Pain Management Flashcards
What are the different types of pain?
- Nociceptive - response to noxious stimulus, somatic or visceral, physiological defense response, something hurts you so you stop doing it [usually acute pain]
- Inflammatory - post tissue damage despite nociceptive defense system
- Neuropathic - Damage to or dysfunction of peripheral of central nervous system, not stimulation of pain receptors, not physiological rather something gone wrong, difficult to treat [can be acute pain]
- Functional - pain sensitivity due to abnormal processing or fx of CNS, no damage or dysfunction, just amplification of pain in response to normal stimulus
What is the difference b/t chronic malignant and chronic non-malignant pain?
Chronic malignant pain - associated with progressive disease like cancer or AIDS
Chronic non-malignant pain - pain NOT associated with life-threatening disease, lasts longer than 6 months after healing pd
What is the 3-step model developed by the WHO to guide management of (cancer) pain?
Step 1 - non-opioid +/- adjuvant [mild pain 1-3/10]
Step 2 - if pain persists or increases, then give opioid for mild to moderate pain +/ non-opioid used in first step and +/- adjuvant used in 1st step [moderate pain 4-6/10]
Step 3 - if pain persists or increases again, then given opioid for moderate to severe pain +/- non-opioid in 1st step and +/- adjuvant in first step [severe pain 7-10/10]
**used to be for cancer, but has since covered all types of pain
What non-opioid analgesics are used to control pain?
Acetaminophen - initial therapy for mild to moderate pain, esp low back pain and osteoarthritis, hepatotoxicity has been reported with excessive use and overdose
NSAIDs - tx of mild to moderate pain, esp pain due to inflammation such as in gout and arthritis
Which opioids are used for mild to moderate pain?
Codeine Hydrocodone Oxycodone Meperidine Tramadol
*weak agonists
Which opioids are used for moderate to severe pain?
Morphine Hydromorphone Oxymorphone Levorphanol Fentanyl Sufentanil Methadone
*strong agonists
Discuss analgesic dosing.
When you first begin to administer analgesics for severe pain, give it by the clock (at fixed intervals). You want to give the next dose before the previous dose effect wears off. Overtime and as the pain subsides, give the analgesic as needed, not by the clock.
What is breakthrough pain and how do you treat it?
Although patients ay be managed for their pain, there are some instances where pts may have a transitory severe pain. A rescue dose of a short-acting supplemental opioid is generally given for relief.
Rescue dose = should not be more than 5-15% of basal daily requirement of opioid
- Transmucosal Fentanyl is most commonly used. It comes in different forms including…
1. oral transmucosal lozenge (lollipop)
2. immediate-release transmucosal tablet
3. effervescent buccal tablet
4. buccal soluble film
5. nasal spray
6. sublingual spray
What is the ceiling effect?
Increase dose but there is no beneficial analgesic effect.
Non-opioids have ceiling.
Pure opioid agonist have NO analgesic ceiling.
Mixed agonist-antagonist (ex. pentazocine, butorphanol, nalbuphine, buprenorphine) have ceiling effects. – therefore these are poor choices in the treatment of pts with severe pain
When used in combination you increase risk of experiencing opioid adverse effect.
What is PCA administration of opioids?
Patient controlled analgesia
Computer/depot that administers preset dose of opioid.
This is the gold standard of tx of post-op pain.
Opioids used in this machine are the strong agonists: morphine, hydromorphone, fentanyl and methadone.
Which analgesics are not recommended for routine dosing?
Meperidine - 3hr half life, but turns in to 15-20 hr half life when normeperidine (metabolite) is producted [AE - dysphoria, myoclonus, seizures]
Mixed agonist-antagonists - dosing is limited by ceiling effect as well as psychotomimetic AE (which is obviously not good with people who have cancer and are therefore more stressed than normal), competition of mixed agonist-antagonist with pure agonist opioid may lead to withdrawal reaction
What are the most common adverse effects of opioids? How do you manage these symptoms?
Pruritus - histamine release from mast cells (manage with hydroxyzine or diphenhydramine)
Constipation - almost universal, no tolerance developed to constipation, use stimulant laxative, stimulant with softener [bulk-forming agent require substantial fluid intake and are not recommended for patients with advanced disease and poor mobility]
Nausea/vomiting - tolerance generally develops within a few days (unlike constipation) and it can be treated with hydroxyzine, metoclopramide or prochlorperazine
Sedation - tolerance develops within a few days, persistent opioid-induced sedation that limits activity can be managed with methylphenidate or modafinil
How do you treat respiratory depression due to opioids?
Tolerance develops quickly and is very rare, but if it happens give naloxone.
What are co-analgesics?
Drugs not labeled as analgesics, but have found uses for analgesics. Usually used in combination with opioids.
Categories: antidepressants, anticonvulsants, glucocorticoids, other drugs
What is the role of antidepressants as opioid adjuvant therapy?
Serotonin and norepinephrine mediate descending inhibition of ascending pain pathways in the brain and spinal cord. Antidepressants therefore, enhance both serotonergic and noradrenergic transmission therefore increases analgesic effect.
Blocking both serotonin and NE uptake gives best analgesic effect. Only blocking serotonin uptake does not gives a good analgesic effect.
Ex. Tricyclic antidepressants (TCAs) and Serotonin and norepinephrine reuptake inhibitors (SNRIs) – both of these inhibit norepinephrine and serotonin reuptake
