How to Provide Adequate Analgesia

DO WITH PP HAS REAL LIFE EXAMPLES

Where in the pain pathway do NSAIDs act?

Transduction

• Decrease production of inflammatory mediator

• Directly affects the stimulation of nociceptors

Where in the pain pathway do Local Anesthetics act?

Transmission

• Block the nociceptor itself from firing an action potential

• Effects the transmission of the impulse to the spinal cord

Where in the pain pathway do Opioids act?

Modulation

• Affect the spinal cords / brain

• Act on the patient’s RESPONSE to pain

  • Knows that there is pain, but doesn’t really care

Where in the pain pathway do general anesthetics act?

Perception

• Trick question

• GA don’t take pain away; they just block the perception of it for the time being

• Can still feel

What are the clinical uses for opioids?

• As premed

• Given in intermittent boluses

  • IV/IM

  • Transmucosal (bupe in cats)

• Given as an infusion

• Epidural

What are 3 different opioids that are used for infusions? What are their doses, and how are they used clinically?

Morphine

• Cheap and effective

• Dose: 0.1-0.2 mg/kg/hr in dogs

  • Lower in cats

Methadone

• Used clinically

• 0.08-0.16 mg/kg/hr

• Risky, shouldn’t be used

• Longer duration of action

Fentanyl

• Useful in cats and smaller dogs as an infusion

• Espensive in larger dogs (BUT STILL EFFECTIVE)

• Dose: 2-10 mcg/kg/hr

• Typically used during surgery or postoperatively

  • Prof said she would use this for infusions most of the time

• Quick acting, but also ELIMINATED FROM BODY QUICKLY

What is THE major way that local anesthetics are used clinically?

PERINEURAL BLOCKS

• For limbs:

  • Brachial plexus

  • RUMM block

  • Femoral and sciatic block

  • Digital

• And for DENTALS:

  • Maxillary

  • Mental

  • Infraorbital

  • Mandibular

Where along the spine are epidurals most commonly placed? What does each desensitize?

Lumbosacral

• Desensitizes perineum, abdomen, hind limbs

Coccygeal (caudal)

• Desensitizes perineum and tail

• Good for if you don’t want your patient to lose the ability to stand

I guess local anesthetics are also used for epidural??

What is intravenous regional anesthesia (IVRA)? What local anesthetic can you use for this?

Injecting local anesthetic into a limb BELOW a tourniquet to prevent anesthetic from getting into general circulation

• Used commonly in cattle and for digit amputation in dogs

• Done with or without GA

USE LIDOCAINE

What are the 3 main clinical uses for lidocaine?

1) Infusion

• Mainly for strong, visceral pain

• NOT in cats; process the drug more slowly and are more prone to toxicity

2) Bolus (1 mg/kg)

3) THEN infusion later (1.5-3 mg/kg/hr)

What is a good multimodal analgesic combination for EXTREMELY painful patients?

Morphine + Lidocaine + Ketamine

What are the 3 clinical uses for alpha-2 agonists for analgesia?

1) Infusion

• Dexmedetomidine 0.5-1.5 mcg/kg/hr

2) As an adjunct to local anesthetic in a perineural block

• Prolongs the effect

3) Epidural

• Not commonly used in small animals

• Used in large animals at times

What are the 3 clinical uses of ketamine for analgesia?

1) Where pain is pre-existing

• Can’t provide pre-emptive analgesia in these animals

2) Situations predisposed to developing chronic pain (ex. amputation)

3) Adjunctive analgesia with difficult-to-manage pain

• Bolus 0.25-0.5 mg/kg

• Infusion 0.3-0.6 mg/kg/hr

Not the first thing you’d reach for, but still good