Chronic Pain

What is pain? A sensory and emotional

experience of discomfort.

Single most common medical complaint.

Qualities of Pain Organic vs. psychogenic Acute vs. chronic Malignant or benign Continuous or episodic

Perceiving Pain Algogenic substances – chemicals

released at the site of the injury Nociceptors – afferent neurons that

carry pain messages Referred pain – pain that is

perceived as if it were coming from somewhere else in the body

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.

A-delta fibers

Pain without apparent physical basis Persists long after healing May spread and increase in

intensity May become stronger than was the

initial pain from the injury

Three 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.

Early Theories of Pain Mechanistic view

Could not account for the role of psychological factors.

Gate-Control Theory – Ronald Melzack (1960s) Described physiological

mechanism by which psychological factors can affect the experience of pain.

Neural gate can open and close thereby modulating pain.

Gate is located in the spinal cord.

Gate-Control Theory

Brain

Spinal Cord

GatingMechanism

TransmissionCells

Frompainfibers

FromotherPeripheralfibers

Tobrain

Brain

Spinal Cord

GatingMechanism

TransmissionCells

Frompainfibers

FromotherPeripheralfibers

Tobrain

Gate is open Gate is closed

Three Factors Involved in Opening and Closing the Gate The amount of activity in the pain

fibers. The amount of activity in other

peripheral fibers Messages that descend from the

brain.

Conditions that Open the Gate

Physical conditions Extent of injury Inappropriate activity level

Emotional conditions Anxiety or worry Tension Depression

Mental Conditions Focusing on pain Boredom

Conditions That Close the Gate

Physical conditions Medications Counter stimulation (e.g., heat, message)

Emotional conditions Positive emotions Relaxation, Rest

Mental conditions Intense concentration or distraction Involvement and interest in life activities

Four Types of Pain Behaviours Facial/audible expression of

distress Distorted ambulation or posture Negative affect Avoidance of activity

Emotions, Coping, and Pain Chronic pain is associated with

higher levels of anger, fear, sadness, anxiety and stress.

Coping with Pain MMPI Scales 1 – 3

Hypochondriasis Depression Hysteria

Neurotic triad – combination of scales 1 – 3 of the MMPI

Three conclusions from the MMPI studies of pain

Chronic pain is associated with very high scores on the three scales of the neurotic triad, although scores on the other scales are within the normal range.

This pattern holds regardless of whether there is a known cause for the pain.

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

Treatment of Chronic Pain Surgical procedures to block the

transmission of pain from the peripheral nervous system to the brain.

Synovectomy – Removing membranes that become inflamed in arthritic joints.

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

Pharmacologic Control of Pain About half of hospitalized patients

who have pain are under-medicated.

Children are at particular risk of poor pain control methods.

Medications are given as: PRN – “as needed” As a prescribed schedule

Types of Pain Medications Peripherally active analgesics – work at the

periphery (e.g., aspirin, Tylenol). Centrally active analgesics – narcotics that

bind to the opiate receptors in the brain (e.g., codeine, morphine, heroin).

Local analgesics – can be injected into the site of injury or applied topically (e.g., novocaine).

Indirectly acting drugs – affect non-pain conditions such as emotions that can exacerbate pain experience.

Psychological Pain Control Methods

Biofeedback – provides biophysiological feedback to patient about some bodily process the patient is unaware of (e.g., forehead muscle tension).

Relaxation – systematic relaxation of the large muscle groups.

Hypnosis – relaxation + suggestion + distraction + altering the meaning of pain.

Psychological Pain Methods

Acupuncture – not sure how it works. Could include: Counter-irritation – may close the spinal

gating mechanism in pain perception. Expectancy Reduced anxiety from belief that it will

work. Distraction Trigger release of endorphins