CAS PS 332 Lecture Notes - Lecture 12: Fluid Ounce, Chronic Pain, Atropa Belladonna

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March 5th, 2020
Lecture 12
Chronic Pain
- Summarize historical approaches to pain management
- Discuss the prevalence, cost, definition and purpose of pain
- Distinguish the four stages of pain
- Explain the primary approaches to measuring pain
- Identify the physiological processes related to pain transduction, transmission, perception and
- Describe the specificity and gate control theories of pain
- Identify contextual influences on pain perception
What is pain? What causes pain?
Early humans related pain to evil, magic and demons.
Relief of pain: responsibility of sorcerers, shamans, priests and priestesses, who used herbs, rites and
ceremonies as their treatments.
Early 19th century pain relief
- Most pain relievers made from plants
o Opium derived from the poppy flower
o Also alcohol or wine, mandrake, belladonna and marijuana
- Overdoses deadly!
Wizard oil:
- Touted as cure for Rheumatism, sprains, bruises, lame back, frost bites, diarrhea, burns and
- Contents: 50-70% alcohol, camphor, ammonia, chloroform, sassafras, cloves and turpentine
- Wizard oil could also be used on horses and cattle
Mrs Windlsow’s Soothing Syrup: was an indispensable aid to mothers and child-care workers.
Containing one grain (65gmg) of morphine per fluid ounce, it effectively quieted restless infants and
small children.
Headache treatment: likely included ethyl alcohol and opium.
Cocaine toothache drops were recommended for tooth pain.
Current impact and prevalence: chronic pain
Chronic pain is PREVALENT and it is a major public health problem.
It is the most common reason people seek treatment.
- Affects 1.5 billion people worldwide
o 10% of the world’s population (11.2% of US pop.)
o More than cancer, heart disease and diabetes combined
- Higher prevalence in women
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o 34.3% women; 26.7% men
- Associated with low income and unemployment
Chronic pain is COSTLY!
- NIH: chronic pain is the costliest medical problem in the US, affecting over 100 million people
- Americans spend $600 billion annually on treatment for chronic pain
o About $2,000 for every person living in the US
- Pain is cause of 80% of all visits to physicians
o Most common reason to see primary care physician
“Fifth vital sign”
What is pain?
- Traditional conceptualization
o A direct consequence of physical injury
o Degree of tissue damage degree of pain
- Strong (1895)
o Physical sensation
o Psychic reaction: psychological causes given equal importance!
- Current definition of pain: an unpleasant sensory and emotional experience associated with
actual or potential tissue damage, or described in terms of such damage (International
Association for the Study of Pain, 1979)
- What is important/surprising about this definition?
o “potential tissue damage”
- What is the purpose of pain?
o Acute pain vs. chronic pain
Acute pain is more adaptive than chronic pain
Four stages of pain
1. Acute
a. Generally result of injury
b. Cuts, burns, childbirth, surgery, etc.
c. Brief duration
d. Adaptive signal to avoid further injury
2. Pre-chronic
a. Between acute and chronic stages
b. Transition point: person either overcomes acute pain, or develops feelings of
hopelessness chronic pain
3. Chronic
a. Lasts 6+ months (often many years)
b. Variability: continuous or intermittent; moderate or severe; felt in any part of the body’s
i. May be due to chronic illness (e.g. rheumatoid arthritis) or an injury that does
not heal promptly
ii. Can exist in the absence of tissue damage
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c. NO BIOLOGICAL BENEFITS: not adaptive result of physiology designed to be protective
d. Worsened by psychological factors (depression, hopelessness, helplessness, stress,
anxiety, etc.)
4. Chronic recurrent
a. Alternating episodes of intense pain and no pain (e.g. migraine headaches)
b. 3+ months
Measuring pain
There is no direct way to measure physiological sensation
- Psychophysical studies
o EMG (electromyography) assess the amount of muscle tension experienced by pain
o Autonomic arousal e.g. measures of heart rate, breathing rate, blood pressure, as a
proxy for pain
- Pain behaviors:
o overt manifestations of the pain experience
o Examples:
Changing the way one sits/walks
Complaining about pain to others
Avoiding activities involving work or leisure
Suffering: emotional component of pain
Sometimes accompanies pain, sometimes does not
- Self-report measures
o Rating scales or diaries
o Assign numerical value to feeling of pain (1-10)
o McGill pain questionnaire (MPQ) rates 3 qualities:
Sensory quality (e.g. throbbing, stabbing, burning)
Affective quality (irritation, fear, anger)
Evaluative quality (related to cognition, severity and significance of pain)
These measures indicate the pain of only one person, you cannot compare two
different patients based on this score!
Visual analog scales: Wong-Baker faces pain rating scale
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