Lecture one (Pain)-Exam 1 Flashcards
What is the definition of pain (both for american academy of pain medicine and margo mccaffery)?
- “An unpleasant sensation and emotional response to that sensation”-AAPM
- “Pain is whatever the person says it is, existing when and where the person says it does”-Margo
What is transduction?
Process that converts a pain stimulus to biologic signal
Transduction
- What are the different tissue injuries?
- What does these tissue injuries cause?
Tissue injury
* Mechanical – pinch, stab
* Thermal - burn
* Chemical – strong acid
Inflammatory response releases chemicals that stimulate sensory nerve fibers
* Prostaglandins
* Histamine
* Cytokines
* Bradykinins
What is transmission?
pain action potential from site of injury to cortex of brain
Ascending tract:
* Which horn?
* What happens in the ascending tract?
* Order neurons?
- Dorsal horn of spinal cord
- Stimulated sensory nerve fibers send impulse / action potential to the spinal cord
- 1st, 2nd, 3rd order neurons
What are the first order neuron?
Site of stimulus to dorsal horn of spinal cord
What is the second order neuron
Dorsal horn of spinal cord -> through brainstem -> to thalamus
* Crosses to opposite side of spinal cord
* Travels through spinothalamic tract (pain track)
Right hand injury=left side of brain is processing it
What is 3rd order neuron?
- Thalamus to cerebral cortex
- Region of cortex stimulated correlates to site of injury
- Opposite side stimulated
Impulse transmitted primarily by what two nerve fiber types?
- A-delta – thin, poorly myelinated, fast, sharp, stabbing, localized
- C – thin, unmyelinated, slow, dull, aching
What are the primary NTs of pain? What is it stimulated by?
Primary neurotransmitters of pain – stimulated by chemicals released during pain response
* Glutamate
* Substance P
Explain the whole process of transmission
What is perception?
Consciously perceiving pain and its characteristics
* Location
* Intensity
* Type
What does perception stimulate and result in?
- Stimulates emotional response
- Results in response
Where is perception processed in the brain?
Somatosensory cortex: different regions correspond to different parts of the body
What is modulation?
How the pain signal is altered by the descending pathway
Explain how pain signal is altered by the descending pathway?
- Descending modulatory fibers generally help to inhibit pain signals
- Noradrenaline/serotonin primary neurotransmitters
- Control (inhibit) communication between the 1st and 2nd order neuron
MODULATION
What are the effects of epinephrine and 5-HT?
Inhibit release of substance P and glutamate from presynaptic vesicles
Stimulate interneuron responsible for releasing endogenous opioids (enkephalin)
* Inhibits release of substance P and glutamate from presynaptic vesicles
* Inhibits postsynaptic neuron from depolarizing
What is nociceptive and neuropathic pain?
Nociceptive: caused by an injury to body tissues
* e.g., post-op, trauma, procedural pain
Neuropathic: caused by damage to or dysfunction of nerves
* e.g., neuropathies, post herpetic neuralgia, phantom limb pain
may be a combination
What is psychogenic pain?
psychologic factors such as headaches or abdominal pain caused by emotional, psychological, or behavioral factors
- What is break through pain?
- What are the three different types?
Break through – pain that occurs scheduled pain medications
* Spontaneous: no identifying factor -> give PRN medication
* Incident: after some stimulus -> give PRN medication
* End of dose: increase dose or frequency of scheduled medication
What are the two subtypes of nociceptive pain? What does this type of pain respond well to?
What are the two subtypes of neuropathic pain? What does this type of pain respond well to?
What is acute pain? (how long and associated with what)
- Of short duration; self-limited (< 3 months)
- Often associated with objective physical signs
Chronic pain:
* length?
* may begin as what?
* what is the cause?
* S/S?
- > 3 months
- May begin as acute pain but continues or recurs over a prolonged period
- Cause often unknown
- Does not look like in pain
What are non-pharmacotherapy treatments?
- Heat / cold
- Massage
- Acupuncture
- Physical therapy
- Stretching / yoga
- Exercise
- Hypnosis
- Biofeedback
What are the first line nonopioid analgesics?
acetaminophen and NSAIDs
Acetaminphen and NSAIDs
* What level of pain do these work for?
* Severe what?
* _ sparing?
* First line for what?
* What are the two dosages?
* What effect is there?
Explain the mechanism of action of NSAIDs to get the two final enzymes
- Phospholipase A2 released in response to inflammation
- Converts phospholipids into arachidonic acid
- Arachidonic acid is a substrate for two enzymes: 5-lipoxygenase (5-LOX) and Cyclooxygenase (COX-1 and COX-2)
NSAID MECHANISM OF ACTION
COX-1:
* Is the enzyme around all the time or needs to be activated?
* What are two eicosanoids are released? What are their actions?
- COX-1 is alaways circulating and active
- Release Thromboxane which promotes platelet aggregation
- Release prostaglandins and prostacyclins which secretes protective gastric mucosa and maintains renal blood flow (vasodilation)
COX-2:
* Is the enzyme around all the time or needs to be activated?
* What does it mediate?
- COX-2 activated at sites of inflammation
- Mediates inflammation, pain, and fever
What does NSAIDs block? What does this reduce?
NSAIDs block COX-1 and COX-2
* Reduce prostaglandin, thromboxane, prostacyclin synthesis
* Reduce inflammation, pain, and fever
What are the two NSAID classification?
Irreversible COX inhibitors (cannot reverse effects on platelets)
* Aspirin
Reversible COX inhibitors
* Non-selective: Inhibit COX-1 and COX-2
* Selective: Inhibit COX-2
What are the examples of cox1 selective, non-selective and cox-2 selective?
What is the most common adverse effect of NSAID? Explain why this happens
- MC adverse effect = gastric ulcers
- This is because of the inhibition of prostaglandins and prostacyclin which decrease GI mucous production, decreases GI blood flow that leads to Ulcer formation
- This is more common with COX-1 inhibition NSAIDs
What are other GI adverse effects of NSAIDs?
- Dyspepsia
- Abdominal pain
- Nausea / vomiting
NSAID adverse effects
- What is the effects of NSAIDS on blood?
- What drugs have the stongest effect on blood?
Increased bleeding risk
* Due to inhibition of thromboxane which decrease in platelet aggregation
Strongest effect with:
* Aspirin – irreversible inhibition
* Increased COX-1 selectivity
- What are the effects of NSAIDs on clotting and cardiovascular events? Explain the reason why
- What drug is this more common with?
- Increased clotting risk and cardiovascular events
- MC with increased COX-2 selectivity
- Less COX-1 inhibition = less inhibition of thromboxane A2
- More COX-2 inhibition = more vasoconstriction (dt decrease prostacyclin)
What are the effects of NSAIDs on the kidneys? Explain the reason why
Kidney effects
* NSAIDs inhibit prostaglandins -> VASOCONSTRICTION
Causes Decrease renal blood flow
* Kidneys think blood pressure is low and retain fluid -> increase blood pressure / peripheral edema
Causes increase risk of renal injury
* Effect more pronounced with underlying decrease in renal perfusion
What is the effects on skin with NSAIDs?
Rash – hypersensitivity reactions rare / cross sensitivity
What are the different black box warnings for NSAIDs?
- What are the contraindications for NSAIDs?
- What are pregnancy consideration?
Contraindications:
* Aspirin allergy – watch for patients with Samter’s triad
* Peptic ulcer. GI bleed or perforation
* Advanced renal impairment
* Cerebrovascular bleeding
Pregnancy Considerations
* Avoid if possible; especially in first and third trimesters
Ketorolac:
* More or less potent?
* What is this drug used for management?
* What is not recommend?
- More potent
- Short-term management of moderate to severe acute pain requiring opioid-level analgesia
- Do not recommend use of oral product for home use
- What is important about the dosage of ketorolac?
- What are the contraindications of ketorolac?
Warning
* Do not exceed 5 days combined (inj + tabs) therapy
Contraindications
* Hypovolemia
* Incomplete hemostasis
* Bleeding disorders or high risk of bleeding
* Concomitant epidural or intrathecal injections
What is ketorolac Recommended for? What are the SE?
- Recommended for after surgery
- SE: GI bleeds+kidney damage
How does acetaminophen work? (MOA)
Inhibits COX-1 and COX-2 in the central
nervous system