7.1 Acute Pain Flashcards
Pain is defined
Pain is defined by
the International Association for the Study of Pain
as
‘An unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage’
Is pain a simple issue
It is a
multifaceted issue,
having sensory and
affective (emotional) component.
Hence objective assessment of pain is difficult. Therefore, pain rating scores
or questionnaires are often used.
assessing acute pain
Verbal category rating scale
Visual analogue scale
Numerical rating scale
Verbal category rating scale
Verbal category rating scale
None, mild, moderate, severe, unbearable or 1–5
Visual analogue scale
Visual analogue scale
10-cm line with anchor points of
‘no pain’ and ‘worst pain imaginable’ at either end;
most common simple scale used in pain research
Numerical rating scale
Numerical rating scale
Similar to a visual analogue scale,
with the two anchors of ‘no pain’ and ‘worst pain
imaginable’,
but has numbers across the scale from 0 to 10
(making an 11-point scale)
Pain questionnaires:
Pain questionnaires:
multidimensional and
more common in chronic pain settings
McGill Pain Questionnaire, Brief Pain Inventory, The Memorial Pain Assessment Card, Neuropathic Pain Scale, Pain diary and so forth
Simple pain rating scales
Advantages
Simple and easy for the patient
Robust and reproducible
Rapidly recorded
Useful for audit
Simple pain rating scales
Disadvantages
Unable to detect subtle differences
Less suitable for research (semiqualitative)
Not suitable for parametric tests
Non-parametric tests must be used (larger samples)
Response can vary
(in same and among different patients)
Subjective measures (inaccurate)
Nociceptive or pain pathway what type of pathway
Nociceptive or pain pathway is an
afferent pathway involving
Three neurons
Two pathways:
Modulation
Three neurons
First order:
peripheral pain fibres (Aδ and C)
Second order:
nociceptive specific neurons
(Lamina I, II) and
wide dynamic range neurons
(WDR respond to both nociceptive and
innocuous pain; lamina III–VI)
Third order:
thalamic projections to somatosensory cortex.
Two pathways:
Two pathways:
Dorsal column–medial lemniscus pathway
(touch and proprioception)
Anterolateral spinothalamic tract
(pain and temperature).
Modulation
Modulation
Spinal: most common and at dorsal horn of spinal cord
Supraspinal centres.
Pain processing involves:
Pain processing involves:
Transduction
Transmission
Modulation
Perception
Transduction:
Transduction:
conversion of noxious stimuli into action potentials.
Transmission
Transmission:
conduction of action potential through neurons
Modulation:
Modulation:
augmentation or attenuation of afferent transmission.
Perception
Perception:
sensory and affective by integration of inputs in the
somatosensory cortex and limbic system.
FIGURE 7.1 Steps involved in pain processing pathways
FIGURE 7.1 Steps involved in pain processing pathways
Excitatory neurotransmitters
Excitatory neurotransmitters –
glutamate, substance P, calcitonin gene–related peptide, neurokinins, histamine, serotonin, bradykinins, prostaglandins and so forth.
Inhibitory neurotransmitters
Inhibitory neurotransmitters –
in descending modulation system:
Cerebral – GABA, noradrenaline and serotonin
Spinal – GABA and glycine
The gate control theory was presented by
explain
The gate control theory was presented
by Wall and Melzack (1965) to
explain factors
influencing pain perception.
It states that pain is a function of
It states that pain is a function of
It states that pain is a function of
the balance between the
information through
large nerve fibres (Aβ) and
that through small nerve fibres (C).
Gate theory and Ab fibres
how does this affect pain
The collaterals of the large sensory
fibers (Aβ) carrying cutaneous
sensory input
activate inhibitory interneurons,
which inhibit (modulate)
pain-transmission information
carried by the small pain fibres (C)
transcutaneous electrical nerve stimulation is a clinical application of
this theory.
