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 Gating Mechanism Transmission Cells From pain fibers From other Peripheral fibers To brain Brain Spinal Cord Gating Mechanism Transmission Cells From pain fibers From other Peripheral fibers To brain 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