Ultrasound in regional anaesthesia - Wiley Online Library

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help promote its use and realise the benefits that regional anaesthesia has over general ... The Achilles' heel of ultrasound-guided regional anaesthesia is that ...
Anaesthesia, 2010, 65 (Suppl. 1), pages 1–12 doi:10.1111/j.1365-2044.2009.06200.x .....................................................................................................................................................................................................................

Ultrasound in regional anaesthesia J. Griffin1 and B. Nicholls2 1 Specialist Registrar in Anaesthesia, South West School of Anaesthesia, Derriford Hospital, Plymouth, Devon, UK 2 Consultant in Anaesthesia and Pain Management, Taunton & Somerset NHS Foundation Trust, Musgrove Park Hospital, Taunton, Somerset, UK Summary

Ultrasound guidance is rapidly becoming the gold standard for regional anaesthesia. There is an ever growing weight of evidence, matched with improving technology, to show that the use of ultrasound has significant benefits over conventional techniques, such as nerve stimulation and loss of resistance. The improved safety and efficacy that ultrasound brings to regional anaesthesia will help promote its use and realise the benefits that regional anaesthesia has over general anaesthesia, such as decreased morbidity and mortality, superior postoperative analgesia, cost-effectiveness, decreased postoperative complications and an improved postoperative course. In this review we consider the evidence behind the improved safety and efficacy of ultrasound-guided regional anaesthesia, before discussing its use in pain medicine, paediatrics and in the facilitation of neuraxial blockade. The Achilles’ heel of ultrasound-guided regional anaesthesia is that anaesthetists are far more familiar with providing general anaesthesia, which in most cases requires skills that are achieved faster and more reliably. To this ends we go on to provide practical advice on ultrasoundguided techniques and the introduction of ultrasound into a department. . ......................................................................................................

Correspondence to: Dr B. Nicholls E-mail: [email protected]

The use of ultrasound imaging techniques in regional anaesthesia is rapidly becoming an area of increasing interest. It represents one of the largest changes that the field of regional anaesthesia has seen. For the first time, the operator is able to view an image of the target nerve directly, guide the needle under real-time observation, navigate away from sensitive anatomy, and monitor the spread of local anaesthetic (LA). This comes at a time when an ageing population presents with an increasing range of comorbidities, thereby demanding a wider choice of surgical and anaesthetic options to ensure optimal clinical care and a decreased risk of complications. The key to successful regional anaesthesia is deposition of LA accurately around the nerve structures. In the past, electrical stimulation or paraesthesia, both of which relied on surface landmark identification, was used for this. However, landmark techniques have limitations; variations in anatomy [1] and nerve physiology [2], as well as equipment accuracy have had an effect on success rates and complications. The introduction of ultrasound may go some way to changing this.  2010 The Authors Journal compilation  2010 The Association of Anaesthetists of Great Britain and Ireland

If the use of ultrasound is to become more widespread amongst anaesthetists, then it must be shown to be clinically effective, practical and cost-effective. The use of ultrasound guidance in daily clinical practice requires a degree of training and an understanding of the equipment and technology. This article will address the benefits and widespread uses of ultrasound in regional anaesthesia. It will provide practical tips on how to achieve success in its use. It will review the evidence that support its use and provide advice on the introduction of ultrasound into a department. Background

Regional anaesthesia, when used alone or in combination with general anaesthesia, offers several potential benefits over general anaesthesia alone: a decrease in morbidity and mortality [3–6]; superior postoperative analgesia [7– 10]; cost-effectiveness [11]; a decrease in postoperative complications [12–14]; and an improved postoperative course (decreased use of opioids and anti-emetics, faster recovery and discharge, increased patient satisfaction) 1

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[7, 15, 16]. Unfortunately, despite these clinical benefits, regional anaesthesia remains less popular than general anaesthesia. Its use is associated with a number of shortcomings. Perhaps the greatest is that general anaesthesia is far more successful and reliable than regional anaesthesia [17, 18]. Even in experienced hands and with the use of nerve stimulation, there is an inherent failure rate. Anaesthetists are more familiar with providing general anaesthesia [19], which is generally achieved faster and using skills that are easier to attain. However, regional anaesthesia does not compete with general anaesthesia, in much the same way as ultrasound-guided regional techniques do not compete with nerve stimulation techniques. What ultrasound can bring to regional anaesthesia is a number of potential advantages that serve to redress some of the shortcomings of the current techniques: direct observation of nerves [21, 24–28]; direct observation of surrounding structures (vessels, muscles, tendons), facilitating the identification of nerves [24–28]; direct observation of LA deposition and spread [24, 25, 27, 29]; avoidance of painful evoked muscle contractions [25]; a decrease in complications such as accidental intraneural or intravascular injection [21, 24, 25, 27, 29, 31, 32]; faster onset of block [24, 25, 27, 28, 30]; longer duration of block [25]; improved block quality [24, 28, 30, 34, 35]; and decreased dose of LA [23, 30]. A number of recent editorials [20–22] have agreed that ultrasound guidance will become the gold standard for regional anaesthesia, but that this transition will take another 5–10 years. Advantages

The single most important advantage that ultrasound brings to regional anaesthesia is the ability to confirm the exact placement and spread of LA; it is the LA that blocks the nerve and not the needle. The needle can be manipulated under real-time observation to the target nerve, and LA placed directly around the nerve, resulting in a faster onset, longer duration and improved quality block using less LA. Hazardous structures such as blood vessels, pleural and viscera can be avoided, and complications can thereby be minimised. Ultrasound frees the operator from using the classically described landmarks. Nerves can be targeted at any point along their course where they can be seen. ‘Blind techniques’ relying on pops, clicks, twitches and the need for multiple trial and error needle passes, with their lack of accuracy, reliability, longer placement times, patient discomfort and injury, can now, for many blocks, be dispensed with. Efficacy and safety Several studies have shown increased efficacy and safety when using ultrasound to aid regional anaesthesia when 2

compared with the traditional landmark and nerve stimulation techniques. Chan et al. [36] undertook a randomised, controlled trial of 188 patients undergoing axillary brachial plexus blocks, comparing ultrasound with nerve stimulation techniques. Block success rate was higher with ultrasound (82.8%, p = 0.01) and combined ultrasound and nerve stimulation (80.7%, p = 0.03), compared with nerve stimulation alone (62.9%). They reported the additional benefits of less axillary pain and bruising. None of the groups reported any major complications. However, one must be mindful that this ultrasound success rate, in the hands of experienced operators using high-end ultrasound machines, was well short of 100%. The authors commented that this was most likely due to mistakes in nerve identification and misinterpretation of circumferential spread of LA. Orebaugh et al. [37], in a larger but non-randomised study of 248 patients requiring any one of four different peripheral nerve blocks (interscalene, axillary, femoral, popliteal), compared ultrasound plus nerve stimulation with nerve stimulation alone. They found a significantly shorter time was needed to perform the blocks with fewer attempts (both p < 0.001) when ultrasound was used. However, they failed to show a statistical difference in the failure rate between the two groups: 2% (3 ⁄ 124) in the ultrasound plus nerve stimulation group and 6% (8 ⁄ 124) in the nerve stimulation group (p = 0.334). Pearlas et al. [35], in a prospective, randomised trial, assigned 74 patients undergoing major elective foot or ankle surgery to receive a sciatic block in the popliteal fossa. Half of the blocks were guided by real-time ultrasound and half by nerve stimulation. Sensory and motor function were assessed by a blinded observer at predetermined intervals for up to 1 h. Block success was identified as loss of sensation to pinprick within 30 min in the distribution of both tibial and common peroneal nerves. They found that the ultrasound group had a significantly higher block success rate compared with the nerve stimulation group (89.2% vs 60.6% respectively, p = 0.005). Onset and progression time for the block was faster in the ultrasound group, without an increase in block procedure time or complications. Casati et al. [38] undertook a prospective, randomised, blinded study to test the hypothesis that ultrasound guidance can shorten the onset time of axillary brachial plexus blocks compared with nerve stimulation when using a multiple injection technique. Thirty patients were randomised to each group. The average number of needle passes was four in the ultrasound group and eight in the nerve stimulation group. Mean (SD), sensory block onset time was shorter in the ultrasound group (14 (6) vs 18 (6) min respectively, p = 0.01). However, no difference was seen in the onset time of the motor block or readiness for  2010 The Authors Journal compilation  2010 The Association of Anaesthetists of Great Britain and Ireland

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Anaesthesia, 2010, 65 (Suppl. 1), pages 1–12 J. Griffin and B. Nicholls Ultrasound in regional anaesthesia . ....................................................................................................................................................................................................................

surgery. An insufficient block was seen in one patient in the ultrasound group and two in the nerve stimulation group. However, procedure-related pain was seen in 14 patients (48%) in the nerve stimulation group compared with only six patients (20%) in the ultrasound group (p = 0.48). In conclusion, the group commented that with multiple injection axillary blocks, ultrasound provided a similar success rate and had a comparable incidence of complications when compared with nerve stimulation. Marhofer et al. [30] conducted a prospective randomised controlled trial comparing ultrasound with nerve stimulation in 60 patients receiving femoral ‘threein-one’ blocks for hip surgery following trauma. The onset time of sensory block in each nerve was significantly shorter with ultrasound guidance when compared with nerve stimulation. The quality of the nerve block was also significantly better in the ultrasound group (p < 0.01). The femoral nerve could be viewed in 95% of the ultrasound group in which there were no cases of vascular puncture compared with 10% in the nerve stimulation group. In a large retrospective study by Sandhu et al. [39], 1146 patients underwent ultrasound-guided infraclavicular blocks. These were carried out by 88 different junior doctors who were supervised by 37 different anaesthetists, and hence this represented a ‘real world’ scenario. Ninety-nine per cent of the blocks were successful (1138 ⁄ 1146), arterial puncture occurred in < 1% of cases and no patients had accidental intravascular injection, local toxicity or symptoms of peripheral nerve injury. Furthermore, the use of ultrasound has shed some light on the failings of nerve stimulation. A study by Beach et al. [40] showed that for adequately imaged nerves, a positive motor response to nerve stimulation did not improve the success of the block. In addition, they found that a block could be successful without positive nerve stimulation. Indeed, muscle stimulation and paraesthesia may not occur even when ultrasound confirms the correct needle position [2]. Other papers have shown that the needle can be intraneural and there can still be failure to provoke muscle contractions by the nerve stimulator [41]. In diabetic patients, it has been demonstrated that nerve stimulation and paraesthesia may be impossible to elicit at currents < 2.4 mA [42]. Biegeleisen [43], in a prospective study of US-guided axillary blocks, found that nerve puncture and intraneural injection of LA does not always lead to nerve injury. In the last year alone there has been a large number of excellent studies published that provide more evidence that ultrasound will soon become the main method of guidance in regional anaesthesia. This has been supported by the recent publication of the UK National Institute for Health and Clinical Excellence (NICE) Interventional Procedure Guidance 285 on ultrasound 2010 The Authors Journal compilation  2010 The Association of Anaesthetists of Great Britain and Ireland

guided regional nerve block, published in January 2009 [44]. Epidural and spinal anaesthesia

In January 2008 NICE published guidelines [45] that suggested that ultrasound could be used in two different ways to facilitate catheterisation of the epidural space. One method is the use of real-time ultrasound imaging to observe the passage of the needle towards the epidural space. The second method (pre-puncture ultrasound) is the use of ultrasound as a guide to the conventional technique, using an initial scan of the patient’s lumbar spine to identify the midline, interspinous spaces and depth of the epidural space. The guidance relates to children, neonates, pregnant women and patients with scoliosis. Neuraxial imaging with ultrasound is particularly challenging as the structures in which we are interested (ligamentum flavum, epidural space and dura) are mostly encased in bone, through which ultrasound will not pass. Visibility is via one or two acoustic windows, the interspinous space and the intralaminar space. These are best imaged when scanning transversely in the midline and longitudinally in the paramedian area respectively (Figs 1 and 2). To understand spinal ultrasound, a thorough knowledge of lumbar spine anatomy is necessary, as certain bony landmarks can be easily identified: sacrum, spinous processes, articular processes (facet joints) and vertebral bodies. The epidural space is hypo-echoic and often not seen clearly. The ligamentum flavum and posterior dura are commonly seen as a single

SP AP PD SC AD VB

Midline ultrasound view of the lumbar spine and the epidural space. The depth to the epidural space is marked (A). SP, spinous process; AP, articular process; AD, anterior dura – ligamentum flavum complex; PD, posterior dura; SC, spinal canal; VB, vertebral body.

Figure 1

3

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AP PD SC AD

Paramedian ultrasound view of the lumbar spine and epidural space. The depth of the epidural space is marked (A). AP, articular process; AD, anterior dura – ligamentum flavum complex; PD, posterior dura; SC, spinal canal.

Figure 2

bright hyperechoic line. Anterior and deep to these structures, the anterior dura and posterior longitudinal ligament can often be seen as being distinct from the vertebral body; the spinal canal lies between these superficial and deeper structures. In neonates and children under six months, the internal architecture of the spinal cord can be clearly seen; this is not so in older children and adults. Efficacy and safety In a randomised controlled trial of 64 children, Willschke et al. [46] compared real-time ultrasound with prepuncture ultrasound. Catheter placement was successful in all children but was quicker to perform in the real-time ultrasound group: a mean of 162 s compared with 234 s (p < 0.01). None of the children in the real-time ultrasound group required supplementary intra-operative or postoperative analgesia, compared with 6% (2 ⁄ 34) in the pre-puncture group. Furthermore, in a case series of 35 neonates, he demonstrated that the tip of the needle and spread of LA could be clearly seen in all cases. Grau et al. [31, 47] conducted two randomised, controlled studies of a total of 372 pregnant women receiving obstetric epidurals. They compared the use of pre-puncture ultrasound with no ultrasound. The mean numbers of puncture attempts were 1.3 and 1.5, compared with 2.2 and 2.6 respectively (p < 0.013 and p < 0.001). In the larger of these studies (n = 300), they showed a faster onset time for the block (4.6 min vs 5.3 min, p < 0.027) and a lower incidence of severe headaches (2.7% vs 10.0%, p < 0.011) in the ultrasound group. However, preparation time was increased at 6 min compared with 4 min (p < 0.001). There was no signif4

icant difference in aspiration of blood, backache or sensory problems. Dural puncture was seen in 0.7% of the ultrasound group and 1.3% of the control group. Patient satisfaction was higher in the ultrasound group. On the premise that epidural anaesthesia may be difficult in pregnancy, Grau et al. [48] went on to evaluate the teaching possibilities of ultrasonography as a diagnostic approach to the epidural region. Two groups of residents performed their first 60 obstetric epidurals under supervision. The control group used a conventional loss of resistance technique while the ultrasound group proceeded in the same way but were supported by pre-puncture ultrasound imaging, giving them information about optimum puncture point, depth and angle. Success was defined as using fewer than three attempts, not changing space or anaesthetic technique, and achieving adequate epidural anaesthesia. In the control group, the success rate for the first 10 epidurals was 60%, increasing to 84% over the next 50 epidurals. In the ultrasound group, success rate started at 86% and increased to 94%. The authors concluded that the study showed the possible value of ultrasound imaging for teaching and learning obstetric regional anaesthesia. Arzola et al. [49] imaged 61 pregnant women undergoing epidural analgesia with a midline, transverse ultrasound approach. They found a good level of success in the ultrasound determined insertion point (91.8%) and in the measured and actual depth to the epidural space. The mean (SD) ultrasound determined depth of the space was 4.66 (0.68) cm; the actual depth of the space as measured by the epidural needle was 4.65 (0.72) cm. It is unsurprising that NICE have targeted the use of ultrasound in these groups. In children, the quality of image is superior because of the lesser depths involved, the relatively larger acoustic windows and the reduced ossification of the surrounding bony structures [50]. While in pregnancy it has been shown [51] that the optimum puncture site available on the skin for lumbar epidural space cannulation is smaller, the soft-tissue channel between the spinal processes is narrower, and the skin–epidural space distance is greater than in the non-pregnant patient. Furthermore, the visibility of the ligamentum flavum, dura mater and epidural space is decreased during pregnancy. An increased incidence of obesity and oedema obscures anatomical landmarks (the spinous processes and the midline), and hormonal changes result in softer ligaments, making the loss of resistance technique less reliable. Ultrasound can be used to pre-scan the lumbar spine in difficult cases, confirming both the midline and the depth to the ligamentum flavum and epidural space, decreasing the failure rate and the incidence of complications. Realtime epidural guidance is not routinely used; both  2010 The Authors Journal compilation  2010 The Association of Anaesthetists of Great Britain and Ireland

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visibility of the needle and the practicalities of holding the probe and manipulating a loss of resistance technique means that a minimum of three hands are necessary. The development of probe supports and needle guidance devices may see this as a realistic possibility in the future, but as for now, real-time guidance is reserved for experts. Experience with spinal anaesthesia reflects that found with epidurals, being used to assess the vertebral level [52] and to identify normal spaces in difficult cases [53], but ultrasound is still not routinely used to guide the needle. Pain medicine

The use of ultrasound in pain medicine has lagged behind its use in regional anaesthesia, and initial studies were primarily concerned with identifying anatomy sonographically and the feasibility of performing established techniques using ultrasound. More recently, comparative studies comparing fluoroscopic and computerised tomography-guided techniques with ultrasound have begun to appear and these are now contesting the ‘gold standard’ for pain interventions. Although X-ray gives better definition for bony structures than ultrasound, it lacks the ability to demonstrate musculoskeletal and peripheral nerve structures. Although limited by bony shadowing and decreased resolution at depth, ultrasound for spinal injections has included cervical and lumbar facet joint injections, lumbar medial branch blocks, peri-radicular injections, caudal and sacro-iliac joint injections. Greher et al. [54] first described the feasibility of ultrasound-guided facet joint injections and Galiano et al. [55], in a prospective, randomised clinical trial, showed that the ultrasound approach to lumbar facet joints is clinically feasible, and results in a significant decrease in procedure duration and radiation dose compared with computerised tomography. However, formal comparison with fluoroscopy is still awaited. Nerve root injections are difficult with ultrasound, and the trans-foraminal approach is limited by poor visibility; reliable needle placement within the foramina is unachievable with present equipment and approaches. Sympathetic blocks are one of the mainstays of pain medicine, and the use of ultrasound for stellate ganglion blocks was initially describe by Kapral et al. in 1995 [56]. A recent case report [57] suggests improved safety with the use of ultrasound: less risk of damage to the thyroid gland and vessels, vertebral artery and oesophagus. The ability to monitor the spread of the LA subfascially along the longus coli muscle may help to decrease the incidence of complications such as recurrent laryngeal nerve palsy, and intrathecal and epidural spread [58].  2010 The Authors Journal compilation  2010 The Association of Anaesthetists of Great Britain and Ireland

Peripheral nerve injections using ultrasound include the occipital nerve, suprascapular nerve, intercostal nerve, ilio-inguinal and ilio-hypogastric nerve, pudendal nerve and lateral cutaneous nerve of thigh. Eichenberger et al. [59] were able to locate the occipital nerve with ultrasound and reliably block it. This compares well with the recommended three-needle fluoroscopy technique that is used to accommodate the variable anatomy of the nerve. More recent studies comparing ultrasound and fluoroscopy for piriformis injections [60] (for piriformis syndrome) and glenohumeral joint injections [61] have shown improved accuracy with ultrasound. Ultrasound has the potential to influence the diagnosis and treatment of many pain conditions, not only with the increased accuracy of injection techniques but also with the potential to diagnose common musculoskeletal problems. Further outcome studies to confirm the benefits of ultrasound in comparison to fluoroscopy are eagerly awaited. Paediatrics

Regional anaesthesia is usually performed under general anaesthesia in children. Absolute distances are smaller and the nerves lie closer to the skin. Ultrasound would therefore seem an obvious choice in this area, improving block efficacy and safety even though the incidence of peripheral nerve block-related complications is already exceptional low (1:10 000) in paediatric practice [62]. Where ultrasound offers benefits over established techniques is in fascial plane blocks such as rectus sheath, ilioinguinal and transversus abdominis blocks, in which the endpoint relies on clicks and pops. Ultrasound decreases the risk of intramuscular and intraperitoneal injection, bringing science to an imperfect art. Local anaesthetic volume reduction studies as described below enhance the safety of regional anaesthetic techniques in children. Willschke et al. [32] conducted a randomised controlled trial of 100 children with a mean age of 41 months. They showed that LA could be placed around 100% of ilio-inguinal and iliohypogastric nerves using ultrasound, but only 50% when a fascial click technique was used, as detected by ultrasound after injection (p < 0.0001). Heart rate increase on incision was 6% and 22% in the two groups respectively (p < 0.0001). Additional analgesia was necessary in 4% and 26% respectively (p = 0.004). The mean volume of LA required to produce an effective block was significantly lower at 0.19 ml.kg)1 compared with 0.3 ml.kg)1 (p < 0.0001). Furthermore, a smaller proportion of patients required postoperative rectal analgesia: 6% compared with 40% (p < 0.0001). No complications were reported in either group. 5

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Cost analysis

The initial cost of a modern portable ultrasound system is often used as an argument against ultrasound and its introduction into a department. A typical machine costing in the range of £15 000–£20 000 and with a conservative average life span of five years, at 1000 procedures per year, equates to a cost of £3.00–£4.00 per patient event. Sandhu et al. [33] compared the costs of administering infraclavicular nerve blocks by either nerve stimulator or ultrasound. The per case cost of the ultrasound machine ($17 000), spread over 5000 blocks, was $3.40. Time saving in block onset and placement came to 21 min. Theatre time at $8.00 per min meant a $168.00 saving per nerve block. Over 5000 blocks, this is a saving of $84 000. We know that ultrasound-guided blocks are also safer, more efficacious and with fewer complications (potential reduction in litigation costs); less LA is used and the incidence of conversion to general anaesthesia is lower. Further cost savings would be expected in day surgery patients as they are able to bypass recovery and are discharged sooner with a decreased incidence of postoperative nausea and vomiting. In addition, the ultrasound machine can also be used for central line and arterial line placement, and in the intensive care unit for assisting in procedures such as drainage of pleural effusions or ascitic fluid. Practical tips for ultrasound-guided regional anaesthesia

The premise of ultrasound-guided regional anaesthesia is the visual location of the nerve, guidance of the needle to the nerve and the spread of LA around the nerve and, in a perfect world, if all these criteria are met, then a 100% success rate should be achievable. Attention to detail and the development of good practical skills can go along way towards achieving this goal. Visual location of the nerve To optimise demonstration of nerves and surrounding structures, it is important to understand the equipment and its limitations, and to have a good, sound anatomical knowledge of the structures being viewed. The probe

Probe

Crystal Array

Frequency

Field depth

Linear

Linear

6–13 MHz

Curvilinear

Curved face

2–5 MHz

6

used should match the procedure being performed (Table 1). Choosing the wrong probe can make identification of the anatomy difficult (Figs 3 and 4). It is important to use the highest frequency probe available for the depth of image being scanned. Needle guidance The ‘holy grail’ in ultrasound-guided regional anaesthesia is to find a needle that defies the laws of physics and can be seen at any depth and at any angle. To this end, needles have been coated and scored, the tips multifaceted and needle guides designed [63], all to increase their reflectivity and ease of use. At present, there is no single needle that is significantly more echogenic than another. Facettipped needles appear to have more ‘feel’ and may decrease the chances of intraneural needle placement. In general, large needles are more readily visible on ultrasound and the visibility of all needles becomes less as distance from the probe increases. Identification of the needle can be improved by: rotating the needle, as ultrasound reflecting from the bevel can improve visibility; gentle in-and-out movements (‘jiggling’); or injection of small volumes of fluid–‘hydrolocalisation’ [64]. The needle can be introduced using either an in-plane approach in which the needle is passed along the long axis of the probe, parallel to the probe face, or an out-ofplane approach in which the needle passes at right angles to the long axis of the probe. Use of the in-plane technique means that the entire needle can be seen (Fig. 5), that there is excellent visibility of the needlenerve interface, and that a technique such as that described as the ‘walk-down’ can be used [65]. However, it can be difficult to keep the whole needle within the narrow (often < 1 mm) beam, and the method often requires unfamiliar needle approaches to blocks and may demand the use of a longer needle with increased passage through muscle and other tissues, causing additional pain. Use of the out-of-plane technique can mimic established techniques, allows more needle movement in a larger field of vision and provides a shorter distance for the needle to travel between the skin and the nerve. However, the tip of the needle may be difficult to see (Fig. 6) and there is poorer demonstration of the nerveneedle interface. Table 1 Different types of probe and their uses.

Resolution

Blocks

1.8–6 cm

0.5 mm axial 1 mm lateral

5–16 cm

2 mm axial 3 mm lateral

Brachial plexus, abdominal wall, femoral and distal sciatic, peripheral nerves Neuraxial,lumbar plexus and proximal sciatic

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BPR SA

SM

Figure 5

Block needle seen in ‘in-plane’ view.

View with correct linear array probe of interscalene area. SA, anterior scalene muscle; SM, middle scalene muscle; BPR, brachial plexus roots.

Figure 3

Needle

SM

BPR SA

Figure 6

View with incorrect curvilinear array probe of interscalene area. SA, anterior scalene muscle; SM, middle scalene muscle; BPR, brachial plexus roots.

Block needle seen in ‘out-of-plane’ view.

Figure 4

Needle LA UN

Local anaesthetic injection Using ultrasound, the volume of LA needed is reduced, and general consensus appears to suggest that at least a 50% decrease in volume is common; volumes as low as 5 ml have been used with good clinical effect in interscalene blocks used for postoperative analgesia [66]. The ideal pattern of spread and minimum volume for individual nerve blocks has still to be determined, but circumferential spread appears to be the ideal (Figs. 7 and 8). The incidence of complications and neurological sequelae can be decreased by not deliberately contacting the nerve and with attention to detail as described below: • Injection should be painless. • There should be no resistance to injection.  2010 The Authors Journal compilation  2010 The Association of Anaesthetists of Great Britain and Ireland

Acceptable local anaesthetic (LA) spread. UN, ulnar nerve in the forearm.

Figure 7

• The LA should be clearly seen during injection. If it is not, consider intravascular injection. Look for ‘smoke’ in the vessels (the microbubbles in the injectate will 7

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Needle LA

FP

UN

Unacceptable, subfascial local anaesthetic (LA) spread. UN, ulnar nerve in the forearm; FP, fascial plane.

Figure 8

appear as white hyperechoic artefacts within the vessels). If this is seen, stop injection immediately and reposition the needle. • If the needle tip is not within the ultrasound beam, move the probe to demonstrate the needle tip before injecting. • The nerve often appears brighter and more easily identified after injection of LA around the nerve. • If the nerve swells during the injection, stop immediately as the injection may be intraneural. Introduction of ultrasound into a department

The success of the introduction of any new technique into a department is dependant upon the availability of the equipment and the training of the individuals using that equipment. The purchase of an ultrasound machine by a department has been made easier with NICE guidance No. 285 [44, 45]. Most purchases are made on the premise of increased success, decreased complications, improved patient care and, importantly, cost-effectiveness. The evidence supporting the use of ultrasound in regional anaesthesia is growing all the time and the majority of anaesthetic departments in the UK now have access (although often limited) to some form of ultrasound machine capable of imaging nerves. The choice of ultrasound machine is individual, often dictated by resources and personal preferences, but they should ideally have the following capabilities: • Ease of use, to accommodate multiple users of varying levels of experience. • Portability, to allow multiple areas of use; can be cart based or truly portable. 8

• A selection of probes: linear, curvilinear and phased array. • Doppler facilities: colour flow and power to identify vessels and flow. • Harmonic imaging, beam steering or compound imaging to provide improved image quality and resolution. • Image and video capture functionality for training, audit and clinical governance reasons. • A long warranty of three to five years and a long predicted clinical life. The successful use of ultrasound is highly operatordependent and as such has a distinct learning curve. Practitioners using ultrasound without training have been shown to have more complications and lower success rates. For this reason, the introduction of ultrasound into a department should be structured, and predicated on training and supervision. Recommendations for training and a proposed curriculum have been published by the Royal College of Radiologists [67]. The proposed training should be modular and it is recommended that training should be specific to the requirements of the trainees and to the department. It is also understood that different specialties require different levels of training and these can broadly be divided in levels 1, 2 and 3 [68]: • Level 1 (basic) is training that can be achieved within recognised postgraduate training programmes. • Level 2 (intermediate) requires specific sub-speciality training. • Level 3 (advanced). Within anaesthesia, most trainees are only likely to achieve some of the competencies included in Level-1 training. Guidelines for ultrasound-guided regional anaesthesia have recently been published [69]. These propose sensible recommendations both for training and the competencies needed to practice the technique. In general, all recommendations agree on the need to develop basic ultrasound skills including: understanding the equipment used; image acquisition and optimisation; image interpretation; and needling techniques. These skills can be achieved by a mixture of theoretical and practical training, and should follow the suggested outline: • Knowledge of ultrasound and equipment: o Basic physics of ultrasound. o Machine characteristic and use. o Optimisation and storage of the image (resolution, gain, focus etc.). o Patient care, safety and infection control. • Knowledge of anatomy relevant to commonly used techniques: o Brachial plexus anatomy – interscalene, supraclavicular, infraclavicular, axillary and terminal peripheral nerve regional anaesthetic techniques.  2010 The Authors Journal compilation  2010 The Association of Anaesthetists of Great Britain and Ireland

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Table 2 Training models for ultrasound-guided regional anaesthesia.

Training model

Advantages

Disadvantages

Live models (anywhere)

Readily accessible Usually compliant Nerve structures seen Large numbers present – good for anatomical variations Cheap and mobile-use anywhere, reusable Home made – (gelatine, olives, pasta) Commercial – expensive Demonstration of nerves Use of nerve stimulator Vascular landmarks present Needling techniques, single injection and catheter techniques As close to real as possible Observe all nerves easily Good needling technique Injection of saline, catheter techniques Mimics normal techniques and ergonomics

Variable anatomy and echogenicity Not able to needle Purely for scanning

Phantoms (anywhere)

Animals (Europe, North America, Australasia – not UK) Cadaveric preparations (anatomy departments UK, Europe and worldwide)

Poor realism, no nerves Agar ⁄ gelatine preps – tracking of needle path Needling techniques only Limited life span Animal anatomy Unfamiliar approaches Ethical and cultural objections Expensive

Visibility often poorer than living Limited access to some areas No pulsations or Doppler signal – loss of landmarks Acquisition of preparations (cost)

Table 3 Level of difficulty for each block with recommendations on choice of probe and needling technique. Techniques Superficial cervical plexus, interscalene Axillary, terminal branches (ulnar, median, radial) Femoral, saphenous, ankle Rectus sheath, ilio-inguinal, iliohypogastric Supraclavicular Infraclavicular Obturator, sciatic- (all approaches including popliteal) Intercostal Lumbar plexus ⁄ thoracic paravertebral ⁄ lumbar epidural

Recommended probe

Needling techniques

Level of difficulty

HFL

IP ⁄ OOP

Basic

HFL

IP ⁄ OOP

Basic

HFL HFL

IP ⁄ OOP IP ⁄ OOP

Basic Basic

HFL HFL (depth < 5 cm) LFC (depth > 5 cm) HFL (depth < 5 cm) LFC (depth > 5 cm) HFL HFL (upper thoracic paravertebral) LFC

IP only IP ⁄ OOP

Intermediate Intermediate

IP ⁄ OOP

Intermediate

IP recommended IP ⁄ OOP

Intermediate Advanced

HFL, High frequency linear > 10 MHz; LFC, Low frequency curvilinear 2–5 MHz; IP, in-plane; OOP, out-of-plane.

Lumbar plexus anatomy – femoral, saphenous, obturator, sciatic, popliteal and tibial. o Abdominal wall anatomy – rectus sheath, ilioinguinal, transversus abdominus plane. o Spinal anatomy – paravertebral, intercostal, epidural, caudal and psoas compartment. • Practice on models and phantoms. • Simulation of techniques – models, animals or cadavers. o

 2010 The Authors Journal compilation  2010 The Association of Anaesthetists of Great Britain and Ireland

• Supervised performance of techniques. • Independent practice. At present all assessments during training are optional and there is no consensus on whether ultrasound-guided regional anaesthesia should be certificated and accredited. Table 2 outlines the advantages and disadvantages of training models. Table 3 divides blocks into levels of difficulty. 9

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J. Griffin and B. Nicholls Ultrasound in regional anaesthesia Anaesthesia, 2010, 65 (Suppl. 1), pages 1–12 . ....................................................................................................................................................................................................................

Conclusions

Since the first papers on ultrasound in regional anaesthesia were published in 1994, there is now an overwhelming weight of evidence (> 1500 papers) supporting its use. We are now at a point at which worldwide opinion is shifting behind the use of ultrasound as the main method for needle guidance in regional anaesthesia. Indeed, direct ultrasound observation improves the outcome in most peripheral nerve techniques in adults and children. Anaesthetists can now directly see relevant nerve structures in both the upper and lower limb at all levels. For neuraxial techniques, further studies are needed to establish whether ultrasonography can lead to improvement in performance. However, there have been promising results in children, neonates and in pregnancy. In pain medicine, ultrasound guidance is still a technique in evolution. However, for an increasing number of blocks, evidence is now appearing with regard to feasibility and improved outcome. Safety and efficacy aside, for ultrasound to be truly embraced there are still mental obstacles to overcome, financial resources to provide and training to be delivered. It is when these are achieved that the full list of potential advantages that ultrasound brings to regional anaesthesia will be seen. Conflicts of interest

Dr Nicholls has received honoraria and equipment loans from Sonosite, B Braun and GE. Dr Griffin declares no conflicts of interest. References 1 Wedel DJ. Ultrasonographic findings of the axillary part of the brachial plexus. Regional Anesthesia and Pain Medicine 2001; 92: 1271–5. 2 Perlas A, Niazi A, McCartney C, Chan V, Xu D, Abbas S. The sensitivity of motor response to nerve stimulation and paresthesia for nerve localization as evaluated by ultrasound. Regional Anesthesia and Pain Medicine 2006; 31: 445–50. 3 Urwin SC, Parker MJ, Griffiths R. General versus regional anaesthesia for hip fracture surgery: a metaanalysis of randomized trials. British Journal of Anaesthesia 2000; 84: 450–5. 4 Rodgers A, Walker N, Schug S, et al. Reduction of postoperative mortality and morbidity with epidural or spinal anaesthesia: results from overview of randomized trials. British Medical Journal 2000; 321: 1493. 5 Ballantyne JC, Carr DB, deFerranti S. The comparative effects of postoperative analgesic therapies on pulmonary outcome: cumulative meta-analyses of randomized, controlled trials. Anesthesia & Analgesia 1998; 86: 598–612.

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Anaesthesia, 2010, 65 (Suppl. 1), pages 1–12 J. Griffin and B. Nicholls Ultrasound in regional anaesthesia . ....................................................................................................................................................................................................................

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 2010 The Authors Journal compilation  2010 The Association of Anaesthetists of Great Britain and Ireland