Lecture
Pain
● Acute: soft tissue damage, infection, inflammation
● Chronic: linked with long term illness or disease, may have no apparent cause, can
trigger other issues, difficult to assess and diagnose
○ Types of chronic pain
■ Chronic benign: 6month+, intractable to treatment (ex low back pain)
■ Recurrent acute pain: series of intermittent episodes (migraine)
■ Chronic progressive: 6 month+, increasing severity (rheumatoid
arthritis)
Prevalence and impact
● Affect 1/10 canadians
● Rates are even higher for those over 65 and women
● Costs in healthcare utilization and lost productivity are approx. 10$ billion annually
● Over 4$ billion spent annually on OTC meds (2007)
Why pain is difficult to study
Factors that influence symptoms can include
● Cultural differences
○ Some cultures report pain sooner and more intensely
○ Linked to cultural norms
● Gender
○ Women Are more sensitive to pain
○ Menstrual cycle is an indirect contributor
○ Linked to differences in emotional processing of pain
● Coping styles
○ Catastrophizing heightens pain experience
■ Predicts greater post-surgical pain
■ More intense labour pain
○ Resilience and positive emotions lowers pain
Measuring pain
● Personal report of pain (acute/chronic) can be very subjective
● There is no “gold standard” in measuring pain outcomes
● More commonly used assessment tools include:
○ Verbal reports: pt uses their experience and vocabulary to describe pain,
throbbing pain vs shooting pain vs dull ache, McGill Pain Questionnaire
(MPQ), 1975; Pain Catastrophizing Scale (MPQ), 1995
● Pain behaviour
○ Observable behaviours that arise from pain
1) Facial and audible expressions of distress
2) Distortions in posture and galt
3) Negative affect
4) Avoidance of activity
● Pain is viewed as a complex biopsychosocial even involving:
○ Psychological
, ○ Behavioural
○ Physiological
Physiology of pain
● Nociception
○ Refers to the system that carries signals of the damage and pain to the brain
○ Nociceptive neurons have cell bodies in the dorsal root ganglia
○ Can detect mechanical, thermal and chemical stimuli
○ Polymodal nociception
○ Nociception transmission: bidirectional axons synapse in dorsal horn of spinal
cord
○ Signal and continues to brain where its processed
Nociception occurs through several types of peripheral nerve fibers
Theories of pain
● Traditional model: suggested pain resulted from transmission of pain signals to the
brain; degree of pain was dictated by tissue damage
● Gate control theory
○ Proposed that psychological factors contributed to pain experience
○ Neural pain gate can open/close to modulate pain signals to the brain
○ A-delta and C fibers open the gate, A beta fibers close the gate
○ Gate control theory: other factors can contribute to opening/ closing of the
gate
Pain
● Acute: soft tissue damage, infection, inflammation
● Chronic: linked with long term illness or disease, may have no apparent cause, can
trigger other issues, difficult to assess and diagnose
○ Types of chronic pain
■ Chronic benign: 6month+, intractable to treatment (ex low back pain)
■ Recurrent acute pain: series of intermittent episodes (migraine)
■ Chronic progressive: 6 month+, increasing severity (rheumatoid
arthritis)
Prevalence and impact
● Affect 1/10 canadians
● Rates are even higher for those over 65 and women
● Costs in healthcare utilization and lost productivity are approx. 10$ billion annually
● Over 4$ billion spent annually on OTC meds (2007)
Why pain is difficult to study
Factors that influence symptoms can include
● Cultural differences
○ Some cultures report pain sooner and more intensely
○ Linked to cultural norms
● Gender
○ Women Are more sensitive to pain
○ Menstrual cycle is an indirect contributor
○ Linked to differences in emotional processing of pain
● Coping styles
○ Catastrophizing heightens pain experience
■ Predicts greater post-surgical pain
■ More intense labour pain
○ Resilience and positive emotions lowers pain
Measuring pain
● Personal report of pain (acute/chronic) can be very subjective
● There is no “gold standard” in measuring pain outcomes
● More commonly used assessment tools include:
○ Verbal reports: pt uses their experience and vocabulary to describe pain,
throbbing pain vs shooting pain vs dull ache, McGill Pain Questionnaire
(MPQ), 1975; Pain Catastrophizing Scale (MPQ), 1995
● Pain behaviour
○ Observable behaviours that arise from pain
1) Facial and audible expressions of distress
2) Distortions in posture and galt
3) Negative affect
4) Avoidance of activity
● Pain is viewed as a complex biopsychosocial even involving:
○ Psychological
, ○ Behavioural
○ Physiological
Physiology of pain
● Nociception
○ Refers to the system that carries signals of the damage and pain to the brain
○ Nociceptive neurons have cell bodies in the dorsal root ganglia
○ Can detect mechanical, thermal and chemical stimuli
○ Polymodal nociception
○ Nociception transmission: bidirectional axons synapse in dorsal horn of spinal
cord
○ Signal and continues to brain where its processed
Nociception occurs through several types of peripheral nerve fibers
Theories of pain
● Traditional model: suggested pain resulted from transmission of pain signals to the
brain; degree of pain was dictated by tissue damage
● Gate control theory
○ Proposed that psychological factors contributed to pain experience
○ Neural pain gate can open/close to modulate pain signals to the brain
○ A-delta and C fibers open the gate, A beta fibers close the gate
○ Gate control theory: other factors can contribute to opening/ closing of the
gate
