Presentation on pain mechanisms and treatment to uOttawa mini-medical school lecture series

1. The Paradox ofThe Paradox of
PainPain
Colin J.L. McCartney
MBChB PhD FRCA FCARCSI FRCPC
Head and Chair
Anesthesiology and Pain Medicine
The Ottawa Hospital and University of
Ottawa

2. Conflicts of Interest:
None

3. Overview
• Why we suffer pain?
• How we suffer pain?
• Psychology of pain
• Pathological pain
– Acute and Chronic Pain
• Pain Treatment
• Pain Research
• Future Challenges

4. MBChB, Edinburgh University 1986-1991
Focus on patient care
Choosing Anesthesiology
Specializing in Pain Medicine
Regional Anesthesia and Acute Pain
Research in acute and chronic pain

6. Overview
• Why we suffer pain?
• How we suffer pain?
• Psychology of pain
• Pathological pain
– Acute and Chronic Pain
• Pain Treatment
• Pain Research
• Future Challenges

7. Why we suffer pain?
• Protective mechanism
• Adaptive mechanism
• Pain systems:
-Somatic
-Visceral
-Neuropathic

8. What if we didn’t have pain?

9. Mycobacterium Leprae
• Gram +ve aerobic
rod
• Affect skin,
nerves and
mucous
membranes

10. Overview
• Why we suffer pain?
• How we suffer pain?
• Psychology of pain
• Pathological pain
– Acute and Chronic Pain
• Pain Treatment
• Pain Research
• Future Challenges

11. Pain Physiology

12. The Pain Pathway
Descartes 1645

13. Is Pain that Simple?

14. Is Pain that Simple?

15. Is Pain that Simple?

16. Gate Control Theory
Melzack, Wall 1965

17. International Anesthesiology Clinics 1971

18. Types of Pain
• Acute vs Chronic vs Cancer
• Somatic vs Visceral vs Neuropathic

19. Somatic Pain
• Intensity (VAS)
• Duration
• Characteristics
• Periodicity
• Localization
• Current and
previous Rx

20. Visceral Pain

21. Neuropathic Pain
• Injury to nerves or
nervous system
• Lancinating/Burning
• Acute and chronic
• Difficult Rx

22. Overview
• Why we suffer pain?
• How we suffer pain?
• Psychology of pain
• Pathological pain
– Acute and Chronic Pain
• Pain Treatment
• Pain Research
• Future Challenges

23. Psychology of Pain
• Cultural factors
• Past experience
• Meaning of the situation
• Attention, anxiety and distraction
• Feelings of control
• Placebo effect
• Psychogenic pain

24. Pain or pleasure?

25. Cultural Factors

26. Past Experience

27. Situation

28. Attention, Anxiety and Distraction

29. Feelings of Control

30. Placebo effect

31. Psychogenic Pain
• Very uncommon
• No such thing as separation of physical and
psychological self
• Somatization
• Munchausen’s disorder

32. Psychology of pain
• Pain is significantly influenced by
psychology
• “It’s only pain”
• “Pain is good for you”
• It’s all in your mind”

33. Overview
• Why we suffer pain?
• How we suffer pain?
• Psychology of pain
• Pathological pain
– Acute and Chronic Pain
– The Burden of Pain
• Pain Treatment
• Pain Research

34. Acute Pain
• How much is there?
• Why treat it?
• How do we treat it?
• What can happen if we don’t treat it?

35. Postoperative Pain Experience:
Results from a National Survey Suggest Postoperative Pain
Continues to be Undermanaged
0
10
20
30
40
50
60
70
80
90
Anypain
Slight
Moderate
Severe
Extreme
Apfelbaum 2003
Warfield 1995

36. Dangers of Poor Pain Management
• Cardiovascular effects
• Respiratory effects
• Gastrointestinal effects
• Immune effects
• CNS effects
• Chronic pain
• Impact on rehabilitation

37. Can acute pain cause chronic pain?

38. 35% Patients had chronic pain one year
after knee replacement
30,000 Knee replacements p.a. in Canada

39. Step 3:
Step 1 and Step 2
strategies +
Use of controlled-release
opioid analgesics
AND/OR
Local anesthetic
techniques
WHO: Pain Management Options
Step 2: Step 1 strategy +
Intermittent doses of
opioid analgesics
Step 1:
Non-opioid analgesics:
Acetaminophen, NSAIDs
AND
Local anesthetic
infiltration
Mild Pain Moderate Pain Severe Pain

40. Barriers to good pain
management
• Knowledge translation: translating
clinical research into practice (15
years)
• Bench to bedside
• Novel basic science research
• Societal attitudes to patients with
pain: Stoicism, “high pain tolerance
etc”

42. Getting Good Pain Management
• Speak to your anesthesiologist
• Ask for regional anesthesia if
possible
• Ask for multimodal analgesia:
combinations of NSAIDS,
acetaminophen, local anesthetic
techniques and other agents
• Focus on pain control not pain relief

44. Prolonging the benefit?
• Efficacy unquestioned
• Cultural and systemic barriers remain
• Further studies examining these areas
needed
A&A 2017

46. Chronic Pain
“An unpleasant
sensory and
emotional
experience
associated with
actual or potential
tissue damage, or
described in terms
of such damage”

47. John Bonica and the
multidisciplinary
pain clinic
• John J. Bonica 1917-1994
• Understood the multidimensional
biopsychosocial nature of pain
• Developed the first multidisciplinary pain
clinic at University of Washington in 1961
• Organized first international pain symposium
in 1973 and helped to develop IASP

48. AKA Johnny “Bull” Walker
Light heavyweight champion of Canada in 1939
and world champion for six months in 1941

49. The Cost of Pain
• Quality of life1
– impaired activities
of daily living
– mood changes
– decreased
involvement in
activities
– Impact on family
• Medical expenses2
• Lost income and
productivity ($65
bn pa)1
1. Won A et al. J Am Geriatr Soc. 1999;47:936-
42.
2. Coda BA et al. Bonica’s Management of
Pain. 2001:222-40.

50. Chronic Pain
• Common
• Pain> 6 months
• Physical
• Emotional
• Social Factors
• Somatic e.g. low
back pain
• Neuropathic: e.g.
Post-herpetic
neuralgia
• Visceral: e.g.
Angina Pectoris

51. Chronic Pain Treatment:
Biopsychosocial Model

52. Pharmacotherapy
• Somatic pain:
NSAIDS,
Acetaminophen,
Opioids,
Antidepressants
(TCAs)
• Neuropathic pain:
TCAs, anticonvulsants,
topical agents

53. • Gabapentin
• Amitryptiline
(limited by side
effects)

54. Psychotherapy
Colin McCartney
FOR PAIN FOR
Locus of control
Encourage independence
Goal setting
Encourage exercise
Encourage return to meaningful activity

55. Injections
• May be beneficial in selected patients
for short periods of time to facilitate
rehabilitation
• Rarely: certain patients may benefit
from implantable devices such as
nerve stimulators and intrathecal
infusions

56. Chronic Pain
• Huge problem
• Costly to society
• Costly to the individual
• Poorly treated
• Much research (basic and clinical)
research required

57. The Mystery of Pain
“An unpleasant
sensory and
emotional
experience
associated with
actual or potential
tissue damage, or
described in terms
of such damage”

60. Managing chronic pain
30 yr old male
Excruciating lancinating pain down leg
Related to nerve injury during surgery

61. Managing chronic pain
Locus of control
Encourage
independence
Goal setting
Encourage exercise
Encourage return to
meaningful activity

62. Cancer Pain
• 60 year-old thoracic surgeon
• Nerve infiltration pain
• Intrathecal infusion

63. Gate Control Theory
Melzack, Wall 1965

64. Future of Pain Research
• Pain genomics
• Pharmacogenomics of pain relief
• Better drugs with less side effects
• Pain psychology
• Pain prevention: patient
identification, better surgery,
transitional pain
• Avoidance/reduction of opioids after
surgery

65. THE LANCET • Vol 353 • May 8, 1999

66. Pain Genetics

67. Pharmacogenomics

68. Genetics of Pain
3 variants (haplotypes) of gene
encoding COMT predicting low,
moderate and high sensitivity to pain
Encompass 96% of humans
Low COMT levels predict high pain
sensitivity and risk of developing
TMD
Inhibition of COMT in rat model
increases pain sensitivity Diatchenko L et al 2005

69. CPSP is likely 50% influenced by genetic
determinants
Identifying genetic basis of CPSP could
lead to significant improvement in
treatment
Prediction of CPSP, Pharmacogenomics
Improved treatments
CJA 2015

71. • 8% of all surgery leads to pain disability at 1
year
• Canada-world leader in opioid prescription
• 80% of heroin addicts report using
prescription pain drugs

72. • Persistent opioid use 3.1% at 6
months after surgery
• ER visits related to opioid use have
tripled in the last 4 years

73. Risk of Developing Persistent
Opioid Use after Major
Surgery
Soneji N et al JAMA Surg 2016

74. Pain Management 2016

75. Transitional Pain Service
Pre-operative review, acute
postoperative and long-term follow up
Patients identified early and referred
Co-ordinated care by pain physicians,
psychologists, physiotherapists and
advanced practice nurses
Bypasses long wait times for chronic
pain clinic

76. Regional anaesthesia
techniques
Systemic drug interventions
Modified surgical
techniques
Focus on postoperative pain
CONTROL and rehabilitation

77. Substance Use Team at TOH
DR. Lisa Bromley, Director
Dr. Mereille St. Jean
Dr. Cathy Smyth
Dr. Helen Tsu

78. Overview
• Why we suffer pain?
• How we suffer pain?
• Psychology of pain
• Pathological pain
– Acute and Chronic Pain
• Pain Treatment
• Pain Research

79. Questions:
cmccartney@toh.ca