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
Examples:
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
nhttp://www.youtube.com/watch?v=0Ck9ji9aS8M
nThe Pain Message
nhttp://www.youtube.com/watch?v=n8y04SrkEZU&feature=related
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
nRelaxation
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
nTension
nDepression
nMental Conditions
nFocusing on pain
nBoredom
nAcute vs Chronic Pain
nhttp://www.youtube.com/watch?v=kmdYt0OAJbs
nhttp://www.youtube.com/watch?v=hmo-UuCNW74
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
nRest
nVerbalization
nGuarding
nCrying
nRelaxation
nWithdrawal
nAggression
nAlcohol/drugs
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
MPQ
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
Multi-dimensional:
Memorial Pain Assessment Card
nRapid
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
nhttp://www.youtube.com/watch?v=kmdYt0OAJbs
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
nMassage
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
nMeditation
nPeaceful or pleasant imagery
nSelf-hypnosis
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
nhttp://www.npr.org/templates/story/story.php?storyId=7654964
Yoga
nhttp://www.youtube.com/watch?v=ccBWVAIc3qk
nA Chronic Pain Sufferer
nhttp://www.npr.org/templates/story/story.php?storyId=1139836
Hypnosis
nAn Acute Pain Example
nhttp://www.youtube.com/watch?v=zsKsRnTX8I0 Go to 7:00
n
nA Chronic Pain Example
n(New Medicine Video)
Complementary and Alternative Medicines (
(30% of Americans Use)
nPBS – The Alternative Fix
nA Shocking Statistic
nhttp://www.pbs.org/wgbh/pages/frontline/shows/altmed/view/2_hi.html (1st 4 min)
nWhere is the Evidence (acupuncture)
nhttp://www.pbs.org/wgbh/pages/frontline/shows/altmed/view/3_hi.html
nhttp://www.healthandhealingny.org/complement/index.asp
nhttp://takingcharge.csh.umn.edu/therapies/mind-body/what
nhttp://www.ahc.umn.edu/cahcim/members/home.html (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
n
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
nhttp://www.youtube.com/watch?v=2vibK_NjOVc
Psychological Pain Methods
nAcupuncture – not sure how it works. Could include:
nCounter-irritation – may close the spinal gating mechanism in pain perception.
nExpectancy
nReduced anxiety from belief that it will work.
nDistraction
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:
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
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