Pain Flashcards
What is pain?
An unpleasant sensory or emotional experience. Purely a perception, no way to quantify. Whatever the patient says it is, need a sense of emotion to sense pain
How is tissue damage related to pain? How is pain related to the number of nerves involved?
May not be proportional
Also not proportional to the number of nerves involved (except on the skin).
What is the issue of the subjective nature of pain?
Undertreatment
How can a functional MRI be used with pain?
Can determine whether or not pain is actually being felt
What are the 3 effects of pain on the body?
Amplifies the body’s stress response (SNS) to traumatic injury
Stimulates endocrine and metabolic systems, causes abnormalities
Retards patient’s recovery from trauma, surgery and disease
What is acute pain?
Pain lasting less than 6 months and subsides once the healing process is accomplished
What is chronic pain?
Complex. Involves altered anatomy and neural pathways. Constant and prolonged, lasting longer than 6 months.
What is the cousins’ pain theory?
Severe, unrelieved acute pain results in abnormally enhanced physiological responses that lead to pronounced and progressively increasing pathophysiology.
Will increase organ dysfunction, increasing morbidity and mortality
What is the pathophysiology of pain?
SNS stimulation causes the heart to beat more and harder (needs more oxygen) but less oxygen is being delivered.
Arterial hypoxemia and suppression of immune functions (predisposition to infections and sepsis)
Infections could also be due to lifestyle changes
What causes chronic pain syndrome?
Result of acute, unrelieved pain like multiple trauma, phantom limb pain, repeated back surgeries (get up and walk around after)
Neuromuscular disorders like fibromyalgia, rheumatoid arthritis, MS
May be from a known or unknown cause
What causes pain to be felt?
Specialized receptors on free nerve endings (almost all nerves) are stimiulated by mechanical damage, extreme temperature or chemical irritation.
What are the 2 types of neurons involved in pain and what do they feel?
A-delta for the initial quick, sharp pain that causes the body to withdraw (mom, protective pain)
C for the second dull pain (dad) that has learning and behavioural modifications and causes immobilization
What is transduction in the pain pathway?
Local biochemical changes released by damaged tissue in the nerve ending that generate a signal
Nociceptors distinguish between noxious and innocuous stimuli
Na channels cause cell depolarization
What is transmission in the pain pathway?
Movement of the signal from the site of pain to the spinal cord and central strucures in the brain
Requires neurotransmitters
What is perception in the pain pathway?
Synthesis and analysis in the brain to generate emotional responses (only in vertebrates above fish)
Can change in your head via training
What is modulation in the pain pathway?
Endogenous systems (endorphins) in place that can inhibit pain at any point along the pathway, modulating transmission and perception Serotonin also modulates perception
What are the substances released by damaged tissue during transduction?
Bradykinin
Serotonin
Substance P (well known pain transmitter)
Histamine (inflammation and exacerbation)
Prostaglandin (NSAIDS target)
What drugs help stop transduction?
NSAIDS like aspirin, ibuprofen, diclofenac minimize prostaglandins
Corticosteroids (cortisone, dexamethasone) inhibits prostaglandins and other inflammatory mediators
What do opioids do?
Bind to receptors and inhibit the release neurotransmitters
Endorphins or medical
What are the size and speed differences between the pain transmission fibres?
A delta: Large diameter, fast signal transfer
C: Small diameter
Which fibres are involved in chronic pain?
C fibres
Where are endorphins released?
Descending fibres in the spinal tract and higher cortical centres.
Why do antidepressants decrease pain?
Because they interfere with the reuptake of serotonin and norepinephrine which can modulate pain perception.
How can endorphins play a role in chronic pain syndromes?
Many people with chronic pain disorders have messed up endorphins.
What activates the descending pain modulation system?
Stress, fear, hunger, thirst, fatigue, prolonged motor activity (exercise) and hypnosis
What is the gate control theory?
There are spinal gates in each dorsal horn that only allow only a certain amount of heat, touch or pain to be transmitted at each point at one time
Vibration trumps all
What is nociceptic pain?
Normal pain with tissue damage
Injury, trauma, infection, post operative pain, mechanical lower back pain
What is neuropathic pain?
Primary lesion or dysfunction of the peripheral or central nervous system
Could be known or unknown cause, trigeminal neuralgia, polyneuropathy
What is visceral pain?
Arising from an internal organ and is massively amplified in the brain
MI, appendicitis, small bowel obstruction
What are some examples of mixed type pain?
Postherpetic neuralgia, neuropathic lower back pain, arthritis, sports/exercise injuries
What is hyperalgesia?
Intense pain in response to mildly painful stimulus
type of neuropathic pain.
What is allodynia?
Pain in response to completely innocuous stimulus
Type of neuropathic pain
