Pain- Ross Flashcards
Acute pain is required for survival.
Response to pain has a genetic component: ex _______
red hair feels more cold for any given stimulus
Noxious stimulus=
thermal/mechanical/ chemical
Pain=
somatic superficial
somatic deep
visceral: organ
neuropathic
Sensory unit=
sensory nerve cell body in dorsal root ganglion + its
central to SC and peripheral extensions + its cutaneous and visceral endings
**creates clinical useful maps: somatic sensory: dermatomes (area of sensory information from one dorsal root)
A-alpha and A-beta are both ____
FAST pathways
–signal pressure, stretch and other tissue movements to dorsal columns then somatosensory cortex
Vs A-delta and C pathways–> send from:
from tissue and skin nociceptors to spinothalamic
Peripheral sensory pathway:
peripheral sensory nerve carries _____
sensory afferents fibers
**pain receptors are called: nociceptors
free nerve endings with their cell bodies in the dorsal root ganglia
primary afferents classified by size:
A-beta & A-alpha: fast, light touch
A-delta: carry sharp pain
C fibers= (unmyelinated) slower, dull burn pain
Pain (nociceptor) and stretch receptor’s are present in the skin as well as:
deep somatic and visceral structures
-carried by A delta and c fibers: they respond to heat, cold, intense mechanical distortion, ph changes, application of chemical irritants
nociceptors transmitters are _____
**ATP, serotonin and histamine
- open up sodium channels and propagate depolarization
- when conduction in these peripheral n. is abolished one is unable to detect pain
sensitization: describes how the threshold activation of a nociceptor can be:
- decreased?
- increased?
decreased by chemical mediators such as prostaglandin (easier to feel pain)
- increased by serotonin, thromboxanes and endorphins (harder to feel pain)
- sensitization explains why an innocuous stimuli (light touch) can produce pain (allodynia) or the opposite can occur
SC Pain Pathways Dorsal Horn
-in the SC gray matter of dorsal horn the:
end of afferent n. releases the transmitters glutamate, calcitonin and substance P (neuropeptide)
-ascending pathways: contralateral thalamus then to cortex, frontal lobes (emotional input here: fear and pain)
Convergence theory=**
of referred pain: visceral and somatic afferents converge on same area dorsal root) of sc
ex. MI pain hurts the right arm
Visceral pain** (describe)
-**Vagus carries sensation from esophagus, stomach, small bowel and proximal colon
- *spinoreticulothalamic pathway slower conducting
- -from gut,periosteum and peritoneum
It’s the forebrain ( _______) that sends signals to somatosensory cortex, cingulate cortex and insular cortex. The Cortex interprets the signal of pain (emotional/rational input) and ______
(thalamus)
-modulates it.
Descending pathways:
1. Pain modulation at Cortex SS to thalamus 2. ICortex to PAG 3. to Rvm medulla
Nocireceptive pain signal to thalamus and limb is carried by _____
lateral spinothalamic tract**
the dorsal columns=
fine touch and proprioception, vibration :length and tension (unconscious proprioception) and localization of pain
the posterior spinocerebellar tract=
length and tension of muscle fibers (unconscious proprioception)
Other Descending Pathways
- Areas of limbic forebrain, amygdala and Hypothalmus also project to PAG
- PAG (periaqueductal grey matter) modulates ascending pain transmission through the rostral ventromedial medulla (RVM)
-there is release of endorphins (enkephalin)
endorphins turn on/off cells that inhibit (green) or facilitate control of nociceptive signals (red)
In addition to endorphin connections:
-Noradrenergic=
-Sertonergic=
-locus ceruleus (pons) to sc blocking spinal nociceptive neurons
- medulla to dorsal horn cells
- (rationale to use SSRI)
In addition to endorphin connections:
-Noradrenergic=
-Sertonergic=
-**at the locus ceruleus (pons) to sc blocking spinal nociceptive neurons
- **at the medulla to dorsal horn cells
- (rationale to use SSRI)
Pain sites: first site: 2nd site ? 3rd site? 4th?
- nocireceptor
- dorsal horn
- PAG
- thalamus
electrical stimulation (acupuncture or TENS unit) of afferents stimulate the ________ pathways that will inhibit pain and can produce analgesia similar to opioids
descending
we have an ______ receptor in the dorsal ganglion
**opioid
the nociceptor can cause withdraw reflexes as well as:
other autonomic findings such as pallor, diaphoresis and tachycardia
Amount of stimulus needed to perceive pain is approximately the same in
all persons BUT ______
Pain perception is not the same for everyone
Cortical influence of Pain:
multiple factors influence patients rating of pain such as _______
emotional state
intoxicants
psychological state
-pain linked to fear
Why Physiology Matters:
pain detection: at nociceptor
pain transmission: ascending tract of sc
pain modulation: descending tracts from cortex
pain expression: cortical : cognitive process involved with interpretation and expression of pain
What inhibits pain at the detection system?
- local anesthesia
- Nerve blocks
- NSAIDs
What inhibits the pain transmission system?
- opioids
- Acetaminophen
- tricyclic antidepressants
FACES pain scale used for children older than ___
6
Neonates:
-what is the best tool for assessing pain?
facial expression -furrowed brow forehead bulge nasolabial furrow Cry : high pitched and drawn out
Pain from undiagnosed cause
can be acute or chronic:
-____ is the most frequent example
cancer
Acute Pain PO vs IV
- depends on etiology and your location
- *IV medications for acute musculoskeletal, and visceral pathology, appropriate for monitored situations
- **PO medications more for acute on chronic issues or acute pain that is not “severe”
consider narcotic first if pain is severe ie >___
> 8/10**
Morphine
Fentanyl (sublimaze)
Hydromorphone (dilaudid)
opioids:
are intact at several areas of the ____
pain pathway
- at the nociceptor, inhibits the reception of stimulus
- in the Spinal cord by inhibiting upward transmission
- at the mid brain (previous slide)
-at the limbic system (thalamus) centrally via beta endorphins (not shown on previous slide)
opioid:
-___ receptor agonists**
u (mu) receptor agonists: high affinity for enkephalins and beta endorphin
partial agonist : partial response with decreased intrinsic activity so functional as partial antagonists
–buprenorphine, butorphanol
Morphine causes the release of _____
**histamine. which may produce transient hypotension and nausea,
Fentanyl causes:
- *less cardiovascular depression than morphine
- high doses can cause chest wall rigidity (>5 micrograms)
Fentanyl is used for ____
break through pain in opioid-tolerant cancer Pts, Wait >2 hrs before treating another episode
Oxycodone:
-possible OD with ____
- lower incidence of nausea
- Possible inadvertent acetaminophen OD with combo agents **
Codeine=
- natural alkaloid, 30-60 mg PO
- 30-60 mg PO
For Ex. Headache
-pain management options?
phenothiazines: high success rate 95%
ergotamines : sumatriptan, dihydroergotomine
anti-psycotics: droperidol, haldol
anti-seizure: valproate
steroids : decadron
**opioids have not shown greater efficacy, and lead to drug seeking behavior
Non-Opioid
intranasal lidocaine for migraine
trigger point injection
neuropathic pain: tx?
musculoskeletal pain ?
- gabapentin
- benzodiazapines
bladder pain (for cystitis)?
pyridium
Cancer pain?
antidepressants
When you prescribe narcotics, you MUST check prescription drug monitoring program=
PDMP**
Neuropathic pain=
-tx options?
=pain induced by nerve root or peripheral nerve disease
anti-epileptic drugs : phenytoin,carbamazepine,gabapentin or pregabalin
topical drugs: Capsaicin
spinal injections
lidocain infusions trigeminal neuralgia and facial pain
Complex regional pain syndrome (1 and 2)
=sustained pain after limb injury in absence of damage to nerves (1); if damage to n then 2
-theories are numerous : artificial connection been efferent sympathetic and somatic pain afferents, abnormal adrenergic sensitivity in injured nociceptors, yet another constant bombardment of pain triggers central sensitization
red flags for abuser
on multiple controlled substances
hx of drug addiction
hx of multiple providers prescriptions, multiple pharmacies
out of town/state
gets angry when alternatives are suggested
hx inconsistant
Chronic Opioid Therapy (components)
-proper pt selection
informed consent and a COT plan
Initiation and titration
Monitoring: pain intensity, urine drug screens
