Wk 1 Pain & Anaesthesia Flashcards
Clinical signs indicative of opioid overdose
bradycardia, miosis, hypotension
A 20 yr old female pricked her left hand while sewing. Which area of her brain would have received the pain signals and perceived them as pain?
right somatosensory cortex (pain stimuli transmitted to opposite side of somatosensory cortex)
Describe the mechanisms of action of morphine at the receptor level and how its effect relates to the body’s endogenous system of transmitting and regulating pain
Opioid receptor agonist - morphine activates both the μ (Mu) and ᴋ (Kappa) receptors. Endorphins and enkephalins are endogenous opioids produced by the body that attach to opioid receptors on cell membrane of the afferent neuron and inhibit the release of excitatory neurotransmitters - enhances endogenous opioid response to reduce pain
What is drug tolerance and what does it mean for chronic pain management?
The gradual decrease in the effectiveness of a drug given repeatedly over a period of time. Prolonged administration causes cellular adaptations leading to tolerance and dependence. It means the opioid dose needs to gradually increase to manage the same amount of pain.
What are some of the possible undesired effects of opioids?
- suppression of respiratory centre (↓ RR & SPO2)
- sedation & sleep
- euphoria & dysphoria
- miosis
- N&V
- hypotension & bradycardia
- tolerance, dependence, addiction
- constipation
- spasms of sphincter muscle (delayed gastric emptying, urinary retention)
types of adjuvant medications used to manage neuropathic pain
- tricyclic depressants (e.g. amitriptyline)
- membrane-stabilising agents (e.g. anticonvulsants e.g. gabapentin, pregabalin)
- often used in combo with opioids for cancer-associated nerve pain
The rationale for the use of non-opioid analgesics such as paracetamol, anti-depressants and anticonvulsants in chronic pain management
- To reduce the amount of opioid analgesic used to manage the same level of pain
- Reduce dependency and reliance on opioid analgesics
- Can delay dose increases overtime from opioid tolerance
- To manage breakthrough pain
What is the drug used for opioid overdose? What is the mechanism of action? Is it short or long-acting?
Naloxone (Narcan), opioid/narcotic antagonist. Reverses opioid overdose by throwing opioid analgesic off receptors. Short-acting while opioids are often long-acting so additional doses of naloxone may be required
Altered organ dysfunctions in relation to opioid overload (liver and renal)
liver disease: may accumulate active drug and increase depressant effects of opioids
renal disease: can extend half-lives of opioids that are excreted in an active form and cause respiratory depression
Morphine and fentanyl - which is hydrophilic and which is lipophilic and how does that affect the route of administration and onset of action?
morphine is quite hydrophilic - crosses slowly into CNS. Fentanyl is highly lipophilic - rapid onset and short duration of action, administered subcut and transdermally.
morphine
opioid analgesic, µ and κ receptors agonist
codeine
Weak opioid, metabolised to morphine, has cough suppressing effect, for mild-to-moderate pain
fentanyl
highly potent analgesic used in moderate-to-severe pain, used during anaesthesia, comes in various formats, including transdermal patch and lozenge
methadone
long-half life thus risk of accumulation, monitor for dependence
tramadol
weak opioid
