Clinical Pain Management E-Book

• Herausgeber: John Wiley & Sons
• Kategorie: Fachliteratur
• Sprache: Englisch

Seitenzahl: 795

Veröffentlichungsjahr: 2011

Beschreibung

Clinical Pain Management takes a practical, interdisciplinary approach to the assessment and management of pain. Concise template chapters serve as a quick reference to physicians, anesthetists and neurologists, as well as other specialists, generalists, and trainees managing pain. Based on the International Association for the Study of Pain's clinical curriculum on the topic, this reference provides to-the-point best-practice guidance in an easy-to-follow layout including tables, bullets, algorithms and guidelines.

Leseprobe

Table of Contents

Cover

Table of Contents

Dedication

Title page

Copyright page

List of contributors

Foreword

Part 1: Basic Understanding of Pain Medicine

Chapter 1 The challenge of pain: a multidimensional phenomenon

Introduction

Chapter 2 Epidemiology and economics of chronic and recurrent pain

Introduction

Epidemiology of chronic and recurrent pain

Musculoskeletal pain

Chronic widespread pain

Headache

Factors associated with chronic and recurrent pain

Economic impact of chronic pain

Conclusions

Chapter 3 Basic mechanisms and pathophysiology

Introduction

Primary afferent neurons

Nociceptor subtypes

Nociceptors and noxious stimulus detection

Organization of the “pain system”

Sensitization and persistent pain

Analgesic targets

Chapter 4 Psychosocial perspectives on chronic pain

Introduction

Modeling the network of biological, psychological and social determinants of pain

Psychosocial factors in best practice

The person in pain

Caregivers

Pain management

Conclusions

Chapter 5 Identification of risk and protective factors in the transition from acute to chronic post surgical pain

Introduction

Definition and epidemiology of CPSP

Understanding risk and attributing causality to outcomes

Factors associated with CPSP

Preventive analgesia

Summary and conclusions

Chapter 6 Placebo/nocebo: a two-sided coin in the clinician’s hand

Introduction

Before we begin: a few facts on placebo/nocebo

Proposed mechanisms of placebo/nocebo effects

Neurobiology of placebo analgesia

Neurobiology of nocebo hyperalgesia

The coin in the clinician’s hand

Conclusions

Acknowledgments

Part 2: Assessment of Pain

Chapter 7 Clinical assessment in adult patients

Introduction

The history

Physical examination

Musculoskeletal examination

Neurological examination

Conclusions

Chapter 8 Measurement and assessment of pain in pediatric patients

Introduction

Assessing pain in children

Obtaining a pain history

Approaches to measuring pain in children

Tools for assessing pain in children

Choosing the right pain assessment measure

Frequency of pain assessment and documentation

Conclusions

Acknowledgments

Chapter 9 Laboratory investigations, imaging and neurological assessment in pain management

General principles

Common laboratory, imaging and neurological investigations for the patient with chronic pain

Conclusions

Acknowledgments

Chapter 10 Psychological assessment of persons with chronic pain

Introduction

Components of a psychological assessment

Assessment measures

Substance abuse assessment

Electronic diaries and web-based assessment

Future directions

Part 3: Management

Chapter 11 Introduction to management

Overview

Start with the basics

Conclusions

Chapter 12 Managing chronic pain in primary care

Introduction

Basic mechanisms and the scientific basis for understanding the subject

Impact on clinical practice

Features of best clinical practice for managing chronic pain in primary care

Conclusions

Part 4: Pharmacotherapy

Chapter 13 Nutrition and pain management: dietary soy as an analgesic modality

Diet as an analgesic modality

Soybeans: their significance and destiny in the human diet

Hyponociceptive effect of soy: preclinical evidence

Hyponociceptive mechanisms of soy

Analgesic effect of soy protein: clinical evidence

Clinical considerations in using soy protein

Current and future research endeavors

Acknowledgments

Chapter 14 Antidepressant analgesics in the management of chronic pain

Introduction

Basic mechanisms

Basic understanding of mechanisms and their impact on clinical practice

Best clinical practice for antidepressants in some CNCP conditions

Fibromyalgia

Headache

Low back pain

Arthritis

Adverse events

Choice of agent

Approach to therapy

Chapter 15 Anticonvulsants in the management of chronic pain

Introduction

Anticonvulsants in chronic pain: mechanisms of action

Anticonvulsants in neuropathic pain

Anticonvulsants in migraine

Anticonvulsants in fibromyalgia

Other anticonvulsants currently not used for chronic pain treatment

Safety and dosing

Conclusions

Acknowledgement

Chapter 16 Opioids

Introduction

Mechanism of action

Clinical pharmacology

Patient selection and risk stratification

Monitoring and management

Conclusions

Chapter 17 Topical analgesics

Introduction

Topical NSAIDs

Topical local anesthetics

Topical capsaicin

Topical rubefacients

Peripheral and topical opioids

Investigational topical agents

Chapter 18 Other pharmacological agents

Introduction

Non-steroidal anti-inflammatory drugs

Acetaminophen

Skeletal muscle relaxants

Cannabinoids

Part 5: Interventional

Chapter 19 Diagnostic and therapeutic blocks

Introduction

Diagnostic blocks

Peripheral nerve blocks

Occipital nerve blocks

Lateral femoral cutaneous nerve block

Sympathetic blocks

Diagnostic and therapeutic blocks for neck and back pain

Conclusions

Chapter 20 Neuromodulation therapy

Introduction

Types of neuromodulation therapy

Conclusions

Chapter 21 Neurosurgical management of pain

Introduction

Anatomic

Neuromodulatory

Neuroablation

Peripheral nervous system

Spinal cord

Brainstem

Intracranial

Conclusions

Acknowledgment

Part 6: Physical Therapy and Rehabilitation

Chapter 22 Physical therapy and rehabilitation

Chronic pain and rehabilitation

Treatment approaches

Part 7: Psychological

Chapter 23 Pain self-management: theory and process for clinicians

Introduction

What is self-management?

Background: Stanford self-management program model

Content, process and strategies to enhance self-efficacy

Effectiveness of pain self-management programs: main findings

Getting started: conducting a needs assessment

Focus groups

Conclusions and resources

Acknowledgments

Chapter 24 Psychological interventions: cognitive behavioral and stress management approaches

Introduction

Mechanisms underlying and evidence supporting psychological interventions

Best clinical practice

Conclusions

Chapter 25 Pain catastrophizing and fear of movement: detection and intervention

Introduction

Pain catastrophizing (maladaptive coping)

Fear of movement associated with pain

Assessment of catastrophizing

Treatments aimed at reducing catastrophizing

Assessment of fear of movement

Treatments aimed at reducing fear of movement

Conclusions

Part 8: Complementary Therapies

Chapter 26 Complementary and alternative medicines

Introduction

Definition of CAM

Asking about CAM

Absence of evidence or evidence of absence

Why do patients use CAM?

A question of quality

Making sense in the information age

Finding the evidence base

Integrating CAM into pain medicine

Part 9: Specific Clinical States

Chapter 27 Chronic low back pain

Introduction

Clinical evaluation

Trivial findings and the “pseudo-diagnosis”

Natural history

Progression to chronic low back pain

Treatment of chronic LBP with only common degenerative changes

Conclusions

Chapter 28 Fibromyalgia syndrome and myofascial pain syndromes

Introduction

Definition and classification

Prevalence

Course and prognosis

Diagnosis of fibromyalgia syndrome

Diagnosis of myofascial pain syndrome

Basic mechanisms

Impact of basic understanding on clinical management

Treatment of fibromyalgia syndrome

A stepwise treatment approach to fibromyalgia syndrome

Treatment of myofascial pain syndrome

Conclusions

Chapter 29 Clinical pain management in the rheumatic diseases

Introduction

Basic mechanisms in rheumatic pain

Clinical practice

Treatment

Obstacles to optimal pain management

Conclusions

Chapter 30 Headache

Introduction

Evaluation and diagnostic testing

Migraine

Chronic daily headache

Tension-type headache

Cluster headache and other trigeminal autonomic cephalgias

Trigeminal neuralgia

Conclusions

Chapter 31 Orofacial pain

Introduction

Orofacial nociceptive processes

Clinical aspects

Chapter 32 Visceral pain

Introduction

Basic mechanisms of visceral pain

Evidence-based treatment strategies

Management of common visceral pain syndromes

Conclusions

Chapter 33 Pelvic and urogenital pain

Introduction

Pain-specific treatment

Disease-specific treatment

Conclusions

Chapter 34 Neuropathic pain

Introduction

Basic mechanisms

Clinical picture

Clinical examination

Other diagnostic procedures

Management of neuropathic pain

Pharmacotherapy of neuropathic pain

Conclusions

Chapter 35 Complex regional pain syndrome

Introduction

Development of the validation process

CRPS and genetics

Sensory characteristics and pathophysiology of CRPS

Autonomic nervous system

Inflammatory characteristics

Behavioral–premorbid psychological aspects

Functional restoration

Pharmacologic and interventional therapies

Conclusions

Chapter 36 Cancer pain management

Introduction

Basic mechanisms

Assessment

Management

Adjuvant therapies

Continuity of care and multidisciplinary management

Part 10: Special Populations

Chapter 37 Pain in older persons: a brief clinical guide

Introduction

Age-related change in pain sensitivity and nociceptive processing

Clinical pain assessment of the cognitively intact older adult

Clinical approach to pain assessment in persons with dementia

Psychosocial interventions

Other non-pharmacological approaches to pain management

Pharmacological therapies

Acknowledgments

Chapter 38 Pain in children

Introduction

Significance of recurrent and chronic pain in children

Basic mechanisms

Clinical practice: evaluation and management

Evidence base for pharmacological treatments

Evidence base for psychological treatments

Evidence base for physical therapy interventions

Evidence base for complementary and alternative medicine therapies

Putting it all together: a treatment algorithm

Chapter 39 Pain in individuals with intellectual disabilities

Introduction and overview

Defining ID and conceptual issues

Scope of the problem of pain in individuals with ID

Pain assessment tools

Pain management

Conclusions

Acknowledgments

Chapter 40 Pain and addiction

Introduction

Prevalence, neurobiology and definitions

Neurobiology of addiction

Defining opioid addiction in a patient with pain

Screening and risk stratification

Universal Precautions in pain management

Strategies for treating the high risk patient

Chapter 41 Pain and psychiatric illness

Introduction

Conclusions

Index

This book is dedicated to our patients, their families and all people suffering with pain.

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Library of Congress Cataloging-in-Publication Data

Clinical pain management : a practical guide / edited by Mary E. Lynch, Kenneth D. Craig, Philip W.H. Peng.

p. ; cm.

Includes bibliographical references.

ISBN 978-1-4443-3069-4

 1. Pain. 2. Pain–Treatment. I. Lynch, Mary E. II. Craig, Kenneth D.,

1937- III. Peng, Philip W. H.

 [DNLM: 1. Pain–therapy. 2. Palliative Care–methods. WL 704 C6415 2011]

RB127.C593 2011

616'.0472–dc22

2010024524

ISBN: 978-1-4443-3069-4

A catalogue record for this book is available from the British Library.

This book is published in the following electronic formats: ePDF 9781444329728; Wiley Online Library 9781444329711; ePub 9781444329735

List of contributors

Lene Baad-Hansen Associate Professor, Department of Clinical Oral Physiology, Aarhus University, Aarhus, Denmark

Cathrine Baastrup MScPharm, Danish Pain Research Center, Aarhus University Hospital, Aarhus, Denmark

Misha Bakonja MD, Professor, Department of Neurology, University of Wisconsin, Madison, USA

Diaa Bahgat MD, Instructor, Department of Neurological Surgery, Oregon Health & Science University, Portland, USA

Allan I. Basbaum PhD FRS, Department of Anatomy, University of California at San Francisco, San Francisco, USA

Fabrizio Benedetti MD, Professor of Physiology and Neuroscience, Department of Neuroscience, University of Torino Medical School, Torino, Italy; National Institute of Neuroscience, Torino, Italy

Klaus Bielefeldt MD PhD, University of Pittsburgh Medical Center, Division of Gastroenterology, Pittsburgh, USA

Sharon Bishop BNurs MHlthSci, Clinical Nurse Specialist, Department of Neurosurgery, Regina General Hospital, Regina, Canada

Eduardo Bruera MD, Professor and Chair, Department of Palliative Care and Rehabilitation Medicine Unit 008, University of Texas M.D. Anderson Cancer Center, Houston, USA

Kim J. Burchiel MD FACS, Professor and Chair, Department of Neurological Surgery, Oregon Health and Science University, Portland, USA

Chantel C. Burkitt BA, Department of Educational Psychology, University of Minnesota, Minneapolis, USA

Eugene J. Carragee MD, Professor and Vice Chairman, Department of Orthopedic Surgery, Stanford University School of Medicine, Redwood City, USA

Daniel J. Cavanaugh PhD, Department of Anatomy, University of California at San Francisco, San Francisco, USA

Stéphanie Chevalier PhD, McGill Nutrition & Food Science Centre, McGill University Health Centre, Montreal, Canada

Alexander J. Clark MD FRCPC, Professor of Anesthesia, Dalhousie University, Halifax, Nova Scotia, Canada

Alexis Codrington PhD, Alan Edwards Pain Management Unit, McGill University Health Centre, Montreal, Canada

Beverly Collett FRCA FFPMRCA, Consultant in Pain Medicine, University Hospitals of Leicester, Leicester, UK

Kenneth D. Craig PhD, Professor Emeritus, Department of Psychology, University of British Columbia, Vancouver, Canada

Gilbert J. Fanciullo MD MS, Professor of Anesthesiology, Dartmouth Medical School, Lebanon, NH, USA; Director, Head of Pain Medicine, Department of Anesthesiology, Dartmouth-Hitchcock Medical Center, Lebanon, NH, USA

Perry G. Fine MD, Professor of Anesthesiology, Pain Research Center, School of Medicine, University of Utah, Salt Lake City, USA

Nanna Brix Finnerup MD PhD, Associate Professor, Danish Pain Research Center, Aarhus University Hospital, Aarhus, Denmark

Mary-Ann Fitzcharles MB ChB FRCP(C), Montreal General Hospital Pain Center, Montreal General Hospital, McGill University, Montreal, Canada; Division of Rheumatology, McGill University, Montreal, Canada

Gerald F. Gebhart PhD, Professor and Director, Center for Pain Research, Department of Anesthesiology, University of Pittsurgh, Pittsburgh, USA

Stephen Gibson PhD, Deputy Director, National Ageing Research Institute, Caulfield Pain Management Center, Royal Melbourne Hospital, Melbourne, Australia

Padma Gulur MD, Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, and Harvard Medical School, Boston, USA

Maija Haanpää MD PhD, Chief Neurologist, Rehabilitation Orton, Helsinki, Finland; and Pian Consultant, Department of Neurosurgery, Helsinki University Hospital, Helsinki, Finland

Heather D. Hadjistavropoulos PhD, Professor, Department of Psychology, University of Regina, Regina, Canada

Thomas Hadjistavropoulos PhD ABPP, Professor, Department of Psychology and Center on Aging and Health, University of Regina, Regina, Canada

Winfried Häuser MD, Associate Professor, Department Internal Medicine I and Interdisciplinary Center of Pain Medicine, Klinikum Saarbrücken, Germany

Peter Henningsen MD, Professor, Department of Psychosomatic Medicine and Psychotherapy, Technische Universität München, München, Germany

Fred M. Howard MD MPH, Professor of Obstetrics & Gynecology, University of Rochester School of Medicine, Rochester, USA

David Hui MD MSc FRCPC, Palliative Oncology Fellow, Department of Palliative Care & Rehabilitation Medicine Unit 1414, University of Texas M.D. Anderson Cancer Center, Houston, USA

Gordon Irving MB BS FFA(SA) MSc MMed, Clinical Assistant Professor, University of Washington Medical School, Seattle, USA

Robert N. Jamison PhD, Associate Professor, Departments of Anesthesia and Psychiatry, Brigham and Women’s Hospital, Harvard Medical School, Chestnut Hill, USA

Troels Staehelin Jensen MD PhD, Professor, Danish Pain Research Center, Aarhus University Hospital, Aarhus, Denmark; Department of Neurology, Aarhus University Hospital, Aarhus, Denmark

Roman D. Jovey MD, Medical Director, CPM Centers for Pain Management; Physician Director, Addictions and Concurrent Disorders Center, Credit Valley Hospital, Mississauga, Canada

Joel Katz PhD, Department of Psychology, York University, Toronto, Canada; Department of Anesthesia and Pain Management, Toronto General Hospital, Toronto, Canada; Department of Anesthesia, University of Toronto, Toronto, Canada

Jeffrey L. Koh MD, Professor, Anesthesiology and Perioperative Medicine, Oregon Health & Science University, Portland, USA

Krishna Kumar MB MS FRCS(C) FACS, Clinical Professor of Neurosurgery, University of Saskatchewan; Medical Office Wing, Regina General Hospital, Regina, Canada

Sandra M. LeFort Professor, School of Nursing, Memorial University of Newfoundland, St. John’s, Canada

Mary Lynch MD FRCPC, President Elect Canadian Pain Society; Professor Anesthesia, Psychiatry and Pharmacology, Dalhousie University, Haifax, Nova Scotia, Canada; Director, Pain Management Unit, Queen Elizabeth II Health Sciences Center, Halifax, Nova Scotia, Canada

Anjali Martinez MD, Assistant Professor, Obstetrics and Gynecology, George Washington University, Washington DC, USA

Michael McGillion RN PhD, Assistant Professor, Lawrence S. Bloomberg Faculty of Nursing, University of Toronto, Toronto, Canada

Patrick J. McGrath OC PhD FRSC FCAHS, Vice President Research, IWK Health Center; Professor of Psychology, Pediatrics and Psychiatry, Canada Research Chair, Dalhousie University, Halifax, Nova Scotia, Canada

Ronald Melzack Professor Emeritus, Department of Psychology, McGill University, Montreal, Canada

Harold Merskey DM FRCPC, Professor Emeritus of Psychiatry, University of Western Ontario, London, Canada

Tim F. Oberlander MD FRCPC, Professor, Pediatrics, University of British Columbia, Vancouver, Canada; R. Howard Webster Professor in Early Child Development, University of British Columbia, Vancouver, Canada; Complex Pain Service, BC Children’s Hospital, Vancouver, Canada

M. Gabrielle Pagé Department of Psychology, York University, Toronto, Canada

Tonya M. Palermo PhD, Associate Professor, Anesthesiology, Pediatrics and Psychiatry, Seattle Children’s Hospital, University of Washington School of Medicine, Seattle, USA

Don Young Park MD, Clinical Instructor, Department of Orthopedic Surgery, Stanford University School of Medicine, Redwood City, USA

Philip W.H. Peng MBBS FRCPC, Director, Anesthesia Chronic Pain Program, University Health Network and Mount Sinai Hospital, Toronto, Canada; Associate Professor, University of Toronto, Toronto Western Hospital, Toronto, Canada

Antonella Pollo MD, Assistant Professor, Department of Neuroscience, University of Torino Faculty of Pharmacy, Torino, Italy; National Institute of Neuroscience, Torino, Italy

James P. Rathmell MD, Chief, Division of Pain Medicine, Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Boston, USA; Associate Professor, Department of Anesthesia, Harvard Medical School, Boston, USA

Jana Sawynok PhD, Professor, Department of Pharmacology, Dalhousie University, Halifax, Nova Scotia, Canada

Marcus Schiltenwolf MD, Professor, Universität Heidelberg, Stiftung Orthopädische Universitätsklinik, Heidelberg, Germany

Barry J. Sessle Professor and Canada Research Chair, Faculties of Dentistry and Medicine, University of Toronto, Toronto, Canada

Yoram Shir MD, Director Alan Edwards Pain Management Unit, McGill University Health Centre, Montreal, Canada

Christine Short MD FRCPC, Assistant Professor, Dalhousie University, Halifax, Nova Scotia, Canada; Department of Medicine, Division of Physical Medicine and Rehabilitation, Halifax, Nova Scotia, Canada; Department of Surgery, Division of Neurosurgery, Queen Elizabeth II Health Science Center, Halifax, Nova Scotia, Canada

Stephen D. Silberstein MD, Professor of Neurology, Jefferson Medical College, Thomas Jefferson University, Philadelphia, USA

Maureen J. Simmonds PhD PT, Professor and Director, School of Physical and Occupational Therapy, Associate Dean, (Rehabilitation), Faculty of Medicine, McGill University, Montreal, Canada

Blair H. Smith MD MEd FRCGP FRCP Edin, Professor of Primary Care Medicine, University of Aberdeen, Scotland, UK

Dawn A. Sparks DO, Assistant Professor of Anesthesiology, Pain and Pediatrics, Dartmouth Medical School, Hanover, NH; Pain Clinic, Dartmouth-Hitchcock Medical Center, and Pediatric Pain Specialist, Children’s Hospital at Dartmouth (CHad), Lebanon, NH, USA

Boris Specktor MD, Center for Pain Medicine, Massachusetts General Hospital, Boston, USA; Assistant Professor, Department of Anesthesiology, Emory University School of Medicine, Atlanta, USA

Pam Squire MD CCFP CPE, Assistant Clinical Professor, University of British Columbia, Vancouver, Canada

Michael Stanton-Hicks MBBS DrMed FRCA ABPM FIPP, Pain Management Department, Center for Neurological Restoration, Cleveland, USA; Consulting Staff, Children’s Hospital CCF Shaker Campus, Pediatric Pain Rehabilitation Program, Cleveland Clinic, Cleveland, USA; Chair, Department of Palliative Care & Rehabilitation Medicine, University of Texas, Houston, USA

Jennifer N. Stinson RN-EC PhD CPNP, Scientist, Child Health Evaluative Sciences, and Department of Anesthesia and Pain Medicine, The Hospital for Sick Children, Toronto, Canada; Assistant Professor, Lawrence S. Bloomberg Faculty of Nursing, University of Toronto, Toronto, Canada

Michael J.L. Sullivan PhD, Professor, Department of Psychology, McGill University, Montreal, Canada

Peter Svensson Professor and Chairman, Department of Clinical Oral Physiology, Aarhus University, Aarhus, Denmark; Department of Maxillofacial Surgery, Aarhus University Hospital, Aarhus, Denmark

Frank J. Symons PhD, Associate Professor, Department of Educational Psychology, Center for Neurobehavioral Development, University of Minnesota, Minneapolis, USA

Brian R. Theodore PhD, Department of Anesthesiology & Pain Medicine, University of Washington, Seattle, USA

Rolf-Detlef Treede MD, Medical Faculty Mannheim, University of Heidelberg, Mannheim, Germany

Dennis C. Turk PhD, Department of Anesthesiology & Pain Medicine, University of Washington, Seattle, USA

Judith Versloot PhD, Faculty of Dentistry, Toronto, Canada

Ashwin Viswanthan MD, Instructor, Department of Neurological Surgery, Oregon Health & Science University, Portland, USA

David Walk MD, Associate Professor, Department of Neurology, University of Minnesota, Minneapolis, USA

Mark A. Ware MBBS MRCP(UK) MSc, Assistant Professor, Departments of Anesthesia, Family Medicine, Pharmacology and Therapeutics, McGill University, Montreal, Canada

C. Peter N. Watson MD FRCP(C), Department of Medicine, University of Toronto, Toronto, Canada

Karen Webber MN RN, Associate Professor, School of Nursing, Memorial University of Newfoundland, St. John’s, Canada

Timothy H. Wideman PT, Department of Psychology, McGill University, Montreal, Canada

Amanda C. de C. Williams Reader in Clinical Health Psychology, University College London, London, UK

Lonnie K. Zeltzer MD, Director of Pediatric Pain Program, Mattel Children’s Hospital at UCLA, Los Angeles, USA; Professor of Pediatric Anesthesiology, Psychiatry and Biobehavioral Sciences, David Geffen School of Medicine, UCLA, Los Angeles, USA

Foreword

This excellent guide to clinical pain management covers every important facet of the field of pain. It describes recent advances in diagnosing and managing clinical pain states and presents procedures and strategies to combat a wide range of chronic pains. Unfortunately, many people suffer various forms of pain even though we have the knowledge to help them, but our educational systems have failed. This book is a valuable contribution to the field of pain by providing up-to-date knowledge that will stimulate a new generation of health professionals who are dedicated to abolishing pain.

Despite the impressive advances and optimistic outlook, many chronic pains remain intractable. Some people who suffer chronic headaches, backaches, fibromyalgia, pelvic pain and other forms of chronic pain are helped by several therapies that are now available, but most are not. For example, we have excellent new drugs for some kinds of neuropathic pains, but not for all. The continued suffering by millions of people indicates we still have a long way to go.

The field of pain has recently undergone a major revolution. Historically, pain has been simply a sensation produced by injury or disease. We now possess a much broader concept of pain that includes the emotional, cognitive and sensory dimensions of pain experience, as well as an impressive array of new approaches to pain management. Chronic pain is now a major challenge to medicine, psychology, and all the other health sciences and professions. Every aspect of life, from birth to dying, has characteristic pain problems. Genetics, until recently, was rarely considered relevant to understanding pain, yet sophisticated laboratory studies and clinical observations have established genetic predispositions related to pain as an essential component of the field. The study of pain therefore now incorporates research in epidemiology and medical genetics.

Clinical Pain Management: A Practical Guide highlights a mission for all of us: to provide relief of all pain, pain in children and the elderly, and for any kind of severe pain that can be helped by sensible administration of drugs and other pain therapies. We must also teach patients to communicate about their pain, and inform them that they have a right to freedom from pain. If we can pursue these goals together – as members of the full range of scientific and health professions – we can hope to meet the goal we all strive for: to help our fellow human beings who suffer pain.

Ronald Melzack

McGill University

Montreal, Quebec, Canada

2010

The editors would like to thank Ms. Sara Whynot for considerable assistance with every phase of the manuscript.

Part 1: Basic Understanding of Pain Medicine

Chapter 1

The challenge of pain: a multidimensional phenomenon

Mary Lynch1, Kenneth D. Craig2 & Philip W.H. Peng3

1 Dalhousie University, Pain Management Unit, Queen Elizabeth II Health Sciences Centre, Halifax, Nova Scotia

2 Department of Psychology, University of British Columbia, Vancouver, Canada

3 Department of Anesthesia, Wasser Pain Management Center, Mount Sinai Hospital, University of Toronto, Ontario, Canada

Pain is one of the most challenging problems in medicine and biology. It is a challenge to the sufferer who must often learn to live with pain for which no therapy has been found. It is a challenge to the physician or other health professional who seeks every possible means to help the suffering patient. It is a challenge to the scientist who tries to understand the biological mechanisms that can cause such terrible suffering. It is also a challenge to society, which must find the medical, scientific and financial resources to relieve or prevent pain and suffering as much as possible.

(Melzack & Wall The Challenge of Pain, 1982)

Introduction

The International Association for the Study of Pain (IASP) taxonomy defines pain as “an unpleasant sensory and emotional experience associated with actual or potential tissue damage or described in terms of such damage” [1]. Pain is divided into two broad categories: acute pain, which is associated with ongoing tissue damage, and chronic pain, which is generally taken to be pain that has persisted for longer periods of time. Many injuries and diseases are capable of instigating acute pain with sources including mechanical tissue damage, inflammation and tissue ischemia. Similarly, chronic pain can be associated with other chronic diseases, terminal illness, or may persist after illness or injury. The point at which chronic pain can be diagnosed may vary with the injury or condition that initiated it; however, for most conditions, pain persisting beyond 3 months is reasonably described as a chronic pain condition. In some cases one can identify a persistent pain condition much earlier, for example, in the case of post-herpetic neuralgia subsequent to an attack of shingles, if pain persists beyond rash healing it indicates a persistent or chronic pain condition is present.

Exponential growth in pain research in the past four decades has increased our understanding regarding underlying mechanisms of the causes of chronic pain, now understood to involve a neural response to tissue injury. In other words, peripheral and central events related to disease or injury can trigger long-lasting changes in peripheral nerves, spinal cord and brain such that the system becomes sensitized and capable of spontaneous activity or of responding to non-noxious stimuli as if painful. By such means, pain can persist beyond the point where normal healing takes place and is often associated with abnormal sensory findings. In consequence, the scientific advances are providing a biological basis for understanding the experience and disabling impact of persistent pain. Table 1.1 presents definitions of pain terms relevant to chronic pain.

Table 1.1 Definitions of pain terms.

Source: Based on Merskey H, Bogduk N, eds. (1994) Classification of Chronic Pain, Descriptions of Chronic Pain Syndromes and Definitions of Pain Terms, 2nd edn. Task Force on Taxonomy, IASP Press, Seattle.

AllodyniaPain due to a stimulus that does not normally provoke painAnesthesia dolorosaPain in a region that is anesthetic dolorosaDysesthesiaAn unpleasant abnormal sensation, whether spontaneous or evokedHyperalgesiaAn increased response to a stimulus that is normally painfulHyperpathiaA painful syndrome characterized by an abnormally painful reaction to a stimulus, especially a repetitive stimulus as well as an increased thresholdNeuropathicPain initiated or caused by a primary pain lesion or dysfunction in the nervous systemNociceptorA receptor preferentially sensitive to a noxious stimulus or to a stimulus that would become noxious if prolongedPainAn unpleasant sensory and emotional experience associated with actual or potential tissue damage or described in terms of such damageParesthesiaAn abnormal sensation, whether spontaneous or evoked (use dysesthesia when the abnormal sensation is unpleasant)

Traditionally, clinicians have conceptualized chronic pain as a symptom of disease or injury. Treatment was focused on addressing the underlying cause with the expectation that the pain would then resolve. It was thought that the pain itself could not kill. We now know that the opposite is true. Pain persists beyond injury and there is mounting evidence that “pain can kill.” In addition to contributing to ongoing suffering, disability and diminished life quality, it has been demonstrated that uncontrolled pain compromises immune function, promotes tumor growth and can compromise healing with an increase in morbidity and mortality following surgery [2,3], as well as a decrease in the quality of recovery [4]. Clinical studies suggest that prolonged untreated pain suffered early in life may have long-lasting effects on the individual patterns of stress hormone responses. These effects may extend to persistent changes in nociceptive processing with implications for pain experienced later in life [5]. Chronic pain is associated with the poorest health-related quality of life when compared with other chronic diseases such as emphysema, heart failure or depression and has been found to double the risk of death by suicide compared to controls [6]. Often chronic pain causes more suffering and disability than the injury or illness that caused it in the first place [7]. The condition has major implications not only for those directly suffering, but also family and loved ones become enmeshed in the suffering person’s challenges, the work place suffers through loss of productive employees, the community is deprived of active citizens and the economic costs of caring for those suffering from chronic pain are dramatic.

Chronic pain is an escalating public health problem which remains neglected. Alarming figures demonstrate that more than 50% of patients still suffer severe intolerable pain after surgery and trauma [8]. Inadequately treated acute pain puts people at higher risk of developing chronic pain. For example, intensity of acute postoperative pain correlates with the development of persistent postoperative pain, which is now known to be a major and under-recognized health problem. The prevalence of chronic pain subsequent to surgery has been found in 10–50% of patients following many commonly performed surgical procedures and in 2–10% this pain can be severe [9].

The epidemiology of chronic pain has been examined in high-quality surveys of general populations from several countries which have demonstrated that the prevalence of chronic pain is at least 18–20% [10–12]. These rates will increase with the aging of the population. In addition to the human suffering inflicted by pain there is also a large economic toll. Pain accounts for over 20% of doctor visits and 10% of drug sales and costs developed countries $1 trillion each year [13].

Chronic pain has many characteristics of a disease epidemic that is silent yet growing; hence addressing it is imperative. It must be recognized as a multidimensional phenomenon involving biopsychosocial aspects. Daniel Carr, in a recent IASP Clinical Updates, expressed it most succinctly: “The remarkable restorative capacity of the body after common injury … is turned upside down (and) hyperalgesia, disuse atrophy, contractures, immobility, fear-avoidance, helplessness, depression, anxiety, catastrophizing, social isolation, and stigmatization are the norm” [14].

Such is the experience and challenge of chronic pain and it is up to current and future generations of clinicians to relieve or prevent pain and suffering as much as possible. The challenges must be confronted at biological, psychological and social levels. Not only is a better understanding needed, but reforms of caregiving systems that address medical, psychological and health service delivery must be undertaken.

References

1 Merskey H, Bogduk N. (1994) Classification of Chronic Pain. IASP Press, Seattle.

2 Liebeskind JC. (1991) Pain can kill. Pain 44:3–4.

3 Page GG. (2005) Acute pain and immune impairment. IASP Pain Clinical Updates XIII (March 2005):1–4.

4 Wu CL, Rowlingson AJ, Partin AW et al. (2005) Correlation of postoperative pain to quality of recovery in the immediate postoperative period. Reg Anesth Pain Med 30:516–22.

5 Finley GA, Franck LS, Grunau RE et al. (2005) Why children’s pain matters. IASP Pain Clinical Updates XIII(4):1–6.

6 Tang N, Crane C. (2006) Suicidality in chronic pain: review of the prevalence, risk factors and psychological links. Psychol Med 36:575–86.

7 Melzack R, Wall PD. (1988) The Challenge of Pain. Penguin Books, London.

8 Bond M, Breivik H, Niv D. (2004) Global day against pain, new declaration. http://www. painreliefhumanright.com

9 Kehlet H, Jensen TS, Woolf CJ. (2006) Persistent postsurgical pain: risk factors and prevention. Lancet 367:1618–25.

10 Lynch ME, Schopflocher D, Taenzer P et al. (2009) Research funding for pain in Canada. Pain Res Manag 14(2):113–15.

11 Blyth FM, March LM, Brnabic AJ et al. (2001) Chronic pain in Australia: a prevalence study. Pain 89(2–3):127–34.

12 Eriksen J, Jensen MK, Sjogren P et al. (2003) Epidemiology of chronic non-malignant pain in Denmark. Pain 106(3):221–8.

13 Max MB, Stewart WF. (2008) The molecular epidemiology of pain: a new discipline for drug discovery. Nat Rev Drug Discov 7:647–58.

14 Carr DB. (2009) What does pain hurt? IASP Pain Clinical Updates XVII(3):1–6.

Chapter 2

Epidemiology and economics of chronic and recurrent pain

Dennis C. Turk & Brian R. Theodore

Department of Anesthesiology & Pain Medicine, University of Washington, Seattle, USA

Introduction

Pain is among the most common symptoms leading patients to consult a physician in the USA [1]. Data from the National Health Interview Survey [2] indicates that during the 3 months prior to the inventory 15% of adults had experienced a migraine or severe headache, 15% had experienced pain in the neck area, 27% in the lower back and 4% in the jaw. Extrapolating to the adult US population these percentages would translate to 31,066,000 for migraine, 28,401,000 head neck pain, 52,325,000 for low back pain and 9,535,000 for jaw pain. The National Center for Health Statistics estimates that about 25% of the US population has chronic or recurrent pain, and 40% state that the pain has a moderate or severe degrading impact on their lives [3].

Chronic and recurrent pain has not only significant health consequences, but also personal, economic and societal implications. It impacts on quality of life, productivity, healthcare utilization and has both direct and indirect costs. This chapter provides a summary of the prevalence of some of the most common chronic and recurrent pain disorders and describes their economic impact.

Epidemiology of Chronic and Recurrent Pain

In a review of 15 epidemiological studies from industrialized nations, Verhaak et al. [4] noted that the point prevalence for chronic non-cancer pain (CNCP) in an adult population ranges 2–40%, with a median of 15%. Similar rates were reported from studies documenting the prevalence of CNCP in epidemiological studies conducted in lower income nations, with a point prevalence of approximately 18% [5]. The adolescent population also reports a prevalence ranging 1–15% [6]. As noted in these reviews, the wide range in the prevalence rate of CNCP is influenced by various factors, including the population sampled (e.g. community vs. primary care), the definition of CNCP by duration (e.g. >1 month, >3 months, >6 months), the type of methodology used in the epidemiological study (e.g. mail-in survey, telephone survey, physical exam), the phrasing of questions included, the focus on the various parts of the body being surveyed and response rates.

Musculoskeletal Pain

Among musculoskeletal locations, the most commonly afflicted region is the lower back. Epidemiological surveys in the USA report a prevalence rate of 25% for low back pain any time during a 3-month period [3], 19% prevalence rate for chronic low back pain during a 12-month period [7] and a lifetime prevalence rate of 29.5% [7]. Similar findings have been reported in other industrialized nations, with prevalence rates for chronic low back pain ranging 13–28% [6]. Over 13 million Americans are permanently disabled by back pain [8]. Low back pain is also the most common of chronic pain conditions reported by adolescents, with prevalence rates ranging 8–44% [6]. Recent reports based on data contained in a large national survey estimated that 46.4 million Americans (21% of the population) had self-reported doctor-diagnosed arthritis [9] and 30.1 million have had neck pain in the past 3 months [10]. The US Centers for Disease Control and Prevention noted that arthritis and other chronic rheumatic conditions (excluding low back) are projected to affect approximately 13% of the US population by year 2010, with an increase to 20% by the year 2030 [11].

Chronic Widespread Pain

In addition to site-specific chronic pain conditions, there are also consistent prevalence rates reported for chronic widespread pain (CWP), ranging 10–14%, in both adults and adolescents [6]. In conjunction with having a diagnosis of CWP, the development of the American College of Rheumatology (ACR) criteria for fibromyalgia syndrome also saw an increase in cases observed in clinical settings [6]. Prevalence rates of fibromyalgia syndrome reported in other industrialized nations range 0.7–4% [6].

Headache

According to the National Headache Foundation more than 45 million Americans experience chronic headaches [12]. Migraine alone affects 18% of women and 6% of men in the USA and has an estimated worldwide prevalence of approximately 10% [13].

Factors Associated with Chronic and Recurrent Pain

Overview of the Biopsychosocial Model

Recurrent and CNCP are not medical conditions that can be solely pinpointed to specific tissue pathology. For the vast majority of patients with back pain, headache and fibromyalgia no objective pathology is detectable. The biopsychosocial model of pain elaborates on the complex interplay of physical, psychological, social and environmental factors that exacerbate and perpetuate the pain condition [14]. For painful conditions that persist beyond the usual period of healing, the development of a pain–stress cycle may result in anger and distress at the situation. A prolonged state of the pain–stress cycle often results in the development of comorbid psychopathology. Individuals with chronic pain are at risk for adopting the sick-role and engaging in maladaptive behaviors that perpetuate the pain–stress cycle, resulting in both physical and psychological deconditioning.

Demographic Factors

The most commonly identified demographic factors that have significant associations with CNCP are age, sex and socioeconomic status [6]. Older age is significantly associated with increased prevalence of CNCP. This increasing trend for prevalence with age was noted among patients with shoulder pain, low back pain, arthritis and other joint disorders, and CWP. Several factors [6] may account for the observed increase in prevalence among older adults, including degenerative processes and recurrent episodes of pain.

There are also pronounced differences in the prevalence rate of various CNCP disorders between males and females. Marked increases in prevalence rates have been observed among females for CNCP disorders such as shoulder pain, low back pain, arthritis, CWP pain, as well as migraine. This sex difference persists even when other factors such as age are accounted for. Several hypotheses may explain these sex differences, and include a difference between the sexes in hormones, body focus, evaluation and appraisal of symptoms, increased sensitivity or lower thresholds among females, differences in symptom reporting and healthcare-seeking behaviors, and differential exposure to risk factors (e.g. childbearing) [6].

Increased prevalence of CNCP has also been observed among individuals with lower socioeconomic status, which includes dimensions such as household income, employment status, occupational class and level of education. Specifically, the strongest associations with CNCP were observed for lower level of education, lower household income and unemployment [6]. However, socioeconomic status may not be a direct risk factor for CNCP, but significantly associated with underlying psychosocial factors consequent to the onset of pain [6].

Psychopathology As a Predisposing Factor

There is some evidence that underlying psychological factors may predispose an individual to develop CNCP, specifically emotional distress. These psychological predispositions may shape the response of an individual during the onset of a pain. A comprehensive review of the link between chronic pain and psychological comorbidity revealed a bidirectional relationship between pain and psychopathology. For example, in a community-based sample in the UK, asymptomatic individuals with higher elevations on anxiety and depressive measures were 2.4 times more likely to develop subsequent low back pain. Similar findings were noted in the First National Health and Nutrition Examination [15], where patients who had depression but not pain were 2.1 times more likely to develop CNCP when assessed again 8 years later. Psychological factors have been shown to be better predictors of back pain and related disability than physical pathology [16,17]. Furthermore, a study on the relationship between migraine and psychological disorders, based on a prospective cohort followed for 1 year, indicated a substantial link between major depression and later onset of migraines [18].

However, the relationship between CNCP and psychopathology is reciprocal; initial pain also predicted later onset of major psychological disorders with approximately the same magnitude. Such comorbid psychopathology may pose as barriers to recovery, negatively impacting on the prognosis of the painful condition, and thus contributing to the overall prevalence rate of CNCP observed during population surveys.

Occupational Factors

Several population-based prospective studies have confirmed occupational-related stressors as a risk factor for CNCP. These factors included high job demands, low requirement for learning new skills and repetitive work. Furthermore, they were associated with later onset of persistent pain, independent of occupational class, shift work, working hours and job satisfaction levels. The association between these stressors and onset of pain was more pronounced among individuals with relatively lower levels of education. In addition, a study conducted by the World Health Organization included a cohort from 14 nations with a 12-month follow-up [19]. The strongest predictor for development of chronic pain was occupational role disability at baseline, due to an injury. Risk of CNCP was 3.6 times greater among those with occupational role disability, and it was a stronger predictor than the presence of initial anxiety or major depressive disorders.

Role of Disability Compensation

The complex and often adversarial nature of the medicolegal system associated with disability compensation may result in contributing barriers to recovery. In examining this area one will often read of “secondary gain”. Secondary gain refers to the notion that a contributing factor to disability may be a patient’s wish to avoid work. There has been significant controversy in this area, and unfortunately several studies that have received widespread attention in the media were later found to have problems methodologically. Thus one must be very cautious in reading and interpreting studies in this area.

More recently it has been found that the prevalence rate of fibromyalgia syndrome has been reported to be equivalent in a non-litigious popu­lation with no disability compensation, relative to populations that had a disability compensation system in place and associated litigation [20]. Therefore, it is possible that the increased incidences of “secondary gain” related to litigation observed in some studies were mediated by the stress of being involved in potentially protracted legal battles. Furthermore, as reviewed in an earlier section on the prevalence rate of CNCP, similarities in the range of prevalence rates have been observed across nations with differing systems of disability compensation and healthcare structures. As noted in a review of “secondary gain” concepts in the literature, there is inconsistent evidence for the isolation of the effect of disability compensation and litigation as a secondary factor that perpetuates the chronic pain condition [21]. At present it is reasonable to conclude that medicolegal and compensation-related conflict and activities may cause additional stress that must be addressed in the overall management plan for each patient.

Economic Impact of Chronic Pain

The economic impact of healthcare in general has been serious enough to have spurred debates about healthcare reforms aimed at managing costs. In addition, there have been calls for legislative reforms to contain the costs of healthcare and to make these costs manageable for all stakeholders. The effect of CNCP is certainly one of the drivers of healthcare costs. For example, in a review of costs documented by a US State Workers’ Compensation system, a small minority of patients with chronic low back pain (7%) were responsible for approximately 75% of the annual costs incurred [22]. According to the National Headache Foundation [12], chronic headaches account for losses of $50 billion a year to absenteeism and medical expenses and an excess of $4 billion spent on over-the-counter medications alone.

In considering the economic impact of CNCP, we differentiate direct costs incurred through healthcare utilization, and indirect costs that are the financial consequences of the often debilitating nature of CNCP and recurrent pain. Finally, current estimates are provided for the total costs of illness associated with CNCP disorders.

Direct Costs

CNCP is associated with a high utilization rate of healthcare services. In the USA, approximately 17% of patients in primary care settings report persistent pain [23]. This subset of patients is also among the highest utilizers of healthcare services. For example, the presence of CNCP was shown to be associated with a twofold increase in the number of primary care visits and hospitalizations, and also a fivefold increase in the number of visits to emergency rooms. In a review of cost data obtained from a large US Workers’ Compensation database, the overall direct costs associated with healthcare utilization increased exponentially as a function of disability duration [24]. Specifically, the cost-per-claim for patients disabled for more than 18 months due to musculoskeletal injuries was $67,612. In contrast, patients disabled for 4–8 months and 11–18 months in duration incurred total medical costs-per-claim of $21,356 and $33,750, respectively. Among the biggest cost drivers for the direct costs associated with healthcare utilization are the costs associated with pharmaceuticals and surgeries.

The cost of pharmaceuticals for pain management amounts to $13.8 billion annually for prescription analgesics and an additional $2.6 billion for non-prescription analgesics [25,26], and these costs are increasing annually. Opioids are the most common class of medication prescribed by physicians in the USA [25,26]. The annual cost estimate for just one type of opioid alone (Oxycontin) is approximately $6,903 per patient [27]. Overall pharmaceutical costs per claim in a Workers’ Compensation setting reveal exponential increases as a function of disability duration due to CNCP. The cost-per-claim for patients disabled for more than 18 months due to musculoskeletal injuries is $11,818. In contrast, patients disabled for 4–8 months and 11–18 months in duration incurred pharmaceutical costs-per-claim of $2,270 and $4,284, respectively [24].

Similar variations in costs are noted for surgical procedures often used to treat CNCP. The most current estimates of surgical costs are available from the US Centers for Medicare and Medicaid Services (CMS) (Table 2.1). These surgical costs range $5,708–23,555 per surgery, with lumbar fusions being the costliest of these surgical procedures for common musculoskeletal disorders. The costs reported by CMS are a conservative estimate, and may not necessarily reflect the true costs billed which vary by geographic region. Taking lumbar fusion as an example, the most recent estimate for the annual frequency of lumbar fusion surgery for degenerative conditions is 122,316 cases during year 2001 [28]. Therefore, costs of lumbar fusions alone amount to approximately $2.9 billion annually. Pharmaceutical and surgical costs, while substantial, are only two aspects of the variety of costs incurred by CNCP patients. Other direct costs that substantially add to the total cost of illness over the lifetime of CNCP include costs associated with physician visits, diagnostic and imaging, injection therapeutics, hospital admissions, physical therapy, complementary and alternative medicine (e.g. chiropractic, acupuncture), psychological services, comprehensive pain management programs and medical and case management services. In addition to these direct costs associated with healthcare utilization, there are substantial indirect costs incurred from the resulting disability due to CNCP.

Table 2.1 Estimated costs of specific musculoskeletal surgeries based on reimbursement schedule of the Center of Medicare and Medicaid Services (CMS). The costs reported by CMS are a conservative estimate, and may not necessarily reflect the true costs billed which vary by geographic region.

Source: CMS Health Care Consumer Initiatives (http://www.cms.hhs.gov/HealthCareConInit/ 02_Hospital.asp).

Type of surgeryCost per surgeryMajor arm and shoulder surgeries – with complications or pre-existing conditions$7,182Two or more hip, knee or ankle surgeries$19,418Replacement of hip, knee, or ankle or reattachment of thigh, foot or ankle$11,916Repair of previous hip or knee replacement$15,552Lumbar fusion – with complications or pre-existing conditions$23,555Lumbar fusion$18,094Cervical fusion – with complications or pre-existing conditions$16,706Cervical fusion$10,853Spine surgeries (excl. fusion) – with complications or pre-existing conditions$8,786Spine surgeries (excl. fusion)$5,708

Indirect Costs

Indirect costs incurred due to CNCP include disability compensation, lost productivity, legal fees associated with litigation for injuries, lost tax revenue, reduction in quality of life and any additional healthcare costs associated with comorbid medical and psychological disorders consequent to CNCP. Projected annual estimates for some of these indirect costs due to back pain alone, range $18.9–71 billion in disability compensation, $6.9 billion in lost productivity due to disability and $7 billion in legal fees [27]. Back pain cases have been estimated to result in approximately 149 million lost work days at an estimated cost of $14 billion [29]. The estimated annual lost productive work time cost from arthritis in the US workforce was $7.11 billion, with 65.7% of the cost attributed to the 38% of workers with pain exacerbations [30]. Lost productive time from common pain conditions among workers cost an estimated $61.2 billion per year. The majority (76.6%) of the lost productive time was explained by reduced performance while at work, and not work absence [31]. The total cost of lost productive time in the US workforce due to arthritis, back pain and other musculoskeletal pain from August 2001 to July 2002 was estimated at approximately $40 billion, including $10 billion for absenteeism and $30 billion for employees who were at work but impaired by pain (“presenteeism”) [31].

On a per-patient basis, using estimates from a Workers’ Compensation setting for chronic musculoskeletal disorders (≥ 4 months’ duration), the average cost of disability compensation ranges $7,328–36,790 [24]. Similarly, the estimated productivity losses, based on pre-injury earnings, ranges $12,547–73,075 [24]. Both estimates have a range that depends on the duration of disability, from 4–8 months at the lower limit to > 18 months for the upper limit.

Total Cost of Illness

Estimates for the total cost (both direct and indirect) of chronic pain exceed $150 billion annually [32]. On a per-patient basis, as estimated using costs available from the Workers’ Compensation setting, total cost of illness per patient ranges $70,486–208,030 depending on duration of disability [24]. Table 2.2 summarizes the total cost of illness due to CNCP, while delineating the associated major direct and indirect costs.

Table 2.2 Estimated total cost of illness due to chronic non-cancer pain.

Type of costPer-patient cost estimate*Annual cost estimateTotal cost of illness$70,486–208,030$150 billion Direct costs$21,356–67,612n.a. Pharmaceuticals$2,270–11,818$16.4 billion Surgeries$5,708–23,555†$2.9 billion‡ Indirect costs   Disability compensation$7,328–36,790$18.9–71 billion Productivity losses$12,547–73,075$6.9 billion

n.a. – No data available.

* Based on a US Workers’ Compensation population.

† Costs per surgery based on US Centers for Medicare and Medicaid Services (CMS) estimates for musculoskeletal surgeries.

‡ Estimated cost of lumbar fusions only.

Conclusions

The estimated population prevalence of CNCP varies from 2% to 40%. This wide range is a result of several factors (e.g. the population sampled, definition of CNCP by duration, body parts targeted, sampling methodology, phrasing of survey items and the survey response rate). Overall, the perpetuation of chronic painful disorders may exceed a total annual cost of $150 billion, which includes direct costs associated with healthcare utilization as well as indirect costs associated with disability compensation losses in productivity, lost tax revenue and out of pocket expenses. Therefore, CNCP and recurrent pain have a significant impact on society, resulting in poorer quality of life for those afflicted, imposing substantially on the costs of healthcare, and exacting societal costs in terms of disability compensation and productivity losses. However, these figures do not reflect the incalculable suffering experienced by patients and their significant others.

References

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3 National Center for Health Statistics. (2006) Health, United States, 2006 with Chartbook on Trends in the Health of Americans. National Center for Health Statistics, Hyattsville, MD.

4 Verhaak PF, Kerssens JJ, Dekker J et al. (1998) Prevalence of chronic benign pain disorder among adults: a review of the literature. Pain 77(3):231–9.

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10 Lawrence RC, Felson DT, Helmick CG et al. (2008) Estimates of the prevalence of arthri­tis and other rheumatic conditions in the United States. Part II. Arthritis Rheum 58(1): 26–35.

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12 National Headache Foundation. (2005) National Headache Foundation: Fact Sheet.

13 Sheffield RE. (1998) Migraine prevalence: a literature review. Headache 38(8):595–601.

14 Turk DC, Monarch ES. (2002) Biopsychosocial perspective on chronic pain. In: Turk DC, Gatchel RJ, eds. Psychological Approaches to Pain Management: A Practitioner’s Handbook, 2nd edn. Guilford, New York. pp. 3–29.

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Chapter 3

Basic mechanisms and pathophysiology

Daniel J. Cavanaugh & Allan I. Basbaum

Department of Anatomy, University of California at San Francisco

Introduction

The ability to experience pain is essential for survival and wellbeing. The pathological consequences of the inability to experience pain are particularly well-illustrated by the extensive injuries experienced by children with congenital indifference to pain [1–3]. The pain system, including afferent fibers (nociceptors) that respond to injury, and the circuits engaged by these afferents, not only generates reflex withdrawal to injury, but also provides a protective function following tissue or nerve injury. In these situations, neurons in the pain pathway become sensitized such that normally innocuous stimuli are perceived as painful (allodynia), and normally painful stimuli are perceived as more painful (hyperalgesia). The sensitization process is presumably an adaptive response in that it promotes protective guarding of an injured area. In some cases, however, sensitization can be long-lasting, leading to the establishment of chronic pain syndromes that outlive their usefulness, persisting well after the acute injury has resolved. In these pathological, often debilitating conditions, aberrant plasticity in the pain pathway establishes a maladaptive condition in which pain no longer serves as an acute warning system.

The ability to prevent or treat such conditions is critically dependent upon a comprehensive understanding of the basic mechanisms through which pain signals are generated by nociceptors and how this information is transmitted to the central nervous system (CNS). In this chapter, we focus on the molecules and cell types that underlie normal pain sensation, with specific emphasis on the nociceptor and on second order neurons in the spinal cord. We also discuss how these processes are altered following tissue or nerve injury and in persistent pain states.

Primary Afferent Neurons

The detection of somatosensory stimuli is initiated by primary sensory neurons that have their cell bodies in the trigeminal and dorsal root ganglia. These pseudo-unipolar neurons extend an efferent branch that innervates peripheral target tissues, and a central afferent branch that targets the spinal cord dorsal horn or medullary nucleus caudalis (for trigeminal afferents). Primary afferents that innervate somatic tissue are traditionally categorized into three classes: Aβ, Aδ and C fibers, based on diameter, degree of myelination and conduction velocity [4]. These physiological differences are associated with distinct functional contributions to somatosensation. Thus, the largest diameter cell bodies give rise to myelinated Aβ fibers that rapidly conduct nerve impulses and detect innocuous mechanical stimulation. In contrast, noxious thermal, mechanical and chemical stimuli are detected by medium diameter, thinly myelinated Aδ fibers, and by small diameter, unmyelinated C fibers. These latter two groups constitute the nociceptors, and represent a dedicated system for the detection of stimuli capable of causing tissue damage, as they are only excited when stimulus intensities reach the noxious range [4]. The Aδ nociceptors mediate the fast, pricking sensation of “first pain,” and the C fibers convey information leading to the sustained, burning quality of “second pain” [5].

Nociceptor Subtypes