47 Pain Flashcards
Physiology of Pain
symptoms of an underlying problem
-nociception involves the physiologic mechanisms of pain processing
Physiology of Pain
4 stages
1 Transduction
2 Transmission
3 Perception
4 Modulation
nociceptors
free nerve endings
Transduction
- process of converting painful stimuli to neuronal action potentials at sensory level
- nociceptors transduce noxious stimuli into action potentials
- chem mediators alter the membrane potential of the pain receptor
- NSAIDs prevent prosaglandin production by inhibiting the action of cyclooxygenase
cyclooxygenase
enzyme that normally converts arachidonic acid to prostaglandin
Transmission
stim nociceptors transmit impulses to the CNS by means of specialized sensory fibers
primary sensory fibers
Ao
C
Ao sensory fiber
myelinated fibers involved in transmission of sharp, stinging, + highly localized pain
C sensory fiber
small, unmyelinated fibers involved in transmission of dull, aching, + poorly localized pain that lingers
2 division of Anterolateral Tract
1 Neospinothalamic Tract
2 Paleospinothalamic Tract
Neospinothalamic Tract
carries Ao fiber input
-projects to thalamus then sensory cortex
Paleospinothalamic Tract
carries C fibers input
-projects diffusely to the reticular formation, mesencephalon, + thalamus
______ cause conscious perception of pain
lower brain centers
many neurotransmitters + neuropeptides involved in synaptic transmission at the spinal cord level
- substance P, glutamate, GABA, cholecystokinin, + calcitonin gene-related peptide
- glutamate may stimulate “wind up” phenomenon that can lead to chronic pain
brain can localize a pain sensation to a particular part of the body because…
nociceptor pathways are kept in specific anatomic order in the cord (sensory dermatome) + somatosensory cortex
Modulation
complex mechanism whereby synaptic transmission of pain signals is altered
-modulated w/in brain/spinal cord by endogenous opioids (enkephalins, endorphins)
mediators of presynaptic inhibition
opiods like endorphins + morphine
rostral pons
secrete NORepinephrine
periaqueductal grap [PAG]
has high concentration of endogenous opioids
Raphe Magnus
receives input fr PAG + Rostral Pons
Opioids + receptor types
have different effects depending on the types of receptors they activate
4 types:
Mu, Kappa, Sigma, Delta
____ + ____ receptors have analgesic activities
Mu (brain) + Kappa (spinal cord)
Gate Control Theory
impulse carried by large myelinated cutaneous fibers (AB) could “close the gate” on nociceptor impulses
–pain signals would be blocked in spinal cord + not allowed to progress to brain
rubbing, pressing, + shaking of the painful area may….
reduce pain
2 major subtypes of Pain
1 Physiologic Pain
2 Pathologic Pain
Physiologic Pain
tissue injury has occurred
Pathologic Pain
occurs after tissue injury, but long-term changes occur both w/inthe peripheral + CNS
-changes occur along somatosensory pathways fr the periphery to the cortex
Acute Pain
results fr tissue injury
-resolved when injury heals
Acute Pain
s/s
INCR hrt rt, resp rt, bp
- pallor
- sweat
- cry/moan
- pacing
- grimacing
Acute Pain
treatment
short term therapy w NONOPIOID + OPIOID meds
- provide adequate pain relief
- may prevent some types of chronic pain
Headache
classifications
classified according to etiologic factors: 1 Migraine 2 Tension 3 Cluster 4 Sinus
Migraine
results fr dysfunction of brainstem areas involved w modulation of craniovascular afferent fibers
Migraine
s/s
- unilateral throbbing
- n/v
- photophobia
- phonophobia
- lacrimation
Chronic Pain
- may be assoc w disease process
- last longer than expected healing time
- ——-more than 6 mth
Chronic Pain
s/s
generally not assoc w s/s of sympathetic activity
-psychological like loss of job, irritability
Fibromyalgia Syndrome
disordered pain mechanism in CNS
- widespread pain affecting all 4 extremities
- hyperalgesia
- trigger or tender points
Fibromyalgia Syndrome
etiology/risk factors
unknown etiology; risk factors may be trauma, sex abuse, stress
Hyperalgesia
is a condition in which you experience an enhanced sensitivity to pain
Fibromyalgia Syndrome
s/s
-widespread pain affecting all 4 extremities
-hyperalgesia
-trigger or tender points
-sleep distrub/insomnia
difficulty concentrating
-fatigue
-ibs
-allodynia
Allodynia
the experience of pain from stimuli that isn’t normally painful.
-People with migraine will often describe this experience by saying, “My hair hurts.”
Cancer Related Pain
may result fr infiltration of organs,
compression of structures by expanding tumor,
or result of cancer treatments
Cancer Related Pain
s/s
mix of sympathetic NS activation + behavioral changes
Neuropathic Pain
results fr tissue injury in which the nerves themselves become damaged or dysfunctional
- may result fr altered central processing of nociceptive input
- —–releasing norepinephrine into nociceptors
Diabetic Neuropathy
cause by damage to lrg peripheral nerves by inflammation + demyelination
-patient education for foot care + glucose control is critical for reducing further complications
Postherpetic Neuralgia
reactivation of latent herpes virus thats been dormant in nerve roots
-herpes zoster is characterized by burning pain that follows a dermatomal pathway + accompanied by a blistering rash
Ischemic Pain
fr sudden/profound loss of blood flow to tissues
Ischemic Pain
mgmt
mgmt aimed at improving blood flow + reducing tissue hypoxia
-removing clot if needed
Chronic Ischemic Pain is assoc w…
atherosclerosis
Referred Pain
perceived in an area other than the site of injury
ex. myocardial infarc felt in jaw or left arm; shoulder pain after pelvic procedure
bc pain is referred to other structures of SAME dermatome
sympathetic NS activation during ACUTE pain can lead to….
INCR hr rt, resp rt, bp, BLOOD GLUCOSE
- dilated pupils
- sweat
- pallow
- DECR gastrointestinal motility
- hypomotility of bladder
pain mgmt interventions can be directed at 3 points:
1 INTERRUPT peripheral transmission of nociception
2 MODULATE pain transmission at spinal cord
3 ALTER PERCEPTION + INTEGRATION of nociceptive impulses in brain
INTERRUPT peripheral transmission of nociception
often 1st step in controlling pain
- application of heat/cold alters bf + reduce swelling
- NSAIDs decr prostaglandin
- —interrupts periph transmission
NSAIDs
side effects
- gastrointestinal bleeding
- decr platelet aggregation
- renal insufficiency
MODULATE pain transmission at spinal cord
cutaneous stim activated large sensory fibers that can block central progression of nociceptive transmission at interneurons
MODULATE pain transmission at spinal cord
examples
- TENS: transcutaneous electrical nerve stim
- massage
- acupuncture
- heat/cold
- therapeutic touch
- epidural + intrathecal analgesia
- dorsal column stimulator
ALTER PERCEPTION + INTEGRATION of nociceptive impulses in brain
opioids work at specific receptor sites located thruout body but concentrated in brain
-opioid analgesic have similar mechanism but vary widely in potency
Opioid Analgesic for alteration of perception + integration in brain
side effects, tolerance
side effects: n/v, resp depression, constipation
tolerance: need for incr dosage to achieve same effect
addiction: withdrawal symptoms if abrupt cessation
- -behavioral pattern of craving + preoccupation w obtaining drug
- -not an expected response to opioid therapy
Opioid Analgesic for alteration of perception + integration in brain
types of meds
MILD: nonopioids: NSAIDs or acetaminophen
MOD: low potency opioids: codeine
SEVERE: potent opioid: morphine/fentanyl
Opioid Analgesic for alteration of perception + integration in brain
DISTRACTION
less able to integrate pain experience when other competition is present
Opioid Analgesic for alteration of perception + integration in brain
IMAGERY
alters perception of painful stim in high brain centers
—produces relaxation + analgesia
Opioid Analgesic for alteration of perception + integration in brain
RELAXATION
conditioned response
—incr bf
Opioid Analgesic for alteration of perception + integration in brain
BIOFEEDBACK
INCR endorphins
—conditioned response
