Anaesthetics (General) Flashcards
Nociception vs Pain
Nociception = Perception of noxious stimuli
Pain = Perception of noxious stimuli + emotional component
Neuropathic Pain
Damage to somatosensory nervous system
- Trigeminal Neuralgia
- Phantom Limb Pain
- Pain following brain or nerve injury
Chronic Pain
Pain that outlasts the tissue injury
Chronic Pain (Hyperalgesia)
Increased feeling of pain to usual mild stimuli
Chronic Pain (Allodynia)
Pain caused by usual stimuli that would not have caused pain
Chronic Pain (Spontaneous)
Spontaneous pain without any stimuli
A(alpha)
- Information carried?
- Myelinated?
- Diameter size?
- Conduction speed?
Carry proprioception information (Body Position)
Myelinated
Largest
Fastest
A(beta)
- Information carried?
- Myelinated?
- Diameter size?
- Conduction speed?
Carry touch sensory information
Myelinated
Large
Fast
A(delta)
- Information carried?
- Myelinated?
- Diameter size?
- Conduction speed?
Carry Pain information (Mechanical, Thermal) –> Sharp, Well localized pain
Myelinated
Small
Slow
C
- Information carried?
- Myelinated?
- Diameter size?
- Conduction speed?
Carry Pain information (Mechanical, Thermal, Chemical) –> Dull, Burning pain
Non-myelinated
Smallest
Slowest
Stimulus for Pain Transmission
A(delta) and C are for Pain transmission
What pathways control pain transmission (Endogenous Pain Control)
Descending inhibitory pathways
- Brain to Dorsal Horn on Spine
Pathways are rich with what kind of neurons
(Endogenous Pain Control)
Enkephalin/Endorphin containing neurons
- Endogenous Opioid Peptides
Expresses opioid receptors
Noradrenergic Pain Inhibitory Pathways
Noradrenergic Pain Inhibitory Pathway
- Locus Coeruleus to Dorsal Horn on Spine
Opioid Receptors are what kind of receptors?
GPCR (Gi/G0)
Opioid Receptors form what kind of complexes
Homeric and Heteromeric Receptor Complexes
Where are opioid receptors expressed
Brain and Spinal Cord
Mu Opioid Receptors are responsible?
Analgesic effect of opioids, also some unwanted effects
Analgesia
Loss of painful sensation
Analgesic
Drug that relieves pain
Opioids Effects
Anti-nociceptive and reduce emotional component of pain
What kind of agonist are Opioids
Agonist / Partial agonist at Mu Receptors
What kind of pain are Opioids used for?
Acute / Chronic pain
Mild pain
Anaesthesia
Opioids of Mechanism of Action
Activates opioid receptors
- Opens K+ Channels
- Inhibits opening of voltage gated Ca2+ channels
–> Causes hyperpolarization of pain transmitting neurons
–> Decreasing excitability of pain neurons
Opioids potential site of actions
- Specific Brain Nuclei
- Dorsal Horn of Spine (Prevent further neurotransmitter release)
- Periphery (Nociceptive Afferent Nerve Terminals)
Unwanted Effects of Opioids
Sedation
Respiratory Depression
Euphoria (Dependence and Tolerance)
NSAIDS effects
Analgesic, Antipyretic (reduce fever), Anti-Inflammatory
What kind of pain are NSAIDS for?
Mild/Moderate Pain
NSAIDS Mechanism of Action
- Inhibit COX-1 and COX-2
- Inhibit Prostaglandin
–> PGE2, PGF2(alpha)
Prostaglandin Effects
Sensitize nerve terminals to pain effects of Bradykinin and 5-HT
Acetaminophen effects
Generic Name: Paracetamol
Analgesic, Antipyretic
No Anti-Inflammatory Effects
Acetaminophen Mechanism
Not fully understood
Inhibit a variant of COX-1 (COX-3?)
Activate and desensitize TRPA1/V1 channels in brain?
Tricyclic Antidepressant Uses
Relieve neuropathic pain
Tricyclic Antidepressant Mechanism of Action
Act within CNS
Inhibits Noradrenaline reuptake
Antiepileptic Drugs Uses
Used to relieve neuropathic pain
Antiepileptic Drugs Mechanism of Action
Blocks voltage gated Na+ Channels
Reduces expression of voltage gated Ca2+ channels on nerve membrane
- Reduces transmitter release
