Lec 1: Pain Flashcards
What is the universally understood as a signal of disease? It is also the most common symptom that brings a patient to a physician’s attention.
Pain
The function of the pain sensory system is to _______
protect the body and maintain homeostasis
It is an unpleasant sensation localized to a part of the body.
Pain
A peripheral nerve is composed of axons of 3 different types of neurons. What are these 3?
Primary Sensory Afferents
Motor Neurons
Sympathetic Postganglionic neurons
Where are the cell bodies of the primary sensor afferents located?
In the Dorsal Root Ganglia (DRG) within the vertebral foramina.
What fiber has the largest diameter and responds maximally to light touch and/or moving stimuli (flutter)? They are present in the nerves that innervate the skin.
A-Beta fiber
This fiber is myelinated and has a small diameter.
A-delta
This fiber is unmyelinated
C fiber
These 2 fibers are present in the skin and deep somatic and visceral structures. They maximally respond to intense stimuli and produce the subjective experience of pain when stimulated. Therefore they are your PRIMARY AFFERENT NOCICEPTORS
A-delta & C fibers
This happens when intense, repeated, or prolonged stimuli are applied to damaged or inflammed tissues, the treshold for activating the primary afferent nociceptors is lowered and frequency of firing is higher for all stimulus.
Sensitization
Give the factors that mediate sensitization. (4)
Bradykinin, Nerve Growth Factor, Prostaglandins, Leukotrienes
If sensitization occurs at the level of the peripheral ner terminal, it is termed as ________
Peripheral Sensitization
If sensitization occurs at the level of the dorsal horn of the spinal cord, it is termed as _______
Central Sensitization
What is the term used when normally innocuous stimuli can produce pain?
Allodynia
What is the term used when there is increase pain intensity in response to the same noxious stimuli?
Hyperalgesia
True or false: Viscera are normally relatively senstitive to noxious stimuli.
False “insensitive”
True or false: deep structures such as joints or hollow viscera characteristically become exquisitel insensitive to mechanical stimulation when affacted by a disease process with inflammation
False. “sensitive”
These receptors cannot be activated by known mechanical or thermal stimuli and not spontaneously active. But, in the presesnce of inflammation, these become sensitive to mechanical stimuli.
Silent Nociceptors
This is released from nociceptors and is a potent vasodilator. It also degranulates mast cells, is a chemoattractant for WBC, and increases the production and release of inflammatory mediators.
Substance P
Reduction of substance P in joints results in _____
reduced severity of experimental arthritis
What is the major neurotransmiter secreted in response to a noxious stimuli?
Glutamate
These 2 substances produce a slower and longer-lasting excitation of the dorsal horn neurons
Substance P and Calcitonin gene-related peptide
Referred pain is due to what mechanism
Convergence of sensory inputs to a single spinal pain-transmission neuron
What determine the convergence pattern of sensory inputs?
by the spinal segment of the dorsal root ganglion that supplies the afferent nerve innervation of a structure.
True or false: because of the convergence and the fact that the spinal neurons are most often activated by inputs from the skin, activity evoked in spinal neurons by input from deep structures is localized by the patient to a place that exactly corresponds to the region of skin innervated by the same spinal segment.
FALSE. Not exactlyyy
This is he spatial displacement of pain sensation from the site of injury that produces it
Referred Pain
This pathway is crucial for pain sensation in humans. Interruption of this pathway produces permanent deficits in pain and temp discrimination.
Spinothalamic Tract
Where does the spinothalamic tract decussate?
@ the anterior white commissure
What thalamic projection mediates the purely sensory aspects of pain? (such as location, intensity, quality)
Thalamic projections to Somatosensory cortex
what thalamic projection mediates emotional responses to pain? They subserve the affective or unpleasant emotional dimension of pain.
Cingulate Gyrus, Other parts of Frontal Lobe, Insular Cortex
What is the constant companion of pain?
Fear
Suggestion that a treatment will relieve pain can have an analgesic effect. This is called….
Placebo Effect
Suggestion that pain will worsen following administration of an inert substance can increase its perceived intensity.
Nocebo Effect
Where are the pain-inhibiting and pain-facilitating neurons found?
Medulla
What could account for the finding that pain can be induced by suggestion or enhanced by expectation and provides a framework for understanding how psychological factors can contribute to chronic pain?
A central circuit that facilittates pain
What do you call the type of pain is characterized by unusual burning, tingling, or electric shock-like quality and may be triggered by very light touch
Neuropathic pain
This is a greatly exaggerated pain sensation to innocuous or mild stimuli
Hyperpathia
Very light moving stimulus evokes exquisite pain
Allodynia
What is the result of damaged primary afferents?
Become highly sensitive to mechanical stimulation and may generate impulses in the absence of stimulation
This is due to the increased concentration of sodium channels in the damaged nerve fiber
Increased sensitivity and spontaneous activity
Damaged primary afferents may also develop sensitivit to what substance?
Norepinephrine
What contributes to neuropathic pain?
Both CNS and peripheral nervous system
This is experienced by pt w/ peripheral nerve damage. It has a burning quality & begins a delay of hrs/weeks and is accompanied by swelling of an extremity, periarticular bone loss, & arthritic changes in distal joints.
Sympathetically maintained pain aka COMPLEX REGIONAL PAIN SYNDROME
If CRPS occurs after an identifiable nerve injury, it is termed as….
CRPS type II aka Posttraumatic Neuralgia or if severe, Causalgia
If CRPS appears without an OBVIOUS nerve injury, what is it called?
CRPS Type I aka Reflex Sympathetic Dystrophy
True or false: Parasympathetic activity can activate undamaged nociceptors when inflammation is present.
False. Sympathetic
What is the first line treatment in acute pain?
Analgesics
These are particularly effective for mild to moderate headache and for pain of musculoskeletal origin.
Aspirin, acetaminophen, NSAIDs
What is the most commonly used analgesic?
COX inhibitors
This causes severe gastric irritation and causes erosion & ulceration of the gastric mucosa leading to bleeding or perforation.
Aspirin
These increases the risks of aspirin and NSAIDs
Old age and history of GIT diseases
This is a significant problem for patient using Aspirin & NSAIDs on a chronic basis
Nephrotoxicity
This rarely produces gastric irritation and does not interfere with platelet function
Acetaminophen
What cox is constitutively expressed?
COX-1
This drug offer a significant benefit in the management of acute postoperative pain because they do not affecr blood coagulation
COX-2-Selective drugs like celecoxib
These drugs are contraindicated postoperatively because they impair platelet-mediated blood clotting and are thus associated with increased bleeding at te operative site.
COX inhibitors
What is the most potent pain-relieving drugs currently available?
Opiods
They have the broadest range of efficacy and providethe most reliable and effective method for rapid pain relief.
Opioids
What are the common side effects of opioids?
Nausea, vomiting, pruritus, constipation
Opioid-realted side effects can be reversed rapidly with?
Narcotic antagonist: NALOXONE
How does opiod produce analgesia?
By activating pain-inhibitory neurons and directly inhibting pain-transmission neurons
What drug may cause hyperexcitability and seizures that cannot be reversed by naloxone?
Normeperidine
What is commonly found in patients who are treated with opiods and other CNS depressants (benzodiazepines)?
Synergistic respiratory depression
What is the most common error made by physicians regarding the dosing of opioids?
Prescribing an INADEQUATE dose.
This uses a microprocessor-controlled infusion device that can deliver baseline continuous dose of an opioid drug as well as preprogrammed additional doses whenever a patient pushes a button.
Patient-controlled Analgesia (PCA)
True or false: COX inhibitors and opioids have additive effects
True
This is used to lower the severity of dose-related side effects
Combination of low doses of opioids and cox inhibitors
Discovering a ________ component to the pain can be useful both diagnostically and therapeutically.
Mechanical component
What are the factors that can cause, perpetuate, or exacerbate chronic pain?
- Disease
- Perpetuating factors initiated by disease (ex damaged sensory nerves)
- Psychological conditions
What is the most common emotional disturbance in patients with chronic pain?
Depression
What are the clues that signify that an emotional disturbance is contributing to the pt’s chronic pain complaint?
- Pain that occurs in unrelated sites
- a pattern of recurrent but separate pain problems beginning in childhood or adolescence
- Pain beginning at a time of emotional trauma
- A history of physical or sexual abuse
- Past or present substance abuse
True or false: patients with chronic pain should be assessed based on emotional and organic factors before initiating therapy.
True
These drugs were first shown to relieve the pain of trigeminal neuralgia
Phenytoin and Carbamezapine
Pain is characterized by brief, shooting, electric shock-like quality.
Trigeminal neuralgia
pain that is of recent onset and resolves
quickly
Acute pain
pain that lasts a long time; pain that
extends beyond the expected period do healing
Chronic pain
the most reliable
measure of pain, with health professionals
tending to underestimate severity.
Self-report
Thunderclap headache or worst headache of your life
Ruptured cerebral aneurysm
leading to subarachnoid
hemorrhage
In non verbal patients, what should you observe?
Observe for specific behaviors Grimacing Guarding Crying – babies feel pain but lack the language to report it
pain arising from a
perturbation of the body
Somatogenic
– pain arising from a
perturbation of the mind
Psychogenic
due to stimulation of peripheral
nerve fibers that respond only to stimuli
approaching or exceeding harmful intensity
Nociceptive pain
caused by damage or disease
affecting the nervous system
Neuropathic pain
Involves the skin (superficial), joints, muscles,
tendon and ligaments (deep)
usually sharp, well-defined and easy to localize
Somatic pain
usually dull, vague and difficult to localize
Involves the internal organs
Visceral pain
pain perceived to be from a part of the body that has been lost or from which the brain no longer receives signals
Phantom pain
Experienced during:
Excitement of sport
During war
Episodic analgesia
This age group’s ability to recognize pain may
be blunted by illness or
drugs
Elderly
