Flashcards in pain management Deck (17):
Peripheral sensory nerve endings acting as sensory receptors (___________), transduce and encode noxious stimuli and send impulses to the ________ horn of the spinal cord via small myelinated (Aδ) and thinly and nonmyelinated (C) afferent nerve fibers.
The Aδ and C fibers from superficial pain pathways (e.g., somatic structures, such as skin) are transmitted via the ______________ tract, whereas those from the deep pain pathways (e.g., viscera and periosteum) are transmitted via the ___________ tract.
What is the mechanism of action for butorphanol?
act as an agonist at κ-receptors and an antagonist at µ-receptors.
T/F: Opioids produce analgesia by binding to mu (µ), kappa (κ) or delta (δ) receptors in the spinal cord and brain. Peripheral opioid receptors are also found in inflamed tissue.
What is the mechanism of action of buprenorphine?
it is a µ-agonist opioid
What is the mechanism of action for lidocaine and other local anesthetics?
Local anesthetics act by blocking sodium channels in excitable membranes and preventing the transfer of nociceptive information.
This drug is can be used for the treatment or prevention of central sensitization. It is an N-methyl D-aspartate (NMDA) receptor antagonist, and subanesthetic doses are thought to have an antihyperalgesic effect.
T/F: High concentrations of ketamine may also block sodium channels, and this may explain the short duration of analgesia (15 minutes) when used for an abaxial sesamoid nerve block.
What is the mechanism of action for tramadol?
Tramadol is a synthetic codeine analogue. It binds weakly to the µ-receptor and inhibits neuronal reuptake of norepinephrine and 5-hydroxytryptamine.
T/F: Drugs that have been administered into the epidural space in horses include local anesthetics, opioids, α2-agonists, ketamine, and tramadol.
Describe the acute pain pathway.
Peripheral sensory nerve endings (nociceptors). transduce and encode noxious stimuli and send impulses to the dorsal horn of the spinal cord via small myelinated (Aδ) and thinly and nonmyelinated (C) afferent nerve fibers. The Aδ and C fibers from superficial pain pathways (e.g., somatic structures, such as skin) are transmitted via the spinocervicothalamic tract. Fibers from the deep pain pathways (e.g., viscera and periosteum) are transmitted via the spinoreticular tract. Pain is perceived by the animal when the signals reach the somatosensory cortex.
Describe peripheral sensitization.
Peripheral sensitization occurs at the level of the injured tissue. Tissue damage results in release of inflammatory mediators including prostaglandins, bradykinin, histamine, hydrogen ions, potassium ions, and substance P. These mediators may stimulate peripheral nerve endings (nociceptors) directly, or they may increase the sensitivity of the nociceptor to other stimuli.
Describe central sensitization.
Nociceptive pathways may be upregulated in response to acute pain and inflammation, resulting in enhanced pain transmission by neurons. N-methyl-D-aspartate (NMDA) receptors are stimulated by the neurotransmitter glutamate, resulting in hyperalgesia (an exaggerated response to a noxious stimulus). Secondary hyperalgesia occurs in the surrounding noninjured area. When this happens, effective pain control is more difficult and higher doses of analgesics are required.
T/F: Allodynia is the result of central sensitization.
False; peripheral sensitization may result in an avoidance of or aggressive response to a stimulus that would normally be considered innocuous (e.g., light touch). This is referred to as allodynia.
Hyperalgesia is an exaggerated response to a noxious stimulus and may be seen as a result of central sensitization.
What is the mechanism of action of NSAIDs?
inhibit cyclooxygenase (COX) enzymes, which are necessary for prostaglandin production during the inflammatory response.
T/F: Tissue inflammation or injury results in down-regulation of peripheral opioid receptors.
False; peripheral opioid receptors are increased in inflamed tissue