Saeid Safari, MD

Anesthesiologist,

Iran University of Medical Sciences

Pain Medicine

Sir William Osler, the eminent 19th-century clinician

What is the Pain?

Medical Definition:

“Pain is an unpleasant sensory and emotional experience

associated with actual or potential tissue damage.”

International Association for the Study of Pain, 1979

“An unpleasant sensation induced by noxious stimuli and

generally received by specialized nerve endings.”

CancerWEB, 2011

Operative Definition:

“Pain is whatever the experiencing person says it is,

existing whenever he/she says it does.”

Margo McCaffery, 1999

Epidemiology

Epidemiology

• 50 million people are partially or totally disabled due to pain

• 70 to 90% of patients with advanced disease from cancer have

significant pain that requires the use of opioid drugs.

• Severe, unrelenting pain interferes with patients' quality of life,

including their activities of daily living, their sleep, and their social

interactions.

Epidemiology

• 80% of elderly patients have chronic pain.

• 66% have pain in the last month of life

• ~ ½ of hospitalized patients with pain are under-medicated.

• Up to 50% of patients who are taking pain medication do not

experience adequate relief

Economics

• Chronic pain causes 700 million lost work days/year in the U.S.

• > $ 9 billion per year on OTC pain products.

• Estimated cost of pain is $150 billion per year

Physiologic Effects of Pain

• Immune System

• Developmental

• Future Pain

• Quality of Life

• Endocrine & Metabolic

• Musculoskeletal

• Cardiovascular

• GI/GU

Psychiatric Disorders in Chronic Pain

• Chronic pain is often comorbid with psychiatric disorders.

• The typical finding is an increased occurrence of psychiatric

disorders among persons with a specific pain condition when

compared with persons with no pain.

• Depression is the most commonly studied psychiatric disorder in

the context of chronic pain.

• A higher occurrence of major depressive disorder among persons

with chronic pain.

• The association of pain with anxiety disorders

• A higher level of disability is often associated with comorbid

depression and anxiety disorders

• Other than depression and anxiety, somatoform disorders,

substance use disorders, and personality disorders have all been

found to be more common among patients with chronic pain

compared with those without chronic pain

• Posttraumatic stress disorder (PTSD) has received particular

attention in the literature.

Pain Behaviors

Reactions to Pain

1. Somatic Motor Reactions

2. Autonomic Reactions

3. Emotional and Psychogenic Reactions

4. Hyperalgesia

1) Somatic Motor Reactions

• Excess neuromuscular excitability throughout the body.

• Withdrawal Reflexes.

• Immobilization Reaction.

• Guarding Reaction.

2) Autonomic Reactions

• Mild Cutaneous pain

• a pressor reaction = rise of blood pressure and heart rate, mediated

by sympathetic stimulation.

• Sever cutaneous, deep and visceral pain

• a depressor reaction associated with hypotension, bradycardia, and

nausea, due to parasympathetic stimulation.

• Such pain is often described as sickening pain and may be

accompanied by vomiting.

Autonomic Response to Pain

• Grimacing

• Restlessness

• Guarding

• Increased respirations

• Increased heart rate

• Increased blood pressure

• Diaphoresis

3) Emotional and Psychogenic Reactions

• Anxiety, fear, crying, depression, as well as the feeling of being hurt

may be felt by the pained person.

• These reactions vary:

- From person to person on exposure to similar pain stimuli

- in the same person according to his emotional state

3) Emotional and Psychogenic Reactions

1. Worry about the cause of pain augment the feeling of pain.

• Thus, Patients suffer than healthy subject to the same degree of

pain.

2. Strong emotional excitement & sever physical exertion may block

the feeling of pain.

• Thus, seriously wounded soldiers in a battlefield suffer little or

no pain till the battle is over.

Four Types of Pain Behaviors

• Facial/audible expression of distress

• Distorted ambulation or posture

• Negative affect

• Avoidance of activity

Emotions, Coping, and Pain

• Higher levels of

1. Depression

2. Anxiety and Stress,

3. Fear,

4. Sadness,

5. Anger

• Fewer observable outward physical changes/signs.

Develops later.

- Shorter duration than 1ry.

- In healthy skin surrounding red area.

- Pain is felt more sever than normal.

Central sensitization explained by

convergence-facilitation theory.

- Develop 30-60 min. after injury.

- Lasts for several hours or days.

- In the area of redness.

- Non-painful stimuli (as touch)

becomes painful.

Mechanism:

Decreased pain threshold due to local

axon reflex releasing substance P

4) Cutaneous HyperalgesiaIncreased skin sensitivity to pain.

1- Primary Hyperalgesia 2- Secondary Hyperalgesia

Pain Terminology, Classifications, and Pathophysiology

Definitions

• An unpleasant sensory and emotional experience associated with

actual or potential tissue damage and modified by individual

memory, expectations and emotions.

• Pain is whatever the experiencing person says it is.

• Highly subjective, leading to under treatment

Types of Pain

1. Acute (<6 months)

2. Chronic (6 months <)

Acute pain:

• lasts less than 6 months, subsides once the healing process is

accomplished.

Presentation of PainAcute

• Often obvious distress

• Can be sharp, dull, shock-like, tingling, shooting, radiation, fluctuating in intensity, and varying in location (occur in timely relationship to noxious stimuli)

• Comorbid conditions not usually present

• May see HTN, increased HR, diaphoresis, pallor…

Chronic• Can appear to have no

noticeable suffering

• Can be sharp, dull, shock-like, tingling, shooting, radiation, fluctuating in intensity, and varying in location (do NOT occur in timely relationship to noxious stimuli)

• Symptoms may change over time

• Usually NO obvious signs

Acute Pain (Nociceptive)

• Somatic

• Superficial (nociceptors of skin)

• Deep [body wall (muscle, bone)]

• Visceral (sympathetic system; may refer to

superficial structures of same spinal nerve)

Acute Pain

• Travels into the spinal cord along the appropriate nerve root.

• Nerve root splits into a front division and a back division and carries pain sensation to the CNS (spinal cord and brain).

• Passed to a short tract of nerve cells (interneurons), which in turn synapse with a nerve tract that runs to the brain .

Acute Pain

• Sent out to the rest of the brain, connecting with thinking and emotional centers.

• A modifier pathway from the brain modifies pain at the synapses in the back part of the spinal cord (acute pain is decreased rapidly after tissue injury).

Chronic pain:

• Complex processes & pathology.

• Usually altered anatomy & neural pathways.

• Constant & prolonged, > 6 months, sometimes for life.

• “Lasting longer than expected time frame”

Altered Neural Structure

• Chronic pain accompanied by:

• Cortical Reorganization

• Brain Atrophy

Chronic Pain

1. Malignant (cancer)

2. Nonmalignant

• Neuropathic (nerve injury)

• Inflammatory (musculoskeletal)

• Mixed or unspecified

• Psychogenic

Peripheral Nerve Fibers Involved in Pain Perception

• A-delta fibers–small, myelinated fibers that transmit sharp pain

• C-fibers–small unmyelinated nerve fibers that transmit dull or

aching pain.

Chronic Pain

• Neuropathic:

• Severe pain disorder that results from damage to the central and

peripheral nervous systems.

• Centrally generated

• Peripherally generated

• Inflammatory:

• Results from the effects of inflammatory mediators.

Chronic Pain Conditions

• Neuralgia

• an extremely painful condition consisting of recurrent episodes of

intense shooting or stabbing pain along the course of the nerve.

• Causalgia

• recurrent episodes of severe burning pain.

• Phantom limb pain

• feelings of pain in a limb that is no longer there and has no

functioning nerves.

• Schematic of cortical areas involved with pain processing and fMRI

Major Categories of Pain

1. Nociceptive pain

(stimuli from somatic and visceral structures)

2. Neuropathic pain

(stimuli abnormally processed by the nervous system)

Nociceptive Pain

• Visceral Pain: Associated with internal organs.

• Nature: Crampy, pressure, deep, dull to sharp, diffuse, referred.

• Somatic pain : Soft tissues/ myalgic.

• Nature: Dull to sharp, throbbing, achy, localized

Neuropathic Pain

• Abnormal neural processing by the peripheral or central nervous

system.

• Signals are amplified or distorted; Synapse receptor numbers are

altered; pathways not originally involved become involved

• Patient Description of Neuropathic Pain:

• Burning, electric, searing, tingling, and migrating or traveling.

Tracking the Path of Pain

• Peripheral receptors

• Neural pathways

• Spinal Cord mechanisms & long tracts

• Brainstem, thalamus, cortex & other areas.

• Descending pathways.

Pain Gate Control

The sites of synapses along the pain pathway are considered as gates through which pain transmission can be facilitated (if the gate is open) or blocked (if the gate is closed).

The main pain gates are:

1- Spinal gate: at the SGR.

2- Brain stem gate: at the nuclei of reticular formation.

3- Thalamic gate: At neurons of PVLNT & intalaminar thalamic nuclei.

3

1

2

Pain Pathways:

1. Painful Stimuli or tissue damage activate specialized nerve cells

(nociceptors), which in turn send pain signals to the spinal cord.

2. Pain signals enter the dorsal horn of the spinal cord, where some are

increased or decreased by the interneuron before continuing up to the

brain.

3. Thoughts, feelings and beliefs change the pain signals into the

individual’s experience of “PAIN".

4. Certain parts of the brain generate signals that travel back down the

spinal cord to reduce or increase pain signals at the interneuron.

Sites of Action Medications

Peripherally (at the nociceptor)

Cannabinoids, NSAIDs, Opioids, Tramadol, Vanilloid receptor antagonists(i.e., capsaicin)

Peripherally Local anesthetics,

(along the nociceptive nerve)

Anticonvulsants (except the gabapentinoids)

Centrally (various parts of the brain)

Acetaminophen Anticonvulsants (except the gabapentinoids), Cannabinoids. Opioids, Tramadol

Descending Inhibitory pathway in the spinal cord

Cannabinoids, Opioids, Tramadol, Tricyclic antidepressants, SHRIs

Dorsal horn of the spinal cord

Anticonvulsants, Cannabinoids, Gabapentinoids, NMDA receptor antagonists, Opioids,. Tramadol, Tricyclic

antidepressants, SNRIs

Pain Assessment and Management

Let’s try an experiment….

Have students take pen and place over nail bed and push. Describe

sensation to neighbour. All the same?

Now try counting backwards from 10 while holding pressure on nail

bed. Is the pain as bad?

Patient Assessment• Assess and reassess

• Use methods appropriate to cognitive status and context

• Assess intensity, relief, mood, and side effects

• Use verbal report whenever possible

• Document in a visible place

• Expect accountability

• Include the family

• Include past physician(s)

• Get old records

• Check for addictive personality

• Site(s)

• Quality

• Severity

• Date of onset

• Duration

• What makes it better/worse

• Impact on sleep, mood,

activity

• Effectiveness of previous medication

Patient Pain History

PQRST mnemonic:

• P: Precipitating and palliating factors

• Q: Quality

• R: Region and radiation

• S: Severity

• T: Time

Instruments

• Single-dimension

• Visual analog scale

• Verbal numerical scale

• Verbal rating scale

• Multidimensional

• Assesses the pain as well as the emotional and behavioral effects

of the pain.

One type has faces—(Whaley & Wong, 198)

Other pain scales are just numeric

Single-dimension Instruments

Verbal rating scale

• No pain = 0

• Mild pain = 1-3

• Moderate pain = 4-6

• Severe pain = 7-9

• Worst ever = 10

Can pain-intensity scales be used ?

• Yes- but, limited by cognitive changes, impaired vision, physical

limitation

• no specific scale more “user friendly”

• 83% of nursing home residents could complete a pain scale

Why have a pain scale?• Sometimes hard to put words to pain

• Pain is multi-faceted (How long? Where? How intense? What kind feeling?

• Visual scales help us understand where pain located.

• Faces help us understand how pain makes patient feel.

• Numeric scales help quantify pain using numbers.

Pain Management

Pharmacological &

nonpharmacological management

Pain Management

Principles of Treatment

• Reduction of Pain:

• Behavioral, Meds, Blocks, Surgery, Complementary

• There is no magic bullet, no single cure

• Rehabilitation:

• Reconditioning & Prevention

• Coping:

• Management of Residual Pain

Treatment Objectives

• Decrease the frequency and / or severity of the pain

• General sense of feeling better

• Increased level of activity

• Return to work

• Decreased health care utilization

• Elimination or reduction in medication usage

Copyright © 2003 American Society of Anesthesiologists. All rights reserved

Treatment of Pain

1. Non-pharmacologic

2. Medications

• Nonsteroidal anti-inflammatory drugs (NSAIDs)

• Acetaminophen

• Antidepressants & anticonvulsants

• Adjuvants

• Narcotics

3. Invasive procedures

Nonpharmacological Management

Non-pharmacologic Pain Management• Cognitive therapies (relaxation,

imagery, hypnosis)

• Biofeedback

• Behavior therapy

• Psychotherapy

• Complementary tx

• Massage therapy

• Art therapy

• Music therapy

• Aroma therapy

• Neurostimulation

• TENS

• Acupuncture

• Anesthesiology

• Nerve block

• Surgery

• Physical therapy

• Exercise

• Heat/cold

• Psychological approaches

Non-Pharmacologic

Cognitive Behavioral Therapy: Yes, ‘A’, Cochrane

“Cortical plasticity related to chronic pain can be modified

by behavioral interventions that provide feedback to the brain

areas that were altered by somatosensory pain memories.”

H. Flor, 2002 & 03

“Individuals can gain voluntary control over … specific

brain region… these effects were powerful enough to impact severe,

chronic clinical pain.”

de Charms, 2005, Nat’l Acad Sci

Non-Pharmacologic

Meditation: Yes, ‘A’, Cochrane

Strong evidence for the use of relaxation & hypnosis in reducing pain in

a variety of medical conditions

Music Therapy: Yes, ‘A’, Cochrane

Non-Pharmacologic

• Pre-Op counseling: Yes, ‘B’, Cochrane

• Ice: Yes, “B”, Cochrane

• Chiropractic: No, ‘B’, Cochrane

• Massage: Yes for cancer, low back & OA pain, ‘B’, Cochrane

• Exercise : Yes; ‘B’, Cochrane

Non-Pharmacologic

• Magnets: Don’t Know ‘I’, Cochrane

• Spinal Cord Stimulation: Don’t know, ‘I’, Cochrane

• Acupuncture: Don’t Know, ‘I’, Cochrane

• TENS: Don’t Know, ‘I’, Cochrane

Acupuncture • Acupuncture has been practiced in China for more than 4000 years as a method for

pain relief.

Mechanism:

1- needles in appropriate body regions are thought to excite certain sensory neural

pathways which feed into the brain stem centers (such as the PAG) involved in the

pain control system, with release of endogenous opioid peptides.

2- simultaneous suppression of pain transmission at the spinal pain-gate by acupuncture

APA offers the following tips on coping with chronic pain:

• Manage your stress. 

• Talk to yourself constructively.

• Become active and engaged. 

• Find support.

• Consult a professional. 

Manage your stress.

• Emotional and physical pain are closely related, and persistent pain

can lead to increased levels of stress. Learning how to deal with

your stress in healthy ways can position you to cope more

effectively with your chronic pain. Eating well, getting plenty of

sleep and engaging in approved physical activity are all positive

ways for you to handle your stress and pain.

Talk to yourself constructively.

•  Positive thinking is a powerful tool. By focusing on the

improvements you are making (i.e., the pain is less today than

yesterday or you feel better than you did a week ago) you can make

a difference in your perceived comfort level. For example, instead of

considering yourself powerless and thinking that you absolutely

cannot deal with the pain, remind yourself that you are

uncomfortable, but that you are working toward finding a healthy

way to deal with it and living a productive and fulfilling life.

Become active and engaged.

• Distracting yourself from your pain by engaging in activities you

enjoy will help you highlight the positive aspects of your life.

Isolating yourself from others fosters a negative attitude and may

increase your perception of your pain. Consider finding a hobby or a

pastime that makes you feel good and helps you connect with family,

friends or other people via your local community groups or the

Internet.

Find support.

• Going through the daily struggle of your pain can be extremely

trying, especially if you’re doing it alone. Reach out to other people

who are in your same position and who can share and understand

your highs and lows. Search the internet or your local community

for support groups, which can reduce your burden by helping you

understand that you’re not alone.

Consult a professional.

• If you continue to feel overwhelmed by chronic pain at a level that

keeps you from performing your daily routine, you may want to talk

with a mental health professional, such as a psychologist, who can

help you handle the physical and psychological repercussions of

your condition.

Using psychological factors in clinical practice

Vigilance to pain

• Patients are distorted by the pain and are urged to react. Pain

patients will have impaired concentration as they are being

interrupted constantly by an aversive stimulus. Keep all

communications clear and brief. Repeat key points often. Expect

patients to talk about the pain often, as it is being brought

repeatedly into attentional focus for them. This is not a sign of a

somatization disorder or hypochondria.

Avoidance

• Patients will naturally avoid pain and painful procedures. Be aware

that this will occur and plan for it. Painful treatments will be

avoided and patients will compensate for any disability caused by

avoidance (e.g. shifted body weight distribution. ¡f a habitual pattern

of avoidance develops, this may lead to chronic pain. Patients must

be given an understanding that pain does not necessarily equal

damage. A credible medical authority must deliver this message.

Anger

• Patients with pain may shout at you, abuse you and generally be

hostile to you. If they are hostile to you they have probably been

hostile to everyone. Most often this will have nothing to do with you.

and you will need to understand that anger normally means

extreme frustration, distress and possibly depression. Anger

functions to push people away and isolate a person. The angry pain

patient is therefore less likely to have received or heard any

information about their problems and be more confused than the

non-angry patient.

Involve the patient

• First, assess the patient’s normal way of coping with pain by simply

asking how he or she has coped with predictable pain, such as a visit

to the dentist. Secondly, match your strategy to the patient’s

preference. ¡f the patient needs information, inform them how much

pain they may expect to feel, what it may feel like and, critically, for

how long (if this information is known). Always slightly

overestimate the time rather than underestimate it. Finally, if

possible. involve the patient in the delivery of any pain management

strategy.

Make sense of the pain

• Always ask the patient what they know and fear about the cause of

the pain, the meaning of the pain and the time course of the pain.

Expect the unexpected. What makes sense to one person is

nonsense to another. What matters is that it is their understanding,

not yours, that will inform their behaviour. Uncertain diagnoses or

unknown diagnoses will lead to increased vigilance to pain and

increased symptom reporting.

Consistency

• Develop a consistent approach to clinical information, patient

instruction and patient involvement within pain management.

Practice should be consistent for each patient and from each

member of the pain team, over time.

Pharmacological management:

Using Pharmacological Options Safely

• Pharmacokinetics

• Pharmacodynamics

• Compliance

• Cost

• Polypharmacy

Pain

Step 1 Nonopioid Adjuvant

Pain persisting or increasing

Step 2 Opioid for mild to moderate pain Nonopioid Adjuvant

Pain persisting or increasing

Pain persisting or increasing

Step 3Opioid for moderate to severe pain

Nonopioid Adjuvant

Invasive treatments Opioid Delivery

Quality of Life

Modified WHO 3- Step Analgesic Ladder

Proposed 4th Step

The WHOLadder

Deer, et al., 1999

8 -10

4 - 7

1 - 3

Pain Severity

• Step 1: non-opioid analgesics

• (COX-2, Aspirin, Acetaminophen, Diclofenac, Ibuprofen, Tenoxicam,

Panadeine, Nurofen. Pain rating 1-2-3)

• Step 2: mild opioid is added (not substituted) to step 1

• (Codeine, Propoxyphene, Tramadol, Sevredol, DHC Continus,

Dihydrocodeine tartate. Pain rating: 4-5-6)

• Step 3: Opioid for moderate to severe pain is used and titrated to effect

• Oxycodone, Morphine, Fentanyl, Pethidine, Ketamine Pain rating 7-10

Remember basic principles:

• Use WHO pain ladder

• Take a careful drug history

• Know the pharmacology of the Rx

• “Start low, go slow”

• Regularly review the regimen

• Remember that drugs may cause illness

Pharmacological management:• Selection of appropriate drug, dose, route and interval

• Aggressive titration of drug dose

• Prevention of pain and relief of breakthrough pain

• Use of coanalgesic medications

• Prevention and management of side effects

Patient Controlled Analgesia (PCA)

Pharmacology of Nociception

Four Steps:

1. Transduction

• NSAIDs, Local Anesthetics & Anticonvulsants

2. Transmission

• Opioids, NMDA Antagonists

3. Perception

• Distraction, Relaxation, Imagery

4. Modulation

• Tricyclic Antidepressants, Opioids, GABA Agonists

Manage side-effects opiates:• Constipation

• Tolerance to nausea and sedation develops in 3-7 days.

• Use adjuvant (coanalgesic) agents with opioid:• Tricyclic antidepressants

• Corticosteroids

• Anticonvulsants

• Muscle relaxants

• Stimulants

Physical Dependence

• A process of neuro-adaptation

• Abrupt withdrawal may → abstinence syndrome

• If dose reduction required, reduce by 25-50% q 2–3 days; avoid

antagonists.

Tolerance

• Reduced effectiveness to a given dose over time.

• If dose is increasing

• suspect opioid tolerance

• disease progression

• psychological/spiritual pain

Addiction

• Acceleration of abuse patterns onto a primary illness.

• Characteristics:

• Psychological dependence

• Compulsive use

• Loss of control over amount and frequency of use

• Loss of interest in pleasurable activities

• Continued use of drugs in spite of harm

Pseudoaddiction

• Drug seeking behavior associated with a person’s need to relieve

pain and suffering, not an obsession with the mood altering affects

of medication.

Wesson et al, 1993

Chronic Pain Medical Issues

• Physical Exam

• History documenting prescribing rationale

• Pain assessment documentation

Legal Issues

• Accurate prescription records

• Controlled substance laws

• Schedule

• Emergency Telephone Prescriptions

• Nursing Home Patients Fax prescriptions

Skilled Prescribing

• Patient –Physician Partnership

• Pain management expectations

• Medication responsibilities

• One physician

• One pharmacy

Role of Invasive Procedures

• Optimal pharmacologic management can achieve adequate pain

control in 80-85% of patients

• The need for more invasive modalities should be infrequent

• When indicated, results may be gratifying

Role of Invasive (“Anesthetic”) Procedures

• Intractable pain*

• Intractable side effects*

*Symptoms that persists despite carefully individualized

patient management

What about the 20% who do not get relief from the WHO ladder

• Has a true pain assessment been accomplished?

• Have you examined the patient?

• Is the pain neuropathic?

• Is the patient receiving their medication?

• Is the medication schedule and route appropriate?

• Have the opioids been titrated aggressively?

• Have invasive techniques been employed?

What about the 20% who do not get relief from the WHO ladder

• Lastly,

• Cosider checking a vitamin D level :

• There is an association between Vitamin D levels & chronic pain in

women.

• Women with levels of 75 – 99 nmol/L had less pain.

• Ann Rheum Dis. August 12, 2008.

Importance of Teamwork

• Complex chronic pain, especially if caused by life-threatening

disease, is best treated by a team.

• The diverse talents of physician, nurse, social worker, chaplain,

working together offers comprehensive control of physical,

emotional, and spiritual pain.

• Palliative care is for ALL patients who are suffering.

So, what about “Pain Clinics”

• Depends on where you live and of what they consist.

• “Most” are not teams, but 1 or more anesthesiologists.

• Most

• Want to do invasive procedures

• Prefer not to manage chronic medications

• Do NOT have Psychologists nor alternative medical practitioners