Pain Management Flashcards
Pathophysiology of Pain
Stimulation
- Receptors (nociceptors) are activated by stimuli
- May differ for different painful conditions
- Neurotransmitters and ions are released:
- Serotonin
- Norepinephrine
- Baradykinin
- Prostiglandin
- Histamin
- Substance P
- Neurokinin
- Potassium and hydrogen
- Release of these substance in the periphery “activates” further neurons reducing the threshold for further inputs
Pathophysiology of Pain
Transmission
- Process by which pain signals ascend throught the spinothalamic tract
- Primary neurotransmitters involved are:
- glutamate/aspartate
- substance P
Pathophysiology of Pain
Perception
- the process that occurs in the cortex allowing an awareness of the experience of pain
- nonpharmacological therapies are based on modifying the patient’s perception of his or her pain
- CBT
- meditation
Pathophysiology of Pain
Modulation
- process of modification of pain signals
- can occur through the ascending or descending pathway
- endogenous systems of modulation include inhibitory neurotransmitters/receptors
- Endogenous opioids
- Blockade of NMDA (N-methyl-D-spartate)
- Serotonin
- GABA (Gamma- aminobutyric acid
Pathophysiology of Pain
Centralization or central sensitization
- an amplification of pain signals originating in the periphery.
- this amplification over time imprints or sustains the pain in the CNS
- thought to explain pain syndroms such as phantom limb pain, reflex sympathetic dystrophy, and hyperalgesia
Pathophysiology of Pain
Allodynia
presence of pain from stimuli that are not normally painful
e.g. a patient with diabetes who experieces pain when placing socks on feet
Pathophysiology of Pain
Hyperalgesia
- normal pain stimuli produce exaggerated pain responses in patients with peripheral or central sensitization
e. g. an immunization in the deltoid muscles cuases patients to experience extreme pain for many days, preventing them from lifting their arm. The injection site has no obvious erythema or signs of an injection site reaction
Acute Pain
1) pain is typically a result of an acute disease process (may be part of an mixed disease process - acute or chronic) and is typically managed as a symptom
2) Pathophysiology is primarily inflammation
3) Treatment goals include cessation of pain or substantial relief
4) Anticipatory anxiety may be involved - patients are worried that pain will worsen or that pain will reoccur when medication wears off.
Chronic Pain
1) a physiologic cause may not be determinable. Chronic pain should be managed as an independant disease state with a monitoring and treatment plan apart from other plans
2) Most types of chronic pain are mixed - somatic and neuropathic
3) Treatment goals include a reduction in pain and an improved quality of life. Patients do not usually achieve remission of their pain. Realistic expectations should be discussed
4) Anxiety and depression are often (30-50%) comorbidities of pain. Most patients develop a tolerance to and dependence on medications
Acute Pain Management
Mild
- manage with acetaminophen or NSAIDs
- consider around the clock dosing
- may require adjuvants in certain situations
- monitor and reassess
Acute Pain Management
Moderate
- manage with acetaminophen or NSAIDs in combination with low dose opioids
- consider around the clock dosing
- may require adjuvants in certain situations as well as potentially agents for breakthrough pain
- monitor and reassess
Acute Pain Management
Severe
- long acting opioid analgesics and combinations with breakthrough medications
- around the clock dosing
- may require adjuvants in certain situations as well as potentially agents for breakthrough pain
- monitor and reassess - patients are at higher risk for adverse effects and require stricter monitoring
Chronic Pain Therapies
Arthritis
Pharmacotherapy:
- first-line agents: acetaminophen, oral and topical NSAIDs, intraarticular steroids
- Tramadol
Nonpharmacotherapy
- aquatic, aerobic, and resistance exercise
- weight loss
Chronic Pain Therapies
Diabetic Neuropathy
Pharmacotherapy:
- primary goal - maintain diabetic control. Agent with highest level of evidence: Pregabalin - most common side effect weight gain
- Second tier agents/therapy - all are considered acceptable agents with weak levels of evidence and showed a significant number of adverse effects in trials
- Gabapentin
- Duloxetine
- Sodium valproate
- Venlafaxine
- Dextromethorphan
- Morphine sulfate
- Tramadol
- Oxycodone
- Capsaicin
Nonpharmacotherapy
- Percutaneous electrical stimulation
Diabetic Neuropathy adjuvants
Pregabalin
Dose: 300- 600mg
Common adverse effect: Sedation, weight gain
Diabetic Neuropathy adjuvants
Gabapentin
Dose: 1800 - 3600mg
Common adverse effect: Sedation, weight gain
Comment: dose should be reduced in renal dysfunction
Diabetic Neuropathy adjuvants
Duloxetine
Dose: 60-120mg
Common adverse effect: nausea, increase blood pressure, headache
Comments: Should not be used if CrCl<30; use with extreme caution with other serotonergic agents, rare LFT changes
Diabetic Neuropathy adjuvants
Venlafaxine
Dose: 75-225mg
Common adverse effect: hypertension
Comments: dose adjustment necessary if CrCl<50
Diabetic Neuropathy adjuvants
Desipramine, Nortriptyline
Dose: 25-150gm
Common adverse effect: Sedation, anticholinergic
Comments: Doses effective for pain may not be therapeutic for depression
Diabetic Neuropathy adjuvants
Topiramate
Dose: 50-200mg
Common adverse effect: Sedation, parasthesia, nopholithiases, secondary angle closure glaucoma, neurocognitive impairment, metabolic acidoses
Comment: titration by 25mg weekly will reduce work-finding difficulty and other neruocognitive effects
Chronic Pain Therapies
Herpetic neuropathy
Pharmacotherapy - should e chosen on basis of comorbid conditions and location of the patient’s neuralgia
1) lidocaine patch
2) Duloxetine
3) Venlafaxine
4) Gabapentin
5) Pregabalin
6) Tricyclic antidepressants
7) Capsaisin 8% patch - Newer option
8) Opioids - short or long acting, depending on severity of pain
Nonpharmacotherapy
- current guidelines do not recommend nonpharmacotherapy
Fibromyalgia
Diagnostic Criteria
1) Widespread pain index (WPI) of 7 or greater and symptom severity (SS) score of 5 or greater, or patients may have a lower WPI (3-6) if SS score is >9
2) Symptoms have been present for >3 months
3) There are not other diagnostic explanations for the pain/symptoms
WPI - - Number of anatomic areas with pain - scale ranges from 0-19
SS - patients are rated from 0-3 on fatigue, cognitive symptoms, waking unrefreshed and somatic symptoms. The final score is 0-12
Fibromyalgia
Pharmacotherapy
1) Tramadol recommended for moderate to severe FM
2) acetaminophen or weak opioids can be considered
3) corticosteroids and strong opioids are not recommended
4) Antidepressants: amitryptyline, fluoxetine, duloxetine, milnapracin. Reduce pain and improve function
5) Pramipexole and pregabalin reduce pain
Fibromyalgia
Nonpharmacotherapy
- heated pool treatment with or without exercise is effective
- patient specific exercise programs includine aerobic exercise and strength training (should be supervised to increase adherence and reduce injury)
- CBT benefit to some patients. Strongest level of evidence among nonpharmacological therapies
Chronic Back Pain
Risk factors
1) Obesity
2) Depression
3) Lifting associated with occupation
Chronic Back Pain
Red Flags
symptoms of cauda equina syndrome or central canal spinal syndrome (medical emergency) - loss of bowel control
1) New-onset bladder incontinence
2) loss of weight
3) pain is worse at rest or in the middle of the night
4) new or worsening redicular symptoms - numbness or tingling
5) new-onset back pain in someone who is taking steroids or who has HIV
6) drop foot
7) focal neurologic deficitys
Chronic Back Pain
Pharmacotherapy
1) !st line agents - acetaminophen and NSAIDs
2) 2nd tier agent - tramadol and long-acting opioids (should only be used for patients who are disables by their pain or not candidates for 1st line agents
3) Skeletal muscle relaxants are of limited benefit and have a high incidence of adverse effects, primarily their sedative properties
4) Patients with a neuropathic component involved my benefit from the addition of an SSRI or anticonvulsant. Duloxetine is approved for treatment of low back pain. Gabapentin has limited data to support its use.
Chronic Back Pain
Nonpharmacotherapy
1) guidelines support the use of yoga, massage, acupuncture, relaxation, exercise and CBT
2) for patients who are obese, weight loss will improve outcomes.
Tools for assessment of pain severity
1) Pain measurement: VAS
2) Brief Pain Inventory
3) McGill Pain Questionaire
Pain measurement: VAS
- 10cm line - patients indicate on where the line corresponds to their pain - yeild a number from 0-100
- this scale may be difficult for some patients to understand
- Pain numberic rating scale. 1-10 - Patients rank their pain. Patients become desensitized to this tool - “always a 20”
Brief Pain Inventory
- patients indicate on a diagram of the body wherey they experience pain
- patients also rate the severity of their pain and the relief they obtain from currently prescribed agents.
- this tool requires a higher education level
- good for ongoing monitoring
McGill Pain Questionaire
- patients are asked to rate their pain and then choose descriptor works for their pain
- this tool requires the patient to have a higher reading level
- good for initial evaluation
Testing methods for Chronic Opioid Therapy
Urine immunoassay
Advantages:
- less expensive
- longer detection window than serum
- less invasive than serum
Disadvantages
- May not detect all medications in class (e.g. synthetic opioids)
- more false positives than GC-MS
Testing methods for chronic opioid therapy
Urine GC-MS
Advantages
- more precise results
- longer detection window than serum
Disadvantages
- Costly
Testing methods for chronic opioid therapy
Quantitative serum testing
Advantages
- shows results for metabolites
- in high-dose patient, may detect aberrant metabolism patter
- provides documentation for provider of serum levels
Opioid risk tool
1) five question tool completed by the patient
2) easily completed in office setting
3) particularly suited for those anticipated to be a low risk
4) patients are asked about family and personal history of substance abuse, mental health history and age
5) yes/no questions
6) tool was originally validated in patients who were not expected to have risks of misusing medications
Diagnosis, intractability, risk, efficacy (DIRE)
1) seven item completed by patient interview
2) correlates with efficacy of long-term therapy
3) better evaluation of environmental factors, which may influence the success of chronic opioid therapy
Cuurent opioid misuse measure (COMM)
1) 17 item questionnaire designed to assess patients for addiction, problematic behaviour, emotional volatility
2) designed to evaluation patients with a history of substance misuse to determine their level of risk while on chronic opioid therapy
3) the COMM is helpful in monitoring patient’s medication-related behaviour while receiving opioid therapy
4A’s of opioid patient assessment
analgesia
adverse effects
aberrant behaviour
activity
Equianalgesic doses of outpatient opioids
Morphine
Equianalgesic dose: 30mg
Brands: MS Contin, Oramorph SR, Long acting, Avinza, Kadian
Adverse effects often limit use - nausea, itching.
May require tid dosing in some patients
Should not be used in patients with renal compromise
Equianalgesic doses of outpatient opioids
(Morphine 30mg)
Hydrocodone
Dose: 30mg
Brands: Lortab, Norco, Vicodin, Zydone, Lorcet (with acetaminophen), Reprexain (with iburpofen)
This short-acting agent may be suitable to test opioid responsiveness, but is not usually suitable for chronic opioid therapy
Equianalgesic doses of outpatient opioids
(Morphine 30mg)
Codeine
Dose: 200mg
Brands: Various generic products
Patients often report itching and nausea < constipation with codeine
Conversion to morphine by 2D6 required for analgesia
Equianalgesic doses of outpatient opioids
(Morphine 30mg)
Hydromorphone
Dose: 7.5mg
Brands: Dilaudid - short acting
Equianalgesic doses of outpatient opioids
(Morphine 30mg)
Oxycodone
Dose: 20mg
Brands: Oxycontin, Percocet, others
Equianalgesic doses of outpatient opioids
(Morphine 30mg)
Oxymorphone
Dose: 10mg
Brand: Opana
Equianalgesic doses of outpatient opioids
(Morphine 30mg)
Tramadol
Dose: 120mg
Brand: Ultram, Ultram ER
Can cause nausea and dysphoria in some pts
Should be avoided with other serotinergic agents
Conversion to 0-desmethyl-metabolit through 2D6 required for analgesia
CIII in some states
Equianalgesic doses of outpatient opioids
(Morphine 30mg)Tapentadol
Dose: 100mg
Brands: Nucynta and nucynta ER
Fewer overall GI adverse effects than other opioids
CII
Approved for both acute and chronic pain
Conversion from morphine equivalents (mg/day) to fentanyl transdermal (mcg/hour)
60-136 : 25 135-224 : 50 225-314 : 75 315-404 : 100 405-494 : 125 495-584 : 150 585-674 : 175 675-764 : 200
Opioid Nasal Spray
1) Butorphanol - useful for some patients with migraines for acute relief but can lead to medication overuse headaches and is not recommended by AAN guidelines
2) Fentanyl nasal spray - indicated only for cancer breakthrough pain in opioid tolerant patients
