Intro to Pain Management Flashcards
What is the definition of pain?
- unpleasant sensory and emotional experiences associated with action or potential tissue damage or described in terms of such damage
What is nociceptive pain?
- due to activation of pain pathways be ongoing tissue damage
- subcategories of nociceptive pain include somatic and visceral (can be activated by mechanical, thermal and chemical means)
What is somatic pain?
- pain arising in the tissues of the body
- sharp, sometimes burning, aching, relatively localized
- osteomyelitis, OA, bone fractures
What is visceral pain?
- pain arising in the organs of the body cavity
- deep, aching, cramping, diffuse and poorly localized
- may illicit symptoms such as nausea, sweating and cardiovascular changes (systemic symptoms)
- endometriosis, crohn’s disease, angina
- not often managed with OTC agents
What is the definition of neuropathic pain?
- caused by direct nerve damage or may be due to abnormal processing of a pain signal in the CNS pain pathways due to sensitization of pain neurons
- more commonly chronic, but can be acute
- it can be paroxysmal or spontaneous
- generally described as burning, tingling, shock-like or shooting
(diabetic neuropathy, post-herpetic neuralgia, MS, phantom limb pain)
What is considered hyperalgesia?
altered perception such that stimuli which would normally induce a trivial discomfort cause significant pain
What is allodynia?
- pain due to stimulus that does not normally evoke pain
After what timeframe is pain considered to be chronic?
if it lasts more than 12 weeks
What is the difference in cause of both acute and chronic pain?
Acute: tissue damage often associated with inflammation
Chronic: neuronal or CNS abnormality
What is incident pain?
a type of breakthrough pain that is made worse by movement
What is breakthrough pain?
- a temporary increase in pain to greater than moderate intensity that occurs on a baseline pain of moderate intensity or less
- causes increased level of psychological distress and significant decrease in function
What are the three tools of assessing pain?
- Numerical rating scale: patients assess their pain on a scale from 0-10, where 0 represents no pain and 10 means that worst pain imaginable
- mild pain (1-3), mild to moderature (4-7) and moderate to severe (8-10) - Visual analogue scale: 100 mm horizontal line, with the left side mean no pain and the right side is the worst pain
- Wong-baker FACES pain rating scale: faces ranging from happy to sad based on how the person is feeling
What is the most accurate evidence of pain/intensity based on?
- based on the patients description and self-reporting
What are the 4 main pieces that are essential to pain information gathering?
- severity of pain
- location of pain
- onset and how long the pain lasts
- quality of pain (description of pain - dull ache, sharp pain, tingling or burning)
What are the global treatment goals of pain management?
- choose pain control options that are appropriate for the patient, family and setting
- delivery interventions in a timely, logical and coordinated manner
- empower patients and their families, enable them to control their course to the greatest extent possible
- many other adjuvant or complimentary therapies, available to patients (massage, chiropractic, OT/PT, acupuncture) – this is considered a multi-modal therapy
What is the role of OTC pain medication?
- effective when treating mild-moderate somatic pain from skin, muscle and joints
- also effective in the treatment of dysmenorrhea and headache
- less useful in the treatment of visceral pain
- effectiveness in neuropathic pain often demonstrates a variable response
(usually not used past a pain level of 4)
What is the mechanism of action of acetaminophen?
- produced analgesic effect through central inhibition of PGs (fever and pain perception) and peripherally blocking the generation of pain impulses
- does NOT have an anti-inflammtory effect because there is minimal effect on the peripheral PG’s
For what conditions is acetaminophen first line treatment for?
mild to moderate pain (low back pain, OA, some headaches) and fever
Where is acetaminophen usually metabolized?
the liver
Where is acetaminophen absorbed from?
from the GI tract
When does acetaminophen usually provide pain relief?
24 to 48 hours
- may be 2-4 weeks in OA
What is the duration of effect in acetaminophen? What about the half life?
4-6 hours
- half life is 1-4 hours (same in immediate and extended release tabs)
What is the adult dose of acetaminophen?
325-650 mg q4-6h (max 4g/day)
acetaminophen is ___ dependent
dose
What is the therapeutic range of acetaminophen?
narrow
What is the paediatric dose of acetaminophen?
PO: 10-15 mg/kg/dose given Q4-6H
PR: 15-20 mg/kg/dose given Q4-6H (max 65 mg/kg/day) (5 doses/day)
Dosing adjustments may be necessary for patients with _______ (CrCl <10 mL/min dose q8h); not used in the elderly
renal dysfunction
What is the drug of choice in patients taking warfarin?
acetaminophen
Are there any drug interactions with acetaminophen?
no
What lifestyle issues can cause liver toxicity?
- hepatitis, liver disease (cirrhosis, alcohol use, binge drinking and fasting
What causes acetaminophen overdose?
acetaminophen forms a toxic metabolite which is normally detoxified by glutathione. This system can be overwhelmed in an overdose as glutathione becomes depletes (starts to use hepatocytes instead)
What is considered a toxic dose of acetaminophen?
7.5 - 10 g or above 150 mg/kg in children over an 8 hour period
What are some of the strategies that can prevent an unintentional overdose of acetaminophen in children?
- can put a warning label on the box, can sell acetaminophen in package sizes that are smaller and can make all doses for kids the same (80 mg/ml vs 160 mg/5ml)
What are the main symptoms of acetaminophen overdose?
- flu like symptoms
- may experience symptoms such as: nausea, vomiting, drowsiness, confusion,, sweating (12-24 hours post ingestion)
- liver damage in 24-48 hours
- hepatic damage may not be apparent for 4-6 days
What is the difference between rapid, extended and immediate release Tylenol?
rapid release: has an effect in 5 minutes earlier than regular extended release acetaminophen
extended release: doses every 6-8 hours, they do this by adding a coating to the outside of the pill that causes immediate pain relief, and then the interior will dissolve and cause additional relief
Why does alcoholism lower the threshold for acetaminophen liver damage?
- possible induction of enzymes
- hepatic dysfunction
- decrease stores of glutathione
- chronic alcohol may result in higher blood levels of NAPQ which is toxic to the liver calls and reduced blood levels of acetaminophen due to increased metabolism of acetaminophen by CYP2E1
- this may result in a higher risk of kidney disease
- patients with a G6PD deficiency should be cautious when they are taking acetaminophen
Does ASA act mostly on the periphery or the central NS?
mostly the periphery - some evidence to show that it provides analgesia through the central mechanism however
Why is ASA not considered to be first line therapy?
- because of all of the SE associated with its use - GI irritation, nausea
What is the recommended dosing of ASA?
325-650 mg Q4-6H (max 4g/day)
How long after starting ASA will that anti-inflammatory dose usually be noticed?
2-4 weeks
What is the general onset of action of ASA?
60 minutes, for a duration of 4-6 hours