clinical aspects of pain Flashcards
define pain
unpleasant sensory and emotional experience associated with actual or potential tissue damage
can you experience pain when you are unconscious
No
how is pain classified
duration- acute/chronic
pathophysiology- nociceptive and neuropathic
what is the most common cause of acute pain
trauma and injury.
what defines chronic pain (timing)
• Pain extends 3-6 months beyond onset
why do we get pain
assists wound repair in- acute pain.
when does pain resolve
upon healing in acute
doesn’t in chronic
what physiologic system regulates the nocioceptive pain mechanisms
opioidergic system
what causes noiceptive pain
tissue damage and painful stimuli at noiceptors.
what are the main benefits of acute pain
part of trauma response, protective to avoid further damage, learning experience.
what are the main adverse effects of acute pain
humanitarian issues, cardiovascular stress, respiratory compromise, hyper coagulation.
what factors effect a persons perception of pain
anxiety depressed gender- socliasation and gonadotropins circadian variation climatic conditions
how is pain assessed
Ideally self reported by patient.
Visual analogue- pain scale
Assess pain at rest and during movement.
what pain management (medication) is used for pain
Non-opiods- parecetamol, aspirin, NSAID.s COX-2 inhibitors
Opiods for mild to moderate pain- codeine, dihyroceodeine, tramadol.
Opiods for moderate to severe pain- morphine, fentanyl, hydromorphone, buprenorphine, methadone.
What is the mechanism of action of NSAID’s
COX inhibitors (act peripherally), decrease prostaglandin synthesis
What is the mechanism of action for opiods
Act at 2 sites in spinal cord
Presynaptically pain signal transmission is reduced
Postsynaptically membrane is hyperpolarised, decreasing the probability of action potential generation
what are the main side effects of non-opiods
due to change in amount of prostaglandins
o Cardiovascular side effects
o Renal side effects
o GI side effects.
what is the main side effects of paracetamol
liver toxicity.
what is the mode of action of paracetamol
inhibit central prostaglandin synthesis
what examples of non-opiods
parecetamol, aspirin, NSAID.s COX-2 inhibitors
what examples of opiods (mild to moderate pain)
codeine, dihyroceodeine, tramadol.
what examples of opiods (moderate to severe)
morphine, fentanyl, hydromorphone, buprenorphine, methadone.
what are the side effects of opioid analgesics
nauseas, vomiting, constipation, vertigo, sosmnolence, dry skin and pruritus.
where are opiod receptors present
found in bowel, pupillary light reflex, control of respiration, chemoreceptor
what is the earliest prediction of respiratory depression which is a side effect of respiratory depression
sedation
why must opiod levels be measured accurately in analgesia
different people will have different plasma levels of opiods in their blood.
what 2 drugs must never be used in renal failure
morphine or codeine
what 2 drugs can be used in renal failure
fentanyl and oxycodone
what are the main benefits of a epidural
High quality pain relief Improved pulmonary function Reduced chest infection and sepsis Reduced cardiac morbidity. Anticipated block from epidural- can be specifically targeted for a specific space.
what drug is commonly used in cancer treatment
morphine
where do spinal opiods work
Act on the dorsal horn
which reaches the brainstem lipophillic or lipophobic morphine
lipophobic
define neuropathic pain
pain due to damage in pain stimulating system e.g stroke or Type II diabetes.
what are the main characteristics of chronic pain
Intense pain
Recurrent pain
Associated with severe co-morbidity and poor quality of life.
define allyodonia
pain to a non painful stimulus/
what are the main features of neuropathic pain
Pain different from normal everyday pain
Pain in absence of ongoing tissue damage
Pain in area of sensory loss!
Paroxysmal or spontaneous pain!
Allodynia
Hyperalgesia
Dysaesthesia
define hyperalgesia
increased pain in response to painful stimuli
define dysaesthesia
unpleasant abnormal sensations “ants crawling on the skin”
what drugs are used to treat neuropathic pain
NSAIDs –poor
Antidepressants- inhibits neuronal reuptake of noradrenaline and serotonin.
Anticonvulsants- dampens down the neuronal pathways.
Opiods
Membrane stabilising drugs
Topical drugs
Other.
what symptoms are antidepressants used for
neuropathic, complex regional pain and tension headache.
what is the mode of action of antidepressants
inhibition of neuronal reuptake or noradrenaline and serotonin.
what are the side effects of antidepressants
constipation, dry mouth, somnolence, heart rate, insomnia.
what are the symptoms for which anticonvusants are used
neuropathic pain
what is the mode of action of antidepressants
o gabapentin- binds presynaptic voltage dependent calcium channels (excreted renally, not metabolised)
o Pregabalin- interacts with special N type calcium channels.
o Carbamazepine- blocks Na and Ca channels. (rashes and liver damage)
what are the side effects of anticonvulsants
sedation, dizziness, ataxia, peripheral odema, nausea, weight gain
what machine is used for spinal cord stimulation
TENS machine
