Pain Flashcards
What is the major hurdle for development of treatment for phantom limb pain?
Lack of randomized controlled trials to give treatment
What are the potential complications of a celiac plexus block?
Diarrhea Postural hypotension (most common) PTX Retroperitoneal hemorrhage paraplegia (disruption of anterior spinal artery or subarachnoid injection) hiccups Pleurisy Abdominal aortic dissection
What is the drug of choice for chronic neuropathic pain?
Methadone due to NMDA antagonism and SSRi
What is the mechanism of hyperalgesia?
Upregulation of NMDA receptors
Increased nitric oxide production
What is the Gaenslen test?
Significant hip flexion + posterior pressure on the sacrum
Indicates SI joint pain
What are the clinical manifestations of SI pain?
Pain at the site that is dull and constant
Worse with compression and distraction
Worse with standing or in one position for awhile
+ Gaenslen’s
What are the clinical manifestations of discogenic pain?
Worse with flexion and increased intraabdominal pressure (coughing/sneezing)
What are the clinical manifestations of facet joint pain?
Worse with facet loading
Not better or worse with flexion or extension
Non radiating
What is the treatment for facet joint pain?
Medial branch blocks
What are the clinical manifestations of spinal stenosis?
Radicular pain
Worse with extension
Better with flexion
How do you diagnose spinal stenosis?
MRI
What are the treatments for acute herpes zoster?
antivirals, corticosteroids, sympathetic blocks
What are the treatments for postherpetic neuralgia?
TCAs Anticonvulsants (lyrica, gabapentin) Lidocaine patches (for allodynia) Topical capsaicin Opiates Tramadol Spinal cord stimulators
How does a spinal cord stimulator work?
Stimulates large nerve fibers in the substantial gelatinosa thereby decreasing excitatory signals and increasing inhibitory signals
What are the analgesic properties due to with low doses of ketamine?
NMDA receptors antagonism
What are the analgesic properties due to with high doses of ketamine?
Opioid receptors
What is the conversion of IT morphine to epidural?
1 mg to 10 mg of epidural
What is the conversion of epidural morphine to IV morphine?
1 mg to 10 mg of IV
What is the conversion of IT morphine to IV morphine?
1 mg to 100 mg
What is the conversion of IV morphine to po morphine?
1 mg to 3 mg
What is the conversion of IT hydromorphone to epidural?
1 mg to 100 mg
What is the conversion of IV hydromorphone to po hydromorphone?
1 mg to 3 mg
What is the conversion of epidural hydromorphone to IV?
1 mg to 10 mg
What is conversion of IT hydromorphone to IV?
1 mg to 1000
What do hydrophobic opioids do in the intrathecal/epidural space?
More likely to taken up in systemic system to act supra spinally and reach IV infusion levels (fentanyl) so have a smaller analgesic effect and respiratory depression effect.
Bind the white matter of the spinal cord in the intrathecal space
Where do hydrophilic opioids act in the intrathecal space?
The dorsal horn
Can cause respiratory depression via rostral spread
What is the rule when converting to different opioids to avoid cross-tolerance?
Do a 20% reduction
What is valproic acid used for?
Chronic neuropathic pain
What is CRPS II?
Caused by nerve damage - CAUSALGIA
Characterized by spontaneous pain, hyperalgesia, allodynia, vasomotor and sudomotor abnormalities, passive and active movement disorders, trophic problems
What is the first line treatment for CRPS II?
Physical therapy
What are the other treatment options for CRPS?
TCA, gabapentins, memantine
Spinal cord stimulators
IT pumps
Somatic and sympathetic nerve blocks
What is CRPS type I?
Autonomic dysfunction precipitated by non-nerve related injury or surgery
NO associated cause!
What are the symptoms of CRPS?
Sudden onset of pain
Sudomotor: increased sweating, erythema, edema
Vasomotor: temp changes
Motor: tremor, decreased ROM, weakness
What is fibromyalgia?
Widespread pain, sleep disturbances, fatigue, depression for over 3 months with no other explainable cause
WPI > 7, SS >5
What is myofascial pain syndrome?
Painful taut band and palpation of this produced same symptoms
What is the first line treatment for mild cancer pain?
APAP
NSAIDs
What is the first line treatment for mild-moderate cancer pain?
Mild opioids: codeine
APAP, NSAIDs
What is the treatment for nerve compression by a mass?
Corticosteroids
What is the treatment for bone pain?
Bisphosphonates
Calcitonin
What is the treatment for visceral pain?
Anticholinergics
What is the treatment for neuropathic pain?
Anticonvulsants, antidepressants, TCAs, local anesthetics
When should neuroablation be used in a cancer patient?
Only as a last resort, if the patient prefers or if there is a single focus to treat.
What are the indications for spinal cord stimulator?
Post-laminectomy syndrome Postherpetic neuralgia Phantom limb pain Cauda equina syndrome CRPS CV angina LE ischemic pain Chronic cervical radiculopathy Nerve root injury
What are the contraindications to spinal cord stimulator placement?
Sepsis Coagulopathy Local infection Spina bifida Somatoform disorder Cognitive disability Trauma obliterating spinal canal Lack of social support Substance abuse Psych disorders
What are the side effects of gabapentin?
Nausea, sedation, dizziness, nystagmus, ataxia, peripheral edema, urinary leakage, suicide
Which chronic pain medication lower seizure threshold?
Tramadol, TCAs
How are nociceptive signals transmitted?
Alpha delta and C fibers in the substantial gelatinous of the dorsal horn of the spinal cord via glutamate
What is the “gate theory” of pain?
Large fibers in the substantial gelatinous open the gate to small afferent fibers that transmit the nociceptive signal
Which nerves does a spinal cord stimulator affect?
Large A-alpha and A-beta fibers in substantia gelatinosa
What structures transmit analgesic signals?
Periaqueductal gray and Rostroventromedial nucleus
When does nerve regeneration occur after cryoanalgesia?
in 1-3 month following
What is cryoanalgesia?
Intense cold to damaged select nerve that causes temporary conduction blocks
What is cryoanalgesia used for?
Post-Thoracotomy pain for intercostal nerves
What is dysesthesia?
Tactile hallucination
What type of pain is phantom limb pain?
Neuropathic and central (due to mechanism)
What is the pathophysiology of phantom limb pain
Misfiring in the somatosensory cortex
What is allodynia?
Pain from a non painful stimulus
What is nociceptive pain?
Pain caused by an actual or threatened damage to non neural tissue
Subtypes: mechanical (scrapes), thermal, chemical
What is psychosomatic pain?
Caused by emotional, mental and behavioral factors
Most common: backache, headache, abdominal pain
What is first line therapy for trigeminal neuralgia?
Carbamazepine
What are the treatments for trigeminal neuralgia after failed medical therapy?
Radio frequency rhizotomy
Microvascular decompression
What is transduction?
The conversion of a painful stimulus to an action potential. Happens at free nerve endings in the dorsal root ganglia
What is transmission?
Done through 1st, 2nd, and 3rd order neurons through the dorsal root ganglia, dorsal horn and thalamus.
What is the best treatment to prevent transmission of pain?
Local anesthetics
What is modulation of pain?
Occurs at any site along the pathway but typically in the dorsal horn at NMDA sites, GABA, neurokinin, AMPA
Which treatments are geared toward transduction?
NSAIDs, SSRIs, locals, antihistamines, opioids,
What is perception of pain?
The final common pathway involves the somatosensory cortex and limbic system
What alters perception of pain?
general anesthesia
opioids
alpha 2 agonists
What are the most common to least common affect nerves from herpes zoster?
Thoracic > V1 > V2 > Cervical > Sacral
How is carbamazepine metabolized?
By the liver
What is the mechanism of action of carbamazepine?
Sodium channel blocker
Inhibits ectopic foci
Has larger volume of distribution and peak plasma concentration in 4-8 hours
What does carbamazepine do in the liver?
Induces P450 – increases metabolism of other anti epileptic drugs: phenytoin
What are the manifestations of carbamazepine toxicity?
Widened QRS, prolonged QT, ventricular arrhythmia, tachycardia, hypotension, mydriasis, dry mouth, flushing, reduction of seizure threshold, urinary retention, AMS, nystagmus, ataxia, hyperthermia
Where is ganglion impar?
Retroperitoneum anterior to the sacrococcygeal junction
What does a ganglion impar block do?
Pain relief for perineal malignancies: perineum, anus, distal rectum, distal urethra, distal third of vagina
How does a TENS unit work?
Uses low voltage (10-30 mA) electrical pulses to stimulate the nervous system
Based on gate theory: large fibers compete for input from small fibers
What are the contraindications for TENS unit?
Demand pacemakers, cardiac dysrhythmias, undiagnosed pain syndrome, mental incompetence, first trimester pregnancy
What is anesthesia dolorosa?
Pain in an area that lacks sensation
Often in the face after rhizotomy for bigeminal neuralgia
What is the treatment for anesthesia dolorosa?
Antidepressants, anticonvulsants, opiates, support
What is stage I of CRPS?
1-3 months: pain, joint stiffness, muscle spasm, rapid hair growth, blood vessel changes leading to temp changes and discoloration
What is stage II of CRPS?
3-6 months: intensified pain, hair loss, edema, bone weakness, weak muscles, joint stiffness,
What is stage III of CRPS?
> 6 months: irreversible changes to bone and joint, muscle atrophy, involuntary spasms, contractures, distortion of limbs, pain involving the entire limb
What does chronic opioid usage lead to?
Disruption of HPA axis: decreased cortisol levels, FH, LSH, estrogen and testosterone levels.
Increased prolactin
Addisonian like symptoms from decreased cortisol
Where is the stellate ganglion?
Lies in close proximity to carotid sheath. Comprised of the inferior cervical and first thoracic sympathetic ganglia
How are nociceptive cation (Na and Ca) channels opened?
Via TRPV1 (transient receptor vanilloid OR ATP purinergic P2X 3 receptor
What does the thalamus do in pain?
Provides higher order neurons to the cingulate cortex (dull, poorly localized pain) and post central gyrus (sharp, localized pain)
What does the dorsal raphe nucleus do?
Provides inhibitory signals via serotonergic pathways through serotonin excretion
What does locus ceruleus do?
Provides inhibition of norepinephrine signals