Pain management Flashcards
What is the physiology of processing pain
- Pain sensation STARTS w/ stimulation of nociceptors
- Receptors are in somatic and visceral structures, and help discriminate noxious from innocuous stimuli
- Nociceptors are activated by mechanical, thermal, or chemical stimuli
- Noxious stimuli may activate cytokines or chemokines that activate/sensitize nociceptors
What are the steps in processing pain
- Transduction: stimulation of nociceptors by mechanical, thermal, or physical stimuli
- Conduction: receptor activation causes AP along afferent fibers (large myelinated or small unmyelinated) to spinal cord.
- Transmission: Nociceptive fibers synapse in dorsal horn and release excitatory NT, while spinothalamic tract brings signal to higher brain structures
- Perception: you experience pain when signals reach higher cortical structures
- Modulation: Glutamate, substance P, endogenous opioids, GABA, NE, and serotonin can modulate pain
What is maladaptive pain
Pathophysiologic pain resulting from damage or abn fxn of nerves in CNS or PNS. Pain circuits rewire themselves anatomically and biochemically= chronic pain, hyperalgesia, or allodynia
Examples of maladaptive pain are
postherpetic neuralgia diabetic neuropathy fibromyalgia IBS chronic headaches
Explain Somatic pain
arise from skin, bone, joint, muscle, or connective tissue
Pain presents as throbbing and well localized
Explain visceral pain
arise from internal organs (colon, pancreas, etc.)
Manifests as pain coming from other structures (referred pain) or as a more localized phenomenon
During stimulation of nociceptors, noxious stimuli may lead to release of
Bradykinins H+ and K+ ions Prostaglandins Histamine Interleukins TNF-a Serotonin Substance P
What kind of pain do different size fibers transmit
Large, myelinated A fibers: sharp, localized pain
Small, unmyelinated C fibers: dull, aching, poorly localized pain
What is the endogenous opiate system
consists of NT like enkephalins, dynorphins, and endorphins
Receptors mu, delta, kappa found throughout the CNS
Where are NMDA receptors found
in the dorsal horn
They can increase the receptors responsiveness to opiates
What is the descending system for control of pain transmission in the CNS
a system that originates in the brain and can inhibit synaptic pain transmission at dorsal horn
NT include endogenous opioids, serotonin, NE, and GABA
What cognitive and behavioral functions can decrease pain
Relaxation
Distraction
meditation
guided mental imagery
What can worsen pain
depression and anxiety
What is inflammatory pain
Body shifting from preventing tissue damage to promoting healing
Pain threshold is reduced and the injured area becomes more sensitive
What does adaptive inflammation do
decreases our contact with and movement of injured area, promoting healing
Increased excitability or responsiveness of neurons in CNS (central sensitization)
Central sensitization is a major cause of
hypersensitivity to pain after injury
What is neuropathic vs functional pain
Neuropathic: result of nerve damage (post-herpetic neuralgia, diabetic neuropathy
Functional: abnormal operation of nervous system (fibromyalgia, IBS, HA)
-both are types of maladaptive pain!
How do patients describe neuropathic and functional pain
burning, tingling, shock like, or shooting
hyperalgesia (exaggerated pain response to normal noxious stimuli)
allodynia (pain response to normally non-noxious stimuli)
-Explains why this type of pain manifests long after actual nerve related injury is identified
What are some etiologies of cancer pain
The disease itself: tumor invasion, organ obstruction
Treatment: chemo, radiation, surgical incisions
Dx procedures: biopsy
Non-pharm therapies for acute and chronic pain are
physical manipulation
heat or cold application
massage
exercise
Transcutaneous electrical nerve stimulation (surgical, traumatic, neuropathy, and MSK pain)
Cognitive, behavioral, and social aspects of pain Tx
Pain is…
subjective
best diagnosed based on patient description, H&P
How can you obtain a baseline pain description
PPQRSTl
Palliative (what makes it better)
Provocative factors (what makes it worse)
Quality (describe the pain)
Radiation (and location)
Severity (how does it compare to other pain you’ve felt)
Temporal (intensity change with time)
Describe acute pain
- Not usually dependent or tolerant to medication
- No psych component, depression, or insomnia (usually)
- Tx goal is pain reduction
- Usually has identifiable cause
Describe chronic pain
- Usually dependent or tolerant to meds
- Psych often a major problem (depression common)
- Significant family issues
- Usually no identifiable cause
- Tx goal is functionality
How do infants present with acute pain
change in feeding habits
increased agitation
calling out
Sx of acute distress are
sharp, dull, shock like, tingling, shooting, radiating, fluctuating intensity, varying location
Occur in a timely relationship with obvious noxious stimuli
Signs of acute pain are
HTN tachycardia diaphoresis mydriasis pallor (signs are NOT diagnostic; sometimes there aren't even obvious physical signs of pain)
What must you pay attention to in chronic pain
mental and emotional factors that alter pain threshold; people can appear to have no noticeable suffering
Symptoms of chronic pain are
sharp, dull, shock-like, tingling, shooting, radiating, fluctuating in intensity, and varying in location
occur withOUT a temporal relationship with a noxious stimuli
Over time, pain stimulus may cause Sx to change (sharp to dull, obvious to vague)
Signs of chronic pain are
Most cases, no obvious signs
But they DO have comorbid conditions!
Outcome of Tx is not predictable (where as it IS predictable in acute pain)
What non-opioid analgesics can be used to alleviate pain
ASA: stop 7-10 days before surgery
Choline and mag trisalicylate: no anti-platelet function bc no acetyl group (750 q8hr for old)
Diflusinal: no acetyl group
APAP: 2g max for old, 3g max for gen pop. <50kg, 750mg max single dose
More nonopioid analgesics (used less) are
Anthranilic acid (Mefenamic acid): max 7 days Indolacetic acid (Etodolac)
Non-opioid analgesics approved for adults are
- Phenylacetic acids: Diclofenac potassium, D. epolamine (patch over intact skin), D. sodium (voltaren gel)
- Propionic acid: Ibuprofen (max 3.2g inflamm, 1.2g analgesia/fever), Ketoprofen, Naproxen (OA), Naproxen sodium (acute pain)
What are pyrrolacetic acids
Ketorolac! Max 5 days
parenteral
oral: only use if continuation of parenteral
nasal: old or <50kg, one spray in one nostril q6-8 hrs
What is the selective cox-2 inhibitor
Celecoxib
if cardiac concern, max 200mg x day
(use ASA before Celecoxib)
What do you need to monitor when taking NSAIDs
upper GI bleed: CBC, stool guaiac
acute renal failure: SrCr
What do you need to monitor when taking APAP
Hepatotoxicity: ALT/AST, PT/INR, albumin, APAP serum concentration
NSAIDS, APAP, and ASA are used in
mild to moderate pain
Can be used with opioid agents
NO alcohol with APAP
avoid OD when combining with products that low key include them already
What underlying factors expose someone taking NSAIDs to nephrotoxicity
Renal impairment
hypovolemia
CHF
Describe the pain scale
Mild: 0-3/4
Moderate: 4-7
Severe: 8-10
What are the Phenanthrenes
Morphine: naturally occurring, high histamine release
Dilaudid (hydromorphone): semi synthetic, low histamine release
Oxymorphone: semi-synthetic, low histamine release
Levorphanol
Codeine: natural, high histamine release
Hydrocodone: semi-synthetic, no histamine release
Oxycodone: semi-synthetic, low histamine release
What is morphine used for
drug of choice in severe pain
can use immediate release product with controlled release product to control breakthrough pain in cancer
What is hydromorphone used for
severe pain
more potent than morphine, no other benefits
What is oxymorphone used for
severe pain
ER formula to deter misuse
can use immediate release with controlled release to control breakthrough cancer pain
What is Levorphanol used for
severe pain
extended half life, good for cancer patients
if w/ chronic pain, wait 3 days for dose adjustment
What is codeine used for
mild-moderate pain and cough suppression
Depends on CYP450 2D6 to metabolize it to morphine
weak analgesic, so use with NSAIDs, ASA, or APAP
NO in kids!!
What is hydrocodone used for
mod-severe pain
best if used with NSAID, ASA, or APAP
only available as a combo product w/ other analgesics
What is oxycodone used for
mod-severe pain
most effective with NSAID, ASA, or APAP
can use immediate release for breakthrough cancer pain
Reformulated to deter misuse
What are the phenylpiperidines
Meperidine (demerol): synthetic, high histamine release
Fentanyl: synthetic, low histamine release
What is Meperidine used for
severe pain (oral route NOT recommended)
do NOT use in renal failure
Can cause tremors, myoclonus, and seizures
Produces Mydriasis (dilation)
Can cause hyperpyrexia or Sz if used w/ MAOI
What is Fentanyl used for
severe pain (no transdermal for acute pain) Transmucosal, intranasal, and sublingual: start low, despite daily opioid use. can Tx breakthrough cancer pain in pt already receiving or tolerant to opioids *Must do REMS program to Rx transmucosal, intranasal, or sublingual forms
What are the Diphenylheptanes
Methadone: synthetic, low histamine release
Methadone treats severe chronic pain, but watch for sedation
Chronic pain can dose q12 hours
Do not titrate sooner than q2 weeks
What is a large reason for lower use of methadone
QT prolongaiton!
can lead to torsades
What are the agonist-antagonist, or partial agonists (all synthetic)
Pentazocine
Butorphanol
Nalbuohine
Buprenorphine (suboxone)
What is pentazocine used for
third line for mod-severe pain
can cause withdrawal in opioid dependent patients
Parenteral dose NOT recommended
What is Butorphanol used for
second line for mod-severe pain
can cause withdrawal in opioid dependent patients
What is Nalbuphine used for
second line for mod-severe pain
can induce withdrawal in opioid dependent patients
What is Buprenorphine* used for
second line for moderate to severe pain
can cause withdrawal in opioid dependent patient
Naloxone may NOT reverse respiratory depression in these patients
Need training to Rx this drug!
What are the central analgesics (synthetics)
Tramadol
Tapentadol
How do you dose tramadol
Max for non-extended release: 400mg/24hr
Decrease dose if >75 or CrCl<30 (max is 300)
How do you dose Tapentadol
First day: can give another dose 1 hr after first dose. Max 700mg
After first day:max dose 600 mg
Need REMS
If taking opioids, you must monitor for
Respiratory depression (RR or end tidal capnography)- higher risk if w/ OSA or COPD
constipation: BM frequency and consistency
Sedation
N/V
Tolerance
Dependence
Addiction/Abuse
Histamine release (urticaria, pruritis, bronchospasm)
Increased sphincter tone (urine retention, biliary spasm)
Hypogonadism (fatigue, depression, amenorrhea)
Opioids to avoid and exercise caution in bc of what they do
Codeine: don’t use in kids or pregnancy
Meperidine: not recommended bc it doesn’t last long , can cause seizures and renal insufficiency and serotonin syndrome
Agonist/Antagonist: can cause opioid withdrawal
Tramadol: caution in old or renal dysfunction. risk of seizure, serotonin syndrome, and hypoglycemia
What is Naloxone
a synthetic opioid antagonist
Duration of action of some opioids can outlast duration of naloxone, so you may need repeat doses
When you give narcan, call 911 ASAP!
What are Tx options for neuropathic pain
anticonvulsants TCA SNRI Opioids topical analgesics (she recommends methadone and tramadol)
What is Gabapentin
anti-convulsant that decreases excitatory NT and nociception through voltage gated calcium channels (esp. w/ a-2 d-1 subunit)
ADE of gabapentin are
peripheral edema weight gain tremor dizziness ataxia fatigue HA abnormality in thinking, amnesia
What is pregabalin (lyrica)
binds a-2d receptor of voltage gated calcium channels in CNS= inhibits excitatory NT
structurally related to GABA, but does NOT bind GABA or benzo receptors
Anti-nociceptive and anti-convulsant activity
decreases Sx of painful peripheral neuropathies
can affect descending noradrenergic and serotonergiv pain transmission from brain to SC
ADE of pregabalin are
peripheral edema weight gain tremor dizziness ataxia
What are adjunct therapies to use for chronic pain
TCA and SNRI: block reuptake of serotonin and NE in order to enhance pain inhibition
What are topically local analgesics/anesthetics that decrease nerve stimulation
Lidocaine patch
NSAID patch: flector, voltaren
OTC salonpas, Tigerbalm
How does tiger balm work
increases blood flow to the area and decreases pain
What is Duloxetine (cymbalta)
potent SNRI
weak dopamine reuptake inhibitor
Does not significantly act on muscarinic chlinergic, H1, a-2 adrenergic receptors, or MAOI
ADE of Suloxetine (cymbalta) are
HA drowsiness fatigue nausea xerostomia insomnia agitation
What is regional analgesia
local anesthetics that can also provide relief of chronic and acute pain by blocking nerve impulses
injections (in joints, epidural/intrathecal space, along nerve roots, or in a nerve plexus) or topicals
What is proven effective in treating focal neuropathic pain
Lidocaine patches
ADE of regional analgesics are
CNS depression and excitation (dizzy, tinnitus, drowsy, disoriented, muscle twitching, seizures, respiratory arrest)
Myocardial depression, hypotension, decreased CO, heart block, bradycardia, arrhythmia, cardiac arrest
Disadvantages of regional analgesics are
need for skillful technical application
need for frequent administration
highly specialized follow up procedures
What are some local anesthetics
Esters: Procaine, Chloroprocaine, Tetracaine
Amides: Mepivacaine, Bupivacaine, Lidocaine, Prilocaine, Ropivacaine
What are some intraspinal epidural opioids
Morphine (can also use subarachnoid)
Hydromorphone (can also use subarachnoid)
Fentanyl
Sufentanil
What is Ziconotide (intrathecal)
Selectively binds N-type calcium channels on nociceptive afferent nerves of dorsal horn
blocks excitatory NT release
reduces sensitivity to painful stimuli
NO action on Mu receptor (endogenous opioid system does have effect on these!)
ADE of Ziconotide are
Serious: confusion, dizziness, hallucinations, urinary retention
Eh: sedation, somnolence, nausea, HA
Ziconotide is FDA approved for
first line in localized neuropathic and nociceptive pain with morphine
with morphine in diffuse neuropathic and nociceptive pain
New guidelines say acute, subacute, and chronic back pain should be treated
first w/ non-pharm (heat, massage, acupuncture, CBT, mindfulness based stress reduction, PT)
Limit meds to chronic back pain or inadequate response to non-pharm Tx
Acute: NSAIDs, skeletal muscle relaxers
Chronic: NSAID (1st line). Duloxetine and tramadol (2nd line)
-There are no long term studies on back pain pts Tx with pain meds
What Tx is or is NOT recommended in fibromyalgia
Use: APAP! also Tramadol, SNRI (duloxetine), AED (pregabalin)
do NOT use: opioids
What Tx is recommended in neuropathic pain (non-cancer)
1st: AED, SNRI, TCA, 5% lidocaine patch
2nd: opioids
Rarely effective: APAP, NSAIDs
How can you Tx cancer pain
mild: NSAIDs, APAP
mod: APAP or NSAID + opioid. TCA. AED. Radiopharmaceutical (bone pain)
severe: opioid, NSAID. TCA, AED
What is heroin derived from
Poppy
Diacetylmorphine (acetyl group helps it cross the BBB) that is metabolized to morphine
UDS will show + for morphine and codeine
Heroin can be contaminated with
quinine, scopolamine, strychnine
a true opioid allergy (rare) is due to
IgE mediated or T cell mediated
will present with bronchospasm!
angioedema may be true allergy, but can also be pseudoallergy
what is a pseudoallergy
common type of reaction to opioids; Sx can resemble a true allergy
Caused by histamine release from cutaneous, mast cells, and non-immunologic effect
Sx: itching, flushing, and sweating
hives, tachycardia, and low BP can be seen in a true or pseudo allergy
Pseudoallergy depends on
concentration of the opioid at the mast cell
If you have flushing, itching, hives, sweating, mild hypotension; or itching, flushing, and hives at injection site…
This may be a pseudoallergy as a result of histamine release! Options include:
non-opioid analgesic
Avoid codeine, morphine, meperidine
Use more potent opioid, less likely to release histamine. In order: Fentanyl, Levorphanol, Hydromorphone, Oxycodone, Hydrocodone
Can also admin an antihistamine, or reduce dose if tolerated
The opioids MC associated with pseudoallergy are
Morphine
Codeine
Meperidine
(these all have “high histamine release”)
If you have severe hypotension, skin rxn (not itch flush hive), difficulty breathing swallowing or talking, or swelling of face lips mouth tongue or pharynx…
This is a true allergy! Use a non-opioid analgesic use an opioid chemical class different than the one you gave (Phenylpiperidine, Diphenylheptanes, or Morphine group)
Meperidine has an active metabolite that can cause
hallucinations and erratic behavior
Normeperidine
What will you NEVER grow tolerant to when taking pain medication
Miosis (pupil constriction)
Constipation
-you will eventually grow tolerant to the other ADE!
