Pharmacology of Pain Transmission & Modulation Flashcards
What can happen IF PAIN GOES UNTREATED?
ACUTE PAIN (a symptom of the disease - protective) can become CHRONIC PAIN (the DISEASE itself)
What are the consequences of pain affecting sympathetic stimulation?
- tachycardia, tachypnoea
- peripheral vasoconstriction
- increased myocardial work
- increased myocardial oxygen consumption
- decreased blood flow (oxygen delivery) to abdominal organs
What are the consequences of pain having neuroendocrine effects?
- adrenocorticotropic hormone release
- increased cortisol
- increased norepinephrine
- increased epinephrine
- decreased insulin
What are the consequences of pain having an effect on stress?
- decreased appetite
- insomnia
- immunosuppression (delayed healing)
- decreased quality of life
What are the categories of pain patients you will encounter?
- healthy, non-painful, in for a routine elective procedure
- healthy, underlying orthopedic issue requiring surgery
- chronic condition resulting in mild discomfort
- undergone some form of trauma in the recent past, will require surgical correction within the near future
The common thread amongst all categories of patients is that at some point they will require…
ANESTHESIA and SURGERY
What is the triad of anesthesia?
- analgesia
- muscle relaxation
- LOSS OF CONSCIOUSNESS
How does our patient being anesthetized affect the PAIN RESPONSE to injury?
- not necessarily perceiving the stimulus as “pain”
- pain pathways are still firing (nociception vs pain)
What besides chronic pain can happen IF PAIN GOES UNTREATED?
- peripheral sensitization
- central sensitization
- hyperalgesia (primary and secondary)
- allodynia
- wind-up pain
What are 2 techniques to treat and reduce pain?
- pre-emptive analgesia: 1st key strategy when pain is anticipated; providing analgesia BEFORE the insult can significantly reduce both intra- & post-operative analgesia
- multimodal analgesia: combined analgesics from two or more drug classes or analgesic techniques that employ different mechanisms of action, targeting different (peripheral or central) pain pathways, thus achieving a synergistic effect at lower analgesic doses
What does pre-emptive analgesia prevent?
- sensitization
What types of procedures or conditions are considered mildly painful?
castration (certain spp/individuals), minor dental procedures, minor laceration repairs, small cutaneous or subcutaneous mass removals, cystitis, mild otitis, chest drains
What types of procedures or conditions are considered moderately painful?
castration (certain spp/individuals), ovariohysterectomy, extracapsular cruciate repair, uncomplicated simple laparotomy, urethral obstruction, early or resolving pancreatitis, localized burn
What types of procedures or conditions are considered severely painful?
complicated/invasive laparotomy, fracture repair, intra-articular surgical procedures, limb amputation, total ear canal ablation, necrotizing pancreatitis, localized/extensive burn
What does a balanced (multimodal) analgesia do?
Inhibits transduction, inhibits transmission, modulates the spinal pathway, AND inhibits perception
Where do local anesthetics work?
- inhibit transduction (inhibit the peripheral sensitization of nociceptors)
- inhibit transmission (inhibit impulse conduction)
- modulate the spinal pathway (inhibit central sensitization)
Where do opioids act?
- inhibit transduction (inhibit peripheral sensitization of nociceptors)
- modulate the spinal pathway (inhibit central sensitization)
- inhibit perception
Where do alpha2 agonists act?
- inhibit transmission (inhibit impulse conduction)
- modulate the spinal pathway (inhibit central sensitization)
- inhibit perception
Where do NMDA antagonists act?
- modulate the spinal pathway (inhibit central sensitization)
where do NSAIDs act?
- inhibit transduction (inhibit peripheral sensitization)
- modulate the spinal pathway (inhibit central sensitization)
