Pain and its management Flashcards
(42 cards)
What is pain?
Unpleasant sensory and emotional experience associated with actual or potential tissue damage, caused by cytokines
Effects of pain
- Danger alert - withdrawal
- Protection - rest injury
- Prevention - learning to avoid injury again
- Suffering
- Impaired function (motor, respiratory, CVS)
Pain pathway
- Pain recognition
- Peripheral conduction
- Spinal processing
- Ascending transmission
- Relay to cortex
- Motor homunculus
- Sensory homunculus detects where pain occurs
What are nociceptors?
- Nociceptors are bare nerve endings, most in skin but some are dormant or in deeper tissues (which are activated by injury)
- Respond to several stimuli (e.g. mechanical/thermal/chemical)
- Sensitized by inflammatory mediators (bradykinin, histamine, prostaglandins)
- Limiting prostaglandins limits pain
What are the two responses to pain?
Fast and slow
Characteristics of fast response to pain
A delta fibres
Large and myelinated
Up to 10m/sec
Sharp, stabbing pain
Characteristics of slow response to pain
C fibres
Small, unmyelinated
1.2 m/sec
Aching, burning
Is the spinal transmission of pain contralateral or ipsilateral?
Contralateral
Is a withdrawal reflex contralateral or ipsilateral?
Ipsilateral
Pathway of visceral pain
Autonomic nerves
What is referred pain?
Pain in one area of the body is felt in another
What is neuropathic pain?
Results from nerve damage e.g. trauma/infection (e.g. Herpes zoster virus)
Difficult to treat
Often becomes chronic
Where is local anaesthetic administered?
Site of injury
What are local anaesthetics?
Bases - proton acceptors
Is lidocaine short or long lasting?
Short
Is bupivacaine short or long lasting?
Long
Characteristics of local anaesthetics
- Ammonium group picks up proton
- Information sent down nerve - sodium enters cell - channel blocks and causes depolarization - depolarization travels along nerve
- Administered extracellularly in ionized from containing proton, it loses the protons and transfers across the membrane where it picks up the proton again
- This ‘blocks up’ the sodium channel which prevents depolarization and transmission of brain signal
What is a spinal block?
- Epidural goes outside of dura
- Action potential blocked at that level
- Paralysis/block of cauda equina
- Moves down by gravity - if moves up could affect intercostals and breathing
What does PGE2 do?
Pain sensitization, renal arteriole dilation, ductus arteriosus patency
What does PGF2-alpha do?
Broncoconstriction, uterine contraction
What does PGI2 do?
Inhibition of platelet aggregation, vasodilation
What does TXA2 do?
Activates platelet aggregation, vasoconstriction
What do steroids do?
Limit the transfer of phospholipids to arachidonic acids
What do NSAIDs do?
Inhibit cycle-oxygenase