Pain Management

Question 1

Categories of pain

Answer 1

-Nociceptive: stimuli from somatic and visceral structures (trauma, surgery)
-Cutaneous
-Visceral: internal organs, poorly localized
-Somatic: muscle, bones, nerves, non-localized
-Neuropathic

Question 2

Process of pain

Answer 2

-Transduction
-Transmission
-Perception
-Modulation

Question 3

Classes of pain management

Answer 3

-Nonopioid analgesics
-Opioid analgesics
-Adjuvant analgesics or co-analgesics

Question 4

WHO Step 1: NSAIDS & acetaminophen

Answer 4

-Work at the site of tissue injury
-Prevent formation of nociceptive mediators (prostaglandins)
-Ibuprofen, Aleve, Advil, Naprosyn, Ketorolac, diclofenac
-Naprosyn has the greatest safety profile
-Nonselective NSAIDs and cyclooxygenase (COX)-2
-Increased risk of cardiovascular events in some patients

Question 5

Nonselective NSAIDS

Answer 5

-Inhibition of prostaglandin synthesis (COX-1 and 2)

Question 6

Selective NSAIDS

Answer 6

-COX-2 only
-Celecoxib, rofecoxib, valdecoxib for RA and osteoarthritis
Rofecoxib and celecoxib for acute pain

Question 7

WHO Step 2: Opioids

Answer 7

s/e: hotn, depressed RR, CNS and hallucinations, n/v, ileus, constipation, urinary retention, histamine release (itching)
-Examples: fentanyl, dilaudid, morphine (MS contin), oxycodone, oxycontin, methadone,

Question 8

IV Opioids

Answer 8

–IV morphine: 5-10 mg Q4-6h (Metabolites accumulate in renal failure = sedation and respiratory depression)
-fentanyl 50-100 mcg q4-6h (Less histamine release = better in hypotension and bronchospasm, Safe in ESRD)
-dilaudid 1-2 mg q4-6h (Safer in ESRD, High concentration / low volume)

Question 9

Epidural analgesia

Answer 9

-Effective analgesia without need or reduced need for systemic opioids
-Incidence of postoperative respiratory problems and chest infections is reduced
-Incidence of postoperative MI is reduced
-Stress response to surgery is reduced
-Motility of intestines is improved
-Local anesthetics: Lidocaine, Mepivicaine, Bupivicaine
-Opioids: Morphine, fentanyl, sufentanil
-Dosing: IV bolus (usually done at initiation), Continuous slow drip

Question 10

Ketamine

Answer 10

-NMDA receptor antagonist that blocks the release of excitatory neurotransmitter glutamate and provides anesthesia, amnesia and analgesia be decreasing central sensitization and the “wind-up” phenomenon
-Initial bolus (subdissociative dose) 0.2-0.3 mg/kg IV over 10 minutes; Then drip at 0.1-0.3 mg/kg/hr

Question 11

Naloxone (Narcan)

Answer 11

-Opioid antagonist: higher affinity for Mu opioid receptors
-Used to reverse opioid OD, resp depression,
-Immediate reversal
-Route: IV, intranasal, subq, IM
-0.4mg for respiratory depression repeat until desired response
2mg for unresponsive / apneic patient
-Effects up to 45 minutes, prepare to have to repeat dose

Question 12

Adjuvant medications: capsaician

Answer 12

-Made from “peppers”
-OTC
-Unknown mechanism of action – thought to desensitize the cutaneous nociceptive neurons
0.025%-0.075% Capsaicin Cream QID

Question 13

Adjuvant medications: lidocaine patch

Answer 13

-Used for post herpetic neuralgia
-May have some utility in rib fractures and back pain
-Mechanism of action
Stabilizes NA ion channel and inhibits nerve impulse initiation
5% patch on for 12 hours, off for 12 hours

Question 14

Serotonin Receptor Agonists (triptans)

Answer 14

-Used in migraine headaches, cyclical vomiting with abdominal pain
-Sumatriptan (Imitrex): 50-100 mg oral q 2 hours or until resolved or 200 mg/day
-s/e: Chest pain, HTN, serotonin syndrome, paresthesia, hot/cold sensitivities, flushing, weakness

Question 15

Tricyclic antidepressants

Answer 15

-Most Useful in neuropathic pain, fibromyalgia
-May have synergy with opiates
-Useful in Chronic Pain (depression)
-No TCAs carry indication for pain management
-Amitriptyline 25 mg daily ( usually need dose escalation to 125mg)
-Usually takes weeks to see response
-Side Effects: Anticholinergic effects, Sedation

Question 16

Anticonvulsants

Answer 16

-Effective especially with neuropathic pain
-Theories for use include membrane stabilization, inhibition of repeated neuronal discharge, and GABA mimetics
-Carbamazepine – Trigeminal neuralgia
-Gabapentin - neuropathic pain
-Lyrica – diabetic neuropathy

Question 17

SSRI/SNRI

Answer 17

-Used if TCA ineffective or not tolerated
-Co treats depression
-First line and approved for diabetic peripheral neuropathy
-Duloxetine (Cymbalta – now off patent)-30mg po daily increase weekly to 120mg daily
-Venlafaxine – Effexor-75mg daily increase weekly (recommended dose 150-225 for pain)

Question 18

Antispasmodics

Answer 18

-Used to treat painful muscle spasm and spasmodic jerks
-Mechanism of action unclear, might be due to sedative effects versus true muscle relaxation
-Cyclobenzaprine – Flexeril (5-10 MG po TID)
-Carisoprodol – Soma (250-350 po QID)
-Methcarbamol – Robaxin (1000mg po QID)
-Baclofen – don’t abruptly stop-withdrawals can be bad! Start 5mg po TID increase by 15mg day every 3 days to total 80mg/24 hours

Question 19

Benzos

Answer 19

-Great short term choice when pain is associated with anxiety
-Clonazepam (2-4 mg po daily) useful in neuropathic pain (GABA potentiation)
-High addiction and abuse potential
-Potentiates sedation and respiratory depression: Especially used in conjunction with opioids!!
-Lorazepam-Ativan (0.5-1mg IV every 4 hrs, 1-2 mg po q 6 hrs)

Question 20

Antihistamines

Answer 20

-Diphenhydramine – Benadryl (25-50mg po, im, iv q 4-6 hr)
-Hydroxyzine – Vistaril, Atarax (25-100mg po or im every 4-6 hr)