Pain Flashcards
What is the definition of pain?
An unpleasant sensory and emotional experience associated with actual or potential tissue damage.
What nerve fibres are responsible for immediate pain and persisting pain?
Immediate - a delta,
Persisting - C fibres
what is the withdrawal reflex?
It occurs where there is a painful stimulus. This information travels to the spinal cord and causes a flexor reflex and a crossed extensor reflex which causes the limb/body part to move away from the stimulus.
How do we perceive pain?
Via spinothalamic tracts.
What are features of A-delta fibres?
They are myelinated.
Conduct sharp, localised pain.
Fast Conduction.
Minority of nociceptors
What are features of C fibres?
Unmeylinated.
Conduct dull, throbbing and diffuse pain.
Majority of nociceptors,
Slow conduction
Explain the transduction of pain
1st there is conversion of noxious stimulus (heat, mechanical or chemical) into action potential in a nociceptor. Therefore the nociceptors respond to stimuli that will potentially damage tissue. The sensation may extend beyond point of assault
Explain the transmission of pain?
Occurs via spinothalamic tracts. First order neurons release Glutamate, substance P or CGRP which binds to either AMPA, NMDA or G-protein coupled receptors to cause a response. There is no single excitatory substance or pain receptor
How can pain be modulated?
Via decending inhibition which has 3 mechanisms; GABA and glycinergic interneurons, decending inhibition from PAG, rostral ventral medulla and dorsal horn, and lastly endogenous opioids.
Also modulated by higher order brain function
What is the gate control theory?
Theory of pain modulation. Based on presynaptic inhibition of pain information produced by mechanical stimuli (mechanoreceptor fibres excite an inhibitory interneuron which inhibits nociceptor fibres before they synapse at the spinal cord)
Describe what can occur when the neuronal activity of pain becomes a conscious experiance?
- Past experiences, current situation and understanding modulate the conscious experience.
- Reticular system then elicits an autonomic response and the limbic system links perception of pain with mood
Describe features of visceral pain?
- Visceral nociceptors respond to distention or ischaemia,
- The pain is more diffuse (less well localised).
- Referred pain can occur
What are associated symptoms of pain?
-Sweating,
-Pallor,
-Nausea,
-Tachycardia,
-Hypertension
(THINK AUTONOMIC NS)
Describe the prevention and preparation of pain
- Anticipation and simple adjustments (let the patient know they may experience some pain).
- Distraction,
- Education,
- Challenge patients misconception,
- Rebranding (eg, tender or pressure)
How do you assess pain?
- SOCRATES,
- Red flags,
- Co-morbidities,
- Psycho-social history and awareness of yellow flag
What is the WHO treatment of cancer pain ladder?
1- Mild pain give simple analgesics.
2 - Moderate pain give mild opioid and continue analgesics,
3 - Severe pain give strong opioid and continue simple analgesics
What drug is used for neuropathic pain?
Amitriptyline or gabapentin
What is the difference with the WHO treatment lader for acute nociceptive pain?
- Start with the strong opioids and continue with analgesics and then work down to mild opioids and simple analgesics and then use simple analgesics on their own
What is neuropathic pain?
Pain arising as a direct consequence of a lesion or disease affecting somatosensory system. Spontaneous and evoked pains and allodynia
What are some causes of neuropathic pain?
Trauma, diabetic neuropathy, postherpetic neuralgia, trigeminal neuralgia and post-stroke neuralgia.
What is the definition of chronic pain?
Pain persisting beyond the usual healing time of the acute injury (usually beyong 12 weeks)
What causes chronic pain?
Peripherally there are prolonged inflammatory responses which results in decreased pain threshold in primary afferents, increased production of substance P and CGRP and recruitment of NMDA receptors.
Spinal cord - Changes in gene and receptor expression in DRG and dorsal horn neurons
What are the non-modifiable risk factors for chronic pain?
- Gender,
- Age,
- Genetic predisposition,
- Lower-socio-economic status,
- History of abuse,
- Compensation from having said injury
What are the modifiable risk factors for chronic pain?
- Past experiences of pain,
- Anxiety and depression,
- Catastrophizing beliefs,
- surgical approach,
- attitudes,
- communication
