The Nature of Pain

What is pain?

nA sensory and emotional experience of discomfort.

nSingle most common medical complaint.


Qualities of Pain

nOrganic vs. psychogenic

nAcute vs. chronic (daily for > 6 months)

nMalignant (indicating injury) or benign (harmless)

nContinuous or episodic


What Initiates Most Pain?

nAlgogenic (pain-causing) substances – chemicals released at the site of the tissue injury (bradykinin, histamine, serotonin, prostaglandins)

nNociceptors – afferent neurons whose dendrites or free nerve endings are sensitive to algogenics


Peripheral Nerve Fibers Involved in Pain Perception

nA-delta fibers – neurons with myelinated axons that quickly transmit sharp localized pain messages to cortex

nC-fibers – neurons with small unmyelinated nerve axons that transmit diffuse, dull burning or aching pain to brainstem and limbic system


Pain Without Detectable Tissue Injury

nCan occur with no obvious damage

nCan persist long after healing of damage

nMay spread and increase in intensity

nMay become stronger than the initial acute pain from the injury



nNeuralgia – an extremely painful condition consisting of recurrent episodes of intense shooting or stabbing pain along the course of the nerve.

nCausalgia – recurrent episodes of severe burning pain often triggered by a gentle sensation

nPhantom limb pain – feelings of pain in a limb that is no longer there and has no functioning nerves.

nSome other chronic pains


Another Puzzle:

nDecreased pain experience despite tissue injury


nSteps in Pain Perception


nThe Pain Message



Gate-Control Theory –
Ronald Melzack (1960s)

nNeural gate can open or close, thereby modulating amount of pain input that reaches the brain

nGate is located in the spinal cord.


Three Factors Involved in Opening and Closing the Gate

nThe amount of activity in the pain fibers.

nThe amount of activity in other peripheral fibers

nMessages that descend from the brain.


Conditions That Close the Gate

nPhysical conditions

nMedications (narcotic analgesics)

nCounter stimulation (e.g., heat, massage)

nAcupuncture, TENS

nSPA (stimulation produced analgesia)

nEmotional conditions

nPositive emotions


nMental conditions

nIntense concentration or distraction

nInvolvement and interest in life activities


Conditions that Open the Gate

nPhysical conditions

nExtent of injury

nInappropriate activity level

nEmotional conditions

nAnxiety or worry



nMental Conditions

nFocusing on pain



nAcute vs Chronic Pain





Four Types of Pain Behaviours

nFacial/audible expression of distress

nDistorted ambulation or posture

nNegative affect

nAvoidance of activity


Pain behaviors

nUse of Medication

nAltered Activity









nHot/cold packs


Three conclusions from the MMPI studies of pain sufferers

nChronic pain is associated with very high scores on the 3scales of the “neurotic triad” (hypochondriasis, depression, hysteria), although scores on the other scales are within the normal range.

nThis pattern holds regardless of whether there is a known cause for the pain. Pattern may disappear if pain goes away.

nIndividuals with acute pain may show moderate elevations of the neurotic triad scales, although scores on the other scales are normal.


Assessing Pain

nDetailed interviews    

nHistory of pain problem

nPatient’s emotional adjustment

nLifestyle, interests before pain

nImpact of pain on lifestyle, relations, work

nFactors that seem to trigger or worsen pain

nSocial context of pain attacks

nHow patient tries to cope


Uni-dimensional Scales

nVerbal Rating Scale (VRS)

nNone, mild, moderate, severe

nNumeric Rating Scale (NRS)

nVisual Analog Scale (VAS)

nPictorial Scale


Multi-dimensional Questionnaires

nMcGill Pain Questionnaire (MPQ)(Melzack)

nThe Brief Pain Inventory (BPI)

nThe Memorial Pain Assessment Card




nExtensively validated in clinical setting

nThree domains of descriptors

nSensory, affective, and evaluative

nTakes up to 15 min

nRelies on strong English vocabulary

nIndividuals with similar pain syndromes choose similar words

nThose with different pains (e.g. arthritis, cancer, phantom limb) choose different words


Multi-dimensional: BPI

nQuicker and relatively easier than MPQ

nWell established reliability in cancer, arthritis, and AIDs.

nSensory, affective and functional status

nUseful for treatment response

nGood choice for patients with progressive disease


Memorial Pain Assessment Card


nSensory and affective PLUS (pain relief)

nReliable in Cancer patients

nValidated and correlates well with longer scales

n…And fits in your pocket


Pain Behavior Ratings

nMay observe individual for level of pain behaviors

nMay ask patient to do various things

n(walk, pick up something, remove shoes while sitting, perform exercise actions)

nMay use video and trained assessors

nMay train family members to make observations at home


Pain Rating Scales

nThe FLACC scale should be used with patients who are nonverbal or noncommunicative


Psychophysiological Measures

nEMG – muscle tension

nHR and skin conductance – autonomic nervous system indicators

nEEG evoked potentials


Qualities of Pain

nOrganic vs. psychogenic

nAcute vs. chronic (daily for > 6 months)

nMalignant (indicating injury) or benign (harmless)

nContinuous or episodic




Clinical Pain

nAny pain that receives or requires clinical care

nMay be acute or chronic

nRequires treatment in and of itself

nMakes procedures go more smoothly, decrease stress and distress, speeds recovery

nBut many people receive inadequate pain treatment. The resulting increase in stress impairs immune function, slows healingand increases the risk of infection


Types of Pain Medications

nPeripherally active analgesics – work at the periphery (e.g. acetominophen(Tylenol) and NSAIDS(aspirin, ibuprofen, naproxen).

nCentrally active analgesics – narcotics that bind to the opiate receptors in the brain (e.g., codeine, morphine, Darvon, Demerol, Percodan, oxycodone).

nLocal anesthetics – can be locally injected or applied topically (e.g., novocaine, lidocaine).

nIndirectly acting drugs – affect non-pain conditions such as emotions that can exacerbate pain experience (tranquilizers, antidepressants)


Pharmacologic Control of Pain

nAbout half of hospitalized patients who have acute pain are under-medicated

nChildren are at particular risk of poor pain control methods.

nMedications are given as:

nOn a prescribed schedule

nPRN – “as needed”

nPCA – patient controlled analgesia

nSituation even worse for chronic pain

nBenign pain/chronic pain may not respond the same


Under-prescribing of Medical Narcotic Analgesics


Other Medical/Physical Treatments

nSurgical procedures to block the transmission of pain from the peripheral nervous system to the brain.

nSynovectomy – Removing membranes that become inflamed in arthritic joints.

nSpinal fusion – joins two or more adjacent vertebrae to treat chronic back pain.

nPhysical therapy may be used to increase mobility


nStimulation of nerves under the skin (acupuncture, TENS, brain or spinal cord stimulation, etc.)






Psychological Pain Control Methods

nPlacebo pain relief

nBiofeedback – provides biophysiological feedback to patient about some bodily process the patient is unaware of (e.g., forehead muscle tension) to allow some learned control over body

nRelaxation & meditation

nHypnosis & self-hypnosis – relaxation + suggestion + distraction + altering the meaning of pain.

nMay combine methods


Pain management strategies

nSlow, deep (diaphragmatic) regular breathing

nProgressive relaxation


nPeaceful or pleasant imagery


nBrief (“cue”) relaxation induction

nExternal focusing (stimuli outside body, engage in activity)


% Relief of Tension Headache

nPlacebo biofeedback  17% reduction

nRelaxation training      37%

nBiofeedback                          43%

nBiofeedback+relaxation 56%


Alternative Routes to Relaxation

nMindfulness meditation






nA Chronic Pain Sufferer




nAn Acute Pain Example

n   Go to 7:00


nA Chronic Pain Example

n(New Medicine Video)


Complementary and Alternative Medicines (CAM)
(30% of Americans Use)

nPBS – The Alternative Fix

nA Shocking Statistic

n (1st 4 min)

nWhere is the Evidence (acupuncture)



CAM Resources




n (training & jobs too)


Pain Behaviors May Be Reinforced

n“Secondary Gains”

nGet attention, care, sympathy

nMay decrease work responsibilities

nDisability payments

Likewise we can use Operant behavior approach to reduce pain behavior


Cognitive strategies

nTraining for self-efficacy in pain control

nRedefinition or reappraisal (transforming your view of pain and ability to cope with it)

nPositive self-talk (e.g. de-catastrophizing)

nPersistence or non-avoidance of activity

nMental distraction (thoughts, visualization, memories, music, mathematics . . .)

nEmotion defusing/problem solving strategies


Interesting Bandura Study

n72 students given self-efficacy for pain control training in preparation for a cold pressor test

nCognitive coping group resisted pain 60% longer than control group or placebo pill group.

nWhat if these groups are pre-treated with either saline or naloxone injections before the pain test?


nNo significant difference in pain tolerance of saline or naloxone groups for the control or placebo pill conditions.

nBUT naloxone eliminated the pain tolerance of the cogntive coping group!


Ramachandran’s Mirror Box



Psychological Pain Methods

nAcupuncture – not sure how it works. Could include:

nCounter-irritation – may close the spinal gating mechanism in pain perception.


nReduced anxiety from belief that it will work.


nTrigger release of endorphins


Integrative model of pain care; Pain Clinics

nStepped care approach to pain management

nLevel one:  Primary responsibility rests with primary care providers

nLevel two:  “Living with Pain Class”

nPatient education and rehabilitation model

nReview of common pain conditions

nPersonal review of medications

nDiscussion of self-management model

nPersonalized exercise plan

nPractice of self-regulatory pain strategies, e.g., breathing, relaxation, activity pacing

nLevel three:  Comprehensive Pain Management Center


Pain management strategies

nIncreasing movement – walking, swimming, physio exercises

nDirect statement of needs/assertiveness

nCoaching significant others to reinforce positive pain behaviour and ignore negative

nIncreasing either mastery or pleasure activities to at least one per day