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Κύρια Basic Sciences in Anesthesia
Basic Sciences in AnesthesiaEhab Farag, Maged Argalious, John E. Tetzlaff, Deepak Sharma (eds.)
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Ehab Farag · Maged Argalious John E. Tetzlaff · Deepak Sharma Editors Basic Sciences in Anesthesia 123 Basic Sciences in Anesthesia Ehab Farag Maged Argalious John E. Tetzlaff Deepak Sharma Editors Basic Sciences in Anesthesia Editors Ehab Farag Departments of General Anesthesia and Outcomes Research, Anesthesiology Institute Cleveland Clinic Lerner College of Medicine, Case Western University Cleveland, OH, USA John E. Tetzlaff Department of General Anesthesia, Anesthesiology Institute Cleveland Clinic Lerner College of Medicine of Case Western Reserve University Cleveland, OH, USA Maged Argalious Center for Anesthesiology Education, Anesthesiology Institute Cleveland Clinic Lerner College of Medicine Cleveland, OH, USA Deepak Sharma Department of Anesthesiology & Pain Medicine University of Washington Seattle, WA, USA ISBN 978-3-319-62065-7 ISBN 978-3-319-62067-1 https://doi.org/10.1007/978-3-319-62067-1 (eBook) Library of Congress Control Number: 2017960173 © Springer International Publishing AG 2018 This work is subject to copyright. All rights are reserved by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publisher, the authors and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, express or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. Printed on acid-free paper This Springer imprint is published by Springer Nature The registered company is Springer International Publishing AG The registered company address is: Gewerbestrasse 11, 6330 Cham, Switzerland V Thanks to my mother, my late father, and my brother and his family for their help, support, and prayers. Ehab Farag Thanks to my parents whose passion for research and scientific discovery proved to be contagious. Thanks to my wife Nermine for her unrelenting faith, her unconditional love, and her impressive emotional intelligence. Thanks to my children Daniel and Sandra, for their cheerful and joyous personalities and their genuine love of family. Maged Argalious Thanks to my wife, Susan, for her patience and tolerance of my late nights that were part of my participation in this project. John E. Tetzlaff My sincerest thanks to my parents Mrs. Renu and Col. PC Sharma, my teachers, and my dear wife Madhu and daughters Deeya and Drishti for their constant support, love, and encouragement. Deepak Sharma Preface The basic sciences are the essence of anesthesiology. Therefore, the American Board of Anesthesiology (ABA) includes an examination on the basic sciences for the ABA certification. The lack of a specific book dedicated to the basic sciences in anesthesiology has driven us to compose this book. We tried our best to follow the syllabus of the ABA basic sciences examination in order to create an accurate resource for study. The motto of this book is to follow Alexander Pope's advice in 1709: "A little learning is a dangerous thing; drink deep, or taste not the Pierian spring: there shallow droughts intoxicate the brain, and drinking largely sobers us again." This message is still relevant today in the field of anesthesiology. The content of each chapter of the book is presented in a comprehensive manner and is conducive for successful study. Every chapter highlights key topics and includes questions testing comprehension of the respective subject matter. Moreover, suggested references are included for further research in the basic sciences. We would like to thank our colleagues for their hard work and dedication in writing the book. In addition, we would like to thank Ms. Maureen K. Pierce and Joanna Renwick from Springer International Publishing for their perseverance during the process. At the end, we hope this book will be helpful in preparing for the ABA basic science examination as well as serve as a tool for practicing anesthesiologists who would like to refresh their knowledge in basic sciences. Ehab Farag Maged Argalious John E. Tetzlaff Cleveland, USA Deepak Sharma Seattle, USA VII Contents I Applied Anatomy 1 Peripheral Nerve Block Anesthesia...................................................................................................................... 3 Sree Kolli and Loran Mounir Soliman 2 entral Neuraxial Anatomy and Anesthetic Application C (Central Neuraxial Blockade).................................................................................................................................... 17 Nathan J. Harrison, Laurie S. Daste, Gary S. McDaniel Jr, Matthew E. Patterson, and Maged Guirguis 3 Anatomy of the Brain and Spinal Cord.............................................................................................................. 41 Matthew K. Whalin and Sona Shah Arora 4 Anatomy of the Airway/Airway Management.............................................................................................. 61 Sekar S. Bhavani and Basem Abdelmalak II Pharmacology 5 Pharmacology: General Concepts......................................................................................................................... 95 Yaqi Hu and Kamal Maheshwari 6 Pharmacology of Non-opioid Intravenous Anesthetics......................................................................... 107 Mohamed Abdalla 7 Pharmacology of Opioids........................................................................................................................................... 123 Juan P. Cata and Shreyas P. Bhavsar 8 Clinical Pharmacology of Drugs Acting at the Neuromuscular Junction.................................... 139 J. Ross Renew, Sorin J. Brull, and Mohammed Naguib 9 Pharmacology of Local and Neuraxial Anesthetics................................................................................... 161 Hesham Elsharkawy and Sree Kolli 10 Pharmacology of Inhaled Anesthetics............................................................................................................... 177 Elizabeth Demers Lavelle and Swamy Kurra 11 Cardiovascular Anatomy and Pharmacology................................................................................................ 195 Maria Bauer 12 Respiratory Pharmacology........................................................................................................................................ 229 Ahmad Maher Adi 13 Renal Pharmacology...................................................................................................................................................... 239 Sekar S. Bhavani 14 Pharmacology of Anticoagulants, Antithrombotics, and Antiplatelet Drugs......................... 249 G. Burkhard Mackensen 15 Perioperative Intravenous Fluid Therapy........................................................................................................ 259 Marta Kelava, David S. Youssef, and Maged Argalious VIII Contents III Physiology 16 Central and Peripheral Nervous Systems......................................................................................................... 271 Jia W. Romito, Ravi Bhoja, and David L. McDonagh 17 Cardiovascular Physiology........................................................................................................................................ 299 Sandeep Khanna 18 Respiratory System Physiology.............................................................................................................................. 329 Siddharth Pawan Dugar, Mani Latifi, and Eduardo Mireles-Cabodevila 19 Physiology of the Autonomic Nervous System............................................................................................ 355 Brian K. Johnson 20 Physiology of Temperature Control..................................................................................................................... 365 Kurt Ruetzler and Andrea Kurz 21 Gastrointestinal/Hepatic Physiology.................................................................................................................. 373 Allen Keebler 22 Renal Physiology.............................................................................................................................................................. 379 Reem Khatib 23 hysiology of the Endocrine System and Metabolic P Complications in Anesthesia.................................................................................................................................... 405 Michael Erin Schoor and Shaheen Shaikh IV Anesthetic Management Topics 24 Preoperative Evaluation of Patients Undergoing Non-cardiac Surgery..................................... 429 Elizabeth A. M. Frost and Daniel Katz 25 Premedication.................................................................................................................................................................... 441 Kenneth C. Cummings III 26 Monitored Anesthesia Care....................................................................................................................................... 451 Ihab Adly Riad and Basem Abdelmalak 27 Blood Products Transfusion...................................................................................................................................... 465 Jacek B. Cywinski 28 Complications in Anesthesia.................................................................................................................................... 483 Fenghua Li and Parikshith Sumathi 29 The Postoperative Period........................................................................................................................................... 505 Verghese T. Cherian 30 Perioperative Pain Management........................................................................................................................... 515 Juan P. Cata and Javier D. Lasala 31 Special Problems in Anesthesia.............................................................................................................................. 527 John E. Tetzlaff IX Contents V Physics in Anesthesia 32 The Anesthesia Machine.............................................................................................................................................. 539 Mark Teen, Theresa Barnes, and Ehab Farag 33 Physical Measurements in Anesthesia............................................................................................................... 565 Anthony James Cartwright and D. John Doyle 34 Breathing Systems........................................................................................................................................................... 587 Jack Buckley and Myroslav Figura 35 Physics of Instrumentation........................................................................................................................................ 597 Verghese T. Cherian and Arne O. Budde 36 Electrical Safety in the Operating Room.......................................................................................................... 613 D. John Doyle 37 Mechanical Ventilation................................................................................................................................................. 627 Aaron J. Douglas 38 tatistics Made Simple: Introduction to Biostatistics and Research S Design for the Anesthesiologist............................................................................................................................. 637 Edward J. Mascha Contributors Mohamed Abdalla, MD Sekar S. Bhavani, MD, MS, FRCS(I) Department of Anesthesiology Cleveland Clinic Lerner College of Medicine of Case Western Reserve University Cleveland, OH, USA Cleveland Clinic Lerner College of Medicine Anesthesiology Institute, Cleveland Clinic Cleveland, OH, USA firstname.lastname@example.com; firstname.lastname@example.com Department of Cardiothoracic Anesthesiology Anesthesiology Institute, Cleveland Clinic Cleveland, OH, USA email@example.com Basem Abdelmalak, MD Anesthesia for Bronchoscopic Surgery Center for Sedation Departments of General Anesthesiology and Outcomes Research, Cleveland Clinic Cleveland, OH, USA firstname.lastname@example.com Maged Argalious Center for Anesthesiology Education Anesthesiology Institute Cleveland Clinic Lerner College of Medicine Cleveland, OH, USA firstname.lastname@example.com Ahmad Maher Adi, MD Department of Cardiothoracic Anesthesiology and Critical Care, Cleveland Clinic Cleveland, OH, USA email@example.com Sona Shah Arora, MD Department of Anesthesiology Emory University School of Medicine Grady Memorial Hospital Atlanta, GA, USA firstname.lastname@example.com Theresa Barnes, MD, MPH Department of Anesthesiology Cleveland Clinic Foundation Cleveland, OH, USA firstname.lastname@example.com, email@example.com Maria Bauer, MD Department of Anesthesiology and Critical Care Medicine The Johns Hopkins Hospital Baltimore, MD, USA firstname.lastname@example.com; email@example.com Shreyas P. Bhavsar, DO Department of Anesthesiology and Perioperative Medicine, Division of Anesthesiology and Critical Care The University of Texas MD Anderson Cancer Center Houston, TX, USA firstname.lastname@example.com Ravi Bhoja, MD Department of Anesthesiology and Pain Management University of Texas Southwestern Medical Center Dallas, TX, USA firstname.lastname@example.com Sorin J. Brull, MD, FCARCSI (Hon) Department of Anesthesiology and Perioperative Medicine Mayo Clinic College of Medicine Jacksonville, FL, USA email@example.com Jack Buckley, MD Department of Anesthesiology UCLA Medical Center Los Angeles, California, USA firstname.lastname@example.com Arne O. Budde, MD, DEAA Department of Anesthesiology and Perioperative Medicine Penn State Health, Milton S. Hershey Medical Center Hershey, PA, USA email@example.com Anthony James Cartwright, MB, ChB, MRCS (Eng.), FRCA Anesthesiology Institute, Cleveland Clinic Abu Dhabi Abu Dhabi, United Arab Emirates email@example.com Juan P. Cata, MD Department of Anesthesiology and Perioperative Medicine The University of Texas – MD Anderson Cancer Center Anesthesiology and Surgical Oncology Research Group Houston, TX, USA firstname.lastname@example.com; email@example.com XI Contributors Verghese T. Cherian, MBBS, MD, FCAI Anesthesiology and Perioperative Medicine Penn State Health, Milton S. Hershey Medical Center Hershey, PA, USA email@example.com; firstname.lastname@example.com Kenneth C. Cummings III, MD, MS Department of General Anesthesiology Cleveland Clinic Cleveland, OH, USA email@example.com Jacek B. Cywinski, MD Department of General Anesthesiology Cleveland Clinic Cleveland, OH, USA firstname.lastname@example.com Laurie S. Daste, MD Department of Anesthesiology Ochsner Medical Center New Orleans, LA, USA email@example.com Aaron J. Douglas, DO Department of Cardiothoracic Anesthesiology Cleveland Clinic Cleveland, OH, USA firstname.lastname@example.com D. John Doyle, MD, PhD Department of General Anesthesiology Cleveland Clinic Abu Dhabi Abu Dhabi, United Arab Emirates firstname.lastname@example.com; email@example.com Siddharth Pawan Dugar, MD Respiratory Institute, Cleveland Clinic Foundation Cleveland, OH, USA firstname.lastname@example.com Hesham A. Elsharkawy, MD, MSc Department of Anesthesiology, Cleveland Clinic Lerner College of Medicine of Case Western Reserve University Anesthesiology Institute and Department of Outcomes Research, Cleveland Clinic Cleveland, OH, USA email@example.com Ehab Farag Department of General Anesthesiology Anesthesiology Institute Cleveland Clinic Lerner College of Medicine Case Western University Cleveland, Ohio, USA Departments of General Anesthesia and Outcomes Research Cleveland Clinic Cleveland, OH, USA email@example.com Myroslav Figura, MD Department of Anesthesiology UCLA Medical Center Los Angeles, California, USA email@example.com Elizabeth A.M. Frost, MBChB, DRCOG Department of Anesthesiology Icahn Medical Center at Mount Sinai New York, NY, USA email@example.com; email@example.com Maged N. Guirguis, MD Department of Anesthesiology and Critical Care Medicine Ochsner Health Systems Louisiana State University School of Medicine New Orleans, LA, USA firstname.lastname@example.com Nathan J. Harrison, MD Department of Anesthesiology and Pain Management Ochsner Health Systems Covington, LA, USA firstname.lastname@example.com Yaqi Hu, MD Department of General Anesthesia Cleveland Clinic Foundation Cleveland, OH, USA firstname.lastname@example.com Brian K. Johnson, MD, MEd Department of Anesthesia and Perioperative Medicine University Hospitals Cleveland Medical Center Cleveland, OH, USA email@example.com Daniel Katz, MD Icahn Medical Center at Mount Sinai New York, NY, USA email@example.com Allen Keebler, DO Department of General Anesthesiology Cleveland Clinic Cleveland, OH, USA email@example.com XII Contributors Marta Kelava, MD, MS Fenghua Li, MD Center for Anesthesiology Education Cleveland Clinic Cleveland, OH, USA email@example.com Department of Anesthesiology SUNY Upstate Medical University Syracuse, NY, USA firstname.lastname@example.com Sandeep Khanna, MBBS, MD G. Burkhard Mackensen, MD, PhD, FASE Department of General Anesthesiology Cleveland Clinic Foundation Cleveland, OH, USA email@example.com Division of Cardiothoracic Anesthesiology, Department of Anesthesiology and Pain Medicine University of Washington Medical Center Regional Heart Center Seattle, WA, USA firstname.lastname@example.com Reem Khatib, MD Department of General Anesthesiology Cleveland Clinic Cleveland, OH, USA firstname.lastname@example.com Sree Kolli, MD Anesthesia Institute, Cleveland Clinic Cleveland, OH, USA email@example.com Swamy Kurra, MBBS Department of Orthopedic Surgery SUNY Upstate Medical University Syracuse, NY, USA firstname.lastname@example.com Andrea Kurz, MD Department of General Anesthesiology Anesthesiology Institute, Cleveland Clinic Cleveland, OH, USA email@example.com Javier D. Lasala, MD Department of Anesthesiology and Perioperative Medicine The University of Texas – MD Anderson Cancer Center Anesthesiology and Surgical Oncology Research Group Houston, TX, USA firstname.lastname@example.com Mani Latifi, MD Respiratory Institute Cleveland Clinic Foundation Cleveland, OH, USA firstname.lastname@example.com Elizabeth Demers Lavelle, MD Department of Anesthesiology SUNY Upstate Medical University Syracuse, NY, USA firstname.lastname@example.com Kamal Maheshwari, MD, MPH Departments of General Anesthesiology and Outcomes Research Anesthesia Institute, Cleveland Clinic Foundation Cleveland, OH, USA email@example.com Edward J. Mascha, PhD Cleveland Clinic Lerner College of Medicine at Case Western Reserve University Cleveland, OH, USA Department of Quantitative Health Sciences Cleveland Clinic Cleveland, OH, USA email@example.com Gary S. McDaniel Jr, BSN, MD Department of Anesthesiology Ochsner Medical Center New Orleans, LA, USA email@example.com David L. McDonagh, MD Department of Anesthesiology and Pain Management University of Texas Southwestern Medical Center Dallas, TX, USA firstname.lastname@example.com; firstname.lastname@example.com Eduardo Mireles-Cabodevila, MD Respiratory Institute, Cleveland Clinic Foundation Cleveland, OH, USA firstname.lastname@example.com Mohamed Naguib, MB, BCh, MSc, FCARCSI, MD Department of General Anesthesia Cleveland Clinic Lerner College of Medicine of Case Western Reserve University Cleveland, OH, USA email@example.com XIII Contributors Matthew E. Patterson, MD Shaheen Shaikh, MD Department of Anesthesiology Ochsner Medical Center New Orleans, LA, USA email@example.com Department of Anesthesiology University of Massachusetts Memorial Hospital Worcester, MA, USA firstname.lastname@example.com Johnathan Ross Renew, MD Loran Mounir Soliman, MD Department of Anesthesiology and Perioperative Medicine Mayo Clinic College of Medicine Jacksonville, FL, USA firstname.lastname@example.com Department of General Anethesiology Cleveland Clinic Cleveland, OH, USA email@example.com Ihab Adly Riad, MD Department of Anesthesiology SUNY Upstate Medical University Syracuse, NY, USA firstname.lastname@example.com Cleveland Clinic Lerner College of Medicine Cleveland, OH, USA Regional Anesthesia, Cleveland Clinic Cleveland, OH, USA Department of Regional Anesthesiology Fairview General Hospital Cleveland, OH, USA email@example.com; email@example.com Parikshith Sumathi, MBBS, DA, MD Mark Teen, MD Anesthesiology Institute, Cleveland Clinic Cleveland, OH, USA firstname.lastname@example.com John E. Tetzlaff Jia W. Romito, MD Department of Anesthesiology and Pain Management University of Texas Southwestern Medical Center Dallas, TX, USA firstname.lastname@example.com Cleveland Clinic Lerner College of Medicine of Case Western Reserve University Department of General Anesthesia, Anesthesiology Institute, Cleveland Clinic Cleveland, OH, USA firstname.lastname@example.com Kurt Ruetzler, MD Department of Outcomes Research and General Anesthesiology Anesthesiology Institute, Cleveland Clinic Cleveland, OH, USA email@example.com Matthew K. Whalin, MD, PhD Department of Anesthesiology Emory University School of Medicine Grady Memorial Hospital Atlanta, GA, USA firstname.lastname@example.com Michael Erin Schoor, MD Department of Anesthesiology and Perioperative Medicine University of Massachusetts Worcester, MA, USA firstname.lastname@example.com David S. Youssef, BA College of Medicine University of Cincinnati Hospital Cincinnati, OH, USA firstname.lastname@example.com 1 Applied Anatomy Contents Chapter 1 Peripheral Nerve Block Anesthesia – 3 Sree Kolli and Loran Mounir Soliman Chapter 2 Central Neuraxial Anatomy and Anesthetic Application (Central Neuraxial Blockade) – 17 Nathan J. Harrison, Laurie S. Daste, Gary S. McDaniel Jr, Matthew E. Patterson, and Maged Guirguis Chapter 3 Anatomy of the Brain and Spinal Cord – 41 Matthew K. Whalin and Sona Shah Arora Chapter 4 Anatomy of the Airway/Airway Management – 61 Sekar S. Bhavani and Basem Abdelmalak I 3 Peripheral Nerve Block Anesthesia Sree Kolli and Loran Mounir Soliman 1.1 Anatomy of the Nerve – 4 1.2 Upper Limb Blocks – 4 1.2.1 1.2.2 1.2.3 1.2.4 I nterscalene Block – 4 Supraclavicular Block – 6 Infraclavicuar Block – 7 Axillary Block – 7 1.3 Lower Limb Blocks – 8 1.3.1 1.3.2 1.3.3 1.3.4 1.3.5 F emoral Nerve Block – 8 Sciatic Nerve Block – 9 Popliteal Sciatic Nerve Block – 10 Ankle Block – 12 Transversus Abdominis Plane (TAP) Block – 13 1.4 Questions and Answers – 13 References – 16 © Springer International Publishing AG 2018 E. Farag et al. (eds.), Basic Sciences in Anesthesia, https://doi.org/10.1007/978-3-319-62067-1_1 1 4 1 S. Kolli and L.M. Soliman Key Points 1. Peripheral nerve is composed of axons of multiple neurons bundled together in fascicles. 2. To achieve good block, local anesthetic should be injected in close proximity to the nerve or in the same fascial plane in which the nerve lies. 3. Advances in ultrasound technology allows real-time visualization of needle advancement toward the nerve, potentially avoiding critical structures. It also allows to visualize the spread of local anesthetic around the nerve. 4. Ultrasound and peripheral nerve stimulators facilitate nerve blockade, but their use does not eliminate the risk of nerve injury. 5. Anesthesia of the shoulder and upper extremity can be obtained by blockade of the brachial plexus (C5-T1). 6. Supraclavicular block does not eliminate the risk of phrenic nerve paralysis. The incidence depends on the volume of local anesthetic injected. 7. Interscalene and supraclavicular block can miss the lower trunk, hence axillary approach to brachial plexus is most optimal for procedures on forearm and hand. 8. Infraclavicuar block avoids the risk of phrenic nerve paralysis, making it an excellent choice in patients with respiratory issues. 9. Femoral nerve block is easy to learn, low risk with minimal complications. It is useful for surgery on the anterior thigh and knee, quadriceps tendon repair, and postoperative pain management of femur and knee surgery. 10. Sciatic nerve block is useful for surgical procedures involving hip, knee, and distal lower extremity. It can be blocked at multiple locations by multiple approaches. 11. Popliteal nerve block is useful for surgery on foot and ankle, combined with saphenous nerve block can provide complete anesthesia of the limb distal to the knee. 12. Transversus abdominis plane (TAP) block provides postoperative analgesia for surgeries on anterior abdominal wall. It is relatively easy and safe block to perform under ultrasound guidance. 1.1 Anatomy of the Nerve A peripheral nerve trunk is composed of axons of multiple neurons bundled together in connective tissue and endoneural fluid (. Fig. 1.1). Each axon is surrounded by endoneurium, which is made up of glycocalyx and a mesh of collagen. Axons are bundled together into groups called fascicles and each fascicle is wrapped in a layer of connective tissue called perineurium. All the fascicles are finally ensheathed in a connective tissue layer called epineurium. The blood vessels run between the fascicles and supply oxygen and nutrients to the axons. 1.2 Upper Limb Blocks The brachial plexus is a neural bundle that provides sensory and motor innervation to the upper extremity. Nerve roots of C5-T1 undergo complex congregation forming components named roots, trunks, divisions, cords, before forming the terminal nerves of the upper extremity (. Fig. 1.2). The plexus can be blocked at several locations, depending on the required region of the upper limb to be blocked. The interscalene space is a potential space between the anterior and middle scalene muscles. The 5 roots of the cervical and the first thoracic spinal nerves give rise to 3 trunks (superior, middle, and inferior) that emerge between the medial and anterior scalene muscles to lie on the floor of the posterior triangle of the neck. The roots of the plexus lie deep to the prevertebral fascia, whereas the trunks are covered by its lateral extension, the axillary sheath. Each trunk divides into an anterior and a posterior division behind the clavicle, at the apex of the axilla. The divisions combine to produce the 3 cords, which are named lateral, median, and posterior according to their relationship to the axillary artery. Individual nerves are formed as these neuronal elements descend distally. 1.2.1 Interscalene Block This is a technique of anesthetizing the roots or trunks of the brachial plexus in the neck between the anterior and middle scalene muscles. The procedure was first well described and popularized by Alon Winnie in 1970 [1]. Interscalene nerve block is typically performed to provide anesthesia or analgesia for surgery of the shoulder and upper arm. A successful block at this level anesthetizes the shoulder and upper arm, but does not reliably block nerve roots innervating the forearm, as the inferior trunk is often not included into the block. 55 Indications: Shoulder surgeries such as rotator cuff repair, acromioplasty, hemiarthroplasty, total shoulder arthroplasty, humerus fractures, elbow surgery. 55 Contraindications: Patient refusal, infection at planned injection site, preexisting neurologic defects, local anesthetic allergy, coagulopathy, contralateral phrenic nerve dysfunction, severe chronic obstructive pulmonary disease 55 Complications: Diaphragmatic paralysis, pneumothorax, hoarseness, Horner's syndrome, epidural/intrathecal injection, local anesthetic (LA) toxicity, infection, hematoma, and allergic reaction. Landmark/Nerve Stimulator Technique The landmarks used for the block are the clavicular head of the sternocleidomastoid muscle, clavicle, and external jugular vein. The patient can be positioned supine or with the back mildly elevated and head rotated away from the side to be blocked. Palpate the sternocleidomastoid that overlies the superior aspects of the scalene muscles. Having the patient lift his or her head off the bed will help define the lateral border of the sternocleidomastoid muscle. The anterior scalene 1 5 Peripheral Nerve Block Anesthesia .. Fig. 1.1 Anatomy of a nerve (Reprinted under Creative Commons Attribution 4.0 International License from OpenStax, Anatomy & Physiology. Houston, TX, OpenStax, Rice University. 2016. Download for free at 7 http://cnx.org/content/ col11496/latest/) Blood vessels Perineurium (around one fascicle) Endoneurium Epineurium covering peripheral nerve Schwann cell Fascicle Myelinated axon .. Fig. 1.2 anatomy Brachial plexus Cords Divisions Trunks Roots C5 Dorsal scapular nerve Suprascapular nerve C6 Nerve to subclavius C7 rd Co La te ra l Lateral pectoral nerve Musculocutaneous nerve Axillary nerve Ulnar nerve rd Co T1 i r ste Po l edia M Median nerve or C8 rd Co Long thoracic nerve Upper subscapular nerve Medial pectoral nerve Thoraco dorsal nerve Lower subscapular nerve Radial nerve Medial cutaneous nerve of the forearm Medial cutaneous nerve of the arm muscle emerges from under the sternocleidomastoid muscle and runs inferiorly and laterally toward the first rib. By placing the fingers under the sternocleidomastoid muscle and inferior to the external jugular vein, sliding them laterally will identify anterior scalene muscle. The interscalene groove separates the anterior from the middle scalene muscle. This groove sometimes is very obvious during palpation, but frequently is subtle and more like a cleft. Once the groove is palpated, several maneuvers can be performed to confirm the groove. During deep inspiration, the groove often is accentuated because the scalenes are accessory muscles of respiration, which tense during inspiration. The groove also can be tracked down toward the first rib and palpate for the subclavian artery, which emerges between the scalenes. Once the interscalene groove is identified the palpating fingers should be gently but firmly pressed between the 6 1 S. Kolli and L.M. Soliman anterior and middle scalene muscles and should not be moved during the entire block procedure to allow for precise redirection of the needle when necessary. The needle is inserted 3–4 cm above the clavicle and advanced at an angle almost perpendicular to the skin plane. The nerve stimulator should be initially set to deliver 0.8–1.0 mA. The needle is advanced slowly until stimulation of the brachial plexus is obtained—seen as twitch of the pectoralis, deltoid, arm, forearm, or hand muscles at 0.2–0.5 mA. This typically occurs at a depth of 1–2 cm in most of the patients and 25–35 mL of local anesthetic is injected slowly with intermittent aspiration to rule out intravascular injection. Ultrasound Technique Apart from precisely locating the brachial plexus, the ultrasound guidance allows to visualize the distribution of the local anesthetic around the plexus. It allows multiple injections around the brachial plexus, therefore eliminating the reliance on a single large injection of LA and may allow for the reduction in the volume of local anesthetic required to accomplish the block. It reduces the risk of injury to the blood vessels and the nerves in the plexus. The block can be performed with the patient in supine, semi- sitting, or semi-lateral decubitus position, with the patient's head facing away from the side to be blocked. The latter position is more suitable for in-plane approach from the lateral side, especially when a catheter is placed that needs to be tunneled away from the surgical drapes. 55 Scanning Technique 1 (Transverse Sweep): The transducer is positioned in the transverse plane just below the level of cricoid. Start by identifying the hyperechoic arc of the trachea and moving the probe posterolaterally until sternocleidomastoid muscle is identified. This muscle is triangular shaped and located anteriorly to the carotid artery and internal jugular vein. Once the great vessels are identified, slide the probe more laterally to identify the scalene muscles and the brachial plexus that lies in between them appearing as hypoechoic trunks. 55 Scanning Technique 2 (Backtracking): The other scanning technique is to identify the brachial plexus in the supraclavicular fossa and then track cephalad into the interscalene space. The transducer is placed over the sternocleidomastoid, 1–2 cm superior to the head of the clavicle. Move laterally to identify the subclavian artery and immediately superior and posterior to the artery, the brachial plexus is seen as a grouping of small hyperechoic circles with hypoechoic centers, similar to a cluster of grapes. The plexus is then traced cephalad to the preferred block region at the level of C6. Once the plexus is identified the needle is inserted in-plane— typically in a lateral to medial direction. As the needle passes through the prevertebral fascia, a certain loss of resistance is often felt. Inject 1–2 ml of local anesthetic to confirm correct location before the rest of the dose (15–25 cc in adults) is injected, visualizing the spread around the plexus. 1.2.2 Supraclavicular Block Often called the "spinal anesthesia of the upper extremity," the supraclavicular block is a technique of anesthetizing the brachial plexus at distal trunks and origin of the divisions, where the brachial plexus is confined to its smallest surface area. The first percutaneous supraclavicular block was performed by Kulenkampff in Germany in 1911, reportedly on himself [2]. The advantages of a supraclavicular technique over other brachial plexus block approaches are its rapid onset and complete and predictable anesthesia for the entire upper extremity and particularly hand surgery. The introduction of ultrasound guidance to regional anesthesia in the last decade has resulted in significant renewed interest in the clinical application of the supraclavicular block, as well as a greater understanding of its mechanics. 55 Indications: Upper extremity surgery including arm, elbow, forearm, wrist and hand. (It is best for areas below the mid-humerus level. Above the mid humerus, the shoulder area, an interscalene block would provide better coverage). However, if enough volume is used it can diffuse to the shoulder area. 55 Contraindications: Patient refusal, infection at planned injection site, preexisting neurologic defects, local anesthetic allergy, coagulopathy, contralateral phrenic nerve dysfunction, severe chronic obstructive pulmonary disease. 55 Complications: Diaphragmatic paralysis, pneumothorax, hoarseness, Horner's syndrome, LA toxicity, infection, hematoma, and allergic reaction. Landmark/Nerve Stimulator Technique Classic Approach The most common supraclavicular technique is the subclavian perivascular approach, described by Winnie and Collins [3]. The interscalene groove is palpated and followed distally until the pulsation of the subclavian artery is felt. This should be at the midpoint of the clavicle, about 1 cm posterior to it. It is important to note that the dome of the lung is medial to the insertion point of the needle. Entry to the sheath can be identified by a "click" as the needle pierces the tough fascia, by paresthesia, or by an appropriate motor response when a nerve stimulator is used. For vertical supraclavicular block, also called the "plumb bob" technique, identify the lateral border of the sternocleidomastoid as it inserts onto the clavicle by asking the patient to raise the head slightly off the bed. The needle entry site is immediately superior to the clavicle, just lateral to the identified lateral border of the sternocleidomastoid. The needle is inserted vertically at 90° to the bed and would result in contact with the brachial plexus in most patients. Ultrasound Technique The patient can be positioned anywhere from supine to sitting upright with their head rotated away from the block site. The probe is placed in the supraclavicular fossa and oriented 7 Peripheral Nerve Block Anesthesia erpendicular to the subclavian artery. The subclavian artery is p identified by its thick wall and brisk pulsations. Immediately superior and postero-lateral to the artery, the brachial plexus is seen as a grouping of small hyperechoic circles with hypoechoic centers, similar to a bunch of grapes. Alternatively, the plexus can be found in the interscalene space and followed distally to its association with the subclavian artery. Deep to the artery the structures of note are the dome of the lung (identified by its characteristic movement and scatter) and the first rib (identified by its hyperechoic surface with dense posterior shadowing). Once the plexus is identified, the needle is inserted in-plane from a lateral to medial direction. The entrance of the needle into the brachial plexus sheath is often associated with a palpable "pop" as the needle passes through the paravertebral fascia/ brachial plexus sheath. After a careful aspiration, 1–2 mL of local anesthetic is injected to confirm the proper needle placement. When the injection displaces the brachial plexus away from the needle, an additional advancement of the needle 1–2 mm deeper may be required to accomplish adequate spread of the local anesthetic. When injection of the local anesthetic does not appear to result in a spread in and around the brachial plexus, additional needle repositioning and injections may be necessary. 1.2.3 Infraclavicuar Block The infraclavicuar brachial plexus block is another way of blocking the brachial plexus below the level of the clavicle. It is functionally similar to the supraclavicular block and is useful for distal arm, elbow, wrist, and hand surgery. Infraclavicuar block avoids the risk of phrenic nerve block, making it an excellent choice in patients with respiratory issues. In the infraclavicuar fossa, the brachial plexus separates into individual cords that are named medial, lateral, and posterior based on their locations relative to the axillary artery. These cords bundle around the axillary artery as it travels inferior to the coracoid and into the axilla. The cords lie deep to the pectoralis muscles and superficial to the lung while the axillary vein runs inferior to the artery. 55 Indications: Surgery on the distal arm, elbow, wrist, and hand. 55 Contraindications: Patient refusal, infection at planned injection site, presence of pacemaker at the site (U/S technique may not be possible due to limitation of probe placement), preexisting neurologic defects, local anesthetic allergy, coagulopathy. 55 Complications: LA toxicity, infection, bleeding, hematoma, pneumothorax, and nerve injury. Landmark Technique The landmarks required for the block are anterior process of the acromion, jugular notch, and the subclavian artery; and coracoid process and the medial clavicular head. The patient is positioned supine with the head tuned to the opposite side and arm abducted and flexed at the elbow. The coracoid process can be identified by palpating the bony prominence just medial to the shoulder by elevating and lowering the arm. The coracoid process meets the fingers of the Vertical Infraclavicuar Block palpating hand as the arm is lowered. Mark the medial clavicular head and draw a line joining these 2 points. The needle insertion point is 3 cm caudal to the mid point of the line joining the coracoid process and the medial clavicular head. The goal is to achieve a hand twitch using a current of 0.2–0.5 mA. Ultrasound Technique The patient can be positioned anywhere from supine to sitting position, and abduction of the arm will bring the artery and plexus closer to the skin. The transducer is placed just medial to the coracoid process with its cranial end below the clavicle. The pectoralis major and minor muscles are identified just above the plexus and vessels. The probe is rotated and moved as needed to obtain a transverse image of the artery. The 3 cords of the brachial plexus appear as hyperechoic circles surrounding the artery. The lateral cord is the closest to the coracoid; the posterior cord is deep to the artery; while the medial cord is the furthest from the coracoid and sometimes lies between the artery and the vein. Once the structures of interest are identified, the needle is inserted in-plane from the superior or inferior end of the transducer. The aim of the block is to surround each cord with local anesthetic, often achieved by injecting local anesthetic around the artery. Appropriate needle position is confirmed by the spread of the local anesthetic around the artery, dissecting the cords away from the artery. The steep angle of the needle for this deep block severely compromises the needle visualization. This can be improved by applying extra pressure on the probe and often injecting small amount of local anesthetic solution also improves needle visualization. 1.2.4 Axillary Block The axillary block is one of the most commonly used regional anesthesia techniques. This block aims to block the terminal branches of the brachial plexus, which include the median, radial, ulnar and musculocutaneous nerves. It is achieved by injecting local anesthetic around the axillary artery as median, ulnar, and radial nerves are all located within the neurovascular sheath. A separate injection is needed to block the musculocutaneous nerve. 55 Indications: Surgeries on hand, elbow, and some forearm operations. 55 Contraindications: Patient refusal, infection at planned injection site, preexisting neurologic defects, local anesthetic allergy, coagulopathy. 55 Complications: LA toxicity, infection, bleeding, hematoma, and allergic reaction. Landmark Technique Surface landmarks required for the axillary brachial plexus block are the axillary artery pulsation, coracobrachialis muscle, and the pectoralis major muscle. With the patient positioned supine and arm abducted at 90° and the axillary arterial pulsation as a point of reference, the median nerve is positioned superficially and immediately above the pulse; the 1 8 1 S. Kolli and L.M. Soliman ulnar nerve is found superficial slightly deeper than the median nerve; the radial nerve is located behind the pulse. The musculocutaneous nerve can be found 1–3 cm deeper and above the pulse, often outside the brachial plexus sheath as it moves distally away from the axillary fossa. Once the axillary artery pulse is felt, the artery is fixed between the index and middle finger, pressed firmly against the humerus. The needle is advanced directly below the pulse until a radial nerve twitch is obtained, and local anesthetic is injected. The needle is withdrawn and reinserted above the artery and advanced slowly; median nerve twitch should be encountered first and on further advancement ulnar twitch should appear. Inject local anesthetic at both these points. The needle is finally brought back to skin and redirected into the coracobrachialis muscle until the tip is close to the musculocutaneous nerve. This is confirmed by the disappearance of the local coracobrachialis twitch and appearance of biceps twitch. Inject the last portion of the local anesthetic dose here. Ultrasound-Guided Technique The patient position is the same as the landmark technique. Palpate the pectoralis major muscle at its insertion into the humerus and place the transducer immediately distal to it and perpendicular to the axis of the arm. Slide the transducer to locate the axillary artery and brachial plexus if not already visualized. Identify the individual nerves and insert the needle in-plane from the cephalad direction toward the posterior aspect of the axillary artery. Local anesthetic should be deposited posterior to the artery first covering the radial nerve. The needle is then withdrawn and redirected superior to the artery and local anesthetic is injected around the median and ulnar nerves. Finally, the musculocutaneous nerve is anesthetized by injecting local anesthetic around it in the coracobrachialis muscle. Frequent aspiration, slow administration of local anesthetic, and avoiding injection at .. Fig. 1.3 Femoral nerve anatomy (Reprinted with permission from Farag and Brown [5]) high pressure are critical to decrease the risk of intravascular injection and nerve injury. 1.3 Lower Limb Blocks 1.3.1 Femoral Nerve Block The femoral nerve block is an essential block that is easy to learn, low risk with minimal complications. It is useful for surgery on the anterior thigh and knee, quadriceps tendon repair, and postoperative pain management of femur and knee surgery. It is frequently combined with other lower extremity blocks, such as sciatic and obturator blocks, to achieve anesthesia of almost the entire lower extremity. 55 Anatomy: The femoral nerve is the largest branch of the lumbar plexus and travels through the pelvis in the groove between the psoas and iliacus muscle. It emerges beneath the inguinal ligament, posterolateral to the femoral vessels (. Fig. 1.3). At the femoral crease, the nerve is on the surface of the iliacus muscle and covered by the fascia iliaca or sandwiched between 2 layers of fascia iliaca. It divides into its branches at or above the level of the inguinal ligament. 55 Indications: Surgery on anterior thigh, knee, quadriceps tendon, and in combination with sciatic and obturator blocks for distal limb and foot surgery. Landmark Technique The patient is positioned supine with both legs extended and the operator should stand on the same side of the patient. Identify the landmarks anterior superior iliac spine and the pubic tubercle, and draw a line joining the 2 points (. Fig. 1.4). Palpate the femoral artery on this line and insert the needle perpendicularly, just lateral to the femoral artery pulsations. A visible or palpable needle Medial Leteral Fascia lata Femoral artery Fascia iliaca IIiopectineal fascia Femoral nerve Femoral vein Local anesthetics Pectineus muscle IIiopsoas muscle 1 9 Peripheral Nerve Block Anesthesia trochanter (GT), posterior superior iliac spine (PSIS), and the sacral hiatus. Draw the first line joining the greater trochanter and the PSIS and mark a midpoint on the line. Draw a second line joining the greater trochanter and the sacral hiatus. Now drop a line perpendicularly from the midpoint of the first line, and the point of needle insertion is where it crosses the second line. The needle is inserted perpendicular to the skin surface and any motor stimulation of the sciatic nerve (hamstring, calf foot, or toe twitches) is acceptable and inject local anesthetic. The patient is positioned supine and the hip and knee are flexed to 90°. Identify and draw a line joining the greater trochanter and the ischial tuberosity. Mark a point half way in the groove between the hamstrings and the adductor muscles. Insert the needle perpendicular to the skin with a slight medial intent to get the sciatic motor response. Inferior Approach (Raj) .. Fig. 1.4 Femoral nerve block – landmark technique (Reprinted with permission from Farag and Brown [5]) twitch of the quadriceps muscle or the patella at 0.2–0.4 mA is the most reliable nerve stimulator response. It is very common to get a sartorius muscle twitch as the nerve to the sartorius muscle branch from the anteromedial aspect of the femoral nerve may be lying outside the iliacus fascia. When injecting local anesthetic, accepting the sartorius muscle twitch results in inconsistent block success, hence it should not be accepted in landmark/nerve stimulation technique. Anterior Approach (Beck) The anterior sciatic nerve block can be performed when the patient cannot be positioned laterally due to postoperative pain, trauma, or the presence of external fixation devices. The patient is positioned supine. Identify and draw a line joining the anterior superior iliac spine and the pubic tubercle. Draw another line parallel to the first one from the greater trochanter (. Fig. 1.5). The point of needle insertion Ultrasound Technique The patient is positioned supine and the ultrasound probe is placed parallel to the inguinal crease. Sliding the transducer medially and laterally, identify the femoral artery and trace upward to the common femoral artery if profunda femoris branch is seen on the initial scan. Immediately lateral to the vessel, and deep to the fascia iliaca is the femoral nerve, which is typically hyperechoic and roughly triangular or oval in shape. Once the femoral nerve is identified the needle is inserted in-plane from a lateral to medial orientation. The goal is to place the needle tip below the fascia iliaca, immediately adjacent to the lateral aspect of the femoral nerve. The correct placement is confirmed by the spread of the local anesthetic in the wedge-shaped tissue space lateral to the femoral artery, either lifting the femoral nerve off the iliopsoas or the spread above the nerve lateral to the artery. 1.3.2 L4 L5 S1 Anterior superior iliac spine Greater trochanter S2 1/3 S3 1/3 Sciatic Nerve Block The sciatic nerve is the largest nerve trunk in the body and arises from the sacral plexus. It exits the pelvis posteriorly via the greater sciatic notch and descends into the thigh between the greater trochanter and the ischial tuberosity. The sciatic nerve provides sensory and motor supply to most of the lower leg via its terminal branches (tibial and common peroneal). Needle insertion site Landmark/Nerve Stimulator Techniques Sciatic nerve Posterior Approach (Labat) [4] The patient is placed in Sim's position (lateral decubitus position with the upper operative leg flexed to 90° at hip and knee. The landmarks are the greater Public tubercle .. Fig. 1.5 Anterior sciatic nerve block (Reprinted with permission from Farag and Brown [6]) 10 1 S. Kolli and L.M. Soliman is where a perpendicular line from the junction of the medial and middle third of the first line meets the second line. Insert the needle perpendicularly until it contacts the femur. Now redirect slightly medially to slide off the femur and advance a few centimeters to get a motor response. In a few patients the sciatic nerve lies immediately posterior to the femur and may be inaccessible. A slight external rotation of the limb can overcome this problem. Ultrasound Technique The use of ultrasound guidance facilitated multiple approaches at several convenient levels to block the sciatic nerve. The common sites are the transgluteal/subgluteal and the anterior approaches. The anterior sciatic nerve block is ideally suited for postoperative patients requiring additional block as positioning them laterally is not easy. The ultrasound guidance not only reduces the risk of vascular injury, it eliminates the need for use of precise geometry to identify the needle entry point. The patient is positioned supine with slight abduction and external rotation of the thigh. The sciatic nerve is imaged approximately at the level of the minor trochanter. At this location, a curved transducer placed over the anteromedial aspect of the thigh will reveal the musculature of all 3 fascial compartments of the thigh: anterior, medial, and posterior. Beneath the superficial sartorius muscle is the femoral artery, and deep and medial to this vessel is the profunda femoris artery. Both of these can be identified with color Doppler ultrasound for orientation. The femur is easily seen as a hyperechoic rim with the corresponding shadow beneath the vastus intermedius. Medial to the femur is the body of the adductor magnus muscle, separated by the fascial plane(s) of the hamstrings muscles. The sciatic nerve is visualized as a hyperechoic, slightly flattened oval structure sandwiched between these 2 muscle planes and is typically visualized at a depth of 6–8 cm. The needle is inserted in-plane or out of plane from the medial aspect of the thigh and advanced toward the sciatic nerve avoiding the femoral vessels. Once the needle tip is close to the nerve or in the fascial plane between the adductors and the hamstrings when the nerve is not clearly visualized, 1–2 mL of local anesthetic is injected to confirm the adequate distribution of the local anesthetic and the rest of the dose in injected in divided doses after negative aspiration. Anterior Approach The sciatic nerve can be easily identified between the greater trochanter and ischial tuberosity, beneath a well-defined muscle plane. The nerve also can be traced backward from the popliteal region in difficult cases. The approach and the actual site of the block is based on the patient's anatomic characteristics and personal preference. A low frequency curvilinear probe is used to identify the bony landmarks at the transgluteal level. The sciatic nerve is located deep to the gluteus muscle, slightly closer to the ischial tuberosity, and appears as an oval or triangular hyperechoic structure. At the subgluteal level the nerve is located Posterior Approach (Transgluteal/Subgluteal) deep to the long head of the biceps muscle and the posterior surface of the adductor magnus. The needle is inserted in- plane typically from the lateral side and advancer toward the nerve. Once in the desired location 1–2 cc of local anesthetic is injected after negative aspiration. Often the nerve is better visualized after the initial injection of local anesthetic and moves away from the needle. The rest of the local anesthetic is injected in divided doses after negative aspiration and absence of high resistance to injection. 1.3.3 Popliteal Sciatic Nerve Block The popliteal block is essentially a block of the sciatic nerve in the popliteal fossa. Sciatic nerve is a nerve bundle that consists of 2 separate nerve trunks: the tibial and the common peroneal nerves. They diverge in the popliteal fossa about 4–10 cm above the popliteal crease (. Fig. 1.6). It is a commonly performed block for surgery on the ankle and foot. The addition of saphenous nerve block to cover the medial lower leg and ankle gives complete analgesia for ankle and foot surgery. 55 Indications: Ankle and foot surgery, Achilles tendon repair. Landmark Techniques Lateral Popliteal Approach The landmarks are popliteal fossa crease, vastus lateralis, and biceps femoris muscles. This block is performed with the patient supine and thus has the advantage of not requiring to place the position prone. The foot on the side to be blocked is positioned elevated to facilitate easy visualization of muscle twitch. The groove between the vastus lateralis and the biceps femoris muscles is palpated and a point in the groove, approximately 7 cm above the popliteal crease or at the level of superior border of patella, is marked for needle point. The needle is inserted perpendicular to the leg into the groove and advanced to contact the femur. The needle is withdrawn to skin and redirected 30° posteriorly to locate the nerve with nerve stimulator. Once the desired muscle twitch is obtained the calculated dose of local anesthetic is injected after negative aspiration. The landmarks used are the popliteal crease, semimembranosus, and the biceps femoris. The patient is positioned prone for this approach with the leg resting on a pillow. The knee is flexed to mark the popliteal crease. Trace the biceps femoris laterally and semimembranosus medially and find the apex of the popliteal fossa. Drop a line from the apex of the fossa to the middle of the popliteal crease and mark a point 5–7 cm proximal and 1 cm lateral to popliteal crease for needle entry (. Fig. 1.7). Posterior Approach Ultrasound-Guided Technique The level at which the sciatic nerve divides into tibial and common peroneal nerve is so variable in individuals that one of the components can be easily missed in the isolated nerve stimulation/landmark technique. The ultrasound guidance correctly identifies the level of division and the local anesthetic can be 11 Peripheral Nerve Block Anesthesia .. Fig. 1.6 Popliteal sciatic nerve block (Reprinted with permission from Yared and Brown [7]) Proximal Medial Lateral Tibial nerve Interosseous nerve of leg Sural nerve Common peroneal nerve Deep branch of common personeal nerve Superficial branch of common peroneal nerve Distal .. Fig. 1.7 Popliteal sciatic nerve block – posterior approach (Reprinted with permission from Yared and Brown [7]) Proximal Tibial nerve Common peroneal nerve Medial Lateral 1 cm Semimembranosus muscle Semitendinosus muscle Biceps femoris muscle 5 cm Gastrocnemius muscle Distal Cephalolateral quadrant 1 12 1 S. Kolli and L.M. Soliman deposited to cover both the divisions. A linear transducer is placed in the popliteal crease to identify the popliteal artery. The tibial nerve can be identified superficial and lateral to the artery as a hyperechoic oval or round structure with honeycomb pattern. Sliding the transducer proximally will identify the common peroneal nerve laterally and can be visualized coming together to form the sciatic nerve before the division. Ultrasound-guided block can be performed in prone, lateral, or supine (with elevation of the leg/flexing the knee and hip to create enough space to place the transducer beneath the knee). Once the nerve is identified, the needle is inserted in-plane avoiding the vascular structures. Local anesthetic is injected close to the nerve, repositioning the needle as needed, and injecting in divided doses to ensure adequate circumferential spread around the nerve. 1.3.4 Ankle Block Ankle block is a simple, easy-to-perform procedure that is highly effective for surgeries involving the foot and toes. It involves blocking the 4 terminal branches of the sciatic nerve (deep and superficial peroneal, tibial, and sural) and the terminal branch of the femoral nerve (saphenous). The ankle block will not provide analgesia/anesthesia for the ankle itself; a popliteal nerve block supplemented by saphenous nerve block is required for surgery on the ankle. The posterior tibial and the deep peroneal are the 2 deep nerves that need injection underneath the fascia, while the 3 superficial nerves (saphenous, sural, and the superficial peroneal) are anesthetized by subcutaneous infiltration. 55 Indications: Surgery on the foot and toes including podiatry surgery, foot/toe debridement/amputation. 55 Complications: Bleeding/hematoma, nerve injury, vascular injury. Landmark Technique The deep peroneal nerve is located immediately lateral to the tendon of the extensor hallucis longus muscle (between the extensor hallucis longus and the extensor digitorum longus). The pulsations of the dorsalis pedis artery are felt here; the nerve is positioned immediately lateral to the artery. With the finger positioned in the groove just lateral to the extensor hallucis longus, the needle is inserted under the skin and advanced until the bone is contacted. From the bone, the needle is withdrawn 1–2 mm, and 2–3 mL of local anesthetic is injected (. Fig. 1.8). From the same needle entry point, advance the needle subcutaneously laterally and medially to the malleoli, injecting 3–5 ml in each direction. These lateral and medial infiltrations block the superficial peroneal and the saphenous nerves respectively. The sural nerve is blocked by infiltrating local anesthetic between the lateral malleolus and the Achilles tendon. The posterior tibial nerve is located just behind and distal to the medial malleolus. The pulse of the posterior tibial 1 3 2 Extensor hallucis longus tendon Deep peroneal nerve Tibialis anterior tendon Saphenous nerve Superficial peroneal nerve Posterior tibial artery Posterior tibial nerve Tibia Fibulla Flexor haliucis muscle Peroneus brevis muscle Sural nerve Tendocalcaneus (Achilles lendon) Ankle section .. Fig. 1.8 1 2 2 1 Ankle block (Reprinted with permission from Brown [8]) artery can be felt at this location; the nerve is just posterior to the artery. The needle is inserted in the groove behind the medial malleolus below the pulse of the tibial artery and advanced to contact the bone. Once bone is contacted, the needle is withdrawn 1–2 mm and local anesthetic is injected after negative aspiration. Ultrasound-Guided Technique The tibial nerve is the largest of the 5 nerves to be blocked and can be easily identified using ultrasound. A linear transducer placed just proximal to the medial malleolus will identify the tibial nerve immediately posterior to the tibial artery. In difficult cases color Doppler can identify the artery and injecting local anesthetic just behind the artery will block the tibial nerve. The deep peroneal nerve can be identified with a transducer placed transversely at the level of the ankle and appears as a small hyperechoic structure. It is small and often not easily identified, but the dorsalis pedis artery can be identified and local anesthetic injected next to it to achieve the block. Sural nerve and saphenous nerve are small hyperechoic structures that may be seen next to the saphenous veins. 13 Peripheral Nerve Block Anesthesia 1.3.5 ransversus Abdominis Plane (TAP) T Block The transversus abdominis plane (TAP) block was first described as a landmark-guided technique involving needle insertion at the triangle of Petit. It has been shown to provide good postoperative analgesia for a variety of procedures. 55 Indications: Postoperative analgesia for laparotomy, appendectomy, laparoscopic surgery, ileostomy closure, abdominoplasty, and cesarean delivery; as an alternative to epidural anesthesia for operations on the abdominal wall. 55 Complications: Bowel perforation/hematoma, infection, intravascular injection, liver laceration. The complications are very rare and the use of ultrasound has further minimized the complications. The anterior abdominal wall (skin, muscles, and parietal peritoneum) is innervated by the anterior rami of the lower 6 thoracic nerves (T7-T12) and the first lumbar nerve (L1). Terminal branches of these somatic nerves course through the lateral abdominal wall within a plane between the internal oblique muscle (IOM) and transversus abdominis muscle. This intermuscular plane is called the transversus abdominis plane. Injection of local anesthetic within the TAP can result in unilateral analgesia to the skin, muscles, and parietal peritoneum of the anterior abdominal wall. .. Fig. 1.9 Transversus abdominis plane (TAP) block – ultrasound technique Questions and Answers 1.4 ??Questions (Choose the Most Appropriate Answer) 1. Landmark Technique The triangle of Petit is an area bounded by the latissimus dorsi muscle posteriorly, the external oblique muscle (EOM) anteriorly, and the iliac crest inferiorly. A needle is inserted perpendicular to all planes, looking for a tactile endpoint of 2 pops. The first pop indicates penetration of the external oblique fascia and entry into the plane between external and internal oblique muscles; the second pop signifies entry into the TAP plane between the internal oblique and transversus abdominis muscles. 2. Ultrasound Technique The probe is placed transversely on the abdomen, at the anterior axillary line, between the costal margin and the iliac crest. The 3 muscle layers should be identified and TAP plane located (. Fig. 1.9). Once the transverse abdominal plane is identified, a skin wheal is made 2–3 cm medial to the medial aspect of the transducer, and the needle is inserted in-plane in a medial to lateral orientation. The needle penetrates through the subcutaneous tissue, EOM, and IOM. As the needle enters the TAP plane a "pop" may be felt. After gentle aspiration, 1–2 mL of local anesthetic is injected to verify the location of the needle tip. When injection of the local anesthetic appears to be intramuscular, the needle is advanced or withdrawn carefully 1–2 mm and another bolus is administered. This gesture is repeated until the correct plane is achieved. At least 20 cc of LA is required to achieve a satisfactory block. 3. A 36-year-old female complains of pain along her medial forearm and hand postoperatively after open reduction internal fixation (ORIF) of a humerus fracture. She received a preoperative interscalene block. Which nerve would have possibly been missed in the block? A. Radial nerve B. Ulnar nerve C. Intecostobrachial nerve D. Median nerve E. Musculocutaneous nerve A 46-year-old male received an interscalene block for a left shoulder arthroplasty resulting in a dense block along his arm, hand, and the majority of his shoulder except the upper portion. What can be done to supplement the block? A. Injecting LA around the C3 to C4 nerve roots B. Injecting LA around C8 to T1 nerve roots C. Perform an intecostobrachial block D. Repeating the interscalene block E. None of the above What patient population is most susceptible to the adverse events from an interscalene nerve block? A. 62-year-old male smoker with severe chronic obstructive pulmonary disease (COPD) B. 37-year-old male with sickle cell trait C. 21-year-old female with exercise-induced asthma D. 75-year-old male with mild coronary artery disease E. 25-year-old female in her first trimester of pregnancy 1 14 1 S. Kolli and L.M. Soliman 4. A 76-year-old patient fractured her proximal humerus after a fall. A peripheral nerve block was planned for post-op pain after ORIF. In an ultrasound-guided supraclavicular approach to the brachial plexus, where are the plexus trunks/divisions in relation to the subclavian artery? A. Anterior and lateral B. Superior and lateral C. Superior and medial D. Superior and posterior E. Anterior and medial 5. A supraclavicular brachial plexus block is placed for shoulder surgery. For optimal postoperative analgesia, the catheter should be placed_______. A. Anterior to the subclavian artery B. Posterior to the subclavian artery C. Superior to the subclavian artery D. As close as possible to the first rib E. Under the first rib 6. What is the most common complication associated with a brachial plexus block using the supraclavicular approach? A. Intravascular injection into the subclavian artery B. Phrenic nerve palsy C. Intravascular injection into the vertebral artery D. Pneumothorax E. Block failure 7. Which of the following is the best indication for a supraclavicular nerve block? A. Shoulder arthroplasty B. Surgery on fifth digit C. Upper limb and hand surgery D. Shoulder arthroscopy E. First rib excision 8. Which portion of the upper extremity may not be completely anesthetized after performing a supraclavicular brachial plexus block? A. Lateral portion of the hand B. Elbow C. Medial portion of the hand D. Posterior medial portion of the forearm E. Anterior lateral portion of the arm 9. Inadequate anesthesia of the lateral part of the forearm following an axillary block is most likely the result of inadequate block of which nerve? A. Ulnar nerve B. Radial nerve C. Intecostobrachial nerve D. Median nerve E. Musculocutaneous nerve 10. Complications of the axillary block include: A. Nerve injury B. Vascular puncture C. Hematoma D. Local anesthetic toxicity E. All of the above 11. To avoid nerve injury while performing axillary block, which of the following should be taken into consideration? A. Avoid injection of local anesthetic when high resistance is encountered B. Avoid injection of local anesthetic when stimulation is obtained with intensity of less than 0.2 mA C. Stop injecting the local anesthetic when the patient complains of severe pain during the injection D. All of the above 12. All of the following statements are true about axillary brachial plexus block except: A. Under ultrasound, the median nerve is a rounded hyperechoic structure B. A curvilinear transducer probe should be used for deeper penetration. C. The structures of interest when performing the block are superficial, 1–3 cm from the skin. D. The axillary artery can be associated with one or more axillary veins and are usually located medial to the artery 13. A patient receives an infraclavicuar block for distal radial fracture fixation and complete anesthesia of hand and forearm are noted. Upon inflation of the surgical tourniquet, the patient complains of pain under the axilla. Which of the following nerves was not blocked? A. Musculocutaneous nerve B. Radial nerve C. Medial brachial cutaneous nerve D. Intecostobrachial nerve 14. Infraclavicuar catheter is placed for analgesia in a patient after elbow arthroplasty and the patient received a bolus followed by continuous infusion. Approximately 12 h after the block, the patient complains of severe pain on the lateral side of the elbow. Motor function in the hand is diminished. All tubing is connected and the pump is working. What is the most likely cause? A. Radial nerve injury from the block B. Normal postoperative pain C. Secondary block failure D. Incorrect drug choice 15. Advantages of infraclavicuar block over axillary block include all of the following except: A. Single needle entry B. Block of medial brachial cutaneous and antebrachial cutaneous nerves C. Easier catheter placement for continuous analgesia D. Easy needle visualization with ultrasound 16. In a typical transverse scan of the inguinal region, the femoral nerve is immediately deep to the following structure: A. The fascia of the ileopsoas muscle B. The fascia iliaca C. The fascia lata D. The femoral artery 15 Peripheral Nerve Block Anesthesia 17. While performing a femoral nerve block using nerve stimulation, all of the following are reliable responses ensuring successful block except: A. A quadriceps muscle twitch B. Stimulation of the femoral nerve at 0.4 mA C. A sartorial muscle twitch D. A patellar twitch 18. A femoral nerve block can be used as an adjunct to control pain in each of these surgeries except: A. Proximal femur surgery B. Knee surgery C. Medial foot surgery D. Proximal anterior thigh surgery 19. Which of the following statements is true regarding the transversus abdominis plane block using ultrasound-guided technique? A. Coagulopathy is an absolute contraindication B. Low volume, high concentration of local anesthetic solution is used ideally C. Saline can be used to identify and open the TAP fascial plane prior to injecting local anesthetic D. It can be reliably used as the sole mode of analgesia after abdominal surgery 20. All of the following statements are true regarding the TAP block except: A. The anterior abdominal wall is innervated by T7 to L1 B. The nerves lie in the plane between the internal oblique and the transversus abdominis muscles C. The aim of the block is to deposit local anesthetic in the plane between the internal oblique and transversus abdominis muscles D. A single injection of 20 cc of local anesthetic will reliably block all the nerves on one side of the abdomen. 21. Sciatic nerve block performed by posterior approach (Labat [4]), all of the following statements are true except: A. The landmarks used are the greater trochanter and the sacral hiatus B. The patient is placed in Sim's position C. The posterior superior iliac spine and sacral hiatus are the bony landmarks D. The landmarks include the greater trochanter and ischial tuberosity 22. Regarding an ultrasound-guided transgluteal approach to a sciatic nerve block, all of the following statements are true except: A. It is indicated for surgery on the tibia, ankle, and foot B. The landmarks used are the greater trochanter and the posterior superior iliac spine C. Combined with a lumbar plexus block, anesthesia of the entire lower extremity can be achieved D. In contrast to common belief, it is a relatively easy block to perform with a high success rate vvAnswers B. The interscalene block is most utilized for shoulder and humeral fracture surgeries but is not sufficient for surgeries involving the hand because the lower nerve roots and trunk of the brachial plexus are missed. 2. A. Injecting local anesthetic around C3 to C4 nerve roots would give a superficial cervical plexus bock and help this patient since these nerve roots supply some sensation to upper part of the shoulder. 3. A. Due to the almost 100% involvement of the ipsilateral phrenic nerve with an interscalene block, it is advisable to be cautious with patients with limited pulmonary function such as patients with severe COPD. 4. D. When using the ultrasound, in the supraclavicular approach for the brachial plexus, the trunks and the divisions appear as compact bunch of grapes superior and posterior to the artery. 5. C. The catheter is usually inserted superior to the subclavian artery in the case of shoulder surgery or in the corner pocket between the artery and the first rib in the case of hand surgery. The correct position of catheter can be confirmed under ultrasound by injecting local anesthetic or 1 ml of air into the catheter and observing the distribution in relation to the artery. 6. B. To minimize phrenic nerve paralysis, try not to inject above the plexus to avoid exposing the nerve to toxic high concentration of local anesthetics. In addition, avoiding injection above the plexus might decrease the incidence of phrenic nerve palsy after the block. 7. C. The supraclavicular block is very efficient for upper limb and hand surgeries. 8. C. Supraclavicular block can be used for shoulder, elbow, or hand surgery; however, it can miss the lower portion of the brachial plexus, thus sparing the ulnar nerve distribution of the medial side of the hand. 9. E. The musculocutaneous nerve is a terminal branch of the lateral cord of the brachial plexus. Without blockade of the musculocutaneous nerve, adequate anesthesia of the lateral forearm is unlikely. Classic teaching is that the musculocutaneous nerve blockade can be accomplished by the injection of local anesthetic into the belly of the coracobrachialis muscle. Ultrasound studies have shown that the musculocutaneous nerve is not in the coracobrachialis muscle in approximately 20% of patients. 10. E. A hematoma can occur during an axillary block, especially if the patient was on anticoagulants or if there are multiple needle punctures to the veins or axillary artery. The most common cause of local anesthetic toxicity during axillary block is inadvertent intravascular injection. To avoid systemic toxicity during an axillary block, avoid fast forceful injection, perform careful frequent aspiration during the injection, and adjust the dose and volume of local anesthetic injected in the elderly and frail patients. 1. 1 16 1 S. Kolli and L.M. Soliman 11. D. To avoid nerve injury during any peripheral nerve block, never inject local anesthetic when abnormally high resistance is encountered on injection. Stop injecting local anesthetic when patient complains of severe pain on injection and when stimulation is obtained with current intensity less than 0.2 mA. Withdraw the needle slightly to obtain the same response with current greater than 0.2 mA before injecting the local anesthetic. 12. B. In order to obtain the best image when performing the axillary brachial plexus block, a linear transducer with high frequency should be used. A higher penetration is not needed as the structures of interest are superficial, 1–3 cm from the skin. A curved low-frequency probe should be used when imaging deeper structures as it allows higher penetration at the expense of lower resolution. 13. D. The intecostobrachial nerve arises from T2 and is not blocked by any approach to brachial plexus. It may be blocked by subcutaneous infiltration of local anesthetic under the ventral side of the proximal arm. 14. C. The patient most likely had sufficient local anesthetic spread from the initial bolus. With resolution of the initial block, the lateral cord was not adequately blocked by the infusion, leading to pain in the musculocutaneous nerve distribution. 15. D. The infraclavicuar approach has many advantages, including single needle entry and the included block of the medial brachial cutaneous and medial antebrachial cutaneous nerves. It is also a good location for catheter placement. Needle visualization with ultrasound is often more difficult due to the steep angle of the needle and the depth of the plexus. 16. B. While all the given structures can be found in a typical transverse scan of the inguinal region, the femoral nerve is typically superficial to the iliopsoas muscle and lateral to the femoral artery. The fascia lata is superficial and can be found in the subcutaneous layer. 17. C. A twitch of the sartorius muscle can be commonly seen when using nerve stimulation for locating the femoral nerve. A band-like contraction of the thigh without movement of the patella is often how sartorius muscle stimulation manifests and can be mistaken for femoral nerve stimulation. Sartorius muscle twitch is not a reliable response because the nerve branches to the sartorius muscle coming off the femoral nerve may be outside the femoral sheath. 18. D. The proximal portion of the anterior thigh is innervated by the ilioinguinal and genitofemoral nerves but not the femoral nerve. 19. C. Coagulopathy is a relative contraindication for the TAP block. The TAP bock depends on the spread of LA in a large plane, and hence, it is a high-volume block. It is used as an adjunct for anterior abdominal wall incisions/drains. It does not provide adequate analgesia as a sole analgesia as it does not block the visceral component. The spread of local anesthetic in TAP block depends on the volume and the site of injection. Saline can be used to hydrodissect and identify the TAP plane without wasting the local anesthetic while trying to identify the TAP plane. 20. D. The anterolateral abdominal wall is innervated by the anterior rami of the lower 6 thoracic nerves (T7 to T12) and the first lumbar nerve (L1). The nerves lie in the fascial plane between the internal oblique and the transverse abdominis muscles. Injection of LA within the TAP can provide unilateral analgesia to the skin, muscles, and parietal peritoneum of the anterior abdominal wall from T7 to L1 depending on the volume and the site of the injection. 21. D. The posterior sciatic nerve block described by Labat [4] involves placing the patient in Sim's lateral position with hip and leg flexed to 90°. The anatomical landmarks used are the posterior superior iliac spine (PSIS), the greater trochanter (GT), and the sacral hiatus (SH). Draw 2 lines joining the 3 bony landmarks. From the midpoint of the PSIS and GT, drop a perpendicular line and mark where it crosses the line joining the GT and SH. This is the point of needle insertion for the block. 22. B. An ultrasound-guided transgluteal sciatic nerve block is relatively easy to perform with a high success rate. It utilizes the greater trochanter and the ischial tuberosity as the bony landmarks. Combined with a lumbar plexus block, anesthesia of the entire lower extremity can be achieved. Combined with a femoral/ saphenous nerve block, anesthesia of the lower limb below the knee can be achieved. References 1. 2. 3. 4. 5. 6. 7. 8. Winnie AP. Interscalene brachial plexus block. Anesth Analg. 1970;49(3):455–66. Kulenkampff D. "Zur anästhesierung des plexus brachialis" [On anesthesia of the brachial plexus]. Zentralblatt für Chirurgie (in German). 1911;38:1337–40. Winnie AP, Collins VJ. The subclavian perivascular technique of brachial plexus anesthesia. Anesthesiology. 1964;25:353–63. Labat G. Regional anesthesia: its technique and clinical applications. 2nd ed. Philadelphia: W. B. Saunders Publishers; 1924. p. 45–55. Farag E, Brown DL. Chapter 14 Femoral block. In: Farag E, Mounir- Soliman L, editors. Brown's atlas of regional anesthesia. 5th ed. Philadelphia: Elsevier; 2016. Farag E, Brown DL. Chapter 13 Sciatic block. In: Farag E, Mounir- Soliman L, editors. Brown's atlas of regional anesthesia. 5th ed. Philadelphia: Elsevier; 2016. Yared M, Brown DL. Chapter 17 Popliteal and saphenous block. In: Farag E, Mounir-Soliman L, editors. Brown's atlas of regional anesthesia. 5th ed. Philadelphia: Elsevier; 2016. Brown DL. Chapter 19 Ankle block. In: Farag E, Mounir-Soliman L, editors. Brown's atlas of regional anesthesia. 5th ed. Philadelphia: Elsevier; 2016. 17 Central Neuraxial Anatomy and Anesthetic Application (Central Neuraxial Blockade) Nathan J. Harrison, Laurie S. Daste, Gary S. McDaniel Jr, Matthew E. Patterson, and Maged Guirguis 2.1 Anatomy – 19 2.1.1 2.1.2 2.1.3 2.1.4 2.1.5 2.1.6 2.1.7 T he Vertebral Column – 19 Ligaments – 21 Landmarks – 22 The Spinal Cord – 22 Meninges – 23 Cerebrospinal Fluid – 23 Blood Supply – 23 2.2 Neuraxial Anesthesia – 24 2.2.1 2.2.2 2.2.3 reoperative Considerations – 24 P Patient Positioning – 25 Needles – 25 2.3 Spinal Anesthesia – 26 2.3.1 2.3.2 2.3.3 2.3.4 2.3.5 I ndications – 26 Contraindications – 26 Technique – 26 Assessment of Neuraxial Blockade – 27 Pharmacokinetics and Pharmacodynamics of Spinal Anesthesia – 28 2.4 Epidural Anesthesia – 29 2.4.1 2.4.2 2.4.3 2.4.4 I ndications – 29 Contraindications – 29 Technique – 29 Pharmacokinetics and Pharmacodynamics of Epidural Anesthesia – 30 2.5 Combined Spinal Epidural – 31 2.6 Ultrasound-Guided Neuraxial Procedures – 31 © Springer International Publishing AG 2018 E. Farag et al. (eds.), Basic Sciences in Anesthesia, https://doi.org/10.1007/978-3-319-62067-1_2 2 2.7 Complications Associated with Neuraxial Anesthesia – 32 2.7.1 2.7.2 2.7.3 2.7.4 ardiovascular – 32 C Respiratory – 32 Gastrointestinal and Genitourinary – 32 Neurologic – 32 2.8 American Society of Regional Anesthesia Guidelines – 34 2.9 Questions and Answers – 37 References – 39 19 Central Neuraxial Anatomy and Anesthetic Application (Central Neuraxial Blockade) Key Points 1. Neuraxial anesthesia can be used as a primary anesthetic, an adjunct anesthetic for intraoperative pain control in addition to general anesthesia or postoperative pain control for surgeries involving the abdomen, perineum, or lower extremities. 2. Absolute contraindications to neuraxial anesthesia include patient refusal, bleeding diathesis, elevated intracranial pressure (except pseudotumor cerebri), infection at site of injection, hypovolemia, and indeterminate neurologic disease. 3. Neuraxial anesthesia can be achieved by injection of local anesthetics (lidocaine, bupivicane, chloroprocaince, etc.) with or without additives into the intrathecal space (spinal) or the epidural space (epidural) 4. As a fetus, the spinal cord spans the entire length of the spine. The spinal cord ends at the L3 level in early childhood, and in adulthood the spinal cord extends from the foramen magnum to the L1-2 level. 5. Local anesthetics exert their effects at the level of the nerve root, producing numbess in a dematomal distribution. 6. Additives can be used to alter the length (epinephrine, clonidine) and onsest (sodium bicarbonate) of blockade. 7. Hypotension is the most common adverse effect of neuraxial anesthesia. It is caused by sympathetic blockade, which can decrease systemic venous resistance, venous return, and cardiac output. This sympathetic blockade extends 2 dermatomes above and below the sensory/motor blockade and is treated with crystalloid bolus and vasopressors. 8. Epidural hemtoma is the most feared complication of neuraxial anesthesia. Particular attention needs to be paid to the coagulation status and platelet functioning of the patient, including medications that may affect these functions. Treatment is surgical decompression and magnetic resonance imaging (MRI) should be obtained early so as not to delay surgery. 9. Post dural puncture headache (PDPH) is a relatively common adverse effect of neuraxial anesthesia. Risk factors include female sex, young age, pregnancy, and history of previous PDPH and the use of cutting-point, large-bore needles. Treatment includes adequate hydration, caffeine, analgesics, and, if warranted, epidural blood patch. 10. Many situations exist in which neuraxial anesthesia and anticoagulation would both be appropriate for a patient at the same time. The American Society of Regional Anesthesia (ASRA) guidelines exist as expert opinion to help guide the practitioner in risk benefit analysis and should be referenced whenever neuaxial anesthesia is considered on an anticoagulated patient. 2.1 Anatomy 2.1.1 The Vertebral Column The vertebral column consists of the bony vertebral bodies, their posterior elements, and the intervertebral disks that form the boundaries of the vertebral canal in which lies the spinal cord and exiting nerve roots. The vertebral canal provides structural support to the body as well as protection for the spinal cord and nerve roots within the spine. The spine consists of 33 vertebrae from the base of the skull to the coccyx. There are 7 cervical, 12 thoracic, 5 lumbar, and 5 sacral vertebrae. The 5 sacral vertebrae are fused to form the sacrum, which is attached to the coccygeal vertebrae, or coccyx. A sagittal view of the spine reveals a double-C shape in which the cervical and lumbar regions exhibit a concave curvature (lordosis), and the thoracic region appears convex (kyphosis) (. Fig. 2.1) [1] . Although the shape of the anatomy of the spine varies at each level, a vertebra generally consists of a vertebral body connected to the vertebrae above and below it by intervertebral disks. At the thoracic and lumbar levels, the vertebral body is a large circular structure connected to a posterior vertebral arch [1]: 55 The vertebral body is joined to 2 pedicles that course ventral to dorsal, which are each fused with a laterally extending transverse process. .. Fig. 2.1 Sagittal view of the spine demonstrating lumbar and cervical lordosis and thoracic kyphosis. Note the spinous process angles, which change according to level of the spine (Reprinted with permission Ochsner Health Systems © 2016. All Rights Reserved) 2 20 2 N.J. Harrison et al. 55 The laminar elements extend medially and dorsally and fuse posteriorly to form a single spinous process. 55 The vertebral body, 2 pedicles, transverse processes, 2 laminae, and spinous process connect to form a hollow circle, which, when stacked with other vertebrae, form a cylinder that encases the spinal cord and its covering. 55 While the vertebral bodies connect to each other by disks anteriorly, each vertebra connects posteriorly by facet joints. The facet joints are formed on each side by a superior articular process from the caudally located vertebra and an inferior articular process from the cephalad vertebra. 55 Intervertebral foramina, or neural foramina, are lateral openings between cephalad and caudal vertebral pedicles through which the nerve roots leave the spinal cord and exit to each side (. Fig. 2.2). The cervical vertebrae differ from the thoracic and lumbar spine by the presence of bilateral transverse foramina, which contain the vertebral arteries as they pass superiorly through C6 and upward to the foramen magnum. The first cervical vertebrae, or the atlas, lacks a body but instead connects with the C2 vertebra, also called the axis. The atlas has a superiorly extending odontoid process, or dens, which essentially exists as the embryologic C1 body. The dens of C2 articulates with the posterior surface of the anterior arch of C1 [2]. The atlas and axis allow increased range of motion of the head and neck. The joint between the occipital bone and C1 forms .. Fig. 2.2 Left oblique view of lumbar spine. Note the nerve roots exiting the neural foramen beneath the pedicles (Reprinted with permission Ochsner Health Systems © 2016. All Rights Reserved) the atlanto-occipital joint, which allows movement of the head, and the atlanto-axial joint between the atlas and axis allows for the twisting motion of the neck. The cervical spine also differs from the remaining vertebrae in that all the spinous processes, except for C7, are bifid. (. Figs. 2.3 and 2.4). The thoracic vertebrae are each connected to bilateral corresponding ribs. The spinous processes of the cervical and lumbar spine are shorter and appear to be in a more horizontal axis, allowing for a more direct trajectory during spinal and epidural needle placement (. Fig. 2.5). The spinous processes of the midthoracic spine on the other hand are more caudally angulated, which requires a compensatory angulation when performing spinal and epidural needle placement. The interlaminar spaces are larger in the lumbar area than in the thoracic spine [3]. The 5 sacral vertebrae fuse prior to birth to form the sacrum: 55 Each sacral vertebral level contains paired anterior and posterior intervertebral foramen from which the sacral nerve roots exit. .. Fig. 2.3 C1 vertebra (atlas) with superior view, inferior view, and anterior view (Reprinted with permission Ochsner Health Systems © 2016. All Rights Reserved) 21 Central Neuraxial Anatomy and Anesthetic Application (Central Neuraxial Blockade) .. Fig. 2.4 C2 vertebra (axis) with views from multiple angles. Note the dens, which serves as the C1 body (Reprinted with permission Ochsner Health Systems © 2016. All Rights Reserved) 55 The transverse and costal processes of S1 fuse to form the bilateral sacral ala, the wing-like lateral processes located superiorly at the base of the sacrum. The sacral alae articulate bilaterally with the ilium to form the sacroiliac joints. 55 The sacrum also joins superiorly with the L5 vertebrae (via the L5/S1 intervertebral disk) and inferiorly with the coccyx (via the sacrococcygeal ligament). 55 The sacrum contains a central canal, which is a continuation of the vertebral canal. The canal terminates at the sacral hiatus, a fissure located in the posterior sacrum where the laminae of the fifth vertebrae do not fuse. 55 The sacral cornu, a landmark for caudal anesthesia, can be found here as bilateral projections on either side of the sacral hiatus [3]. 55 The filum terminale, the most caudal extension of the pia mater, extends to the sacral hiatus. Although the dural sac typically ends at the S2 level in adults, the epidural fat continues to the hiatus, which is what allows access to the epidural space at this level during caudal techniques [4, 5]. 2.1.2 Ligaments Several ligaments surround the vertebral column, and together with the paraspinous muscles, provide support and structure to the spine: 55 The vertebral bodies and intervertebral disks are bound together anteriorly and posteriorly by the anterior and posterior spinal ligaments, respectively in a cephalad to caudal direction along the length of the cervical, thoracic, and lumbar spine. 55 Dorsal to the vertebral canal, the ligamentum flavum is a thick layer of tissue connecting the lamina along the spinal column immediately posterior to the epidural 2 22 N.J. Harrison et al. 55 Therefore, using a midline approach, the order of structures encountered during an epidural placement is skin, subcutaneous tissue, supraspinous ligament, interspinous ligament, ligamentum flavum, and, finally, epidural space. 2 2.1.3 Landmarks When trying to locate the appropriate vertebral level in order to perform neuraxial anesthesia without the assistance of fluoroscopy, it is necessary to know surface landmarks: 55 The C7 spinous process is the most prominent bony landmark in the base of the neck, whereas a line drawn between the lower edges of the scapulae denotes the T7 interspace. These 2 landmarks are useful for locating the desired interspaces for thoracic epidurals and paravertebral blocks [6]. 55 The most important landmarks for labor epidurals and spinal anesthesia are the iliac crests. A horizontal line drawn between the crests (Tuffier's line) generally will traverse the L4/5 interspace, which is below the spinal cord in most adults [6]. 55 Finally, the bilateral posterior superior iliac spines designate the level of the S2 vertebral body, which is the inferior border of the dural sac in adults [6]. 2.1.4 .. Fig. 2.5 The cervical spine spinous processes have a relatively horizontal angle (Reprinted with permission Ochsner Health Systems © 2016. All Rights Reserved) space. When placing an epidural needle, this ligament is used as a landmark to help determine entrance to the epidural space. In some individuals the ligamentum flavum is absent, which can place the patient at a higher risk for unintended dural puncture. 55 The interspinous ligament connects adjacent spinous processes, and the supraspinous ligament is the most superficially located ligament along the posterior surface of the spinous processes. The Spinal Cord As a fetus, the spinal cord spans the entire length of the spine. As the infant ages, the spine lengthens at a faster rate compared to the growth of the spinal cord. As a result, the spinal cord ends at the L3 level in early childhood, and in adulthood the spinal cord extends from the foramen magnum to the L1-2 level. As the spinal cord approaches L1 it tapers off into the conus medularis and eventually becomes the cauda equina, or "horse's tail," a bundle of nerve roots that float relatively freely in the cerebrospinal fluid (CSF) of the spinal canal. A spinal anesthetic performed below L1 would be in the territory of the cauda equina and decrease the potential for spinal cord trauma as the needle theoretically displaces the nerve roots to the side. There are 31 pairs of spinal nerves (8 cervical, 12 thoracic, 5 lumbar, and 5 sacral). The nerve roots exit the spinal column through bilateral intervertebral foramen. In the cervical spine the nerve roots exit above their corresponding vertebral body. At the C7 body, the C7 root exits above and the C8 root exits below (between C7 and T1). Starting at T1, the nerve roots then exit below their respective vertebral bodies [2]. The dural sac, as well as the subarachnoid space, extends below the cauda equina to S2 in adults and S3 in children. The dura often continues to sheath the nerve roots as they exit the spinal canal into the intervertebral foramen. As such there is a risk of subdural or subarachnoid injection even 23 Central Neuraxial Anatomy and Anesthetic Application (Central Neuraxial Blockade) when approaching from a caudal or transforaminal approach. Although the dura mater extends to S2, the pia mater continues as a thin strand of tissue to form the filum terminale, which connects the conus to the coccyx [4]. 2.1.5 Meninges The meninges are the 3 layers of connective tissue surrounding the spinal cord composed of the outermost dura mater, the arachnoid mater, and the innermost pia mater. Superficial to these layers, the epidural space exists as a potential space between the dura mater and the ligamentum flavum. It contains fat, lymphatics, and blood vessels, and it is in this space that local anesthetic can be instilled for epidural anesthesia (. Fig. 2.6). The epidural space communicates freely with the adjacent paravertebral spaces by the intervertebral foramen. Closely adherent to the dura mater is the arachnoid mater. Beneath the arachnoid layer is the subarachnoid space, where cerebrospinal fluid is contained within the spinal column. The innermost layer is known as the pia mater, which is closely adherent with the spinal cord. The pia will extend laterally above T12 to form a dense triangular band between the dorsal and ventral roots known as the denticulate ligament [4]. Radiographic studies also suggest the presence of dorsal median connective tissue or septa within the epidural space, which may lead to an unintentional unilateral neuraxial anesthetic [7]. 2.1.6 Cerebrospinal Fluid The major function of cerebrospinal fluid is to insulate and protect the brain and spinal nerves against trauma. It is found in cerebral ventricles and the subarachnoid space of the brain .. Fig. 2.6 Axial view of the spine reveals a cross-section of the spinal cord and exiting nerve roots, which lie between the anterior and posterior epidural space. The spinal nerve roots exit through the intervertebral foramen (Reprinted with permission Ochsner Health Systems © 2016. All Rights Reserved) and spinal cord. It flows freely across the foramen magnum, allowing for introduction of local anesthetic to the brain in the event of a complete or high spinal. CSF is mostly formed in the choroid plexus of the cerebral ventricles. In adults, normal CSF production is 500 cc/day, yet total CSF volume is only about 150 cc secondary to continuous reabsorption into arachnoid granulations. 2.1.7 Blood Supply The spinal cord is supplied by a single anterior spinal artery and 2 paired posterior arteries. The anterior spinal artery arises from the vertebral artery in the cervical region and supplies the anterior two-thirds (motor innervation) of the spinal cord. The posterior arteries are formed from the posterior inferior cerebellar arteries and cover the posterior one- third (sensory innervation) of the cord (. Fig. 2.7). Below the cervical level, the spinal cord also receives additional blood supply from segmental or radicular arteries, which feeds the anterior spinal artery in the thoracic and lumbar region. The anterior spinal artery receives variable contributions from these arteries and relies heavily on the large artery of Adamkiewicz or great radicular artery (GRA). The GRA typically branches off the aorta around T9-T12, but can be anywhere from T5-L5, and it is almost always on the left [2]. If this artery is damaged, a patient may present with bilateral lower extremity motor deficits from a process called anterior spinal artery syndrome. This syndrome occurs as a result of decreased spinal cord perfusion pressure, which is equal to mean arterial pressure (MAP) – spinal cord pressure. Anterior spinal artery syndrome, therefore, may occur secondary to either a decrease in MAP (hypotension, damaged GRA) or an increased spinal cord pressure (from a variety of factors including increased CSF pressure or mechanical pressure). .. Fig. 2.7 Cross-section of the spinal cord with the midline anterior spinal anatomy and one of the 2 paired posterior spinal arteries on the left side (Reprinted with permission Ochsner Health Systems © 2016. All Rights Reserved) 2 24 2 N.J. Harrison et al. The venous drainage from the spinal cord flows through the vertebral venous plexus. The plexus can be enlarged in situations that obstruct abdominal venous return, such as increased intra-abdominal pressure secondary to gravid uterus or tumors compressing the vena cava. This may result in an increased likelihood of intravascular injection during epidural anesthesia as well as increase the spread of local anesthetic by decreasing the volume of the epidural space. 2.2 Neuraxial Anesthesia 2.2.1 Preoperative Considerations Indications Neuraxial anesthesia may be indicated as the primary anesthetic for major or minor surgeries or as an adjunctive anesthetic for intraoperative pain control in addition to general anesthesia. It is most useful as the primary anesthetic in surgeries involving the abdomen, perineum, or lower extremities. Neuraxial anesthesia is also an option for thoracic and upper abdominal surgeries, although it may not be the optimal choice for a patient with respiratory insufficiency or during prolonged surgeries resulting in compromised respiratory function (such as pneumoperitoneum). This is related to the fact that these patients rely heavily on accessory muscles of inspiration, which are often weakened with high neuraxial anesthesia, despite minimal changes in tidal volume. In these situations, an epidural or spinal may be useful to supplement general anesthesia in providing postoperative pain relief. Continuous epidural anesthesia is also widely used in labor analgesia [6]. Contraindications Absolute contraindications to neuraxial anesthesia include patient refusal, bleeding diathesis, elevated intracranial pressure (except pseudotumor cerebri), infection at site of injection, hypovolemia, and indeterminate neurologic disease [6]. Other disease processes are discussed as relative contraindications and clinical judgment should be used in these situations. Severe aortic or mitral stenosis or left ventricular outflow obstruction when combined with spinal or rapidly achieved epidural anesthesia may result in sudden, severe hypotension and possible cardiac ischemia. These effects are secondary to a sympathetic blockade, leading to vasodilation, venous pooling, and ultimately decreased preload. However, neuraxial anesthesia can be used safely with close monitoring, and when possible, a slowly dosed epidural would be preferred over spinal anesthesia to avoid the abrupt decline in blood pressure. Sepsis or distant infections have been implicated in predisposing the patient to meningitis, epidural abscess, or central nervous system (CNS) infection via hematogenous spread following neuraxial anesthesia. While it is recommended to exercise caution in such patients, it is generally not contraindicated to perform a neuraxial block as it may actually be a better choice for some sick patients. Chronic back pain or preexisting neurological deficits and paresthesia due to prior neurologic disease are generally not contraindications; however, prior symptoms or exacerbations of a disease state may mask or imitate side effects or complications associated with the procedure itself. Some practitioners would defer from performing neuraxial or regional anesthesia on such patients. It is, therefore, important to thoroug