Flashcards in Pain, types of pain, presentation of pain, pain assessment, tx of pain Deck (29):
What is pain?
Unpleasant subjective experience
--due to ascending and descending nervous systems
There are several types of pain. Each card will go through the different types. First is Nociceptive Pain, what are some features?
Response to a noxious stimulus at nociceptors that are located in different tissues
---key physiological function that prevents further tissue damage due to the body's autonomic withdrawal reflex
Classified as either
--somatic (arising from skin, bone, joints) or visceral (arising from internal organs)
Next type of pain is inflammatory pain, what are some features?
Tissue damage occurs despite the nociceptive defense system
--body now changes focus from protecting against painful stimuli to protecting the injured tissue
Inflammatory response contributes to pain hypersensitivity that serves to prevent contact or movement of the injured part until healing is complete
Third type of pain is neuropathic pain, what are some features?
Damage or dysfunction of the peripheral or central nervous system
--feels like burning, tingling, numbness, shooting, stabbing or electric like feeling
opioids + adjuvant analgesics
Fourth type of pain is Functional Pain, what are some features?
Pain sensitivity due to an abnormal processing or function of the CNS in response to normal stimuli
--fibromyalgia or IBS
Pain can be divided into two categories. Acute and Chronic. First lets discuss Acute Pain, what are some features?
Result of injury or surgery --- self limited
Usually nociceptive can be neuropathic
--anxiety and hyperactivity of the SNS
--tx aggressively even before the dx is established
Second category of pain is chronic pain, what are some features?
Pain that persists for months to years
May be nociceptive, inflammatory, neuropathic, or functional
Does not involve Sympathetic Hyperactivity but may be associated with vegetative signs and depressed mood
There is chronic malignant pain and chronic non malignant pain. What is chronic malignant pain?
Progressive disease that is usually life threatening such as cancer or AIDS
What is chronic non malignant pain?
Life threatening disease and lasting longer than 6 months
--low back pain, osteoarthritis, previous bone fractures, peripheral vascular disease
Moving on to pain assessment, what are some tools for this?
Rating scales: classify intensity of pain
Numeric Scales: scale of 0 to 10 (10 being the worst with 8 to 10 being severe)
Visual Analog Scale (VAS): patients place a mark on a 10cm line where one end is no pain and the other end is worst possible pain
Categorical Scale: kids and language barrier
Moving on to treatment of pain, what is the goal of therapy?
Eliminate or reduce pain to the lowest tolerable intensity and prevent it from recurring
Explain the WHO three step ladder for pain management
Mild pain (1-3): Non-opioid analgesic taken on a regular schedule (ex. acetaminophen or ibuprofen)
Moderate pain (4-6): Add opioid for moderate pain taken on a regular schedule. (ex. acetaminophen + codeine or acetaminophen + oxycodone)
Severe pain (7-10): Switch to high potency opioid that is taken on a regular schedule (ex. morphine or hydromorphone)
--throughout this progression adjuvant medications are added as needed to manage adverse effects
What are non-opioid analgesics?
Acetaminophen and NSAIDS
--ceiling effect: max dose past which no further analgesia can be achieved
Acetaminophen is used for what types of pain?
Mild to moderate pain
--low back pain and osteoarthritis
Be careful of hepatotoxicity with excessive use and use of this in alcoholics
NSAIDs are used for what type of pain?
Tx of mild to moderate pain
---inflammation such as arthritis or gout
Moving on to Opioid analgesics which are used in moderate to severe acute and chronic pain. What are some types of opioids for pain?
Mild to moderate pain:
-codeine, hydrocodone, oxycodone, meperidine and tramadol
Moderate to severe pain
-morphine, hydromorphone, oxymorphone, levorphanol, fentanyl, sufentanil and methadone
Explain analgesic dosing when it comes to pain
Should be given in fixed intervals of time
-next dose should be given before the effect of the previous dose as worn off
What is breakthrough pain?
Transitory severe acute pain that occurs on a background of chronic pain
--rescue dosing is used to manage this pain (short acting opioid given in addiction to the long acting opioid patient is already on)
Transmucosal fentanyl formulations are indicated for cancer related breakthrough pain
What is the analgesic ceiling affect?
Dose beyond which there is no additional analgesic effect
--higher doses only produce side effects and no pain relief
What drugs have and which drugs do not have a ceiling effect?
Ceiling: NSAIDs or acetaminophen
No ceiling: pure opioid agonists
--when using opioid plus NSAID the ceiling factor of NSAID should be the dose limiting factor
Mixed Agonist-Antagonist do not have a ceiling effect
What are some routes of administration for pain?
Oral or transdermal for long term use
IV for rapid onset and easiest titration
PCA: patients self administer parenteral analgesics
IM is not recommended
Intraspinal are used postoperatively
Meperidine is not recommended for routine use, why?
Poorly absorbed orally and has a short half life (3 hrs)
--its metabolite normeperidine has a half life of 15-20 hours and is renally excreted therefore produces significant adverse effects when it accumulates (tremulousness, dysphoria, myoclonus and seizures)
Mixed Agonist-Antagonist are not recommended as routine analgesics, why?
Dosing is limited by a ceiling effect
--pentazocine, nalbuphine and butorphanol are associated with psychotomimetic adverse effects
Should not be used in patients already taking a pure agonist opioid (morphine)
---compete for opioid receptors and patients withdrawal
Classic stem will be about a heroin addict in a car accident arrives to the ER and is given one of these meds and starts withdrawing
Combination approach is encouraged why?
Opioid + nonopioid analgesics
--analgesia superior to that produced by either agent alone
So lower doses used and fewer side effects
Moving on to the topic of managing opioid adverse effects, each card will go through an adverse effect and the ways it can be treated. First is Urticaria or pruritus.
Result of mast cell destabilization by the opioid and therefore histamine release
---managed by hydroxyzine or diphenhydramine
Next adverse side effect of opioids is constipation. How is this managed?
Result of opioid effects on the CNS, Spinal cord and myenteric plexus
--reduced gut motor activity and increased stool transit time
Laxative should be prescribed when an opioid is started
--stimulant laxative (senna or bisacodyl) or
--stool softeners (docusate) + stimulant (senna)
If constipation persists
--magnesium hydroxide or lactulose
Bulk forming agents require lots of fluid intake so dont give these to ppl who are bed bound
The next adverse effect is nausea/vomiting. How is this managed?
Tolerance develops within a few days
--however if the symptoms persist then use hydroxyzine, metoclopramine or prochlorperazine
The next adverse effect is sedation. How is this managed?
Tolerance develops within a few days
--however if symptoms do not disappear then use amphetamine, methylphenidate or modafinil