Pain, types of pain, presentation of pain, pain assessment, tx of pain

Question 1

What is pain?

Answer 1

Unpleasant subjective experience

–due to ascending and descending nervous systems

Question 2

There are several types of pain. Each card will go through the different types. First is Nociceptive Pain, what are some features?

Answer 2

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)

Question 3

Next type of pain is inflammatory pain, what are some features?

Answer 3

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

Question 4

Third type of pain is neuropathic pain, what are some features?

Answer 4

Damage or dysfunction of the peripheral or central nervous system
–feels like burning, tingling, numbness, shooting, stabbing or electric like feeling
Tx:
opioids + adjuvant analgesics

Question 5

Fourth type of pain is Functional Pain, what are some features?

Answer 5

Pain sensitivity due to an abnormal processing or function of the CNS in response to normal stimuli
–fibromyalgia or IBS

Question 6

Pain can be divided into two categories. Acute and Chronic. First lets discuss Acute Pain, what are some features?

Answer 6

Result of injury or surgery — self limited
Usually nociceptive can be neuropathic
Associated with:
–anxiety and hyperactivity of the SNS
Tx:
–tx aggressively even before the dx is established

Question 7

Second category of pain is chronic pain, what are some features?

Answer 7

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

Question 8

There is chronic malignant pain and chronic non malignant pain. What is chronic malignant pain?

Answer 8

Progressive disease that is usually life threatening such as cancer or AIDS

Question 9

What is chronic non malignant pain?

Answer 9

Life threatening disease and lasting longer than 6 months

–low back pain, osteoarthritis, previous bone fractures, peripheral vascular disease

Question 10

Moving on to pain assessment, what are some tools for this?

Answer 10

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

Question 11

Moving on to treatment of pain, what is the goal of therapy?

Answer 11

Eliminate or reduce pain to the lowest tolerable intensity and prevent it from recurring

Question 12

Explain the WHO three step ladder for pain management

Answer 12

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

Question 13

What are non-opioid analgesics?

Answer 13

Acetaminophen and NSAIDS

–ceiling effect: max dose past which no further analgesia can be achieved

Question 14

Acetaminophen is used for what types of pain?

Answer 14

Mild to moderate pain
–low back pain and osteoarthritis
Be careful of hepatotoxicity with excessive use and use of this in alcoholics

Question 15

NSAIDs are used for what type of pain?

Answer 15

Tx of mild to moderate pain

—inflammation such as arthritis or gout

Question 16

Moving on to Opioid analgesics which are used in moderate to severe acute and chronic pain. What are some types of opioids for pain?

Answer 16

Mild to moderate pain:
-codeine, hydrocodone, oxycodone, meperidine and tramadol
Moderate to severe pain
-morphine, hydromorphone, oxymorphone, levorphanol, fentanyl, sufentanil and methadone

Question 17

Explain analgesic dosing when it comes to pain

Answer 17

Should be given in fixed intervals of time

-next dose should be given before the effect of the previous dose as worn off

Question 18

What is breakthrough pain?

Answer 18

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

Question 19

What is the analgesic ceiling affect?

Answer 19

Dose beyond which there is no additional analgesic effect

–higher doses only produce side effects and no pain relief

Question 20

What drugs have and which drugs do not have a ceiling effect?

Answer 20

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

Question 21

What are some routes of administration for pain?

Answer 21

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

Question 22

Meperidine is not recommended for routine use, why?

Answer 22

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)

Question 23

Mixed Agonist-Antagonist are not recommended as routine analgesics, why?

Answer 23

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

Question 24

Combination approach is encouraged why?

Answer 24

Opioid + nonopioid analgesics
–analgesia superior to that produced by either agent alone
So lower doses used and fewer side effects

Question 25

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.

Answer 25

Result of mast cell destabilization by the opioid and therefore histamine release
—managed by hydroxyzine or diphenhydramine

Question 26

Next adverse side effect of opioids is constipation. How is this managed?

Answer 26

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

Question 27

The next adverse effect is nausea/vomiting. How is this managed?

Answer 27

Tolerance develops within a few days

–however if the symptoms persist then use hydroxyzine, metoclopramine or prochlorperazine

Question 28

The next adverse effect is sedation. How is this managed?

Answer 28

Tolerance develops within a few days

–however if symptoms do not disappear then use amphetamine, methylphenidate or modafinil

Question 29

Finally respiratory depression is the last adverse effect of opioids. How is this managed?

Answer 29

Pain is a potent stimulus to breathe and pharmacologic tolerance to respiratory depression develops quickly
—naloxone can be used as needed if respirations are compromised