Military Advanced Analgesia and Anesthesia

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MILITARY ADVANCED REGIONAL ANESTHESIA ANDANALGESIA HANDBOOK


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Published by the

Ofce of The Surgeon General

Department of the Army, United States of America

US Army Medical Center and School

Fort Sam Houston, Texas

John P. Murtha Neuroscience and Pain Institute

Johnstown, Pennsylvania

Telemedicine and Advanced Technology Research Center

US Army Medical Research and Materiel Command, Fort Detrick, Maryland


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MILITARY ADVANCED REGIONAL ANESTHESIA ANDANALGESIA

HANDBOOK

Chester Buckenmaier III, MDColonel, Medical Corps, US ArmyWalter Reed Army Medical Center

Associate Professor of Anesthesiology, Uniformed Services University of the Health SciencesMilitary Advanced Regional Anesthesia and Analgesia Initiative

Lisa Bleckner, MDWalter Reed Army Medical CenterAssistant Professor of Anesthesiology, Uniformed Services University of the Health Sciences

Military Advanced Regional Anesthesia and Analgesia Initiative

With original illustrations by

Lieutenant Michael K. Sracic, MD, MC, US Navy

Borden InstituteWalter Reed Army Medical Center, Washington, DC

2008


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Borden Institute

Martha K. Lenhart, MD, PhD, FAAOSColonel, Medical Corps, US ArmyDirector and Editor in Chief

Editorial Staff:

Bruce MastonIllustrator

Douglas WiseIllustrator

Joan ReddingSenior Production Editor

Vivian MasonTechnical Editor

Marcia MetzgarTechnical Editor

This volume was prepared for military medical educational use. The focus of the information is to foster discussion that may form the basis of doctrine and policy. The opinions or assertionscontained herein are the private views of the authors and are not to be construed as ofcial or as reecting the views of the Department of the Army or the Department of Defense.

Dosage Selection:

The authors and publisher have made every effort to ensure the accuracy of dosages cited herein. However, it is the responsibility of every practitioner to consult appropriate informationsources to ascertain correct dosages for each clinical situation, especially for new or unfamiliar drugs and procedures. The authors, editors, publisher, and the Department of Defensecannot be held responsible for any errors found in this book.

Use of Trade or Brand Names:

Use of trade or brand names in this publication is for illustrative purposes only and does not imply endorsement by the Department of Defense.

Neutral Language:

Unless this publication states otherwise, masculine nouns and pronouns do not refer exclusively to men.

Copyright 2008 The Henry M. Jackson Foundation for the Advancement of Military Medicine, Inc.NOCOPYRIGHTEDPARTSOFTHISPUBLICATIONMAYBEREPRODUCEDORTRANSMITTEDINANYFORMORBYANYMEANS, ELECTRONICORMECHANICAL(INCLUDINGPHOTOCOPY, RECORDING, ORANYINFORMATION

STORAGEANDRETRIEVALSYSTEM), WITHOUTPERMISSIONINWRITINGFROMTHEPUBLISHERORCOPYRIGHTOWNER.

Published by the Ofce of The Surgeon General at TMM PublicationsBorden Institute, Walter Reed Army Medical Center, Washington, DC 20307-5001

Library of Congress Cataloging-in-Publication Data

Buckenmaier, Chester. Military advanced regional anesthesia and analgesia handbook / Chester Buckenmaier III, Lisa Bleckner ; Michael K. Sracic, illustrator. p. ; cm. Developed as a supplement to Emergency war surgery. 3rd U.S. revision. 2004. Includes bibliographical references. ISBN 978-0-9818228-2-21. Conduction anesthesia--Handbooks, manuals, etc. 2. Analgesia--Handbooks, manuals, etc. 3. Medicine, Military--Handbooks, manuals, etc. I. Bleckner, Lisa. II. Borden Institute (U.S.) III. Emergency warsurgery. IV. Title.[DNLM: 1. Anesthesia, Conduction--methods--Handbooks. 2. Analgesia--methods--Handbooks. 3. Military Medicine--methods--Handbooks. 4. Pain--drug therapy--Handbooks. WO 231 B922b 2008]

RD84.B79 2008 617.964--dc22 2008031170


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v

CONTENTS

Contributors vii

Preface ix

Prologue xi

1. The Military Advanced Regional Anesthesia and Analgesia Initiative: A Brief History 1

2. Peripheral Nerve Block Equipment 5

3. Local Anesthetics 11

4. Nerve Stimulation and Ultrasound Theory 17

5. Upper Extremity Neuroanatomy 21

6. Cervical Plexus Block 23

7. Interscalene Block 25

8. Supraclavicular Block 29

9. Infraclavicular Block 33

10. Axillary Block 37

11. Peripheral Nerve Blocks of the Arm 41

12. Paravertebral Nerve Block 45

13. Lower Extremity Neuroanatomy 49

14. Lumbar Plexus Block 51

15. Femoral Nerve Block 53

16. Individual Nerve Blocks of the Lumbar Plexus 57

17. Sciatic Nerve Block: Posterior and Alternative Approaches 61

18. Sciatic Nerve Block: Anterior Approach 67

19. Sciatic Nerve Block: Lateral Approach 69

20. Popliteal Nerve Block 73

21. Saphenous Nerve Block 77

22. Ankle Block 79

23. Bier Block 81

24. Continuous Peripheral Nerve Block 83

25. Regional Anesthesia Complications 91


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vi

26. Acute Pain Management in the Field 95

27. Improving Surgical Pain Management With Multidisciplinary Care 103

28. Interventional Chronic Pain Treatment in Mature Theaters of Operation 107

29. Air Transport of the Critically Injured Patient: Controlling Pain During Transport and Flight 113

30. Basic Pediatric Regional Anesthesia 119

31. Acute Pain Nursing in the Field 12532. Novel Medical Acupuncture Treatments for Active Combat Units on the Battleeld 129

Further Reading xiii

Abbreviations and Acronyms xvii


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vii

CONTRIBUTORS

TODD CARTER, MDLieutenant Colonel, Medical Corps, US Air Force

JOHN CHILES, MDColonel (Retired), Medical Corps, US Army

JAMES E. COX, MDColonel (Retired), Medical Corps, US Air Force

SCOTT CROLL, MDLieutenant Colonel, Medical Corps, US Army

STEVE COHEN, MDColonel, Medical Corps, US Army

JOHN DUNFORD, MDAssistant Professor of Anesthesiology, UniformedServices University of the Health Sciences

ERIC ELSTER, MDCommander, Medical Corps, US Navy

CARLO FRANCO, MDAssociate Professor of Anesthesiology and Anatomy,

Rush University Medical CenterBILL FRITZ, MDConemaugh Health System

KURT GRATHWOHL, MDLieutenant Colonel, Medical Corps, US Army

SCOTT GRIFFITH, MDMajor, Medical Corps, US Army

STEPHEN M. KLEIN, MDAssociate Professor of Anesthesiology, DukeUniversity Medical Center

ROBERT S. LENNON, DOBrigadier General (Retired), Medical Corps, USArmy; Associate Professor, Mayo Clinic MedicalSchool

COURTNEY LENNONEnsign, Medical Corps, US Navy

ROBERT LENNON, JDEnsign, Medical Corps, US Navy

RANDALL MALCHOW, MDColonel, Medical Corps, US Army

GREG MALONE, MDCaptain, Medical Corps, US Air Force

GESELLE MCKNIGHT, CRNA, MSNWalter Reed Army Medical Center

BRIAN MCMILLAN, MDMajor, Medical Corps, US Army

JONATHON ROGERS, MDCaptain, Medical Corps, US Air Force

CHRISTINE RUPPRECHT, RN, MSNWalter Reed Army Medical Center

CYNTHIA SHIELDS, MD

Colonel, Medical Corps, US ArmySEAN SHOCKEY, MDMajor, Medical Corps, US Army

KENNETH SON, MDLieutenant Commander, Medical Corps, US Navy

ALEX STOJADINOVIC, MDColonel, Medical Corps, US Army

ANN VIRTIS, MDColonel (Retired), Medical Corps, US Air Force

RONALD WHITE, MD

Major, Medical Corps, US ArmyALON P. WINNIE, MDProfessor of Anesthesiology, NorthwesternUniversity Medical Center

MODELS

MICHAEL ADAMS, MD

BRIAN MCLEAN, MD

AIDAN SHIELDS

MICHAEL SHIGEMASA

NECIA WILLIAMS, MD


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ix

PREFACEAlmost 50 years ago a seminal observation in

the renaissance and subsequent explosive develop-ment of regional anesthesia was made by a residentprosector preparing a cadaver for a nerve blockcourse taught by the residents chairman. Althoughthe dissection was primarily focused on the nerves,the resident noted a consistent relationship betweenthe nerves, muscles, and fascia: the brachial plexus,for example, was surrounded by a fascial sheath,provided in large part by the surrounding muscles,throughout its development and distribution to theupper extremity. As the dissection continued, henoted a similar fascial envelope surrounding theother major plexuses, cervical, lumbar, and sacral.As a result, the resident theorized that it might bepossible to block an entire plexus by injecting localanesthetic through a needle inserted into its sheath,just as in producing epidural anesthesia. He triedit clinically and it worked. After his rst few suc-

cessful single injection blocks, he commented to hisfellow residents how useful such single injectiontechniques would be on the battleeld, especiallysince the use of a catheter would allow analgesia tolast as long as necessary.

Over the subsequent half century many (per-haps too many!) approaches to these fascialenvelopes have been described, and many ofthem have become popular throughout the world.Furthermore, technological advances have keptpace with the increasing use of regional anesthesia,making all the techniques simpler to learn, safer to

administer, and much more successful. Although

regional anesthesia was being utilized frequentlyin hospital clinical practice, it took the MilitaryAdvanced Regional Anesthesia and Analgesia(MARAA) groups vision to recognize the uniquevalue of these techniques during wartime: for cen-turies morphine has been the traditional painkilleron the battleeld, despite producing a high inci-dence of nausea and vomiting, bringing the pos-sibility of abuse and dependence, and never com-pletely abolishing the pain. Continuous plexus orperipheral blocks can relieve pain completely andcan maintain relief as long as necessary. ColonelChester C Buckenmaier III, the founder of MARAA,personally provided the rst successful applica-tion of a continuous peripheral nerve block on thebattleeld: he placed a continuous catheter in theleg of a soldier who had sustained a severe shrapnelinjury to his left calf from a rocket propelled gre-nade. This one catheter with a continuous infusion

of local anesthetic provided complete pain reliefduring this soldiers entire evacuation, the initialsurgery at the combat support hospital in Iraq,transport to Germany, a second surgical procedurethere, transport home to Walter Reed Army MedicalCenter, and four additional surgical proceduresthere, the last being amputation. The catheter wasnally removed after the last procedure, 16 daysafter its insertion!

As impressive as this approach is to the manage-ment of the acute pain of battleeld injuries andsubsequent surgical procedures, its advantages

may go even further: evidence is accumulating that

neural blockade of acute pain may prevent the sub-sequent development of chronic pain (complex re-gional pain syndrome I and II, phantom limb pain,etc); researchers are even predicting that the absenceof excruciating pain following devastating injuriescould prevent the development of posttraumaticstress syndrome. Only time and the data being ob-tained by MARAA will tell.

Military anesthesiologists should be procientin regional anesthesia techniques, which will un-doubtedly play an increasingly important role inproviding pain relief and recovery during wartime.MARAA hopes to make this possible by provid-ing this excellent, brief but complete synopsis ofregional anesthesia as a resource for anesthesiolo-gists serving in the armed forces. Not intended forthe beginner or trainee, this book is carefully struc-tured to provide a quick review of the anatomyand technique of each nerve block, formatted for

easy reference on the battleeld or in the operatingroom. Because of the variable circumstances underwhich a block may be carried out on the battleeld,each technique is described using paresthesia,nerve stimulation, and ultrasound. I am certainthat this book will not only go a long way towardintegrating continuous plexus and peripheralnerve blocks into military medicine, but also, ul-timately (because soldiers arent soldiers forever),both the manual and MARAA will have a positiveimpact on civilian medicine, and in particular theway we manage painful trauma in large-scale civil-

ian disasters.

Alon P. Winnie, MD


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PROLOGUE

The Military Advanced Regional Anesthesia andAnalgesia (MARAA) Handbook was developedas a supplement to Emergency War Surgery ThirdUnited States Revision.In Emergency War Surgery,regional anesthesia is described as a eld friendlyanesthetic requiring minimal logistical supportwhile providing quality anesthesia and analgesia onthe battleeld. Until now, details on how to pro-vide advanced regional anesthesia and acute painmedicine services on the modern battleeld wereunavailable. The contributors to this MARAA hand-book have collaborated to provide a useful resourcefor managing the pain of battleeld trauma.

Rapid advancement in medical science has beenthe hallmark of US military medicine throughoutthe nations history. The recent wars in Iraq andAfghanistan are no exception. Life-saving advancesin body armor, rapid medical evacuation from pointof injury, availability of blood products, improved

far-forward surgical and critical care capability, andrapid air evacuation of casualties to level IV medi-cal facilities have contributed to a less than 10%died-of-wounds rate in the current conicts. Themilitary medical triumph represented by this sta-tistic is undeniable, although the achievement hasresulted in other problems, particularly in the man-

agement of acute pain. Since the US Civil War mor-phine has been the accepted standard for battleeldpain control, because options for pain managementin previous conicts were limited, comprehen-sion of pain mechanisms nascent, and casualties,when they survived, tended to remain near thebattleeld while they recovered. Modern combatcasualty care now emphasizes rapid evacuation toprogressively higher levels of medical care withcritical care support provided at all times (includ-ing transport). Casualties who earlier were kept ina war zone for days to weeks until they were stablefor transport now are transported by plane fromIraq to Germany within 8 to 72 hours of injury.The environment of evacuation aircraftcrowded,deafening, jolting, poorly lit, with limited monitor-ing capabilitiesonly magnies the difculties ofusing opioid-only pain control therapy. Healthcareproviders placed in this situation are less likely

to use adequate doses of morphine because ofvalid patient safety concerns. The large numbersof healthcare providers in the evacuation chainand long evacuation distances further complicateopioid use in these patients.

Fortunately, among the medical advances aris-ing from the current conicts are improved under-

standing and management of pain in war casualties.Through the MARAA organization (see Chapter1), like minded anesthesia providers from the AirForce, Army, and Navy have greatly improved themanagement of pain in combat wounded throughthe application of modern pain treatment medica-tions and technologies, including advanced regionalanesthesia. In the US military, uncontrolled acutepain is now recognized as a disease process of thenervous system, not just a symptom of trauma. Thistext celebrates this advancement, preserving whathas been learned to serve as a new, higher stan-dard for pain management in this and forthcomingconicts.

The purpose of this handbook is to assist withthe education of anesthesiology residents in the artand science of advanced regional anesthesia andacute pain medicine. As John J Bonica stated in TheManagement of Pain, The proper management of

pain remains, after all, the most important obliga-tion, the main objective, and the crowning achieve-ment of every physician. This handbook is dedicat-ed to the US military professionals who have beenwounded in the service of this country. It is our hopethat the knowledge within this text will be used toease the burden of their wounds.


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2

1 MARAA: A BRIEF HISTORY

MARAA also spearheaded the regional anesthesiatracking system (RATS), designed to provide real-time continuous pain management informationon patients from Iraq to the United States. RATS iscurrently being integrated into the Armys onlineTheater Medical Data Store as part of the militarycomputerized patient record. These initiatives haveled to greater pain control for wounded soldiers, andtheir success has been widely recognized in profes-sional and lay journals from Newsweek to Wiredmagazine.

The need for comprehensive pain managementhas recently been recognized at the national legisla-

tive level with the introduction (and passage by theHouse May 26, 2008) of HR 5465, the Military PainCare Act of 2008, which will require that all patientsat military treatment facilities be assessed and man-aged for pain throughout their recovery period. Inaddition, all patients must be provided access tospecialty pain management services, if needed. If thebill is passed, MARAA is in position to organize itsimplementation.

Already, MARAA is expanding its role beyondimproving the care of military beneciaries by en-couraging civilian attendees at its Annual Compre-hensive Regional Anesthesia Workshop (Figure 1-2),

TABLE 1-1

ATTENDEES AT THE FIRST MEETING OFTHE MILITARY ADVANCED REGIONALANESTHESIA AND ANALGESIA INITIATIVE

COL John Chiles, Army Service Consultant

LTC Chester Buckenmaier,Army Service Consultant designee;MARAA President

Lt Col Todd Carter, AirForce

Service Consultant

CAPT Ivan Lesnik, Navy Service Consultant

CDR Dean Giacobbe,Navy

Service Consultant designee

MAJ Peter Baek, Air Force Service Consultant designee

As the service primarily responsible for transport-ing wounded soldiers from the battleeld to theUnited States, the Air Force supported the initiativeand almost immediately issued a memorandumoutlining specic directives to Air Force providersbased on MARAA recommendations. By October2006 MARAA meetings had grown to include over30 senior military anesthesiologists. Nursing supportof anesthesia was recognized early on, and a certi-

ed registered nurse anesthetist from each servicewas added to the board in April 2006. Initial meet -ings focused on approval of the Stryker PainPump2 (Stryker; Kalamazoo, Mich) for use on Air Forcemilitary aircraft and the need for patient-controlledanalgesia pumps on the battleeld and on evacua-tion aircraft. The organization developed a series oftraining modules and consensus recommendationson pain management for anesthesiologists prepar-ing for deployment (available at: www.arapmi.org).

Technology Research Center, and the Henry MJackson Foundation. The rst MARAA meeting washeld in February 2005 (Table 1-1).

Figure 1-2. MAARA Annual Workshop faculty; l-r: Scott M Croll, Alon P Winnie, Chester Buckenmaier.


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held at the Uniformed Services University of theHealth Sciences in Bethesda, Maryland. This yearmarks the 7th year of the workshop, directed by DrBuckenmaier and taught by senior anesthesiolo-gists from around the nation. This years facultyincluded doctors Alon P Winnie, NorthwesternUniversity; Andre P Boezaart, University of Florida;John H Chiles, former anesthesiology consultant tothe Army surgeon general and currently at INOVAMount Vernon Hospital; Laura Lowrey Clark,University of Louisville; Steven Clendenen, MayoClinic; Scott M Croll, Uniformed Services Univer-sity and Walter Reed Army Medical Center; John MDunford, Walter Reed Army Medical Center; CarloD Franco, Rush University; Ralf E Gebhard, Uni-versity of Miami; Roy A Greengrass, Mayo Clinic;Randall J Malchow, Brooke Army Medical Center;Karen C Neilsen, Duke University; Thomas C Stan,Far Hills Surgery Center; and Gale E Thompson,Virginia Mason Medical Center.

Although the recognition of MARAAs successhas so far been directed to its immediate achieve -mentsimproved and systematic pain control forwounded soldiersits ultimate contribution maybe broader in scope. Pat ient care is a multispecialtyteam effort that MARAA recognizes. Therefore,MARAA solicits, evaluates, and appreciates inputfrom other physician subspecialists and from nurs-ing providers; much of the spring 2006 meetingwas devoted to astute ight nurse observationscollected by Lieutenant Colonel Dedecker, a USAir Force nurse in charge of the Patient MovementSafety Program. MARAA meetings remain open toany person interested in attending, and all meetingnotes, data, and recommendations are freely avail-able. As impressive as MARAAs contributions topatient care have been, history may view its greatercontribution as a modern model of how a smallgroup of persons with vision and energy can dra -matically improve an entire eld of care.

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MARAA: A BRIEF HISTORY 1

CHARTER OF THE

MILITARY ADVANCED REGIONAL

ANESTHESIA & ANALGESIA

JUNE 2005

ARTICLE I: NAME AND OBJECT

1. Name. The name of the organization is Military

Advanced Regional Anesthesia & Analgesia (MARAA).2. Object. The object of the organization is the promotionof regional anesthesia and improved analgesia formilitary personnel and dependents at home and on thenations battleelds.

3. Purpose. The organization will work to developconsensus recommendations from the Air Force, Army,and Navy anesthesia services for improvements inmedical practice and technology that will promoteregional anesthesia and analgesia in the care of military

beneciaries. The organization serves as an advisory

board to the individual service anesthesia consultants tothe surgeons general.

ARTICLE II: MANAGEMENT

The organization will consist of the anesthesiologyconsultant of each military service (or their designee)and a second appointee by each service anesthesiologyconsultant (six member board). Each member of

the organization has one vote on issues that requireagreement/collaboration between services. All decisionswill be made by a simple two thirds majority. Issuesthat fail to obtain a two thirds majority consensus will betabled and re-addressed at the next meeting called by thePresident of the organization.

ARTICLE III: DIRECTORS

The organization will select a President of theorganization from organization members each scalyear by simple majority vote. The President will

be responsible for soliciting meeting issues frommembers and setting meeting agendas. The Presidentwill be responsible for generating organizationposition white papers on decisions made by theorganization. The position white papers will provideeach service anesthesia consultant with collaborativerecommendations for issues considered by theorganization. The President can assign the writing ofdecision papers to committee members. The presidentwill have nal editorial authority over any whitepaper recommendations submitted to the serviceanesthesiology consultants.

ARTICLE IV: MEETINGS

1. Meetings. The organization will meet twice yearly.One formal meeting will be at the Uniformed Services

Society of Anesthesiology meeting during the AmericanSociety of Anesthesiology conference. A second meetingwill be scheduled during the Spring. Meetings will becoordinated by the organization president. Organizationmembers can send proxies to attend meetings intheir place (proxy voting is allowed) if approved bythat members service anesthesiology consultant.Teleconferencing is an acceptable means of attending ameeting. Meetings will only be held when a quorumof members (or their proxies) are available. A quorumwill be dened as a majority of voting members withrepresentation from each service.

2. Special Meetings. The president can call for a specialmeeting by organization members on issues requiringprompt attention.

3. Conduct of Meetings. Meetings will be presided overby the President or, in the absence of the President, amember of the organization designated by the President.

4. Meeting Agenda. The President will provide memberswith the meeting agenda one week prior to scheduled

meetings. Members may add new items to the agendaduring meetings with the Presidents request for new

business. Meetings will be concluded with review of oldbusiness.

ARTICLE V: ORGANIZATION SEAL

The organization seal is represented at the head of thisdocument.

Ammendment 1 (6 April 2006): The voting MARAAmembership will include one CRNA vote per service.Representatives will be chosen by each servicesanesthesiology consultants. There will now be 9 total

votes (2 physician and 1 CRNA per service).


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2. PERIPHERAL NERVE BLOCK

EQUIPMENT

INTRODUCTION

The safe and successful application of regionalanesthesia in patients requires specialized train-ing and equipment. In 2005, guidelines for regionalanesthesia fellowship training were published inthe journal Regional Anesthesia and Pain Medicine.

The guidelines were a collaborative effort of a groupof North American regional anesthesia fellowshipprogram directors who met to establish a standard-ized curriculum. An important part of this docu-ment is the categorization of regional anestheticprocedures into basic, intermediate, and advancedtechniques. The Walter Reed Army Medical Center(WRAMC) regional anesthesia fellowship programhas adopted this categorization as well as the pub-lished guidelines (Table 2-1).

This manual will focus on intermediate and ad-

vanced regional anesthesia techniques and acutepain therapies, which may not be included inroutine anesthesia training. Some basic techniquesare covered as well (with the exception of neuraxialanesthesia). The primary purpose of this manual isto serve as a guide for WRAMC resident and fellowanesthesiologists during their regional anesthesiaand acute pain rotations. The facility, equipment,and stafng solutions used at WRAMC may not beentirely workable at other institutions; however, theeditors are condent that other clinicians can benetfrom this systematic approach to regional anesthesia

and acute pain medicine.Contemporary regional anesthesia increasingly

relies on sophisticated equipment, as providersstrive for accurate and safe methods of needle place-ment and anesthetic delivery. This chapter willreview the equipment used at WRAMC as well ason the modern battleeld in the successful perfor-mance of regional anesthesia. Note: The equipmentdisplayed in this chapter is for illustration purposes onlyand should not be considered an endorsement of anyproduct.

TABLE 2-1

CLASSIFICATION OF REGIONAL ANESTHESIA TECHNIQUES AT WALTER REED ARMY MEDICALCENTER

Basic Techniques Intermediate Techniques Advanced Techniques

Anesthesia providers who have completedan accredited anesthesia program should be

familiar with these techniques.

Should be familiar to anesthesia providerswho have completed a supervised

program in regional anesthesia andhave demonstrated profciency in these

techniques (usually 2025 blocks of eachtype).

Should be familiar to anesthesiologists withadvanced or fellowship training in regionalanesthesia appropriate for a subspecialistconsultant in regional anesthesia.

Supercial cervical plexus block

Axillary brachial plexus block

Intravenous regional anesthesia(Bier block)

Wrist block

Digital nerve block

Intercostobrachial nerve block

Saphenous nerve block

Ankle block

Spinal anesthesia

Lumbar epidural anesthesia

Combined spinal-epiduralanesthesia

Femoral nerve block

Deep cervical plexus block

Interscalene block

Supraclavicular block

Infraclavicular block

Sciatic nerve block: posteriorapproach

Genitofemoral nerve block

Popliteal block: all approaches

Suprascapular nerve block

Intercostal nerve block

Thoracic epidural anesthesia

Continuous peripheral nerve blocks:placement and management

Ultrasound guided regionalanesthesia

Thoracolumbar paravertebral blocks

Lumbar plexus block

Sciatic nerve block: anteriorapproach

Obturator nerve block Cervical epidural anesthesia

Cervical paravertebral block

Maxillary nerve block

Mandibular nerve block

Retrobulbar and peribulbar nerveblocks

REGIONAL ANESTHESIA AREA

Regardless of the practice environment (militarycare level III through IV), a designated area for theapplication of regional anesthesia techniques outsideof the operating room will enhance block success.This alternative location for nerve block placementwill prevent unnecessary operating room delays,allow additional time for long-acting local anesthet-ics to set up, and allow the provider to assess thequality of the nerve block prior to surgery. Otheradvantages of a regional anesthesia area include

reduced anesthesia turnover times and improved

patient-anesthesiologist relationships. Finally, theregional anesthesia area greatly enhances residenteducation by providing an instructional environ-ment free from the pressures and distractions of abusy operating room.

The regional block area should have standardmonitoring, oxygen, suction, airway, and emer-gency hemodynamic equipment. Certain militarypractice environments will necessitate adjustmentsor alternatives to this equipment list. Advancedcardiac life support capability and medications

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2 PERIPHERAL NERVE BLOCK EQUIPMENT

Figure 2-1. Representative single injection, 90-mm, insulated

peripheral nerve block needle (StimuQuik, Arrow International Inc,

Reading, Pa; used with permission)

Figure 2-2. Set-up for peripheral nerve block

A: ruler and marking pen for measuring and marking landmarks and

injection points

B: alcohol swabs and 25-gauge syringe of 1% lidocaine to

anesthetize the skin for needle puncture

C: chlorhexidine gluconate (Hibiclens, Regent Medical Ltd, Norcross,

Ga) antimicrobial skin cleaner

D: syringes for sedation (at WRAMC, having 5 mg midazolam and

250 mg fentanyl available for sedation is standard)

E: local anesthetic

F: peripheral nerve stimulator

G: stimulating needle

H: sterile gloves

should be readily available as well as Intralipid(KabiVitrum Inc, Alameda, Calif). Recent data haveshown Intralipid to be an effective therapy forcardiac arrest related to local anesthetic toxicity (seeTable 3-2 for Intralipid dosing).

PATIENT CONSENT FOR

REGIONAL ANESTHESIA

As with any medical procedure, proper consentfor the nerve block and documentation of theprocedure (detailing any difculties) is essential.Counseling should include information on risks ofregional anesthesia, including intravascular injec-tion, local anesthetic toxicity, and potential for nerveinjury. Patients receiving regional anesthesia toextremities should be reminded to avoid using theblocked extremity for at least 24 hours. In addition,patients should be warned that protective reexes

and proprioception for the blocked extremity maybe diminished or absent for 24 hours.Particular attention must be paid to site verica-

tion prior to the nerve block procedure. Sidednessshould be conrmed orally with the patient as wellas with the operative consent. The provider shouldinitial the extremity to be blocked. If another anes-thesia provider manages the patient in the operatingroom, the provider who places the regional blockmust ensure that the accepting anesthesia provideris thoroughly briefed on the details of the blockprocedure.

EQUIPMENT

Needles.A variety of quality regional anesthesiastimulating needles are available on the markettoday. Qualities of a good regional anesthesia needleinclude the following:

Stimulating needles should be insulatedalong the shaft, with only the tip exposed forstimulation.

A comfortable nger grip should be attached tothe proximal end of the needle.

The wire attaching the needle to the stimula-tor should be soldered to the needles shaft andhave an appropriate connector for the nervestimulator.

Long, clear extension tubing must also be inte-gral to the needle shaft to facilitate injection oflocal anesthetic and allow for early detection ofblood through frequent, gentle aspirations.

Stimulating needles are typically beveled at45 rather than at 17, as are more traditionalneedles, to enhance the tactile sensation of theneedle passing through tissue planes and toreduce the possibility of neural trauma.

Finally, markings on the needle shaft in centime-

ters are extremely helpful in determining needledepth from the skin.

Centimeter markings on the needle shaft areparticularly important now that ultrasound tech-nology can provide accurate measurements of skinto nerve distances (Figure 2-1). A typical back tableset-up for a peripheral nerve anesthetic is illustrat-ed in Figure 2-2. Figure 2-3 provides the preferredmethod for all local anesthetic injections.


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PERIPHERAL NERVE BLOCK EQUIPMENT 2

When the needle is correctly placed near the target nerveas confirmed with paresthesia, nerve stimulation, and/orultrasound, an initial Raj test is performed.

Slowly inject 35 mL of local anesthetic. Observe thepatients monitors for indications of local anesthetic toxicity(see Chapter 3). Slow injection of local anesthetic iscrucial to allow the provider time to recognize develop-ing local anesthetic toxicity before it progresses toseizures, cardiovascular collapse, and death.

Gently aspirate for blood after each 35 mL increment oflocal anesthetic is injected. If blood is suddenly noted duringone of the incremental aspirations, the injection should beterminated and the patient closely observed for signs of localanesthetic toxicity.

The slow, incremental injection of local anesthetic withfrequent gentle aspiration for blood is continued until thedesired amount of local anesthetic is delivered.

Raj Test

1. Gently aspirate on the 20-mL local anesthetic

syringe and look for blood return in the clearconnecting tubing. Aspiration of blood suggests anintravascular needle placement; the needle shouldbe removed if this occurs. Gentle aspiration isimportant to avoid the possibility of erroneouslyaspirating blood vessel wall and missing theappearance of blood.

2. Following a negative aspiration for blood, inject 1 mLof local anesthetic solution. Excessive resistance toinjection and/or severe patient discomfort suggestpoor needle positioning in or around the nerve; if thisoccurs, terminate the injection and reposition theneedle. When using stimulation, the initial 1 mL oflocal anesthetic should terminate the muscletwitching of the target nerve. This occurs becausethe stimulating current is dispersed by the saline

containing the anesthetic. Failure to extinguishtwitching with a Raj test should alert the provider tothe possibility of an intraneural injection. The needleshould be repositioned in this case.

3. Gently aspirate for blood a second time. If this seriesof maneuvers does not result in aspiration of bloodor in severe patient discomfort, the local anestheticinjection can continue.

The initial 10 mL of local anesthetic injection should containepinephrine 1:400,000 as a marker for intravascular injectionunless clinically contraindicated (eg, high sensitivity toepinephrine, severe cardiac disease).

Figure 2-3. Procedure for injection of all lo cal anesthetics

Peripheral Nerve Block Stimulators. Peripheralnerve stimulation has revolutionized the practiceof regional anesthesia by providing objective evi-dence of needle proximity to targeted nerves. Inthe majority of peripheral nerve blocks, stimula-tion of nerves at a current of 0.5 mA or less sug-gests accurate needle placement for injection oflocal anesthetic. Chapter 4, Nerve Stimulation andUltrasound Theory, discusses nerve stimulation indetail. A variety of peripheral nerve stimulatorsare available on the market. A good peripheralnerve stimulator has the following characteristics:

a light, compact, battery-operated design withadjustable current from 0 to 5 mA in 0.01 mAincrements at 2 Hz impulse frequency;

a bright and easily read digital display; both a visual and audible signal of an open or

closed circuit between the stimulator, needle,

and patient; and an impulse duration adjustable between 0.1millisecond (ms) and 1 ms.

Continuous Peripheral Nerve Block Catheters.Chapter 24, Continuous Peripheral Nerve Block,provides details on WRAMC procedures for placingand securing continuous peripheral nerve block(CPNB) catheters. The majority of catheters placedat WRAMC and in the eld are nonstimulatingcatheters (Figure 24-1) because of how long thecatheters remain in situ1 to 2 weeks on average

and currently available stimulating catheter systemsrecommend removal after 72 hours (however, newcatheter technology may soon change this limita-tion). In the management of combat wounded, hun-dreds of nonstimulating CPNB catheters have beenplaced to manage pain for weeks, some as long as amonth, without complication related to the catheter.Desirable characteristics of a long-term CPNB cath-eter are listed in Table 2-2. The Contiplex Tuohy (B



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TABLE 2-2

DESIRABLE CHARACTERISTICS OF A LONG-TERM CONTINUOUS PERIPHERAL NERVEBLOCK CATHETER

Easily placed through a standard 18-gauge Tuohy needle

Composed of inert, noninammatory material Centimeter markings to estimate depth/catheter

migration

Colored tip to conrm complete removal from patient

Flexible, multiorice tip

Hyperechoic on ultrasound

Radiopaque

Secure injection port

Capable of stimulation

Nonadherent with weeks of internal use High resistance to breaking or kinking

Low resistance to infusion

Bacteriostatic

System to secure the catheter to the patients skin

Braun Melsungen AG, Melsungen, Germany) CPNBnonstimulating catheter system used at WRAMChas had years of successful long-term use in combatcasualties and remains the recommended CPNBsystem for the eld.

Ultrasound. Some regional anesthesia provid-ers consider recent developments in ultrasound

technology to be the next revolution (after pe-ripheral nerve stimulation) in regional anesthesia.Improvements in ultrasound technology allow forhigh image resolution with smaller, portable, andless expensive ultrasound machines (Figure 2-4).Elements of a superior ultrasound machine for re-gional anesthesia are high image quality, compact

Figure 2-4. Contemporary laptop ultrasound machine (Logiq Book

XP, GE Healthcare, Buckinghamshire, United Kingdom; used with

permission)

Infusion Pumps. Recent improvements inacute pain management on the battleeld wouldhave been impossible without improvements inmicroprocessor-driven infusion technology. The use

TABLE 2-3

DESIRABLE CHARACTERISTICS OF AMILITARY PAIN INFUSION PUMP

Easily identiable by shape and color

Used only for pain service infusions

Lightweight and compact

Reprogrammable for basal rate, bolus amount, lockoutinterval, and infusion volume

Battery operated with long battery life

Program lock-out to prevent program tampering

Simple and intuitive operation

Medication free-ow protection

Latex free

Visual and audible alarms

Stable infusion rate at extremes of temperature andpressure

Inexpensive

Durable for long service life without needingmaintenance

Certied for use in US military aircraft

and rugged design, simple and intuitive controls,easy image storage and retrieval, and ease of porta-bility. Ultrasound for peripheral nerve blocks is dis-

cussed in Chapter 4.

of CPNB and other pain management techniquesduring casualty evacuation depends on this technol-

ogy. Infusion pumps for the austere military envi-ronment should have the attributes listed in Table2-3. The pain infusion pump currently used duringcasualty evacuation for patient-controlled analgesia(PCA), epidural catheters, and CPNB is the AmbITPCA pump (Sorenson Medical Inc, West Jordan,Utah [Figure 2-5]).




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Figure 2-5. Casualty evacuation acute pain management pump (AmbIT PCA pump [Sorenson Medical Inc, West Jordan, Utah; used with permission]) in current use, with op erating instruction quick reference card


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3. LOCAL ANESTHETICS

INTRODUCTION

Compared to general anesthesia with opioid-based perioperative pain management, regionalanesthesia can provide benets of superior paincontrol, improved patient satisfaction, decreasedstress response to surgery, reduced operative andpostoperative blood loss, diminished postopera-

tive nausea and vomiting, and decreased logisticrequirements. This chapter will review the mostcommon local anesthetics and adjuncts used in theUS military for the application of regional anesthetictechniques, with particular emphasis on medica-tions used for peripheral nerve block (PNB) andcontinuous peripheral nerve block (CPNB).

BASIC REVIEW OF LOCAL ANESTHETICS

Local anesthetics are valued for the ability to

prevent membrane depolarization of nerve cells.Local anesthetics prevent depolarization of nervecells by binding to cell membrane sodium channelsand inhibiting the passage of sodium ions. Thesodium channel is most susceptible to local anes-thetic binding in the open state, so frequently stimu-lated nerves tend to be more easily blocked. Theability of a given local anesthetic to block a nerveis related to the length of the nerve exposed, thediameter of the nerve, the presence of myelination,and the anesthetic used. Small or myelinated nervesare more easily blocked than large or unmyelinated

nerves (Table 3-1). Myelinated nerves need to beblocked only at nodes of Ranvier (approximatelythree consecutive nodes) for successful preven-tion of further nerve depolarization, requiring asignicantly smaller portion of these nerves to beexposed to the anesthetic. Differential blockade toachieve pain and temperature block (A-d, C bers)while minimizing motor block (A-abers) can be

TABLE 3 1

NERVE CLASSIFICATION AND SEQUENCE OF BLOCK WHEN EXPOSED TO LOCAL ANESTHETIC

Fiber Type Myelin Diameter(m)

Function Conduction Velocity Time to Block

A-a Yes 1220 Somatic motor and proprioception Fast Slow

A- Yes 512 Light touch and pressure

A- Yes 36 Muscle spindle (stretch)

A-d Yes 14 Pain (fast-localizing), temperature, rm touch

B Yes 13 Preganglionic autonomic

C No 0.31.3 Pain (nonlocalizing ache), temperature, touch,postganglionic autonomic Slow Fast

Local anesthetic structure is characterized byhaving both lipophilic and hydrophilic ends (ie, am-phipathic molecules) connected by a hydrocarbonchain. The linkage between the hydrocarbon chainand the lipophilic aromatic ring classies local an-esthetics as being either an ester (CO) local anes -thetic, in which the link is metabolized in the serumby plasma cholinesterase, or an amide (NHC)local anesthetic, in which the link is metabolizedprimarily in the liver.

The functional characteristics of local anestheticsare determined by the dissociation constant (pK

a),

lipid solubility, and protein binding. The pKais thepH at which a solution of local anesthetic is in equi-librium, with half in the neutral base (salt) and halfin the ionized state (cation). Most local anestheticshave a pK

agreater than 7.4. Because the neutral base

form of the local anesthetic is more lipophilic, it canpenetrate nerve membranes faster. As the pK

aof a

local anesthetic rises, the percentage in the ionized

state increases and the onset of the block is slowed.Once the local anesthetic has passed through the

cell membrane, it is exposed to the more acidic axio-plasmic side of the nerve, favoring the ionized state.The ionized form of the molecule binds the sodiumchannel and blocks conduction.

The potency of local anesthetics is determinedby lipid solubility. As lipid solubility increases, theability of the local anesthetic molecule to penetrateconnective tissue and cell membranes increases,causing the increase in potency.

The duration of action for local anesthetics is de-termined by protein binding. Local anesthetics withhigh afnity for protein binding remain bound to

nerve membranes longer, resulting in an increasedduration of action. Binding to serum a

1-acid glyco-

proteins and other proteins decreases the availabil-ity of free drug in the blood, reducing the potentialfor toxicity in the primary organs. The free fractionof local anesthetic in the blood is increased in condi-tions of acidosis or decreased serum protein, thusheightening the potential for toxicity.

achieved by using certain local anesthetics and de-livering specic concentrations to the nerve.

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LOCAL ANESTHETIC TOXICITY

Shortly after Carl Koller introduced cocaine forregional anesthesia of the eye in 1884 and physi-cians worldwide began injecting cocaine nearperipheral nerves, reports of cocaine poisoningbegan appearing in the literature. Local anesthet-ics are indispensable to the successful practiceof regional anesthesia, and physicians who usethese techniques must be familiar with the signsand symptoms of local anesthetic toxicity. Initialexcitatory symptoms of local anesthetic toxicityare manifestations of escalating drug concentra-tion in the central nervous system, specically theamygdala. Increasing local anesthetic concentra-tion begins to block inhibitory pathways in theamygdala, resulting in unopposed excitatoryneuron function. This process is manifested clini-cally as symptoms of muscular twitching, visualdisturbance, tinnitus, light-headedness, or tongue

and lip numbness. Extreme patient anxiety,screaming, or concerns about imminent death arealso suggestive of toxicity. As the blood concen-tration of local anesthetic increases, these initialsymptoms, without intervention, will progress togeneralized tonic-clonic convulsions, coma, respi-ratory arrest, and death.

The cardiovascular system, though signicantlymore resistant to local anesthetic toxicity than thecentral nervous system, will exhibit arrhythmiasand eventual collapse as local anesthetic concentra-tions increase. The relationship between the blood

concentration of a particular local anesthetic thatresults in circulatory collapse and the concentrationneeded to cause convulsions is called the circula-tory collapse ratio. As this ratio becomes smaller,the interval between convulsions and circulatorycollapse decreases. Generally, this ratio tends to besmall in the more potent, long-acting local anesthet-ics (bupivacaine and ropivacaine) compared withintermediate- and shorter-acting drugs (mepiva-caine and lidocaine). The more potent a local anes-

thetic, the greater potential it has for causing cardiacdepression and arrhythmias.

Local anesthetics have been shown to bemyotoxic in vivo, although little evidence isavailable to determine this phenomenons clinicalrelevance. Nevertheless, practitioners using localanesthetic for PNB or CPNB should consider the

myotoxic potential of these medications in casesof unexplained skeletal muscle dysfunction. Localanesthetics have also been demonstrated to be neu-rotoxic in vitro, but the clinical signicance of thesendings remains theoretical.

A variety of anesthesia textbooks publishmaximum recommended dosages for local anesthet-ics in an attempt to prevent high dose injectionsleading to toxicity. Because local anesthetic toxicityis related more to intravascular injection than to totaldose, some physicians have suggested maximumdose recommendations are irrelevant. It is reasonable

to assume that intravascular injections will occur,and practitioners of regional anesthesia should selecttechniques designed to minimize their occurrence,while maintaining preparation for appropriate treat-ments to use when such injections occur. The siteof injection also affects the blood concentrations oflocal anesthetic. Blood absorption of local anestheticvaries at different injection sites according to thefollowing continuum (from greatest to least absorp-tion): intercostal > caudal > epidural > brachialplexus > femoralsciatic > subcutaneous > intraartic-ular > spinal. Taking these factors into consideration,recommended techniques and conditions for localanesthetic injection are listed in Table 3-2.

Ropivacaine. Ropivacaine (Naropin, AbraxisBioScience Inc, Schaumburg, Ill) has a pK

aof 8.2.

It is chemically similar to both mepivacaine andbupivacaine, but it is unique in being the rst localanesthetic marketed as a pure levorotatory stereoi-somer rather then a racemic mixture (ie, a combina-tion of levorotatory and dextrorotatory molecules).

Levorotatory enantiomers of local anesthetics aretypically less toxic than dextrorotatory enantiomers.Because ropivacaine is less cardiotoxic than bupiva-caine, it is the preferred long-acting local anestheticfor PNB anesthesia for many providers. The motor-blocksparing properties associated with ropiva-caine spinal and epidural analgesia may provide an

advantage over bupivacaine. Ropivacaine is consid-ered the safest long-acting local anesthetic currentlyavailable, but it is not completely safe (cardiovascu-lar collapse has been reported with its use), and allstandard precautions should be observed with itsuse. Ropivacaine is the long-acting local anestheticof choice at Walter Reed Army Medical Centerbecause of its favorable safety prole and efcacywhen used in a variety of regional anesthetics (Table3-3).

Bupivacaine. Bupivacaine (Marcaine, Sensorcaine;

both made by AstraZeneca, London, UnitedKingdom) has a pK

aof 8.1. With an extensive

history of successful use, bupivacaine is thelong-acting local anesthetic to which others arecompared. Although a bupivacaine block is longacting, it also has the longest latency to onset ofblock. Bupivacaine is noted for having a propensityfor sensory block over motor block (differential sen-sitivity) at low concentrations. These factors, as wellas the low cost of bupivacaine compared to newerlong-acting local anesthetics, have established bupi-vacaine as the long-acting local anesthetic of choicein many institutions. When long-duration analgesiais required, the use of bupivacaine for low-volumeinltration or spinal anesthesia is well established.

In spite of the popularity of bupivacaine forregional anesthesia, its use for large-volume tech-niques such as epidural or peripheral nerve anes-thesia may be problematic; prolonged resuscitationfollowing accidental intravascular injection hasbeen reported. The recommended dosages of bupi-vacaine are the lowest of any of the amide local an-

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esthetics. If patient safety were the only issue (otherthan cost, convenience, or availability) involvedin long-acting local anesthetic selection, less toxicoptions would likely be used for large volume-blocks. This issue remains controversial.

Mepivacaine. Mepivacaine (Polocaine [AbraxisBioScience Inc, Schaumburg, Ill]; Carbocaine[AstraZeneca, London, United Kingdom]) has a pK

a

of 7.6. In terms of function and toxicity, mepivacaineis often compared to lidocaine. In dogs, mepivacainehas been shown to be less cardiotoxic than lidocaine.Mepivacaine can be used for inltration anesthesiawith a similar onset to lidocaine but a longerduration. It is considered one of the least neurotoxiclocal anesthetics. In addition to low toxicity,mepivacaine has other properties that make it anattractive local anesthetic for intermediate-actingPNB, particularly in high-risk cardiac patients.

Mepivacaine has excellent diffusion propertiesthrough tissue, allowing block success despiteless than optimal needle position. It also producesintense motor block, which is desirable for a varietyof surgical procedures such as shoulder surgery.Mepivacaine is the preferred local anesthetic toreestablish surgical block via preexisting CPNBcatheters for patients requiring multiple operations.Low toxicity, rapid onset, and dense motor blockmake mepivacaine attractive for this application.

Lidocaine. With a low pKa(7.7) and moderate

water and lipid solubility, lidocaine or ligno-caine (Xylocaine [AstraZeneca, London, UnitedKingdom]) is the most versatile and widely usedlocal anesthetic. Subcutaneous inltration oflidocaine is the favored analgesic technique formany percutaneous procedures (such as venouscannulation). Despite a long history as the preferredagent for short-duration spinal anesthesia, in-trathecal lidocaine use has become controversialbecause of its association with transient neurologic

syndrome. Lidocaine 0.5% is the most commonlocal anesthetic used for intravenous regional anes-thesia. Its low pK

afacilitates distribution of the local

anesthetic into the exsanguinated extremity.For use as an epidural anesthesia, lidocaine 2%

is popular for cesarean sections and other majoroperations of the abdomen and lower extremitiesbecause of its low systemic toxicity, rapid onset,and intermediate length of duration. Lidocaine usefor PNB has also been described; however, mostphysicians prefer longer acting local anesthetics forPNB, so that the duration of analgesia extends wellinto the postoperative recovery period.

REGIONAL ANESTHESIA ADJUNCTS

AND ADDITIVES

The safe practice of regional anesthesia assumesan awake, though possibly sedated, patient who

can manifest early signs and symptoms of evolvingcentral nervous system or cardiovascular local anes-thetic toxicity. Moderate sedation is used by manypractitioners to reduce the pain and anxiety thatmany patients perceive during regional anesthe-sia procedures. Although a variety of intravenousmedications are available for sedation, midazolam,fentanyl, and propofol are common. Deep sedationor general anesthesia is avoided because patientindicators of pending local anesthetic toxicity ornerve injury are masked. Even moderate sedationwith midazolam and fentanyl degrades detectionof these patient indicators of injury. The anesthe-siologist must skillfully titrate sedation to strike abalance between patient comfort and safety duringblock placement.

The use of propofol and propofol with ketaminein the operating room following block placementfor sedation is increasingly common. Ease oftitration and rapid recovery with minimal sideeffects have popularized these medications forsedation complementing the regional block.

Remifentanil has also been successfully infusedfor regional anesthesia sedation and comparesfavorably with propofol.

Epinephrine (1:200,000 or 1:400,000) is one ofthe most common local anesthetic additives. It iscombined with local anesthetics to produce regionalvasoconstriction, resulting in block prolongationand reduced levels of local anesthetic in plasma.Epinephrine added to local anesthetics also servesas a marker of intravascular injection during singleinjection blocks. Accidental intravascular injection isindicated by observation of increased heart rate (10 beats/min), increased systolic blood pressure (15 mmHg), or decreased electrocardiogram T-waveamplitude (depression 25%), associated with aslittle as 10 to 15 g of intravascular epinephrine.Epinephrine containing local anesthetic test doseinjections via epidural and peripheral nerve catheterswith gentle aspiration is an accepted method to

protect against intravascular placement. Based onanimal models, concerns that epinephrine containinglocal anesthetics may enhance ischemia followingnerve injury or circulatory compromise have causedsome physicians to reduce the dose of epinephrine(1:400,000) or limit its use to the test dose.

A plethora of local anesthetic additives havebeen used to enhance block duration and qualityof analgesia. Multiple studies have shown theaddition of opioids to intrathecal local anestheticsprolongs sensory anesthesia without prolongingrecovery from ambulatory procedures. The combi-nation of local anesthetics with opioids for epiduralanesthesia and analgesia is a common practice andhas been shown to reduce local anesthetic require-ments in obstetric patients. Despite the recognitionof opioid receptors outside of the central nervoussystem, the addition of opioids to peripheral nerveinjections of local anesthetics has not been success-ful in improving PNB characteristics.

Clonidine, an a2-adrenoceptor agonist that

provides analgesia via a nonopioid receptor

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mechanism, has been shown to be effective inprolonging analgesia in spinal, epidural, andperipheral nerve blocks. Clonidine 100 g is fre-quently added to local anesthetic for PNBs at WalterReed Army Medical Center to prolong analgesia.Dexamethasone 8 mg added to local anestheticshas also been reported to enhance the duration ofsensory and motor blockade.

The list of medications used to improve regionalanesthesia continues to grow, including drugs suchas midazolam, tramadol, magnesium, neostigmine,and ketamine, as well as others that have hadvarying success. Expanding the list of local anesthet-ic drugs has the potential to improve patient safety,enhance analgesia, and expand the role of regionalanesthesia in perioperative management.

TABLE 3-2

RECOMMENDED TECHNIQUES AND CONDITIONS TO MINIMIZE THE RISK OF LOCALANESTHETIC INTRAVASCULAR INJECTION

Standard monitoring with audible oxygen saturation tone.

Oxygen supplementation.

Slow, incremental injection (5 mL every 1015 seconds). Gentle aspiration for blood before injection and every 5 mL thereafter.

Initial injection of local anesthetic test dose containing at least 515 g epinephrine with observation for heart ratechange > 10 beats/min, blood pressure changes > 15 mmHg, or lead II T-wave amplitude decrease of 25%.

Pretreatment with benzodiazepines to increase the seizure threshold to local anesthetic toxicity.

Patient either awake or sedated, but still able to maintain meaningful communication with the physician.

Resuscitation equipment and medications readily available at all times.

If seizures occur, patient care includes airway maintenance, supplemental oxygen, and termination of the seizure withpropofol (2550 mg) or thiopental (50 mg).

Local anesthetic toxicity that leads to cardiovascular collapse should immediately be managed with prompt institution

of advanced cardiac life support (ACLS) protocols.

Intralipid (KabiVitrum Inc, Alameda, Calif) 20% 1 mL/kg every 35 minutes, up to 3 mL/kg, administered duringACLS for local anesthetic toxicity can be life saving. Follow this bolus with an Intralipid 20% infusion of 0.25 mL/kg/min for 2.5 hours.

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TABLE 3-3

STANDARD ADULT ROPIVACAINE DOSAGES FOR SINGLE INJECTION AND CONTINUOUS REGIONAL ANESTHESIA AT WALTER REED ARMYMEDICAL CENTER

Regional Anesthesia Technique Adult Single Injection* Continuous Infusion of0.2% Ropivacaine(mL/h)

Patient-Controlled Bolus Rateof 0.2% Ropivacaine

(mL bolus/20 min lockout)

Notes

Interscalene 3040 mL of 0.5% ropivacaine 810 23 Often supplemented with an intercostal brachialnerve block

Supraclavicular 3040 mL of 0.5% ropivacaine 810 23 Shortest latency block of the brachial plexus

Infraclavicular 3540 mL of 0.5% ropivacaine 1012 23 Catheter techniques less effective compared tosupraclavicular catheters

Axillary 40 mL of 0.5% ropivacaine 1012 23 Catheter techniques less common

Paravertebral 35 mL of 0.5% ropivacaine perlevel blocked

810 23 Catheters effective in thoracic region only

Lumbar plexus (posteriorapproach)

3040 mL of 0.5% ropivacaine 810 23 Epidural spread is a concern

Femoral 2030 mL of 0.5% ropivacaine 810 23 Catheter techniques may miss the obturator orlateral femoral cutaneous nerves

Sciatic (anterior or posteriorapproach)

2030 mL of 0.5% ropivacaine 810 23 Proximal approaches to the sciatic nervepreferable for catheters

Sciatic (lateral or poplitealapproach)

3540 mL of 0.5% ropivacaine 1012 23 Often the only approach available to the sciaticnerve following polytrauma

Lumbar plexus or femoral + sciatic 5060 mL of 0.5% ropivacainebetween both sites

510 for both catheters 23 on one catheter Infusion rates divided between catheters basedon distribution of patients pain

Epidural 2025 mL of 0.5% ropivacaine 610 thoracic1020 lumbar

23 Opioids often added to infusions

Spinal 515 mg of 1.0% ropivacaine NA NA Opioids often added to injections

*Mepivacaine 1.5% can be used in place of ropivacaine at the volumes noted when a shorter duration block is desirable.Occasionally, a 5 mL bolus per 30-minute lockout is used in selected patients. Generally, total infusion (continuous plus bolus) > 20 mL/h are avoided.NA: not applicable.

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ANDULTRASOUND THEORY

NERVE STIMULATION

The concept of using an electric current togenerate muscle contractions via nerve stimulationis nearly a century old, although the theory behindperipheral nerve stimulation is still poorly under-stood. Actual electrical stimulation of nerves to

evoke a muscle response was rst accomplished in1850 by Herman von Helmohlz during experimentson isolated pieces of nerve and muscle tissues. In1912 Dr VG Perthes described using a nerve stimu-lator to perform peripheral nerve blocks. Recenttechnological advances have made the use of nervestimulation equipment easier and far more accuratethan in past decades.

Ideally, a peripheral nerve stimulator (PNS), incombination with an insulated needle, providesobjective information on needle location by elicitingmuscular twitches in muscle groups served by

targeted nerves. At the most basic level, a PNSworks by generating an electric current and trans-mitting it via a needle insulated along most ofits length, leaving only the needle tip exposedto deliver the current in very close proximityto targeted nerves. A few additional concepts,however, are essential to understanding how thePNS is used in peripheral nerve block procedures.For a nerve to be stimulated, its threshold potentialmust be achieved. To accomplish this, electri-cal energy is applied in the specic amount for

electrons to depolarize the nerve cell membrane(threshold depolarization), causing shifts in intracel-lular and extracellular sodium and potassium ions.The impulse is then propagated along the nerve viasaltatory conduction.

The threshold level of energy for depolariza-tion of the nerve can be achieved by applyinga high current over a short period of time or alower current over a longer period of time; thisis the most basic way to understand the conceptsof reobase and chronaxie. Reobase is dened

as the minimum current necessary to achievethreshold potential over a long pulse. Chronaxieis the minimum duration of stimulus at twice thereobase for a specic nerve to achieve thresholdpotential. Certain nerves have a different chronaxiebased on their physical properties (myelination,size, etc). Also, certain patient conditions, such as

diabetes, have an effect on chronaxie. Large A-alphamotor bers are more easily stimulated than are thesmaller A-delta and C bers, which are responsiblefor pain. The normal pulse duration needed for de-polarization is between 50 and 100 microseconds forA-alpha bers, 170 microseconds for A-delta bers,and 400 microseconds for C bers. By applyingthis knowledge, the duration of the PNS pulse canbe adjusted to keep it above the normal A-alpharange and below the A-delta and C ber level.The stimulation of motor A-alpha bers providesmuscle twitch information while avoiding A-delta

and C bers that cause pain, thus allowing for amore comfortable nerve stimulation experience forthe patient. If the current is too high (eg, > 1.0 mA),the PNS may no longer be able to differentiallystimulate nerve bers.

By understanding the concepts of reobase andchronaxie, adjustments can be made to some nervestimulators to achieve stimulation of targeted nervebers only, or of nerves that may not otherwise bestimulated with a PNS. For example, in diabeticpatients with a prolonged history of elevated blood

glucose levels, nerves may become glycosylated,making stimulation difcult. In these patients, in-creasing the duration of the electric pulse may bethe only way to achieve a minimum current of 0.5mA for stimulating a nerve.

Another important difference between a modernPNS (Figure 4-1) and older models is the abilityto provide constant current output. According toOhms law, I=V/R, where I is the current, V is thepotential difference in volts, and R is the resistanceor impedance. If resistance (impedance) were com-

pletely removed from the equation, then currentwould equal the potential difference. In some

modern PNS models, this equilibrium is achievedby a constant current generator that automaticallyadjusts the current set by the user. The constantoutput maintains the same level of needle tipcurrent regardless of the impedance of body tissueand PNS circuit connections.

The ability to control the intensity and frequency(2 Hz) of the current being applied is an importantaspect of a PNS. Using a higher current for initialnerve stimulation allows for earlier identicationof the nerves location. Decreasing the current once

Figure 4-1. HNS 12 nerve stimulator manufactured by B Braun

Medical Inc (Bethlehem, Pa; used with permission)

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Figure 4-2. Micromaxx Ultrasound Machine manufactured by

SonoSite, Inc (Bothell, Wash)

stimulation has been achieved allows the operatorto place the needle in close proximity to the targetnerve. Constant stimulation of the nerve below 0.5mA but above 0.2 mA generally results in a safe,reliable block. The commonly used 2-Hz frequencyallows for rapid manipulation of the needle to helplocate the nerve.

ULTRASOUND GUIDANCE

Another recent technological advance of extraor-dinary benet to the regional anesthesiologist is theportable ultrasound machine (Figure 4-2), whichallows for real-time visualization of target nerves,as well as surrounding arteries, veins, muscle,and bone. Ultrasound technology also providesthe ability to validate external landmarks againstinternal anatomy. Furthermore, the advantage ofneedle guidance under direct visualization allowsthe operator to avoid vascular structures and more

accurately inject local anesthetic.Most modern ultrasound machines have theability to provide visualization of both supercialand deep structures based on the type of probeused. Basic understanding of ultrasound theory isvitally important for the safe use of this technol-ogy. Ultrasound waves are created by a numberof vibrating piezoelectric crystals contained in thehead of a transducer attached to the ultrasoundmachine. Ultrasound waves penetrate tissues todifferent depths based on the probe frequency.Higher frequency probes, which emit waves at a

frequency between 5 and 13 MHz, provide imageswith greater resolution but do not penetrate deeplyinto tissue. Lower frequency probes, with frequen-cies between 2 and 5 MHz, can penetrate tissuedeeply (up to a depth of 30 cm), but the resolution isfar less than that of the high frequency probes.

The image produced by the ultrasound machinedepends on both the tissues density and its abilityto reect ultrasound waves back to the transducer(ie, the tissues echogenicity). Hyperechoic struc-

tures are those with a greater propensity to reectultrasound energy, and hypoechoic structurestend to absorb this energy. Hyperechoic structures(bone, nerves below the clavicle, vascular walls,and other connective tissues) therefore appearbrighter on the screen, and hypoechoic structures(nerves above the clavicle, blood vessel lumens,lung, and other uid-lled structures) appear

Figure 4-3. (a) Hyperechoic structures and (b) hypoechoic structures

seen on ultrasound

darker (Figure 4-3). Acoustic impedance refersto the reduction in ultrasound wave energy thatoccurs as the wave passes through structures,which accounts for the depth limits on ultrasoundpenetration of tissues.

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The operators knowledge of anatomy is funda-mental to the safe practice of ultrasound-guidedregional anesthesia. Once the nerves are identi-ed, the block is performed with the needle underdirect visualization in the long-axis view (in plane)and the nerve in the short-axis view. Some experi-enced ultrasound operators prefer the out-of-planetechnique (with the needle in short-axis view) for

some blocks. Although this technique results inshorter needle distances to targeted nerves, it doesnot allow visualization of the entire needle duringperformance of the block. Both techniques allowthe needle to be directed away from potentiallydangerous areas and the local anesthetic to bedeposited in multiple locations around the nerve fora safe, successful regional nerve block.

If the operator is uncertain about the needletips proximity to imaged structures, hydrodissec-tion under ultrasound guidance may be used. This

technique involves slowly injecting several millili-ters of local anesthetic (or other uid such as saline)to more precisely dene the needle tip location.For example, if the injected uid spreads awayfrom the targeted nerve, the needle tip is probablyexternal to the nerve sheath. Injected hypoechoicuid also may enhance image clarity of the targetedstructures.

Many compact ultrasound machines are current-ly available with updated software that improvesimage quality to a standard until recently obtain-able only in large, cumbersome, and expensive

machines. Thorough familiarization with the ultra-sound machine being used and its available optionsis necessary to obtain the best possible image forfacilitating needle placement. Many ultrasoundmachine options are available, but most machinesinclude a few basic image adjustment features:

Depth control: allows the user to set a tissue

depth (in cm) that the ultrasound waves willpenetrate. Gain control: allows the user to adjust the screen

grayscale contrast, thus alleviating unnecessaryinterference from poor tissue conduction prop-erties, poor probe-to-tissue interface, or otherproblems.

Doppler mode: allows for differentiation ofstructures containing moving uid such asarteries and veins.

Focus setting, including three basic image reso-lution settings:

o RES (resolution): provides the best detail ofsupercial structures.

o GEN (general): provides the best compromisefor visualizing structures in detail at greaterdepth.

o PEN (penetration): provides the best image ofdeep structures, although image detail is sig-nicantly degraded.

Zoom: magnies image up to 200%. Image freeze and save: allows still pictures of

ultrasound blocks to be saved for documentationof the block procedure.

Patient data screen: allows patient demographicdata to be associated with saved ultrasoundimages.

Other advances in ultrasound software, suchas clearer images through signal harmonics and

three-dimensional ultrasound imaging, continu-ally improve the value of ultrasound technologyas a tool in regional anesthesia. The availability ofthis technology on a laptop, easily portable in theaustere battleeld medical environment, is a par-ticularly exciting advancement.

CONCLUSION

Whether nerve stimulators, ultrasound machines,or both are used to perform regional anesthesia,a basic understanding of how these technologiesfunction when used on live tissues is an importantaddition to, but not a replacement for, detailedanatomical knowledge. This technology can onlyconrm and rene correct needle placement forregional blocks; it should never be considered asubstitute for the physicians understanding of theanatomical basis for each block. Both tools likelyenhance patient safety and improve nerve blocksuccess when used by a trained regional anesthe-siologist. Note: The technology shown to demonstrateconcepts in this chapter should not be considered as anendorsement of these products or companies.

5. UPPER EXTREMITY

NEUROANATOMY

compartments of thearm) The brachial


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NEUROANATOMY

INTRODUCTION

Regional anesthesia of the upper extremity in-volves two major nerve plexuses, the cervical plexusand the brachial plexus. A detailed understanding ofthe anatomy of these nerve plexuses and surroundingstructures is essential for the safe and successful prac-

tice of regional anesthesia in this area of the body.

CERVICAL PLEXUS

The cervical plexus is formed from a series of nerveloops between adjacent anterior rami of cervical nerveroots C1 through C4. The cervical plexus is deep to thesternocleidomastoid muscle and medial to the scalenemuscles. The deep branches of the plexus are motornerves. They include the phrenic nerve (diaphragmmuscle) and the ansa cervicalis nerve (omohyoid,sternothyroid, and sternohyoid muscles). The named

nerves of the supercial cervical plexus are branchesfrom the loops and emerge from the middle of the ster-nocleidomastoid muscle (Figure 5-1):

Lesser occipital nerve(C2): innervates the skinposterior to the ear.

Great auricular nerve(C2C3): innervates the earand angle of the mandible to the mastoid process.

Transverse cervical nerve(C2C3): innervates theanterior neck.

Supraclavicular nerve(C3C4): innervates the areaover the clavicle and shoulder.

The spinal accessory nerve (CN XI) emerges at theposterior border of the sternocleidomastoid muscle,passing supercial to the levator scapulae muscle to in-nervate the trapezius muscle. Stimulation of this nerveduring interscalene block, which causes the shoulderto shrug, is occasionally mistaken as stimulation of thebrachial plexus. Injection of local anesthetic based onthis stimulation pattern will result in a failed intersca-lene block.

BRACHIAL PLEXUS

The brachial plexus is formed from the ve roots(anterior rami) of C5T1. Occasionally contributions tothe brachial plexus come from C4 (prexed plexus) orfrom T2 (postxed plexus). There are seven describedvariations of brachial plexus anatomy, with the mostcommon variant (Figure 5-2) occurring 57% of the time.Asymmetry between the left and right brachial plexus

in the same individual occurs 61% of the time. Brachialplexus anatomy includes the following parts:

Three trunks.The ve roots unite to form the threetrunks of the brachial plexus; superior (C5 and C6),middle (C7), and inferior (C8 and T1). The trunkspass between the anterior and middle scalenemuscles.

Six divisions.Each trunk divides into an anteriordivision (anterior exor compartments of the arm)and a posterior division (posterior extensor

arm). The brachialplexus divisionspass posterior tothe mid-point ofthe clavicle throughthe cervico-axillarycanal.

Three cords.Thedivisions coalesce

to form three cords.The anteriordivisions of thesuperior and middletrunk form thelateral cord. Theanterior division ofthe inferior trunkbecomes the medialcord. The posteriordivisions of allthree trunks uniteto form theposteriorcord. The cords arenamed based on

their relationship to the axillary artery (as thisneurovascular bundle passes in its sheath intothe axilla).

Five terminal branches.The cords give rise tove terminal branches. The musculocutaneousnerve(C5C7) arises from the lateral cord andinnervates the coracobrachialis, biceps brachiiand brachialis muscles, and the skin to the lateral

forearm. The median nerveis a compilation of thelateral cord (C6C7) and the medial cord (C8,T1). It innervates muscles of the anterior forearmand the thenar half of the muscles and skin of thepalm. The ulnar nerveis a branch of the medialcord (C7T1) and innervates the forearm andhand medial to the midpoint of digit four. Theaxillary nerve(C5C6) is a branch of the posteriorcord and innervates the shoulder joint and lateralskin over the deltoid muscle. The radial nerve(C5T1), which is also a branch of the posterior

21

Figure 5-1. Dissection of the supercial cervical plexus in the posterior triangle

5 UPPER EXTREMITY NEUROANATOMY


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cord, innervates all of the muscles of the posteriorcompartments of the arm and forearm and mostof the posterior skin of the upper extremity.Although there are numerous other namedbranches of the brachial plexus, familiarizationwith the plexus as outlined above is adequatefor most upper extremity regional anesthesiaprocedures.

Considerable controversy has arisen about theexistence of a nerve sheath surrounding thebrachial plexus and including the artery, vein, andinvesting connective tissue. Anatomical dissectionof the brachial plexus consistently reveals a distin-guishable sheath of brous tissue surrounding thebrachial plexus, vasculature, and loose investingconnective tissue. In Figure 5-3, the platysma mus-cle has been reected, exposing the brachial plexussheath just posterior to the omohyoid muscle andlateral to the sternocleidomastoid muscle. In Figure

5-4, the omohyoid muscle has beenretracted, and the sheath has beenlled with normal saline. The nervesof the brachial plexus can now be seenthrough the window created by theuid-lled sheath.

The existence of nerve sheathsis not unique to the brachial plexusand can be demonstrated onneurovascular structures throughoutthe human body. The practice ofregional anesthesia depends on theanatomical fact of the sheath. Thesheath improves the success of singleinjection blocks and continuousperipheral nerve catheters bycontaining the local anesthetic nearnervous tissue targets and allowingthe anesthetic to surround and bathethe nerves.

Figure 5-4. Sheath injected with normal saline. Note the nerve tissue

visible within the sheath.

Figure 5-3. Sheath prior to injection with salineFigure 5-2

22

6. CERVICAL PLEXUS BLOCK the diaphragm; (4) contributions to the accessorynerve (CN XI), which innervates the sternocleido-

percial cutaneous surgeries of the head and neck.This block is also useful as a supplement to other


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INTRODUCTION

The cervical plexus block provides anesthe-sia and analgesia to the head and neck region.Depending on the type of surgery, the plexus canbe blocked either at a supercial or a deep level.The supercial branches (Figure 6-1) of the plexusinnervate the skin and supercial structures of

the head, neck, and shoulder. The deep branches(Figure 6-2) innervate the muscles of the deepanterior neck and the diaphragm. The deep cervicalplexus block is used for deeper surgeries of theneck, such as carotid artery or thyroid surgery, andthe supercial cervical plexus block is used for su -

ANATOMY

The cervical plexus is formed from the anteriorrami of the C1 through C4 nerve roots; it liesanterior to the cervical vertebrae and posterior tothe sternocleidomastoid muscle. There are ve main

components of the cervical plexus: (1) the cutaneousbranches, which supply the lesser occipital, greaterauricular, transverse cervical, and supraclavicularnerves; (2) the ansa cervicalis, which innervates theinfrahyoid and geniohyoid muscles; (3) the phrenicnerve, which is the only motor nerve to innervate

Figure 6-1. Superfcial cervical plexus Figure 6-2. Deep cervical plexus

( ),mastoid and trapezius muscles; and (5) directmuscular branches, which supply prevertebralmuscles of the neck.

Bilateral deep cervical plexus blocks, whichwould result in total diaphragmatic paresis, shouldnot be performed. Also, patients with chronic respi-ratory conditions may not be suitable candidates foran ipsilateral deep cervical plexus block. Caution

must be taken when placing a deep cervical plexusblock because of the close proximity of the vertebralartery and the dural sleeve. Placing the block tooclose to the vertebral artery may result in an intra-vascular injection; placing it too close to the duralsleeve may result in a subarachnoid injection.

ppregional techniques of the upper torso.

23

6 CERVICAL PLEXUS BLOCK

PROCEDURE

is contacted, withdraw the needle 1to 2 mm. Injectthe local anesthetic


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24

PROCEDURE

Landmarks

Superfcial Cervical Plexus(Figure 6-3). Identifyand mark the posterior border of the sterno-cleidomastoid, as well as the midpoint of themuscle.

Deep Cervical Plexus(Figure 6-4). Position the

patient supine with the head turned toward thenonoperative side. Palpate the transverse processof C6 (Chassaignacs tubercle) at the level of thecricoid cartilage. Palpate the mastoid processbehind the ear. Draw a line between the mastoidprocess and Chassaignacs tubercle. The trans-verse processes of the other cervical vertebraewill lie on or near this line. The rst palpabletransverse process below the mastoid process isC2. Palpate and mark the transverse processes ofC2 to C4 (the C4 transverse process lies approxi-

mately at the level of the mandible). Insert theneedle medially and caudally so that the needletip is resting on the transverse process.

Needles

22-gauge, 5-cm, short bevel needle.

Injection

Superfcial Cervical Plexus.Insert the needle at themidpoint of the posterior border of the sternocleido-

mastoid muscle to approximately half the depth ofthe muscle, and inject 3 to 4 mL of local anesthetic.Also perform a subcutaneous injection of additionallocal anesthetic cephalad and caudad along thelength of the sternocleidomastoid muscle posteriorborder.

Deep Cervical Plexus.Attach a 10-mL controlsyringe to the needle. Once the transverse process

Figure 6-3

Figure 6-4

jslowly with frequent aspirations.After completing the injection,remove the needleand repeat theblock at the next level. (Many in-stitutions perform only a super-cial cervical plexus block, and thesurgeon inltrates deeper struc-tures as required.)

Local Anesthetic

Superfcial Cervical Plexus.510mL.

Deep Cervical Plexus.35 mL ateach level or 15 mL at C3 only.

Teaching Points. Cautionshould be exercised in patientsreceiving a deep cervical plexus

block for carotid endarterec-tomy surgery. These patientswill likely have atheromatousplaques that could be dislodgedwith excessive head hyper-extension or cause cerebralischemia with head rotation.For carotid endarterectomies,the surgeon must inltratethe carotid body with localanesthetic because the cervicalplexus does not innervate thisstructure.

7. INTERSCALENE BLOCK between the anterior and middle scalenemuscles; C6 corresponds to the level of the

h hO C O


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Figure 7-2

cricoid cartilage. By blocking the plexus at thislevel, the local anesthetic is deposited aroundthe upper roots (C5, C6) that innervate themuscles of the shoulder, specically the deltoid,supraspinatus, infraspinatus, and teres major(Figure 7-1 through 7-3). Occasionally, theremay be proximal spread to the cervical plexus(C3, C4) and cervical sympathetic chain, which

can result in Horners syndrome and hoarsenesspost block; this is not considered a complica-tion, but the patient should be made aware ofthese possible side effects before the procedureis performed.

The interscalene block always results inhemidiaphragm paresis because of the closeproximity of the phrenic nerve (C3C5) to the in-

Figure 7-3. Dermatomes anesthetized with the interscalene block (dark blue)

INTRODUCTION

The interscalene approach to the brachial plexusis particularly well suited for operations on theshoulder, clavicle, or upper arm. The approachpreferentially blocks nerves of the brachial plexus(C5C7), with variable proximal spread to the cervi-cal plexus (C3C4), while usually sparing the ulnarnerve (C8T1). The nerves of the brachial plexusemerge from their respective intervertebral foram-ina and course posterior to the vertebral artery. Theythen pass between the anterior and middle scalenemuscles as the trunks (superior C5C6, middle C7,inferior C8T1) of the brachial plexus.

ANATOMY

The interscalene block is performed at the levelof the C6 vertebral body (Chassaignacs tubercle)

terscalene groove. Any patient who cannot tolerate a reduction in pulmonary function greater than 30% shouldnot receive this block. Even healthy patients may need reassurance that their feeling of dyspnea is transient.

The inter-scalene block

is not ap-propriate forsurgery ofthe hand andforearm, spe-cically in theulnar distribu-tion of C8, T1.Because it isperformed atthe upper roots

of the plexus,the block typi-cally spares theulnar aspectof the hand.Additionally,C3, C4 nerveroots (capearea) are notconsistentlyblocked.

Figure 7-1

25

PROCEDURE

7 INTERSCALENE BLOCK


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PROCEDURE

Landmarks.Place the patient supine with the headturned toward the nonoperative side. Identify thecricoid cartilage, which indicates the C6 level. Palpatethe lateral border of the sternocleidomastoid muscle(SCM), and move your ngers laterally into the in-terscalene groove (between the anterior and middlescalene muscles). Ensure that the clavicular head of

the SCM, rather than the more medial sternal head,is being palpated. The external jugular vein oftencrosses the border of the SCM muscle at this point.If this is the case, the initial needle insertion shouldbe

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