Exam 2 Pain Flashcards
What is transduction?
A-delta & C-fibers send signals from periphery to the CNS
What is allodynia?
Reduced threshold to pain stimulus
What is hyperalgesia?
Increased response to pain stimulus
What are 2 inflammatory mediators?
Bradykinin
Prostaglandin
What are 6 excitatory mediators?
- Glutamate
- Calcitonin gene-related peptide (CGRP)
- Nerve growth factor (NGF)
- Asparte
- ATP
- Substance P
What is transmission?
Pain signal is sent through three-neuron afferent pathway along the spinothalamic tract
Where are second-order neurons?
Dorsal horn to thalamus
Where are third-order neurons?
Thalamus to cerebral cortex
Where are first-order neurons?
Periphery to dorsal horn
What is modulation?
Pain signal is modified (inhibited or augmented) as it advances to cerebral cortex
Where is the most important site of modulation?
Substantia gelatinosa in the dorsal horn
Which laminae make up the substantia gelatinosa?
Laminae 2 & 3
Spinal neurons can release ___ & ___ to inhibit pain signals?
Gaba & glycine
The descending pathway releases ____, ____, & ____ to inhibit pain?
NE, 5-HT, & endorphins
Pain is augmented by ______ & _____?
Central sensitization & wind-up
What neurons are affected by wind-up & sensitization?
Second-order neurons
What is supraspinal inhibition?
Supraspinal structures send fibers down the spinal cord to inhibit pain at the dorsal horn.
What is segmental inhibition?
Pain is stopped in the second-order neuron & spinothalamic tract.
What is Perception & where does it happen?
Processing of afferent pain signals in the cerebral cortex & limbic system
What medication classes affect transmission?
Local anesthetics
opioids
What medication classes affect modulation?
Opioids
alpha2 agonists
NMDA antagonists
What medication classes affect perception?
Opioids
alpha2 agonists
general anesthetics
What medication classes can inhibit transduction?
NSAIDs
antihistaminics
opioids
local anesthetics
cannabinoids
Somatostatin (SST)
Neuropathic pain can be ____ &/or _____?
Central & peripheral
Visceral pain can be __ &/or __?
True & parietal
Somatic pain can be __ &/or __?
Superficial & deep
What is the most common kind/cause of acute pain?
Nociceptive (physiologic)
What are the types of nociceptive pain?
Somatic & visceral
What is parietal pain?
Localized or referred sharp, stabbing pain
What are types of nonmalignant pain?
Neuropathic
musculoskeletal
inflammatory
What causes neuropathic pain?
An injury to the nervous system
What is sensitization?
Repeated stimuli reduce the threshold of primary afferent nociceptors progressively.
What are the risk factors for developing CRPS?
Previous trauma or surgery
nerve injury
female
work-related injury
What is the difference between type 1 & 2 CRPS?
Type 2 has a documented prior nerve injury
What are the S/S of CRPS?
Spontaneous pain
hyperalgesia
allodynia
active & passive movement disorders
Describe type 1 CRPS?
Pain disproportionate to injury, pain persists beyond the time the tissue-damaging process has ended
What is the most common site of type 2 CRPS?
Brachial plexus
Where is the pain with type 2 CRPS?
Generally localized to the area around the injured nerve
What are first-line treatments for chronic pain?
TCA’s
SNRI’s
Gabapentanoids
Topicals
What are second-line treatments for chronic pain?
Tramadol
combination of first-line treatments
What are third-line treatments for chronic pain?
Specialist referral
interventional therapies
SSRI’s
anticonvulsants
NMDA antagonists
Capsaicin
What are fourth-line treatments for chronic pain?
Neuromodulation
What are fifth-line treatments for chronic pain?
Low dose opioids
What are sixth-line treatments for chronic pain?
Targeted drug delivery (pain pump)
What is the MOA for Tricyclic antidepressants?
Inhibit serotonin & norepinephrine re-uptake.
Also block histamine, adrenalin, acetylcholine & sodium channels
What is the TCA dose for chronic pain?
20 – 30% of the effective antidepressant dose
What is the MOA of SNRI’s?
Facilitate descending inhibition by blocking serotonin & noradrenaline re-uptake.
What medication class is helpful in diabetic neuropathy, osteoarthritis, fibromyalgia, & chronic low back pain?
SNRI’s
Why is carbamazepine not a first-line drug in treating chronic pain?
Due to its sedative effects.
What is the MOA for capsaicin?
Binds to the TRPV 1 receptor located on the A-delta & C-fibers → release of substance P depolarizing the nerve → desensitization.
What is the MOA of tramadol?
Mu-opioid agonist & inhibits serotonin & norepinephrine reuptake.
What are some examples of somatic blocks?
Trigeminal nerve
paravertebral
facet
trans sacral
What are some examples of sympathetic blocks?
Stellate ganglion
celiac plexus
sympathetic chain blocks.
What is the hallmark of neuropathic pain?
Elevated extracellular glutamate levels
What post-synaptic cells take up glutamate?
Glial cells
What are the benefits of targeted drug delivery?
Bypasses first metabolism & blood-brain barrier.
Increased potency & decreased side effects
What type of medication is ziconotide?
An N-type calcium channel antagonist
