. recorded none in 2000 ultrasound-guided blocks. In their most recent report, Barrington and Kluger13 give the incidence at 0.87 per 1000 peripheral nerve blocks. Most of these events were associated with axillary brachial plexus blocks. Sites et al.6 reported a frequency of 0.6 per 10 000 (95% CI 0.2 to 1.2) for unintended venous puncture and 1.2 per 10 000 (95% CI 0.7 to 2.0) for unintended arterial puncture. Again, these results are in accordance with the present study, and all conclude that there might be a trend towards a reduced risk of systemic toxicity of local anaesthetic compared with the use of nerve stimulation alone.7,8 With this in mind, it should be noted that nerve stimulation was used in combination with ultrasound in three of the four cases of systemic toxicity reported in our study. Given that ultrasound guidance offers visualisation of the local anaesthetic injection, some explanation is required as to why any toxic intravascular doses are given. These include losing sight of the needle as it approaches the target structures, and the incorrect identification of the surrounding structures.15 Firm pressure on the ultrasound probe can compress the vein, allowing an inadvertent intravenous injection to go unnoticed.16,17 The observance of three main principles should enhance safety: that the relevant anatomical structures should be identified for each patient before performing the block, that local anaesthetic spread should always be seen, and if a problem occurs during injection, it should be stopped and the needle repositioned before continuing.18,19 The second case of local anaesthetic toxicity described received a large dose of lidocaine (9 mg kg−1). Recommendations were not followed in this case.
The ability to visualise the nerve, the needle and the local anaesthetic injection has led some clinicians to dispense with older techniques and rely only on ultrasound guidance for peripheral nerve blocks, but neurological complications still occur. Recent reports suggest that their incidence with ultrasound guidance is similar to that with older techniques.20 Sites et al.6 have shown a high incidence (1.8 per 1000 blocks; 95% CI 1.1 to 2.7) of postoperative neurologic symptoms lasting longer than 5 days. The Australasian Regional Anaesthesia Collaboration has reported that 0.5% of patients require referral to a neurologist for assessment, and that the incidence of neurological complications attributable to a peripheral nerve block is 0.4 per 1000 blocks (95% CI 0.08 to 1.1 per 1000).14
Because we assessed the immediate neurological complications in all patients, and complications after discharge in a smaller cohort, our results are not readily comparable, but none of our complications were serious, and the symptoms reported by 307 patients were not related to the block. Symptoms, in the vast majority, were present before surgery and were due to the disorder that made it necessary. Pain was reported only in the area of the scar and not in a nerve territory. One can hypothesise that all the symptoms described (tingling, numbness, abnormal sensation, pain, weakness) were related to the surgery and/or the tourniquet.
The incidence of neurological complications observed after axillary brachial plexus blocks performed with nerve stimulation with a similar study design is 2 out of 10 000 blocks.10 Our study indicates a clear trend towards fewer nerve complications with ultrasound guidance.
This study has several limitations. There is a risk of bias from unobserved or unmeasured events. The lack of a control group, for example with nerve stimulation, does not permit determination of cause and effect. Selectively identifying neurological complications only during ‘active weeks’ could also create a selection bias. After hospital discharge, we did not perform a systematic clinical examination to identify possible postoperative nerve injuries that had gone undetected. This may have had an impact on the outcome. However, symptoms of neurological complications are evident immediately after the block, and were reported when they occurred. We are, however, confident that we detected all systemic toxicity of local anaesthetics. Another limitation is the lack of recording of personal patient data and specifics of the blocks. Another possible bias may have arisen because the anaesthesiologists who participated were volunteers.
In conclusion, we report a large series of ultrasound-guided axillary brachial plexus blocks in a multicentre study. The incidence of systemic toxicity of local anaesthetic in 27 031 blocks was 1.5 per 10 000, and the overall incidence of postoperative neurologic symptoms was 0.37 per 10 000.
Acknowledgements relating to this article
Assistance with the study: the authors wish to thank all the following investigators: Cazals (Centre Hospitalier Bourg en Bresse), Bloc, Leclerc and Mercadal (Centre Hospitalier Privé Claude Gallien, Quincy), Doris and Proust (Clinique de l’Europe, Le Port-Marly), Fabre and Sidier (Polyclinique du Parc Rambot, Aix en Provence), Fricault and Liné (Polyclinique de la Thiérache, Wignehies), Marchand-Maillet, Dufeu and Milan (Centre Hospitalier Universitaire Saint-Antoine, Paris), Eyrolle (Centre Hospitalier Universitaire Cochin, Paris), Carré, Dessieux, Le Naourès, Mesli and Ecoffey (Centre Hospitalier Universitaire Pontchaillou, Rennes), Adelving, Cimino and Pillet (Clinique de Fontaine, Fontaine Lès Dijon), Lelarge and Malinovsky (Centre Hospitalier Universitaire, Reims), Bonnemaison and Dufour (Centre Hospitalier Côte Basque, Bayonne), Thevenin (Hôpital Privé de l’Estuaire, Le Havre), Quenet (Clinique des Maussins, Paris), Bilaine (Pôle Santé Sud, Le Mans), Langlois and Raingeval (Clinique Jouvenet, Paris), Benistand (Clinique St Georges, Nice), Fournet, Gandara, Lefebvre, Sellier and Tilly (Clinique Jeanne D’Arc, Nantes), Aveline (Centre Hospitalier Privé Sévigné, Cesson Sévigné), Le Bret, Lefebvre, Kayembre, Rannou and Rose (Clinique La Francilienne, Pontault-Combault), Miliani (Centre Hospitalier Universitaire La Timone, Marseille), Kiffer and Vignaux (Clinique Paofai, Papeete), Boselli, Christin, Dabouz, Javault and Truc (Centre Hospitalier Universitaire, Lyon), Delcourt (Polyclinique St André, Reims), Meyrieux (Polyclinique du Tondu, Bordeaux), Al Nasser (Clinique du Parc Lazare, Beauvais), Pambet (Clinique de la Châtaigneraie,), Gentili and Martin (Centre Hospitalier Privé Saint-Grégoire, Saint-Grégoire), Radjef (Centre Hospitalier Victor Provo, Roubaix), Senlis (Clinique des Acacias, Cucq), Schinkel (Centre Hospitalier Universitaire, Angers), Jaziri (Centre Hospitalier Privé de l’Ouest, Trappes), Beylacq (Centre Hospitalier Universitaire, Bordeaux), Buntinx (Centre Hospitalier Universitaire Nord, Marseille), Murat (Centre Chirurgical Floréal, Bagnolet), Fuzier (Centre Hospitalier Universitaire, Toulouse), and the team of Centre d’Investigation Clinique, Danjou, Bense, Plesse (Centre Hospitalier Universitaire Pontchaillou, Rennes).
Financial support and sponsorship: supported by a grant from the French Ministry of Health, Projet Hospitalier de Recherche Clinique 2009, Paris, France
Conflicts of interest: none.
Presentation: presented as an abstract at the meeting of the French Society of Anesthesiology and Intensive Care, September 2013 and at the ASA meeting, October 2013.
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