Pain Assessment and Management + Chronic Pain Flashcards
1
Q
How is chronic cancer pain mediated?
A
- Inflammatory signalling in tissue
- stimulation and firing of pain receptors in periphery
- Prolonged firing of nociceptive C-fibres
- Pain signalling travels to spinal cord
- First degree sensory neurons synapse
- Central pathways carry signal to contralateral thalamus
- Thalamic fibres project pain to every lobe of brain
2
Q
List and describe an approach to pain assessment
A
- Position
- Quality
- Radiation
- Severity (clinical tools)
- Timing
- Understanding (meaning of pain)
- Values (attitudes towards disease)
3
Q
Describe common etiologies of pain
A
-
Nociceptive pain
- Visceral pain (Peritoneum, pleural cavity)
- Somatic pain (skin, muscle, bones, ligaments)
-
Neuropathic pain
- Allodynia (perception of pain to non-painful stimuli)
- Hyperalgesia (exaggerated pain response to painful stimuli)
- Hyperpathia (altered pain perceptions)
4
Q
Describe the WHO analgesic ladder
A
- Non-opioid +/- adjuvant
- Weak opioid +/- non-opioid +/- adjuvant
- Strong opioid +/- non-opioid +/- adjuvant
5
Q
Opioid receptors
A
- Mu Agonism
- Delta
- Kappa
6
Q
Codeine
A
- Weak opioid
- naturally occuring opium alkaloid
- pro-drug
- converted to morphine in liver
- 10% lack liver enzyme to convert to morphine (genetic polymorphism CYP2D6)
- oral, parenteral, SR, combination with acetaminophen
- q3-4h, 3-5 h duration
7
Q
Tramadol
A
- Weak opioid
- Serotonin and NE reuptake inhibitors
- oral, alone or combo with acetaminophen
- CYP2D6 metabolism
- Accumulation in renal and hepatic failure
- Drug-drug interactions (SSRI, SNRI)
8
Q
Morphine
A
- Naturally occuring opium derivative
- metabolized by liver, excreted by kidneys
- M3G metabolite : no analgesia, neurotoxicity
- M6G metabolite: analgesic, binds to u receptors
- oral, SR, suppositories, IV.
- Onset 45-60 minutes
- Half life 4-6 hours
- SR onset 3-4 hours
- q8-12 hours
9
Q
Hydromorphone
A
- Semi-synthetic opioid
- H3G : potent metabolite excreted by kidneys
- Oral, CR, IV, rectal
- highly soluble
- q4h, 4-6h duration
10
Q
Oxycodone
A
- Semi-synthetic morphine cogener
- Oxymorphone metabolite accumulates in Renal failure
- q3-4h, 3-5 h duration
11
Q
Fentanyl
A
- Synthetic opioid
- highly potent mu agonist
- 100:1 morphine
- no known active metabolites
- Good in renal failure
- Causes less constipation
- Patch may not work in cachexia
- lack of oral route, poor compliance, anxiety
- DO NOT use conversion table when switching FROM fentanyl to morphine
12
Q
Opioid dose equivalency table
A
- Morphine 10 mg po
- Hydromorphone 2 mg po
- Oxycodone 5 mg po
- Codeine 100 mg po
- Tramadol 100 mg po
- Fentanyl 25 ug/hour (see table)
13
Q
Tolerance
A
- Incomplete cross tolerance: unpredictable when rotating to different opioid.
- Dose reduction 25-30%
14
Q
Breakthrough dosing
A
- Not predictable based on dose of regularly scheduled opioid
- half of regularly scheduled dose or 10% daily dose
- adjust with adjustment of regular dose
- > 3 re-evaluation of regularly scheduled dose
15
Q
Incident Pain
A
- With movement that is not normally painful
- Predictable
- Try regularly scheduled dose pre emptively
- Fentanyl sl, intranasal, sc, iv
16
Q
Side effects of opioids
A
- nausea and vomiting (attenuates after few days)
- prokinetic antinauseant prn
- Constipation
- Durable SE
- Sedation
- attenuates
- if persistent can rotate, opioid sparing adjuvants, interventional techniques, ritalin
- Respiratory depression (narcosis)
- aggressive titration
- long acting used as breakthrough
- multiple opioids
17
Q
Naloxone
A
- Central opioid antagonist
- Reversal of respiratory depression and analgesia.
- Raise RR without causing pain crisis
- Small doses to avoid withdrawal
- Goal is improvement of ventilation
- Short half life 30-90 minutes, may need infusion if on long acting opioid.
18
Q
Opioid intoxication (narcosis)
A
- Altered mental status
- Miotic pupils
- Decreased bowel sounds
- Low to normal heart rate and BP
- Hypoventilation
19
Q
Opioid narcosis management
A
- If RR > 12 and 02 sat >90% RA, monitor
- End tidal C02
- If sat <90 and RR <12 but breathing spontaneously, give 0.04-0.05 mg naloxone IV/IM
- If apneic, ventilate with BVM and give 0.2 to 1 mg naloxone IV/IM.
- Infusion = 2/3 of total bolus doses given.
- Goal of treatment is adequate ventilation, NOT mental status
- Watch for withdrawal
20
Q
Concerns about opioid addiction and tolerance in palliative care?
A
- Addiction : psychological dependence where harms of use > benefits
- Rare in patients with pain, with no hx of abuse
- Tolerance : requirement of higher doses to manage same pain normal.
- rotation, adjuvants
- usually disease progression > tolerance
- Physical dependence: normal with opioids.
21
Q
Opioid rotation
A
- change of route of administration (loss of oral route, delayed gastric empyting, bowel obstruction, delirium)
- escalating pain not responsive to dose escalation
- unacceptable side effects or neurotoxicity