Intro to analgesia Flashcards
define nociception
Perception of a noxious stimuli
define pain
Unpleasant sensory or emotional experience associated with tissue damage
Subjective experience with a strong emotional affective component
define chronic pain
> 3 months of pain, despite appropriate treatment
Embedded with emotional, environmental and social factors
3 benefits of pain
- Withdrawal from damaging situations
- Protection of damaged tissue while it heals
- Avoidance of similar experiences in the future
describe the pain pathway
transduction: Afferent nerve endings (nociceptors) translate a noxious stimulus into a nociceptive impulse
transmission: Process of sending signals along the spinal cord to the brain
modulation: Dampening or amplification of pain signals in periaqueductal Gray area (midbrain) and descending pathways (spinal cord)
perception: The conscious awareness of the experience of pain (nociception). Product of transduction, transmission, modulation, emotion and psychology.
describe the pain pathway in terms of the anatomy
site of injury to spinal cord to brainstem to cerebrum
role of a beta fibres
touch
2 roles of a delta fibres
pain and temperature
3 roles of c fibres
pain, temp, touch
difference bewteen the 3 types of nerve fibres
a beta- widest, most myelinated, fastest conduction
a delta: myelinated, medium conduction speed
c fibres- non-myelinated, narrowest
describe the type of pain felt by the a delta and c fibres
a delta- sharp, well-localised pain
c fibres- dull, diffuse, burning pain
how do we classify pain
- Pathophysiology
- Causes
- Duration
- Severity
example of nociceptive pain
tissue damage
example of neuropathic pain
damage to a central or peripheral nerve
describe the type of pain felt for nociceptive pain
ache, sharp, stabbing, throbbing
describe neuropathic pain
Numbness, burning, prickling, electric shock, tingling
examples of causes of pain
mechanical- stretch, compression, chearing, spasm
chemical- internal e.g. inflammation, ischaemia, external e.g. acids, irritants
thermal e.g. burns
mediators that increase pain
Local pain mediators: Kinins e.g. bradykinin, prostaglandins, ATP
Modulators of the pathway: substance P, CGRP, Glutamate
mediators that decrease pain
modulators of the pathway- endogenous opioids e.g. beta-endorphin, GABA, serotonin, noradrenaline
problems with assessing pain
Subjective/qualitative
5 ways to approach pain relief
treat underlying cause non-pharmacological measures analgesia adjuvant treatments complementary medicine
types of analgesic drugs
Non-opioid (e.g. paracetamol/NSAIDs)
Weak opioids (e.g. codeine, dihydrocodeine, tramadol)
Strong opioids (e.g. morphine, diamorphine, fentanyl)
Adjuvants
clinical uses of analgesics
Perioperative pain relief
Medical and surgical emergencies
Palliative care
Management of chronic conditions e.g. rheumatoid arthritis and pain syndromes e.g. lower back pain
describe the WHO analgesic ladder
mild pain: non-opioids e.g. paracetamol +/- NSAID
moderate pain: weak opioids e.g. codeine
severe pain: strong opioids e.g. morphine
3 examples of opioids
morphine, tramadol, codeine
MOA opioids
Mu receptors. G-protein coupled receptor. CNS. Reduce sympathetic response to pain.
therapeutic effects of opioids
Analgesia, euphoria, sedation, anti-tussive
side effects of opioids
Drowsiness, Respiratory depression, constipation, N+V, hypotension, itching, coma, pupillary constriction
Addiction, tolerance and physical dependence
examples of NSAIDs
Ibuprofen, naproxen, diclofenac, aspirin
MOA of NSAIDs
Cyclooxygenase inhibition (COX1/COX2) inhibit production of prostaglandins in periphery and spinal cord
therapeutic effects of NSAIDs
anti-inflammatory, analgesic, antipyretics, anti-thrombotic
unwanted side effects of NSAIDs
Gastric ulcers and bleeding, N+V, Kidney injury, rashes, MI and stroke (?via hypertension), bronchospasm
examples of adjuvants
antidepressants e.g. amitriptyline, corticosteroids, neuroleptics, local anaesthetics, muscle relaxants
5 examples of neuropathic agents
tricyclic antidepressants e.g. amitriptyline
anti-epileptic drugs e.g. gabapentin, pregablin, carbamazepine
ketamine
cannabinoids
botox
define hyperalgaesia
increased amount of pain associated with a mild noxious stimulus
define allodynia
pain evoked by a non-noxious stimulus
NICE guidelines for chronic pain
Patient-centred care
Good communication
Antidepressants can be considered
Acupuncture, psychotherapy and group exercise programmes (NICE 2020)
Does not recommend paracetamol, non-steroidal anti-inflammatory drugs, benzodiazepines, opioids, anti-epileptic drugs, local anaesthetics, ketamine and antipsychotics.
