Pain Flashcards
(17 cards)
what are the name of the receptors that detect pain
noiciceptors
What are the two different fibres that carry pain signals called
a- delta and c
what are the difference between a delta and c fibres
A- primary, no interneuron, mylenated, sharp/ stinging pain, mechanical
C- secondary pain, interneuron and non mylenated to delay response, burning/ aching pain, mechanical/ chemical/ thermal pain
Describe how pain gets from finger tip to sensory cortex
noiciceptors are triggered, mast cells release inflammatory mediators such as arachidonic acid and histamine, afferent neurons carry electrical signals to spinal cord. All pre-synaptic neurons meet at dorsal root ganglion then enter spinal cord through dorsal horn, the grey matter aspect of spinal cord, impulses cross the synapse then travel up the spinal cord to the thalamus, the information is processed then spread to relevant areas of the brain such as the sensory cortex in the parietal lobe.
what is the pain gate theory
there is a limited number of electrical signals, if the non-pain signals are stimulated it may outcompete the pain signals and therefore reduce the pain signals being passed through the dorsal horn
what are some examples of non pharmacological pain relief
massage, heat therapy, transducer electrical therapy, reassurance
where in the brain is pain localised
somatosensory cortex
how does ibuprofen work
Mast cells at the site of injury degranulate and release chemicals called inflammatory mediators. As the concentration of arachidonic acid increases, the body converts it into prostaglandins by releasing cyclooxygenase (COX) enzymes. The prostaglandins lower the threshold of nociceptors which increases the pain felt by the patient. The COX-2 enzyme is thought to increase pain transmission. NSAIDs work by preventing the COX enzymes from converting arachidonic acid into prostaglandins.
what are the four pain medications that a paramedic can hold
ibuprofen, paracetamol, morphine, entonox
When would ibuprofen be used (and when would it not)
arthritis, soft tissue injury
it would not be used for neuropathic pain due to it not treating the pain itself but instead limiting the inflammatory markers present peripherally- pain that comes from within cannot be treated as it only works on the markers on the surface, pain on the surface such as soft tissue injuries will be well treated
what are some side effects of ibuprofen
Ibuprofen can induce gastrointestinal disturbances that include:
- discomfort
- nausea
- diarrhoea
- occasional bleeding and ulceration
Other known side effects include:
- hypersensitivity reaction (such as rashes and bronchospasms)
- headaches
- dizziness
- nervousness
- depression
- hypertension
Note: use with caution in patients over 65 years of age who have not recently used and tolerated NSAIDs.
How does paracetamol work
Paracetamol works in a similar way to ibuprofen by preventing the synthesis of prostaglandins.
Its main site of action is within the central nervous system and it is thought to reduce pain through interactions in the brain.
Paracetamol is also useful in treating high temperature and fever, as fever is caused by elevated levels of prostaglandins acting on the hypothalamus (responsible for control of thermoregulation) and increasing the firing rate, resulting in increased heat production.
What level of pain would paracetamol be given
Paracetamol can achieve effective pain relief in the treatment of mild to moderate pain and pyrexia.
If the patient is in severe pain, paracetamol should be co-administered with morphine.
what are the theories of how entonox work
Some believe that Entonox influences the pain centres of the brain by activating the peri-aqueductal grey area of the mid-brain. Once inhaled, Entonox stimulates the release of opioid peptides and serotonin, which then act on opioid receptors.
Others suggest that Entonox has an analgesic effect by inhibiting the NMDA receptor (NMDA receptors are involved in many CNS pathways).
What are some cautions when using entonox
Paramedics should be cautious in patients with COPD where there is chemoreceptor sensitivity as the high concentration of oxygen may cause respiratory depression and an increase in PaCO2.
Entonox is contraindicated in all cases where there is trapped air within the body as gaseous expansion can be dangerous.
How does morphine work
Morphine acts on mu (µ) opioid receptors that are located in many areas of the body.
1. Firstly, it prevents cell depolarisation within the posterior dorsal horn by closing calcium channels and opening potassium channels on pre-synaptic neurons. This works to stop the action potential (electrical conduction) reaching the somatosensory cortex, and hence the perception of pain.
2. Secondly, it stimulates the release of β endorphins at the spinal cord through stimulation of the body’s own pain defence mechanism. Evidence suggests that morphine may even be working at peripherally injured sites although the mechanism for this action is as yet unclear.
What are the contraindications of morphine
hypersensitivity
hypotension
resp depress
infants under 1
head injury GCS <9 AVPU(P)
