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Peripheral nerve location techniques George Corner and Calum Grant Print Publication Year: 2012 Published Online: Nov 2012 Publisher: Oxford University Press ISBN: 9780199586691 eISBN: 9780191755507 DOI: 10.1093/med/9780199586691.003.0010 Item type: chapter

Safe and effective peripheral block requires injection of an appropriate dose of local anaesthetic solution close to the target nerve, and the localization techniques described here allow the anaesthetist to position the needle tip correctly, either next to the nerve or in the correct fascial plane. Patient discomfort should be minimized and care taken to avoid trauma to surrounding structures (e.g. blood vessels and pleura) as well as to the nerves themselves. A wide range of methods, from the solely anatomical to the technologically complex, is now available, but it must be stressed that a thorough understanding of the relevant anatomy is fundamental to all of the nerve localization techniques described in this chapter. No technological aid, ultrasound included, is a surrogate for knowledge of both the relevant anatomy and the specific block technique, nor is it an excuse for ignoring the principles of patient selection and management during (and after) block performance. The possible localization techniques are: 1. Anatomical landmarks: surface anatomy is used in conjunction with knowledge of the standard course of the nerve to identify where the local anaesthetic should be injected (e.g. saphenous block below the knee). The correct depth of injection may be further refined using tactile sensation: a ‘pop’ is noted as a short bevel needle penetrates the deep fascia covering the correct myofascial plane (e.g. ilioinguinal nerve). 2. Elicitation of paraesthesiae: gentle contact of needle tip with nerve will generate paraesthesiae in its distribution. 3. Electrical stimulation: low current stimulation of the motor component of a mixed peripheral nerve will generate a ‘twitch’ in the muscles supplied by it. 4. Ultrasound guidance: the preceding two techniques rely on a knowledge of standard anatomy to identify the initial needle insertion point, but real-time ultrasound scanning allows the relevant nerves (and surrounding structures) to be identified first. Thus individual variation can be allowed for, and (often) both needle position and local anaesthetic spread visualized. 5. Complex imaging: modern radiological techniques have a key role in chronic pain practice (see Chapter 23), but their lack of ‘portability’ means that they are rarely used in anaesthesia. However, developments in operating theatre design and advances in technology may mean that this changes in the future. The main focus of this chapter is on paraesthesiae, electrostimulation, and ultrasound guidance.

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Pain and autonomic nerve blocks Mick Serpell and Andreas Goebel Print Publication Year: 2012 Published Online: Nov 2012 Publisher: Oxford University Press ISBN: 9780199586691 eISBN: 9780191755507 DOI: 10.1093/med/9780199586691.003.0023 Item type: chapter

The sympathetic nervous system was, for a long time, the target for pain relieving techniques, but they are now used much less frequently than in the past because the mechanisms of pain are better understood. The role of the sympathetic nervous system in the generation and maintenance of pain may have been overemphasized previously (Schott 1998) so the rational for sympathetic block in chronic pain management is being reevaluated. Systemic medication, stimulation techniques, physical therapy, and psychological techniques are all used much more widely than previously. When it is used, sympathetic block can be produced in one of three ways: 1. Direct injections of the sympathetic chain or related ganglia using local anaesthetic or neurolytic solutions; 2. Venous injection, with the circulation excluded by tourniquet, of drugs which deplete adrenergic transmitters —intravenous regional sympathetic block (IVRSB); and 3. Systemic administration (by intravenous infusion) of #-adrenergic antagonist drugs. The analgesic effect of most nerve block techniques (e.g. an epidural in labour or coeliac plexus for cancer pain) is a result of the interruption of transmission in afferent nociceptive fibres, but the effects of sympathetic nerve block can be more complex. The sympathetic nervous system is directly involved in the pathophysiology of some painful states (‘sympathetically maintained pain’), and the analgesic action is due primarily to block of sympathetic efferent activity. There may also be disruption of reflex control systems so that peripheral or central sensory processing is altered. Finally, peripheral vasodilatation can relieve pain due to ischaemia.

Upper limb blocks David Coventry Print Publication Year: 2012 Published Online: Nov 2012 Publisher: Oxford University Press ISBN: 9780199586691 eISBN: 9780191755507 DOI: 10.1093/med/9780199586691.003.0017 Item type: chapter

Nerve block techniques can play a major role in the management of procedures on the upper limb, providing both anaesthesia for operative surgery and analgesia thereafter. Brachial plexus block can greatly simplify the anaesthetic management of patients with significant medical co-morbidity, particularly those with respiratory or cardiovascular disease, obesity, diabetes, altered conscious level, or a compromised or difficult airway. In addition, prolonged infusion techniques for more major surgery may facilitate earlier limb mobilization and have the potential to reduce hospital stay and improve functional outcome. The pattern of block is partly determined by the approach used, and it is important to relate the surgical requirements to the features of the specific method because each has its limitations in regard to the extent of block and the risk of side effects (Table 17.1). Local infiltration or distal individual nerve blocks can also be used to supplement brachial plexus techniques or to produce a restricted field of block according to surgical need. This would include local anaesthesia for brief surgical procedures, those not requiring a proximal arm Page 2 of 7 PRINTED FROM OXFORD MEDICINE ONLINE (www.oxfordmedicine.com). © Oxford University Press, 2015. All Rights Reserved. Under the terms of the licence agreement, an individual user may print out a PDF of a single chapter of a title in Oxford Medicine Online for personal use (for details see Privacy Policy). date: 26 January 2017

tourniquet, and those where additional general anaesthesia is employed for other indications such as iliac crest bone graft harvesting. In recent years, the development of ultrasoundguided approaches has stimulated widespread interest and reappraisal of many of these techniques, leading to hopes of more successful blocks and fewer side effects (Chapter 10). Although there is a lack of well-controlled, large-scale studies comparing rates of block efficacy and complications when ultrasound or peripheral nerve stimulation is used, there is a growing volume of work in the literature to support the former’s routine use for upper limb blocks (McCartney et al. 2010).

Regional anaesthesia in children Steve Roberts Print Publication Year: 2012 Published Online: Nov 2012 Publisher: Oxford University Press ISBN: 9780199586691 eISBN: 9780191755507 DOI: 10.1093/med/9780199586691.003.0022 Item type: chapter

Regional anaesthesia is now firmly placed at the heart of paediatric anaesthesia. However, it differs from adult practice in that it is almost always performed in combination with general anaesthesia. Indeed, as a general rule, it would be neither safe nor possible to attempt regional blocks in the awake child. This is because a child cannot be guaranteed to remain still and calm; and paraesthesiae and peripheral nerve stimulation are techniques that would be difficult for young children to understand or accept. The possible exceptions to this are teenagers undergoing relatively minor surgery or premature infants undergoing hernia repair.

Lower limb blocks Colin McCartney Print Publication Year: 2012 Published Online: Nov 2012 Publisher: Oxford University Press ISBN: 9780199586691 eISBN: 9780191755507 DOI: 10.1093/med/9780199586691.003.0018 Item type: chapter

Peripheral nerve blocks of the lower limb can provide profound intraoperative anaesthesia and postoperative analgesia without many of the side effects of central techniques. However, spinal and lumbar epidural anaesthesia and analgesia remain the most commonly performed regional techniques for lower limb surgery, and all anaesthetists should be competent in these methods. Central blocks have several disadvantages, especially when used for postoperative analgesia, and in the last decade the use of peripheral nerve blocks has become more common. This is related to a number of factors including the association of continuous epidural analgesia with increased side effects such as urinary retention and pruritis compared to peripheral (especially continuous) techniques, fear of epidural haematoma with newer more potent anticoagulants, and the significant incidence of failure of continuous epidural analgesia (up to 20% in some studies). In addition, the emergence of better techniques for localizing nerves and the availability of improved equipment have increased the popularity of blocks of the lumbar and sacral plexus. Lower limb peripheral nerve block techniques can be challenging, especially in obese individuals, but the view Page 3 of 7 PRINTED FROM OXFORD MEDICINE ONLINE (www.oxfordmedicine.com). © Oxford University Press, 2015. All Rights Reserved. Under the terms of the licence agreement, an individual user may print out a PDF of a single chapter of a title in Oxford Medicine Online for personal use (for details see Privacy Policy). date: 26 January 2017

that all nerve blocks of the lower limb are difficult and unreliable is incorrect. The aim of this chapter is to present simple techniques which give consistent results and may be used routinely. The use of ultrasound has, in a number of cases, increased our ability to locate lower limb nerves and appropriate techniques have been included. Only brief reference will be made to techniques which have not been found useful in routine clinical practice.

Epidural block Graeme McLeod Print Publication Year: 2012 Published Online: Nov 2012 Publisher: Oxford University Press ISBN: 9780199586691 eISBN: 9780191755507 DOI: 10.1093/med/9780199586691.003.0014 Item type: chapter

Epidural block has now become well established as an adjunct to general anaesthesia and is regarded as the most effective means of providing pain relief after surgery and during labour (Dolin et al. 2002). Regardless of the type of surgery and means of assessing pain, epidural block provides better pain relief than parenteral opioids (Block et al. 2003). Several factors have contributed to this: 1. Placement of a catheter in the epidural space is a relatively straightforward procedure; 2. Epidural block may be extended for several days into the postoperative period if needed; 3. Quality pain relief allows effective coughing and early mobilization; and 4. Acute pain teams are available to provide continuity of management. There are, however, disadvantages: 1. Visceral sensation remains intact and general anaesthesia is needed as a supplement for major surgery of the thorax and abdomen; 2. Surgery to the trunk requires thoracic epidural block, but inexperienced anaesthetists tend to insert catheters several dermatomes below the ideal, ‘mid-incisional’ level, resulting in inadequate pain relief and lower limb motor block; 3. Performance of the block adds to anaesthesia time; and 4. Pre-existing neurological conditions, coagulation disorders, and pharmacological thromboprophylaxis are weightier contraindications to epidural block than to other regional techniques because bleeding into the epidural space is not always immediately apparent, cannot be controlled directly, and may only be revealed when it causes symptoms.

Regional anaesthesia of the trunk John McDonnell and Dominic Harmon Print Publication Year: 2012 Published Online: Nov 2012 Publisher: Oxford University Press ISBN: 9780199586691 eISBN: 9780191755507 DOI: 10.1093/med/9780199586691.003.0016 Item type: chapter

The use of peripheral nerve blocks in the trunk has been an area of significant development and expansion in recent years even though most methods were first described long ago. Two factors, other than the general increase in interest in regional anaesthesia, have been relevant: 1. Concerns about the systemic effects and complications of epidural analgesia coupled with a desire to deliver equally high-quality postoperative analgesia; 2. The availability of ultrasound scanning to identify the target tissue planes, a more definitive

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method than the elicitation of a fascial ‘pop’ as the needle is advanced. This should increase both efficacy and safety.

Sacral epidural (caudal) block Edward Doyle and Jon McCormack Print Publication Year: 2012 Published Online: Nov 2012 Publisher: Oxford University Press ISBN: 9780199586691 eISBN: 9780191755507 DOI: 10.1093/med/9780199586691.003.0015 Item type: chapter

The sacral approach to the epidural space provides a reliable and effective block for operations which involve low lumbar and sacral dermatomes. The technique of using a single injection of local anaesthetic via the caudal approach combines the advantages of simplicity with a high success rate and a low incidence of side effects. It can be combined with general anaesthesia to reduce the requirement for anaesthetic agent and systemic opioid, allowing rapid pain-free recovery with minimal postoperative vomiting and an early resumption of oral intake. Over 50,000 such blocks are performed annually in the UK (Cook et al. 2008), with satisfactory analgesia being achieved in 95–97% of them (Mercan et al. 2009). The benefits are multifaceted, the technique producing better patient satisfaction and less analgesic requirement than infiltration of local anaesthetic solution for surgery (Siddiqui et al. 2007), and being as effective as lumbar epidural block for total hip arthroplasty (Kita et al. 2007). Caudal analgesia also has a place in the management of chronic pain, with evidence accumulating to support the injection of caudal steroids for low back pain (Conn et al. 2009). Success depends upon accurate localization of the sacral hiatus for access to the sacral epidural space, but there are considerable anatomical differences in its size and shape. These variations may make identification difficult and needle insertion impossible in some cases.

Spinal anaesthesia Jonathan Whiteside and Tony Wildsmith Print Publication Year: 2012 Published Online: Nov 2012 Publisher: Oxford University Press ISBN: 9780199586691 eISBN: 9780191755507 DOI: 10.1093/med/9780199586691.003.0013 Item type: chapter

Spinal anaesthesia is induced by the injection of local anaesthetic into the subarachnoid space, and is generally regarded as one of the most reliable of regional block methods. It has the particular advantage that very small doses of local anaesthetic produce profound effects so that systemic toxicity is not a problem. However, other drugs, such as opioids, coadministered by the same route to produce more prolonged pain control may have systemic effects. The second major advantage is that needle insertion is relatively straightforward with cerebrospinal fluid (CSF) providing both a clear indication of successful needle placement and a medium through which local anaesthetic solution usually spreads readily. The popularity of the technique has waxed and waned since its introduction by August Bier in 1898. Widespread use in the 1930s and 1940s was followed by a sharp decline in the 1950s, coinciding with improvements in general anaesthetic techniques (notably the Page 5 of 7 PRINTED FROM OXFORD MEDICINE ONLINE (www.oxfordmedicine.com). © Oxford University Press, 2015. All Rights Reserved. Under the terms of the licence agreement, an individual user may print out a PDF of a single chapter of a title in Oxford Medicine Online for personal use (for details see Privacy Policy). date: 26 January 2017

introduction of the neuromuscular blocking drugs) and the adverse publicity regarding neurological sequelae in the Woolley and Roe case (Cope 1954, Hutter 1990). However, the technique has regained a significant place in anaesthetic practice over the last four decades, having been used in all age groups from premature neonates to the most elderly, and in a wide range of clinical situations. Lumbar puncture is usually performed below the termination of the spinal cord, which is at or about L1 in the adult, the subarachnoid space ending at the level of the second sacral vertebra (Chapter 12). The tough dura mater and flimsy arachnoid are closely applied to each other, but there remains a potential (subdural) space between them. If the whole bevel of the spinal needle is not within the subarachnoid space, some of the solution may be deposited within the subdural space and this can account for some failures (Fettes et al. 2009). The posterior subarachnoid space contains several membranous structures (see Figure 12.7) and, in the lumbar region particularly, the septicum posticum may be well developed. These structures can lead to maldistribution of solutions, and account not only for failure to achieve adequate block, but also for neurotoxicity and the development of the cauda equina syndrome (CES). The site of action is primarily the nerve roots, but the dorsal root ganglia and the superficial parts of the cord may be affected also (Greene & Brull 1993). Differential effects may result in wide differences in the rostral levels of different types of block: up to seven segments between sympathetic and sensory block (Chamberlain & Chamberlain 1986), and 2.5 segments between sensory and motor block (Freund et al. 1967).

Regional anaesthesia in obstetrics Catriona Connolly and John McClure Print Publication Year: 2012 Published Online: Nov 2012 Publisher: Oxford University Press ISBN: 9780199586691 eISBN: 9780191755507 DOI: 10.1093/med/9780199586691.003.0021 Item type: chapter

Effective and safe regional anaesthesia in obstetrics requires a sound knowledge of the anatomy of the nervous system and reproductive tract, the physiology of pregnancy, and the pharmacology of local anaesthetic drugs. The anaesthetist learns to apply this knowledge through performing regional techniques under close senior supervision on the labour ward and in the operating theatre. The need to provide trainees with such supervised experience was the justification for introducing specialists in obstetric anaesthesia in the mid 20th century in the UK, largely through the efforts of the Faculty (now Royal College) of Anaesthetists and the Obstetric Anaesthetists Association. It was James ‘Young’ Simpson (Simpson 1848) who originally proposed that ‘local anaesthesia’ might be used as an alternative to general anaesthesia, but this was not realized in obstetrics until 1900 when Kreis (1900) used spinal anaesthesia during operative vaginal delivery. Sacral epidural analgesia (with procaine) was first used during labour by Stoeckel (1909) who also warned of the risk of ‘impairing the force of labour’, but regional analgesia, especially lumbar epidural block, is now widely available, there being several reasons for its popularity. The main alternative methods—parenteral and inhalational—have the potential to produce centrally mediated side effects in both mother (e.g. amnesia for the birth, confusion, disorientation, and nausea) and child. In the neonate, the effect can extend from mild neurobehavioural abnormalities, detectable only by sophisticated Page 6 of 7 PRINTED FROM OXFORD MEDICINE ONLINE (www.oxfordmedicine.com). © Oxford University Press, 2015. All Rights Reserved. Under the terms of the licence agreement, an individual user may print out a PDF of a single chapter of a title in Oxford Medicine Online for personal use (for details see Privacy Policy). date: 26 January 2017

testing (Brockhurst et al. 2000), to severe respiratory depression with failure to initiate normal respiration at birth. Regional analgesia offers the possibility of maternal pain relief without clouding of consciousness or neonatal depression and has minimal effect on uterine blood flow or the fetus itself (Halpern et al. 1998). Further, low-dose combinations of local anaesthetic and opioid for epidural analgesia are now commonplace and associated with improved maternal satisfaction, a shorter second stage, and a lower incidence of instrumental delivery than earlier high dose local anaesthetic techniques (Cooper et al. 2010b, Hein et al. 2010, James et al. 1998). Additionally, bladder function is better preserved and allows a lower incidence of catheterization during labour (Wilson et al. 2009). Most elective and emergency operative deliveries are now performed under epidural or spinal anaesthesia, so reducing considerably the number of general anaesthetics required and contributing, almost certainly, to the decline in maternal deaths due to anaesthesia in the UK (Reports 1991–2008). Thus pregnant women now have high expectations of safe, effective pain relief in labour, and regional anaesthesia for operative delivery if it is required. It is crucial that these expectations are realistic so written and verbal information should be available in both the antenatal setting (well before the pain of labour interferes with decision-making) and the labour ward for access in early labour. Patient information leaflets, in many languages, are available free-of-charge from the Obstetric Anaesthetists Association Website (www.oaa-anaes.ac.uk/content.asp?ContentID=185). Complete pain relief cannot be guaranteed so it is imperative that women understand that this is the case and that strategies are in place to deal with partial or complete failure of regional block.

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