Pain management Flashcards
Learning Objectives
• At the end of the session, you will be able to
• Understand the importance of pain management
• Define, Classify and Describe different types of pain
• Describe the key steps in pain assessment
• Describe the principles of pain management
Compare and Contrast the different types pain
medications, including basic dose conversion and titration
- key features of drugs, specific dosage forms
- what to note when starting doses
- some dose titrations are key
- management of side effects as a whole class (N/V/Constipation)
1
The total concept of pain involves 4 key factors which are __, __, __ and __.
Physical
Psychological
Social
Spiritual
A poor __ or __ of pain can cause patients to over-report pain.
- past experience
2. anticipation
Pain is a __ and __ response that varies daily between individuals. It can reflect the quality of __ and may be evidence of __.
- physiologic
- psychological
- care/life
- under-treatment
Chronic pain is defined as pain that persists even after __. This duration varies depending on the __ and may last anywhere from 4-6wks to 3months.
- sufficient time provided for an insult/injury to heal
2. type of injury
There are 4 types of pain classified according to pathophysiology, which are __, __, __ and __.
Nociceptive Pain, Neuropathic Pain, Referred Pain and Ischemic Pain
Nociceptive pain is due to actual nociceptive input (in terms of __. It can be subdivided into __ and __.
- tissue damage
2. somatic and visceral pain
Somatic pain occurs when nociceptors are triggered by noxious stimuli (__, ___ or __ types). These signals are carried by small myelinated A delta fibers (__ stimuli) and C fibers (__) to the dorsal horn of the spinal cord.
- mechanical, thermal or chemical
- mechanical and thermal
- all three stimulus types
Somatic pain can be subdivided into __ and __ somatic pain. Somatic pain is __ to the site of injury, is constant and sometimes feels like it is __.
- cutaneous
- deep
- tender and localized
- throbbing or aching
Visceral pain is mediated by __ receptors. It is poorly __ and often referred to a __ which may be tender. Patients may find it difficult to pinpoint the exact location.
- stretch
- localized
- distant cutaneous site
Patients may describe it as __, __ and __ (eg, appendicitis, cholecystitis). It is a good idea to relate to __ to find possible pressing forces on viscera.
- deep, dull, and cramping
2. patient history
Neuropathic pain is caused by __ in either the peripheral or central region. It may be due to __ or its __ (diabetes, infection, cancer, drugs, radiation).
- injury to the nerves
- disease
- treatment
Neuropathic pain is often described as prolonged, severe, __, __ , or squeezing , and is often
associated with __. If severe, neuropathic pain may be accompanied by weakness.
- burning
- lancinating
- focal neurologic deficits
In neuropathic pain, there may be no __, but areas of __ (allodynia). It is also characterized by its relative __, making it the most challenging type of pain to treat.
- area of tenderness
- exquisite sensitivity to normally innocuous stimuli
- resistance to opioids
__ neuropathic pain results from abnormal nerve generation while __ neuropathic pain results from reorganization of central somatosensory processing.
- Peripheral
2. central
Referred pain is pain __. It may occur because signals from different part of body travel along the __ going to the spinal cord and the brain.
• i.e. Obstructed bile duct produces pain near right side of scapula
• i.e. Hip injury pain referred to the knee
- located away from its point of origin
2. same pathways
Ischaemic pain is caused by __ to tissue (poor/no perfusion to area), leading to tissue hypoxia and damage. This causes a release of inflammatory mediators and chemicals that stimulate nociceptors
• i.e. Angina Pain
loss of blood flow
Pain that feels aching, stabbing, throbbing, or pressure is likely to be __ pain, originating from __.
- Somatic (Nociceptive)
2. skin, muscle, bone
Gnawing, cramping, aching, or sharp pain is likely to be __ pain, originating from __.
- Visceral
2. Organs or viscera
Burning, tingling, shooting, or electric /shocking pain is likely to be __ pain, originating from __.
- Neuropathic
2. nerve damage
Pain evaluation of patients can be subjective via __ (even if tissue damage cannot be observed) or objective via autonomic signs associated with acute pain, (increase __) especially in unconscious patients.
- signs of distress
2. RR, HR, BP, diaphoresis
When taking pain history, the usage of __ can help elicit more details. History should be __ and we have to look out for __ (consider total concept).
- open-ended questions
- taken separately for each pain
- signs of psychological distress
The SOCRATES framework can help get a good pain history:
• S__: Where is it?
• O__: When did it start? How did it start?
• C__: How does it feel? (look for neuropathic pain)
• R__: Does it run anywhere?
• A__: A ny other symptoms?
• T__: How long have you had it?
• E__: What makes it worse/better?
• S__: How bad is it? (using 1-10 subjective scores)
- site
- Onset
- Character
- Radiation
- Associations
- Time course
- Exacerbating/relieving factors
- Severity
The goal of pain assessment is to: • \_\_ the pain • Identify pain syndrome (Acute/chronic/breakthrough, Cancer/Non cancer related) • Infer \_\_ (Nociceptive/Neuropathic) • Evaluate physical and psychosocial \_\_ • Assess degree and nature of \_\_ • Develop a therapeutic strategy
- Characterize and Quantify
- pathophysiology
- comorbidities
- disability
General tool for quantifying pain intensity is via the __. When assessing pain for children and elderly who do not verbalize well, the __ tool is preferable (ensure the score is patient-reported and not by healthcare professionals!!).
- Numerical rating scale
2. Wong-Baker Faces Rating Scale
For patients who cannot self-report pain (i.e. < 3 years old), the FLACC scale (f_, L_, A_, C_, C_) is recommended. Each factor is scored 0-2, and the sum is reported on a scale of 0-10.
- face, legs, activity, cry, consolability
The __ assessment tool is based on a 10cm line where patient can make a marking on the line to indicate where their pain is. It is mainly used in the research setting to attempt a more ‘objective’ measure of pain.
visual analog scale
The __ assessment tool allows patients to assess their pain using various adjectives i.e. annoying, dreadful, agonizing etc..
adjective rating scale
The __ pain questionnaire is often used to measure effectiveness of analgesics. It measures 3 dimensions of pain:
- Sensory (location, temporal pattern, quality)
- Affective (emotional response)
- Evaluative (perceived intensity)
McGill-Melzack
Pharmacotherapy options for pain management include:
- __ (opioids and non-opioids)
- __ blocks
- Adjuvant analgesics (neurophatic, musculoskeletal)
- Analgesics
2. Nerve
Alternative methods for pain management include:
- Electric stimulation (TENS/PENS)
- a__
- __ therapy
- c__
- Surgery
- Acupuncture
- Physical
- Chiropractics
The 3 key principles of pain management:
- Treat the __ where possible
- Ask what is the __ behind the pain
- Pharmacological Treatments via __
- underlying cause
- Pain Mechanism(s)
- WHO LADDER
WHO treatment guide for cancer recommends:
- __ ROA recommended
- Regular __ of analgesia
- __ regimen
- Treat according to __
- Constant __ (attention to detail)
- PO
- intervals
- Individualize
- patient’s perception
- monitoring
We should match analgesic choice to severity of pain and titrate to response.
• __ titration for severe pain.
• __ titration for moderate pain.
• __ titration for mild pain.
- Rapid
- Slower
- Even slower
20% of cancer pain requires multi dimensional approach:
- __ of pain syndrome, use of 2nd line agents and/or __ interventions.
- reassessment
2. non-pharmacological
Based on WHO pain ladder, a pain score of 1-3 (mild pain) should be treated using:
- __ if patient is not on analgesics (aspirin generally avoided due to __ effect)
- __ and __ if patient is already on analgesics (i.e. max dose)
- Paracetamol/NSAIDs
- irreversible anti-platelet
- Short-acting opioid and bowel regimen
Paracetamol is dosed 500-1000mg doses every 6 to 8 hourly; Max dose: __. It is the most commonly used non-opioid but we have to be cautious of overdose from using different __.
- 4g/day
2. combination products
Paracetamol has a low incidence of (1), high oral/rectal (2), multi-preparations available and is __(3)_____ with opioids. However, it lacks ___(4)______ and can cause __(5)____ with large doses (avoid > 3 grams/day for elderly).
- ADR
- bioavailability
- synergistic
- anti-inflammatory action
- hepatotoxicity
Paracetamol is metabolized in the __ and eliminated in the __. We should watch out for patients with compromised __ function.
- liver
- kidney
- liver and kidney
When choosing NSAIDs, there is no preference and any cost-effective NSAID __ by patient can be used. Alternatively, we may consider the PO equivalent of max tolerated __ dose.
- tolerated
2. ibuprofen
If two NSAIDs are tried in succession without efficacy, we should __.
use another approach to analgesia
COX‐2 selective NSAIDs are associated with lower incidence of __ side effects and do not inhibit __. However, they are more __ than traditional NSAIDs.
- GI
- platelet aggregation
- expensive
NSAIDs are extensively protein bound and excreted mainly in __. They can appear in __ and cross the __.
- urine
- milk
- placenta
NSAIDs can cause __ side effects and reversible platelet inhibition. They should be avoided if patients are on chemotherapy (may develop __). Coxibs would be preferable in this case.
- GI
2. thrombocytopenia
NSAIDs can cause:
• __ effects: edema, HTN, renal failure
• CNS: headache, dizziness, nervousness and visual disturbance
• Cardiovascular effects: edema, cerebrovascular accident, hypertension, MI
• __ (esp classical NSAIDs i.e. indomethacin & mefanamic acid, diclofenac)
• __ : hemolytic anemia, pancytopenia, thrombocytopenia
Other SE:
________ platelet inhibition, ____
- Renal
- Hypersensitivity reaction
- Hematological
- reversible
- GI SE
NSAIDs should be avoided in: • Elderly (>65 years) • \_\_ disorder • \_\_, bronchospasm • \_\_ disease (ulcers, bleeding) • Cardiovascular disease • \_\_ or Hepatic dysfunction • Receiving \_\_
- Bleeding
- Asthma
- GI
- Renal
- anticoagulants
NSAIDs DRUG INTERACTIONs
- Increased risk of bleeding (Anticoagulants and Antiplatelet drugs)
- Increased risk of __ (ACE inhibitors, ciclosporin, tacrolimus, or diuretics)
- Increased risk of GI ulceration (__)
- Reduced __ effects (ACE inhibitors, beta blockers, and diuretics)
- nephrotoxicity
- corticosteroids
- antihypertensive
Adjuvants for neuropathic pain includes: __, __, antidepressants, antiepileptics and topical lidocaine.
- Gabapentin
2. pregabalin
__ can be used as an adjuvant for: Bone pain, neuropathic pain, raised intracranial pressure, liver capsule stretch pain
Corticosteroids
NSAIDs and bisphosphonates are adjuvants for __ pain.
Bone
Muscle relaxants e.g. __ and __ are useful adjuvants for Cramps or muscle spasm
- baclofen
2. benzodiazepines
Hyoscine butylbromide are useful adjuvants for __.
Intestinal colic
Based on the WHO ladder, a patient with a pain score of 4-6 (moderate pain) should be started on a __ agonist. A patient with a pain score of 7-10 (severe pain) should be started on a __ agonist.
- weak opioid
2. strong opioid
Opioids can have effects other than analgesia as a__, a__, s__ and for severe __ (in patients as an allergic alternative).
- antitussives
- antidiarrheals
- sedatives
- Headache
Codeine Phosphate has good onset of __, but a short duration of 4-6h. It can cross the placenta and enter the breast milk. Codeine is metabolized in the __ to morphine and excreted in the __.
- 0.5-1h (PO)
- liver
- urine
The Equianalgesic dose of codeine is: 200mg (oral) codeine = __ mg(IM/SC) Morphine = __mg (IV) codeine
- 10
2. 100
Codeine phosphate and Tramadol are major substrates of __ and may have reduced effects from __ such as chlorpromazine, fluoxetine, miconazole, paroxetine, quinidine and quinine.
- CYP2D6
2. CYP2D6 inhibitors
Codeine causes __ but patients are expected to develop tolerance after 2 weeks. It can also cause __ (no tolerance will develop).
- drowsiness
2. constipation
Tramadol is an opioid agonist that also inhibits reuptake of __ and __, allowing it to have good __ and __ analgesic effect.
- noradrenaline
- serotonin
- somatic and neuropathic
Tramadol is favorable clinically due to its lesser __ and __ side effects compared to other opiates along with a __ potential for abuse.
- cardiovascular
- respiratory
- “Low”
Tramadol has a onset of action of __ with a duration of 9hrs (allowing for longer intervals). It is metabolized exclusively hepatically via __ to a active metabolite and excreted __.
- within 1hr
- CYP2D6
- in the urine
Dosing adjustment for codeine and tramadol are necessary in patients with __ or __ impairment.
- liver
2. renal
Tramadol comes in __ and __ ROAs but regardless of ROA, has a max dose of __ (unlike other opioids who do not have ceiling doses).
- injection
- tablet
- 400mg/day
At high doses of Tramadol, it can __ which explains why it should be avoided in patients __ i.e. patients with brain tumors or patients on drugs with __ (Neuroleptic agents, SSRIs and TCAs).
- lower the seizure threshold
- pre-disposed to epileptic activity
- CNS activity
Tramadol can cause CNS side effects: __, headache, somnolence and GI side effects: __, ___
- Dizziness
2. Constipation, nausea
__ may increase risk of seizures if used together with Tramadol while concomitant use of warfarin and tramadol may lead to __.
Carbamazepine can ______ half-life of tramadol by 33 to 50%
- Naloxone, neuroleptic agents, SSRIs, TCAs
- elevated prothrombin times
- decrease
Morphine has a good onset of action: __ (PO) and __ (IV). It is metabolized in the __ to active metabolites and excreted mainly in the __.
active metabolite: _____
- 30min (PO)
- 5-10min (IV)
- liver
- urine
- morphine-6-glucuronide
The oral : parenteral ratio of morphine is __.
3 : 1
Morphine is available in a variety of ROAs: : Injection, mixture, tablet and capsule. Dose adjustments are required for __. Excessive sedation may occur in patients with __.
- renal impairment
2. cirrhosis
Morphine can cause GI side effects of __ (tolerance usually develops), __ (with chronic use) and __ (reason for bowel regimen).
- Nausea
- vomiting
- Constipation
Morphine can cause __ (may be increased with antipsychotics), drowsiness, __ (secondary to histamine release) and __ (esp in epidural or intrathecal use).
- hypotension
- pruritis
- urinary retention
Patients on morphine should avoid the following as they may increase its effects/toxicity:
- CNS depressants
- __
- __ (some manufacturers recommend 14 day wash out)
- Herbs/nutraceuticals (Avoid valerian, St John’s wort, kava kava, gotu kola)
- _____ increase hypotensive effect of morphine
- Alcohol
- MAOI
- antipsychotic
Fentanyl has an almost immediate onset: __ (IM), __ (IV). It is mainly metabolized hepatically via __ and excreted in __.
- 7-15min
- almost immediate
- CYP3A4
- urine
Fentanyl is about 100 times more potent than morphine. The equianalgesic dose is 100 mcg (IM) fentanyl = __ mg (IM) morphine
10mg
__ is a great opioid in the sense that it has no dose adjustments for hepatic/renal impairment (only requires monitoring in hepatic impairment).
Fentanyl
Transdermal fentanyl is used only if: • intolerable undesirable side effects from \_\_ • \_\_ failure • inability to \_\_ • ‘tablet phobia’ or poor \_\_
- morphine
- renal
- swallow
- oral compliance
Transdermal fentanyl patches achieve steady state concentrations after __ (delayed onset) and have a duration of action of __ (48h for fast metabolizers). The elimination half life post patch removal is __.
- 36-48h
- 72h
- 13-22h
Patients may experience withdrawal symptoms when switching from PO morphine to TD fentanyl despite satisfactory pain relief due to __. These withdrawal symptoms include: e.g. colic, diarrhoea, nausea, sweating and restlessness.
Different impact on peripheral and central µ opioid receptors.
The rate of absorption of TD fentanyl may be increased in __ patients or if the patch’s skin area gets __ due to external heat source i.e. electric blanket/heat pad. __ may be a sign of fentanyl overdose.
- febrile
- vasodilated
- A very sedated patient
It is preferable to place patches on __ areas. __ the hair is preferred over shaving (may shave off epithelial layers and increase absorption rate). Used fentanyl patches should be __ before disposal as it still contains some drug.
- less hairy skin
- Cutting
- folded inward
TD fentanyl have an onset of __ and can accumulate in the __, with effects lasting 12h after the patch is removed. As such, no __ is required when switching patches. However, when switching from TD fentanyl to another opioid, __ is required to provide time for fentanyl to be excreted.
- 6h
- subcutaneous fat
- break
- a break of 12h
Methadone is a µ opioid receptor agonist, an __ receptor channel blocker and a presynaptic blocker of __ re-uptake. It is available as oral tablets and have an onset of __. Its duration of action increases from 4-5h to 6-12h with repeated doses.
- NMDA
- serotonin
- 30min
Methadone is mainly metabolized in the liver via __, CYP2B6, and CYP2C19. Therefore, it makes sense that Methadone levels will be affected by __ inducers/inhibitors. It is excreted mainly in the urine.
CYP3A4
Avoid __ and herbs/nutraceuticals for patients on Methadone (i.e. St John’s wort, valerian, kava kava, gotu kola. As Methadone is metabolized by CYP3A4 (intestinal), avoid __.
- ethanol
2. grapefruit juice
For methadone, dosage adjustment is required for __ impairment. Avoid in __.
- renal
2. severe liver disease
Generally for opioids, tolerance for adverse effects may develop over time; however, constipation and __ (especially bad for methadone) may persist.
Other possible side effects of methadone include: h__, d__ and N/V.
- sweating
- Hypotension
- Drowsiness
Oxycodone has a good onset of action: __min (PO) with a long duration of action: __ (IR) and __ (CR). It is metabolized hepatically to active metabolites and excreted in the urine.
- 20-30
- 4-6h
- 12h
Dosage adjustment of oxycodone is required in __ impairment. Its adverse effects are similar to other opioids: d__, __ and constipation.
- renal/liver
- drowsiness
- N/V
Oxycodone is an useful morphine alternative with about __ the potency and a longer duration of action (__ vs morphine 4h).
- double
2. 6h
Since oxycodone is metabolized to active (more potent) metabolites by __ , __ inhibitors (i.e. chlorpromazine, fluoxetine, miconazole, paroxetine, quinidine, quinine) are expected to __ effects of oxycodone. Oxycodone is also a major substrate of CYP3A4.
- CYP2D6
- CYP2D6
- decrease
Patients on oxycodone should avoid __ and __ i.e. valerian, St John’s wort, kava kava, gotu kola as they may increase CNS depression.
- ethanol
2. Herbs/Nutraceuticals
Tapentadol requires no dose adjustment in __ renal impairment and __ hepatic impairment. Dosages exceeding __ mg daily on the first day of therapy or __ mg daily on subsequent days have not been evaluated and are not recommended.
- mild/moderate
- mild
- 700
- 600
Pethidine requires dose adjustment in renal and hepatic impairment. The equianalgesic dose is __ mg (IV) pethidine = __ mg (IM/SC)morphine.
- 75
2. 10
Pethidine is not commonly used in palliative care as:
• Quick onset, short duration of action (2-3h). Not
good for regular analgesia, and increases risk of
__
• Toxic metabolite (norpethidine) which accumulates if given regularly, esp. in Renal failure
• Norpethidine decreases __
• More __ than morphine
- dependence
- seizure threshold
- emetogenic
Pethidine has a quick onset __ (IV) and __ (SC). It is indicated for __ pain and has less prominent CVS/GIT side effects compared to morphine.
- 5min
- 10-15min
- acute
A minimal 24h morphine PO dose of __-__ mg is required before patients are candidates for conversion to __mcg/h fentanyl patch.
A minimal 24h morphine PO dose of 30mg is required before patients are candidates for conversion to 12.5mcg/h fentanyl patch. (refer to manufacturer’s table)
- 45-134
2. 25
The equianalgesic dose ratio for tramadol and morphine is __ : __.
5 Tramadol : 1 Morphine
Conversion of morphine to methadone is complicated and done __.
stepwise over 3 days
When switching from 1 opioid to another, a __ is common (especially in __ patients or patients with __ dysfunction).
Converting to methadone requires larger reduction (75-90%); depends on the dose of prior opioid.
- 25-50% dose reduction
- elderly
- organ
Dose reductions when switching opioids may not be necessary when:
Converting to __ (6h onset delay)
Patients have __ (likely to be under-treated)
- transdermal fentanyl
2. severe pain
General principles of opioid use:
- Choice and dose based on __
- Dose on a __
- Switch to __ to improve compliance
- Consider alternatives if ineffective
- severity of pain
- regular basis
- SR preparation
Breakthrough opioid doses are dosed at __. They may be dosed hourly as needed.
1/6 of the total daily dose
The total daily dose should be re-titrated when __. It also depends on the __ of the regimen.
- breakthrough doses used daily exceeds 3 or 4.
2. patient’s tolerance
For patients previously on a weak opioid switching to morphine, give __ or modified release __. For frail, elderly and opioid naïve patients switching to morphine, give half of the standard dose (i.e. __).
- 10mg q4h
- 20-30mg q12h
- 5mg q4h
Naloxone is an opioid antagonist used for treating __. It has a rapid onset of __ (IV), is metabolized in the liver and excreted in the kidney. In children, it is dosed by __ while adults follow the hospital’s dosing protocol.
- over dosage of opioids
- within 2min
- body weight
Common side effects of opioids include:
• N__ (tolerance expected within 1-2wks)
• C__ (unlikely to develop tolerance)
• S__, mental clouding (Advise against driving, tolerance possible)
- Nausea/Vomit
- Constipation
- Somnolence
Psychostimulants i.e. c__, d__ and m__ are used in the management of sedation and cognitive dysfunction in opioids.
- caffeine
- dextroamphetamine
- methylphenidate
Myoclonus caused by opioids can be managed using __ and __. Pruritis can be managed using antihistamines but we should avoid __ i.e. cetirizine.
- clonazepam
- anti-convulsants
- the sedating ones
There are 3 strategies for treating adverse effects from opioids:
• Dose reduction (using __)
• Changing to a different __
• __ management
- adjuvants
- opioid or route of administration
- Symptomatic
Monitor the following for patients on opioid therapy: • Pain relief • Side effects • \_\_ (physical and psychosocial) • \_\_ behaviors
- Function
2. Drug related
Psuedo-addiction and addiction both lead to aberrant drug-related behaviour. However, pseudo-addiction is caused by __ and is reduced __. As the 2 can co-exist, knowing the patient well and __ are critical factors in distinguishing them.
- uncontrolled pain
- using improved pain control
- having a good history
Addiction is unlikely to be due to pain management and is more commonly due to patients __. For such patients, __ can be drawn up to help reduce opioid abuse.
- having a history of addiction and substance abuse
2. opioid contracts
What are the two types of tolerance?
- tolerance to SE is desirable
2. tolerance to analgesia is seldom
tolerance does not cause ________
addiction