7 – Pharmacology of Pain Transmission & Modulation

Question 1

Pain experience comprises

Answer 1

1. Detection of tissue injury by the NS (NOCICEPTION)
2. CONSCIOUS perception of pain (noxious stimuli)
3. Behavioural responses or changes which occur to protect the individual from further discomfort

Question 2

If pain goes untreated

Answer 2

• Goes from acute pain (symptom of a disease) to CHRONIC pain (DISEASE itself)

Question 3

Sympathetic simulation consequence if don’t treat pain

Answer 3

• Tachycardia
• Peripheral vasoconstriction
• Increased myocardial work
• Increased myocardial O2 consumption
• Decreased blood flow to abdominal organs

Question 4

Neuroendocrine consequences if don’t treat pain

Answer 4

• Increased cortisol
• Increased NE + E
• Decreased insulin

Question 5

Stress if don’t treat pain

Answer 5

• Decrease appetite
• Insomnia
• Immunosuppression
• Decreased quality of life

Question 6

Categories of patients (4)

Answer 6

• Healthy, non-painful
• Healthy, underly orthopedic issue
• Chronic condition resulting in mild discomfort
• Undergone some trauma in recent past
  **at some point they will require anesthesia and surgery

Question 7

Role of anesthesia: triad

Answer 7

1. Analgesia
2. Muscle relaxation
3. LOSS of consciousness
   **if do correctly=wont think it is painful

Question 8

How does our patient being anesthetized affect the PAIN RESPONSE to injury?

Answer 8

• Not necessarily perceiving the stimulus as ‘pain’
• Pain pathways are still firing (nociception vs. pain!)

Question 9

Pain pathways

Answer 9

1. Transduction
2. Transmission
3. Modulation (CNS)
4. Perception (CNS)

Question 10

If pain goes untreated, ‘steps’

Answer 10

• Peripheral sensitization
• Central sensitization
• Hyperalgesia (primary and secondary)
• Allodynia (non-painful stimulus but get a painful response)
• Wind-up pain

Question 11

Techniques to treat and reduce pain

Answer 11

1. Pre-emptive analgesia
2. Multimodal analgesia

Question 12

Pre-emptive analgesia

Answer 12

• 1st key strategy when pain is anticipated
• Providing analgesia BEFORE insult can significantly reduce both intra- and post-operative analgesia requirements
• *prevents sensitization and wind-up

Question 13

Multimodal analgesia

Answer 13

• Combines analgesics from 2 or more drug classes or analgesic techniques
  o Target different pain pathways
• *synergistic effect at LOWER analgesic doses
• **often side effects are dose dependent)

Question 14

Mild level of pain examples

Answer 14

• Minor dental procedure
• Minor laceration repair
• Cystitis
• mild otitis

Question 15

Moderate level of pain examples

Answer 15

• Ovariohysterectomy
• Uncomplicated laparotomy
• Urethral obstruction
• Localized burn

Question 16

Severe level of pain examples

Answer 16

• Fracture repair
• Limp amputation
• Total ear canal ablation
• Necrotizing pancreatitis
• Localized/extensive burn

Question 17

Local anesthetics

Answer 17

• Inhibits sodium channels
• Provide complete pain relief at the effected nerve site

Question 18

Opioids

Answer 18

• Decrease pain perception, anxiety and distress
• Most effective when given BEFORE pain onset
• Rapid onset (IV administration), long duration (IM administration)
• *depends on route and lipophilicity of drug

Question 19

Alpha 2 agonists provide

Answer 19

• Sedation
• Analgesia
• Anxiolysis (decrease anxiety and stress)

Question 20

Alpha 2 agonists examples

Answer 20

• Dexmedetomidine (Domitor)
• Xylazine (Rompun)

Question 21

Alpha 2 agonists effect

Answer 21

• Modulation of perception, central sensitization, and impulse conduction

Question 22

N-methyl-D-aspartate (NMDA) antagonists

Answer 22

• Analgesic properties
• Important when addressing ‘wind-up’ pain
• NMDA receptors important in development of central sensitization
• Low dose=improve opioid efficacy
• Excitatory effects in the CNS (usually use with sedation)
• Stimulatory effects on cardiovascular

Question 23

NMDA example

Answer 23

• Ketamine
  o Need to make sure the heart is functioning

Question 24

NSAIDs

Answer 24

• Analgesic
• Antipyretic
• Anti-inflammatory
• Prevent sensitization

Question 25

NSAIDs effect on

Answer 25

- Modulation of spinal pathway - transduction

Question 26

Treating pain: mild postoperative pain

Answer 26

- Non-opioid analgesics o NSAIDs + o local anesthetic infiltration

Question 27

Treating pain: moderate postoperative pain

Answer 27

- NSAIDs + - local anesthetic infiltration + - intermittent doses of OPIOIDS

Question 28

Treating pain: severe postoperative pain

Answer 28

- NSAIDs + - Local anesthetic peripheral neural blockage (with or without catheter) + - Use of sustained release of OPIOIDS +/- - NMDA antagonist (KETAMINE) +/- - Ancillary pain management techniques

Question 29

Ancillary pain management techniques (2)

Answer 29

- Manipulative therapies - Alternative therapies

Question 30

Manipulative therapies

Answer 30

- Temperature: application of heat (improve circulation) or cold (decrease inflammation)

Question 31

Ancillary techniques

Answer 31

- Acupuncture - Laser therapy