Department of Anaesthesia and Intensive Care Medicine, Medical University of Vienna, Waehringer Guertel 18-20, A-1090 Vienna, Austria
* Corresponding author. E-mail: peter.marhofer{at}meduniwien.ac.at
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Abstract |
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Keywords: anaesthetic techniques, regional ; measurement techniques, ultrasound ; nerve, block
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Introduction |
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Our group has performed more than 4000 nerve blocks under direct ultrasound guidance since the technique was first implemented as a routine procedure 10 years ago. The success rate has been almost 100%. In addition to this high success rate compared with the conventional guidance technique of nerve stimulation, significant improvements have also been obtained in terms of sensory and motor onset times. This superior quality of perioperative analgesia has greatly improved patient satisfaction among adults and children alike.
In this review article, we discuss the present state of ultrasound guidance in regional anaesthesia by revisiting both our own findings and other recent publications available on the subject. The technological background is described, suitable equipment is recommended, and a detailed account is given of which types of nerve block lend themselves to sonographic guidance and how they can be performed in a straightforward and safe manner.
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Rationale |
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Before the advent of ultrasound in regional anaesthesia, it was impossible to verify precisely where the needle tip was located relative to the nerves and how the local anaesthetic was distributed. Ultrasound visualization of anatomical structures is the only method offering safe blocks of superior quality by optimal needle positioning. In addition, the amount of local anaesthetic needed for effective nerve block can be minimized by directly monitoring its distribution.39
The use of ultrasound for nerve block was first reported by La Grange and colleagues in 1978, who performed supraclavicular brachial plexus blocks with the help of a Doppler ultrasound blood-flow detector.35 These early reports did not have much clinical impact because the scope for visualizing anatomical structures by ultrasound was still limited. It was confined to identifying vessels by Doppler ultrasound. Over the past 10 yr, however, dramatic progress has been made. The latest ultrasound images40 50 obtained for regional anaesthesia have come a long way compared with several years ago.8 39 66
In two recent editorials, Greher and colleagues21 and Peterson51 discussed various important aspects of using ultrasound to identify nerve structures in regional anaesthesia. While both agree that ultrasound will be the guidance technique of the future, the transition from the conventional technique of nerve stimulation will take another 10 yr or even longer to complete. There are significant mental obstacles to be overcome, and the financial resources are not going to be redistributed rapidly. However, if our patients are entitled to optimal anaesthetic care, then the optimal technique of applying nerve block must eventually prevail.
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Equipment |
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The connective tissue inside the nerves (perineurium and epineurium) reflects ultrasound waves in an anisotropic manner. Essentially, the angle and intensity of the reflection depends on the angle of the ultrasound wave relative to the long axis of the nerve. The true echogenicity of a nerve is only captured if the sound beam is oriented perpendicularly to the nerve axis. Consequently, linear array transducers with parallel sound beam emission offer advantages over sector transducers, which are characterized by diverging sound waves, such that the echotexture of the nerves will only be displayed in the centre of the image.
Ultrasound-guided nerve block can be performed with most modern ultrasound systems. They should be equipped with software to visualize both superficial tissues and musculoskeletal structures. High-resolution ultrasound (HRUS) systems are provided with software that allows optimal visualization of tissue contrast. Colour and pulsed-wave Doppler imaging is also required to identify vessels. The equipment should include a high-capacity hard disk to store images and short film sequences, as well as a CD burner to store the data files directly in TIF, JPG, BMP and MPG4 formats.
Appropriate portable ultrasound units have also been developed in recent years. These units are significantly less expensive than large systems.
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Sonographic appearance of peripheral nerves |
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Performing ultrasound-guided nerve block |
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The next step is to perform subcutaneous infiltration in order to render the procedure painless. We use 22-gauge 4080 mm needles with a facette tip (PajunkTM, Geisingen, Germany). Depending on the type of nerve block, the puncture will be performed 510 mm distal or proximal to the probe with ultrasound imaging in the transverse plane. Figure 3 illustrates that the identification of the needle is only possible when the needle crosses the ultrasonographic level of the probe. The needle itself is identified as a hypoechoic structure and a dorsal acoustic shadow is generated by the needle. In addition, the needle is also identified by direct needle movement and tissue displacement. It is important to fill the needle system with local anaesthetic before puncture to avoid air inclusion. Once the needle is optimally in place, the local anaesthetic is administered under direct sonographic visualization until the nerve structures are surrounded by local anaesthetic. If the local anaesthetic spreads in the wrong direction, the needle can be repositioned accordingly.
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The option of directly seeing the distribution of the local anaesthetic by ultrasonography minimizes the doses to be administered for effective nerve block, which is particularly relevant in multiple block procedures (e.g. 3-in-1 or sciatic nerve blocks). Older and sick patients benefit the most from this advantage.38
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Upper extremity nerve blocks |
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Interscalene brachial plexus block
This type of block is indicated for surgical procedures in the shoulder and upper arm area. Winnie originally placed the puncture at the level of the laryngeal prominence on the lateral border of the sternocleidomastoid muscle with the needle in a perpendicular direction.63 This needle direction used to cause major complications, such as puncture of the epidural space,36 59 or inadvertent administration of local anaesthetic into the vertebral artery (with a risk of seizures).58 The technique was later modified by Meier and colleagues, who used a more cranial puncture site with a more tangential orientation of the needle.41 The success rate varies between 5011 and 94%.10 58
The brachial plexus can be readily visualized by ultrasound imaging at the level of the posterior interscalene space (Fig. 4). Probing is started lateral to the larynx by visualizing the thyroid gland, the carotid artery and the internal jugular vein. Between these two vessels, the vagus nerve can be observed. As the probe is moved sideways to the lateral border of the sternocleidomastoid muscle with a slight caudal movement of the tip of the probe, the nerve structures become visible in a transverse view as multiple round or oval hypoechoic areas between the anterior and median scalene muscles.
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The entire brachial plexus near the subclavian artery can be visualized by moving the ultrasound probe away from the interscalene position described above to a supraclavicular position (Fig. 6). As the structures of interest are close to the skin, a high-frequency linear probe (12 MHz or preferably 14 MHz) can be used for optimal resolution. While it is difficult to identify each of the three trunks and the anterior and posterior divisions in a precise manner because of their close proximity, the individual structures of the brachial plexus at this level are adequately mapped for all practical purposes as the probe is slowly moved in a craniocaudal direction. The puncture site is located cranially to the ultrasound probe. Local anaesthetic should be administered to the extent of encircling the trunks (usually 1015 ml).
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Infraclavicular brachial plexus block
The vertical infraclavicular brachial plexus (VIP) block has been one of the most popular approaches to the brachial plexus since it was described by Kilka and colleagues in 1995.30 The success rate varies between 88%45 and 95%.21 It has been said that anatomical landmarks can be readily identified with this approach, but serious complications have been described.46 The puncture site is located halfway between the jugular notch and the ventral aspect of the acromion.
In an ultrasound investigation into the reliability of the VIP point, Greher and colleagues suggested a somewhat different position.21 Their findings indicated that the predicted VIP point and the infraclavicular puncture site defined by ultrasound imaging coincided in fewer than 20% of patients. According to Greher and colleagues, the VIP point is only correct when the distance between the jugular notch and acromion is 22 cm. For each centimetre less or more, the puncture site should be moved 2 mm laterally or medially, respectively. Neuburger and colleagues47 confirmed these observations in a clinical study and corrected the VIP points accordingly.
The findings of Greher and colleagues21 suggest that all infraclavicular brachial plexus blocks should be performed under ultrasound visualization. The distance between the brachial plexus and the pleura can be increased by selecting a more lateral approach, to avoid inadvertent puncture of the cervical pleura.
In 1999, Kapral and colleagues presented their lateral infraclavicular approach to the brachial plexus, which is as safe as the axillary approach in terms of complications while offering an additional spectrum of blocked nerves (musculocutaneous, thoracodorsal, axillary and medial brachial cutaneous nerves).29 These findings were confirmed in children.12 Figure 7 illustrates the brachial plexus lateral to the vessels around the puncture site for VIP block; Fig. 8 was obtained further laterally near the coracoid process. Both figures illustrate the greater distance of the brachial plexus from the pleura at the approximate VIP point due to the deliberately lateral position of the ultrasound probe.
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In a recent study by the Vienna group, ultrasound guidance for lateral infraclavicular block of the brachial plexus was found to be successful in 100% of children, providing both surgical anaesthesia and a complete spectrum of blocked nerves.40 In addition, the acute pain caused by brachial plexus puncture under nerve stimulation guidance as a result of muscle contractions was totally eliminated by ultrasound guidance.
Axillary brachial plexus block
This technique continues to be the most popular approach to the brachial plexus. Although complications are rare, one author reported three cases of permanent neurological injuries.56 Also, the reported success rates of 7080% are hardly acceptable.3 45 These poor rates may be caused by failure to block the radial nerve after needle puncture above the axillary artery.42 There are many open questions about the axillary approach despite its popularity.
Retzl and colleagues described the use of high-resolution ultrasonography to identify nerves at the axillary level.52 They observed that the position of the main nerves of the brachial plexus was not constant relative to the axillary artery but changed significantly on applying even mild pressure (e.g. during palpation of the axillary artery). This observation may help to explain the high failure rate of axillary brachial plexus blocks.
Ultrasound guidance for axillary brachial plexus anaesthesia should be performed with a high-frequency probe (12 MHz or higher). The median nerve can be readily visualized, as it is located next to the axillary artery all the way down to the cubital level. The ulnar nerve is located medial to the artery and remains closer to the skin surface than the median nerve all the way down to the proximal forearm. The radial nerve, which is located below the artery, may be somewhat problematical.42 While it is sometimes difficult to visualize because of the acoustic shadow cast by the artery, the anaesthetist can still move the probe slightly in a dorsal direction to visualize the radial nerve at the level of the humerus, where it branches off from below the artery to enter the radial nerve sulcus.
Figure 9 gives a view of all three nerves in the transverse plane. The brachial and antebrachial cutaneous nerves from the medial cord can also be visualized with a 14-MHz probe (not shown). From the indicated position, a 22-gauge 4-cm needle is inserted 12 cm below the artery (right-hand side in Fig. 9), blocking each of the three major nerves with 58 ml local anaesthetic. The reader is referred to Koscielnak-Nielsen and colleagues34 and Fanelli and colleagues10 for a detailed description of this multi-injection technique, which has remained essentially unchanged except that nerve stimulation has been replaced by ultrasound guidance. Although this has been denied in the literature,42 61 ultrasound visualization will even reveal septal structures between the nerves in around 10% of patients.
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Lower extremity nerve blocks |
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Three-in-one block
Thirty years ago, Winnie and colleagues64 succeeded in blocking the femoral, obturator and lateral cutaneous femoral nerves with a single inguinal perivascular injection. This approach came to be known as the 3-in-1 block. Much like the upper extremity blocks guided by nerve stimulation, this technique has a failure rate of up to 20%.48 60 The 3-in-1 block is ideally suited for ultrasound guidance with a high-frequency (10 MHz or more) linear probe because of the relatively superficial position of the femoral nerve distal to the inguinal ligament, lateral to the femoral artery, and below the iliopectineal fascia (Fig. 12). The puncture is performed 1 cm distal to the probe with a 22-gauge 4-cm needle, injecting 20 ml of local anaesthetic. Ultrasound monitoring will allow the anaesthetist to reposition the needle in the event of maldistribution above the iliopectineal fascia.
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Psoas compartment block
This more central approach to the lumbar plexus is also suitable for direct visualization by ultrasound. A wide variety of approaches to the psoas compartment have been suggested,4 6 49 65 along with different methods of nerve identification.6 49 63 None of the approaches have success rates above 7080%, and all involve serious complications.1 44 49
In 2001, Kirchmair and colleagues31 reported their results on posterior paravertebral sonography to provide a basis for ultrasound-guided psoas compartment blocks. Using a 5-MHz curved-array ultrasound probe, they succeeded in visualizing the lumbar paravertebral region, but not the lumbar plexus, in 20 volunteers. In their next study, they performed ultrasound-guided punctures of the psoas compartment on cadavers with additional CT scanning and observed that the needle could be accurately placed in the psoas compartment in 98% of cases.32
Despite this seemingly good result, psoas compartment blocks are difficult to perform under ultrasound guidance because the lumbar plexus is located relatively deep at the level of the psoas compartment [5.5 (1.4) cm at L2/3; 5.5 (1.4) cm at L3/4; and 5.8 (1.3) cm at L4/5].31 Therefore, the quality of ultrasound imaging is reduced, and clear anatomical reference points are not present. Also note that the needle must be orientated longitudinally to the ultrasound probe. More studies are needed to explore the potential of ultrasound guidance in psoas compartment blocks.
Sciatic nerve block
The good success rates reported for sciatic nerve blocks, in the range of 8797%,5 7 43 are presumably related to the large size of this nerve,17 which, however, also increases the risk of inadvertent intraneuronal puncture. Ultrasound guidance can minimize this risk and increase the success rate to almost 100%. Subtotal anaesthesia may result from the fact that the sciatic nerve bifurcates into a tibial and a peroneus branch at the level of the infrapiriform foramen in 11% of patients.2 Ultrasound guidance will allow the anaesthetist to detect this division and modify the procedure such that both branches are effectively blocked. Ultrasound guidance can also be used to block the posterior femoral cutaneous nerve, a branch of the sacral plexus innervating posterolateral thigh segments that cannot be blocked by conventional means because it is separated from the sciatic nerve at the level of the proximal thigh.
Preliminary attempts to visualize the sciatic nerve by ultrasound have involved a number of problems. First, the ultrasound beam has to be perpendicular to the nerve because of its anisotropic behaviour. The nerve is embedded in muscles, which filter out the high frequencies, thereby reducing the quality of the image. A 512 MHz linear probe can be used to visualize the nerve at all levels down to the popliteal region. Ultrasound-guided puncture should be performed in the subgluteal region, where the nerve is relatively close to the skin surface (Fig. 13).
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Epidural anaesthesia |
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Grau and colleagues demonstrated the usefulness of this approach in a number of studies. They first visualized the lumbar epidural space of pregnant women, since puncture is complicated in this group by weight gain, oedema and less elastic collagen fibres.18 In their next study, they succeeded in identifying all relevant landmarks in the thoracic epidural space by ultrasonography.19
The quality of the images presented in these studies was poor. Also note that these studies did not involve the use of ultrasound to actually guide the puncture in real time, but were only performed to evaluate anatomical landmarks before, and anticipate the depth of, puncture. However, even this off-line application significantly reduced the number of puncture attempts (1.3 (0.6) vs 2.2 (1.1) attempts).20 Throughout these studies, Grau and colleagues used 5-MHz curved-array probes and a combination of transverse and longitudinal scans.
The potential of ultrasound-guided epidural puncture is somewhat limited by the interfering bone structure and the relatively deep position of the epidural space, which detracts from the quality of the images obtained. Further studies are needed to define the usefulness of ultrasound guidance in epidural anaesthesia.
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Indications for pain therapy |
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A new ultrasound-based approach to facet nerve block has been developed and tested on cadavers, volunteers and patients.23 In the past, the only way to diagnose and specifically treat facet syndrome, a common cause of low back pain, has been to block the lumbar facet nerve under visualization by fluoroscopy or CT scanning. The newly developed approach based on ultrasound guidance is simpler and involves no exposure to radiation.
Studies involving the use of ultrasound guidance are also under way for cervical facet nerve block and several other types of acute and chronic pain management. The preliminary results of these studies are encouraging. All the results that have been obtained so far emphasize the great potential of ultrasound guidance in invasive pain therapy.
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Preliminary experience in children |
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Children can be managed with high-frequency linear ultrasound probes (10 MHz or higher) because the nerves are very close to the skin. We routinely use ultrasound guidance for ilioinguinal nerve blocks, lower extremity nerve blocks (3-in-1, sciatic and popliteal) and brachial plexus blocks. The ilioinguinal nerve can be readily visualized medial to the anterior superior iliac spine between the external and internal abdominal oblique muscles (Fig. 14), with a small amount of local anaesthetic providing sufficient perioperative surgical anaesthesia. Despite its popularity, the success rate of this technique is poor when it is performed blind.55 Better results can be achieved with ultrasound guidance.
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Conclusions |
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The benefits of directly visualizing targeted nerve structures and monitoring the distribution of local anaesthetic are significant. In addition, ultrasound monitoring allows the anaesthetist to reposition the needle in the event of maldistribution. It is therefore justified to expect anaesthetists to acquire the skills to use ultrasound guidance in clinical practice. The technique can be established in a cost-efficient manner as portable ultrasound systems with high-frequency probes are now available. It is hoped that these systems will promote the routine use of ultrasound guidance in regional anaesthesia.
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Footnotes |
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References |
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2 Bergmann RA, Thompson SA, Afifi AK, Saadeh FA. Compendium of Human Anatomy Variation. München: Urban and Schwarzenberg, 1988; 4949
3 Büttner J, Kemmer A, Argo A. Axilläre Blockade des Plexus brachialis. Reg Anaesth 1988; 11: 711[Medline]
4 Büttner M. Kontinuierliche periphere Techniken zur Regionalanästhesie und SchmerztherapieObere und untere Extremität. Bremen: Uni-Med, 1999; 1248
5 Chang PC, Lang SA, Yip RW. Reevaluation of the sciatic nerve block. Reg Anesth 1993; 18: 1823[ISI][Medline]
6 Chayen D, Nathan H, Chayen M. The psoas compartment block. Anesthesiology 1976; 45: 959[ISI][Medline]
7 Davies MJ, McGlade DP. One hundred sciatic nerve blocks: a comparison of localisation techniques. Anaesth Intensive Care 1993; 21: 768[ISI][Medline]
8 De Andrés J, Sala-Blanch X. Ultrasound in the practice of brachial plexus anesthesia. Reg Anesth Pain Med 2002; 27: 7789[CrossRef][ISI][Medline]
9 De Filho GR, Gomes HP, da Fonseca MH, Hoffman JC, Pederneiras SG, Garcia JH. Predictors of successful neuraxial block: a prospective study. Eur J Anaesthesiol 2002; 19: 44751[ISI][Medline]
10 Fanelli G, Casati A, Garancini P, Torri G. Nerve stimulator and multiple injection technique for upper and lower limb blockade: failure rate, patient acceptance, and neurologic complications. Study Group on Regional Anesthesia. Anesth Analg 1999; 88: 84752
11 Fanelli G, Casati A, Beccaria P, Cappelleri G, Albertin A, Torri G. Interscalene brachial plexus anaesthesia with small volumes of ropivacaine 0.75%: effects of the injection technique an the onset time of nerve blockade. Eur J Anaesthesiol 2001; 18: 548[CrossRef][ISI][Medline]
12 Fleischmann E, Marhofer P, Greher M, Waltl B, Sitzwohl C, Kapral S. Brachial plexus anaesthesia in children: lateral infraclavicular vs axillary approach. Paediatr Anaesth 2003, 13: 1038[CrossRef][ISI][Medline]
13 Fornage BD. Peripheral nerves of the extremity: imaging with ultrasound. Radiology 1988; 167: 17982[Abstract]
14 Frerk CM. Palsy after femoral nerve block. Anaesthesia 1988; 43: 1678
15 Giaufre E, Dalens B, Gombert A. Epidemiology and morbidity of regional anesthesia in children: a one-year prospective survey of the French-Language Society of Pediatric Anesthesiologists. Anesth Analg 1996; 83: 90412[Abstract]
16 Gimenez A, Martinez-Noguera A, Donoso L, Catala E, Serra R. Percutaneous neurolysis of the celiac plexus via the anterior approach with sonographic guidance. Am J Roentgenol 1993; 161: 10613[Abstract]
17 Graif M, Seton A, Nerubai J, Horoszowski H, Itzchak Y. Sciatic nerve: sonographic evaluation and anatomic-pathologic considerations. Radiology 1991; 181: 4058[Abstract]
18 Grau T, Leipold RW, Horter J, Conradi R, Martin E, Motsch J. The lumbar epidural space in pregancy: visualization by ultrasonography. Br J Anaesth 2001; 86: 798804
19 Grau T, Leipold RW, Delorme S, Martin E, Motsch J. Ultrasound imaging of the thoracic epidural space. Reg Anaesth Pain Med 2002; 27: 2006[CrossRef]
20 Grau T, Leipold RW, Conradi R, Martin E, Motsch J. Efficacy of ultrasound imaging in obstetric epidural anesthesia. J Clin Anesth 2002; 14: 16975[CrossRef][ISI][Medline]
21 Greher M, Retzl G, Niel P, Kamholz L, Marhofer P, Kapral S. Ultrasonographic assessment of topographic anatomy in volunteers suggest a modification of the infraclavicular vertical brachial block. Br J Anaesth 2002; 88: 6326
22 Greher M, Kapral S. Is regional anesthesia simply an exercise in applied sonoanatomy? Anesthesiology 2003; 99: 2501[CrossRef][ISI][Medline]
23 Greher M, Schabert G, Kamholz LP, et al. Ultrasound-guided facet nerve block: a sono-anatomical study of a new methodological approach. Anesthesiology 2004; in press
24 Jöhr M, Sossai R. Colonic puncture during ilioinguinal nerve block in a child. Anesth Analg 1999; 88: 10512
25 Jöhr M. Regionalanästhesie. In: Kinderanästhesie, 5th edn. München: Urban and Fischer, 2001; 1736
26 Kapral S, Krafft P, Eibenberger K, Fitzgerald R, Gosch M, Weinstabl C. Ultrasound-guided supraclavicular approach for regional anesthesia of the brachial plexus. Anesth Analg 1994; 78: 50713[Abstract]
27 Kapral S, Krafft P, Gosch M, Fleischmann D, Weinstabl C. Ultrasound imaging for stellate ganglion block: direct visualization of puncture site and local anesthetic spread. a pilot study. Reg Anesth 1995; 20: 3238[ISI][Medline]
28 Kapral S, Krafft P, Gosch M, Fridrich P, Weinstabl C. Subdural, extra-arachnoid block as a complication of stellate ganglion block: documentation with ultrasound. Anasthesiol Intensivmed Notfallmed Schmerzther 1997; 32: 63840[ISI][Medline]
29 Kapral S, Jandrasits O, Schabernig C, et al. Lateral infraclavicular plexus block vs. axillary block for hand and forearm surgery. Acta Anaesthesiol Scand 1999; 43: 104752[CrossRef][ISI][Medline]
30 Kilka HG, Geiger P, Mehrkens HH. Infraclavicular plexus blockade. A new method for anaesthesia of the upper extremity. An anatomical and clinical study. Anaesthesist 1995; 44: 33944[CrossRef][ISI][Medline]
31 Kirchmair L, Entner T, Wissel J, Moriggl B, Kapral S, Mitterschiffthaler G. A study of the paravertebral anatomy for ultrasound-guided posterior lumbar plexus block. Anesth Analg 2001; 93: 47781
32 Kirchmair L, Entner T, Kapral S, Mitterschiffthaler G. Ultrasound guidance for the psoas compartment block: an imaging study. Anesth Analg 2002; 94: 70610
33 Kirvela O, Svedstrom E, Lundbom N. Ultrasonic guidance of lumbar sympathetic and celiac plexus block: a new technique. Reg Anesth 1992; 17: 436[ISI][Medline]
34 Koscielnak-Nielsen ZJ, Stens-Pedersen HL, Lippert FK. Readiness for surgery after axillary block: single or multiple injection techniques. Eur J Anaesthesiol 1997; 14: 16471[ISI][Medline]
35 La Grange P, Foster PA, Pretorius LK. Application of the Doppler ultrasound bloodflow detector in supraclavicular brachial plexus block. Br J Anaesth 1978; 50: 9657[Abstract]
36 Mahoudeau G, Gaertner E, Launoy A, Ocquidant P, Loewenthal A. Interscalenic block: accidental catheterization of the epidural space. Ann Fr Anesth Reanim 1995; 14: 43841[ISI][Medline]
37 Marhofer P, Schrögendorfer K, Koinig H, Kapral S, Weinstabl C, Mayer N. Ultrasonographic guidance improves sensory block and onset time of three-in-one blocks. Anesth Analg 1997; 85: 8547[Abstract]
38 Marhofer P, Schrögendorfer K, Andel H, et al. Combined sciatic nerve3 in 1 block in high risk patient. Anaesthesiol Intensivmed Notfallmed Schmerzther 1998; 33: 399401
39 Marhofer P, Schrögendorfer K, Wallner T, Koinig H, Mayer N, Kapral S. Ultrasonographic guidance reduces the amount of local anesthetic for 3-in-1 blocks. Reg Anesth Pain Med 1998; 23: 5848[CrossRef][ISI][Medline]
40 Marhofer P, Greher M, Sitzwohl C, Kapral S. Ultrasonographic guidance for infraclavicular plexus anaesthesia in children. Anaesthesia 2004; 59: 6426[CrossRef][ISI][Medline]
41 Meier G, Bauereis C, Maurer H, Meier T. Interscalenäre Plexusblockade: anatomische Voraussetzungenanästhesiologische und operative Aspekte. Anaesthesist 2001; 50: 33341[CrossRef][ISI][Medline]
42 Meier G, Maurer H, Bauereis C. Axillary brachial plexus block. Anatomical investigations to improve radial nerve block. Anaesthesist 2003; 52: 5359[ISI][Medline]
43 Morris GF, Lang SA, Dust WN, Van der Wal M. The parasacral sciatic nerve block. Reg Anesth 1997; 22: 2238[ISI][Medline]
44 Muravchick S, Owens WD. An unusual complication of lumbosacral plexus block: a case report. Anesth Analg 1976; 55: 3502[Abstract]
45 Neuburger M, Kaiser H, Rembold-Schuster I, Landes H. Vertical infraclavicular brachial-plexus blockade. A clinical study of reliability of a new method for plexus anesthesia of the upper extremity. Anaesthesist 1998; 47: 5959[CrossRef][ISI][Medline]
46 Neuburger M, Landes H, Kaiser H. Pneumothorax in vertical infraclavicular block of the brachial plexus. Review of a rare complication. Anaesthesist 2000; 49: 9014[CrossRef][ISI][Medline]
47 Neuburger M, Kaiser H, Ass B, Franke C, Maurer H. Vertical infraclavicular blockade of the brachial plexus (VIP). A modified method to verify the puncture under consideration of the risk of pneumothorax. Anaesthesist 2003; 52: 61924[CrossRef][ISI][Medline]
48 Niesel HC. Beinnervenblockaden. In: Regionalanästhesie, Lokalanästhesie, Regionale Schmerztherapie. Stuttgart: Georg Thieme, 1994; 42942
49 Parkinson SK, Mueller JB, Little WL, Bailey SL. Extent of blockade with various approaches to the lumbar plexus. Anesth Analg 1989; 68: 2438[Abstract]
50 Perlas A, Chan VWS, Simons M. Brachial plexus examination and localization using ultrasound and electrical stimulationa volunteer study. Anesthesiology 2003; 99: 42935[CrossRef][ISI][Medline]
51 Peterson MK. Ultrasound-guided nerve blocks. Br J Anaesth 2002; 88: 6214
52 Retzl G, Kapral S, Greher M, Mauritz W. Ultrasonographic findings of the axillary part of the brachial plexus. Anesth Analg 2001; 92: 12715
53 Rosario DJ, Jacob S, Luntley J, Skinner PP, Raftery AT. Mechanism of femoral nerve palsy complicating percutaneous ilioinguinal field block. Br J Anaesth 1997; 78: 3146
54 Sandhu NS, Capal LM. Ultrasound-guided infraclavicular brachial plexus block. Br J Anaesth 2002; 89: 2549
55 Splinter WM, Bass J, Komocar L. Regional anaesthesia for hernia repair in children: local vs caudal anaesthesia. Can J Anaesth 1995; 42: 197200[Abstract]
56 Stark RH. Neurologic injury from axillary block anesthesia. J Hand Surg 1996; 21: 3916
57 Steiner E, Nael C. Sonography of peripheral nerves: basic principles. Acta Anaesthesiol Scand 1998; 42 (Suppl. 112): 468[ISI]
58 Tetzlaff JE, Yoon HJ, Brems J. Interscalene brachial plexus block for shoulder surgery. Reg Anesth 1994; 19: 33943[ISI][Medline]
59 Tetzlaff JE, Yoon HJ, Dilger J, Brems J. Subdural anesthesia as a complication of an interscalene brachial plexus block. Case report. Reg Anesth 1994; 19: 3579[ISI][Medline]
60 Thierney E, Lewis G, Hurtig JB, Johnson D. Femoral nerve block with bupivacaine 0.25 per cent for postoperative analgesia after open knee surgery. Can J Anaesth 1987; 34: 4558[Abstract]
61 Thompson GE, Rorie DK. Functional anatomy of the brachial plexus sheath. Anesthesiology 1983; 59: 11722[ISI][Medline]
62 Williams SR, Chovinard P, Arcand G, et al. Ultrasound guidance speeds execution and improves the quality of supraclavicular block. Anesth Analg 2003; 97: 151823
63 Winnie AP. The interscalene brachial plexus block. Anesth Analg 1970; 49: 45566[Medline]
64 Winnie AP, Ramamurthy S, Durrany Z. The inguinal paravascular technic of lumbar plexus anesthesia: the 3-in-1 block. Anesth Analg 1973; 52: 98996[ISI][Medline]
65 Winnie AP, Ramamurthy S, Durrani Z, Radonjic R. Plexus blocks for lower extremity surgery. Anesthesiol Rev 1974; 1: 116
66 Wu TJ, Lin SY, Liu CC, Chang HC, Lin CC. Ultrasound imaging aids infraclavicular brachial plexus block. Ma Zui Xue Za Zhi 1993; 31: 836[Medline]