Pain Management Flashcards
Pain
An adverse sensory and emotional experience
Nociception
Perception of pain by the nervous system
* processed similarly in all mammals
4 Stages of Nociception
- Transduction
- Transmission
- Modulation
- Perception
Transduction
Conversion of mechanical energy into electrical energy (nerve impulses)
Transmission
Nerve impulse conducted along peripheral nerves leading to spinal cord
Modulation
Change in nerve impulse
- impulses modified once in spinal cord
- amplified or suppressed
- advanced along spinal cord to brain once finished
Perception
What and where it occurs
Impulse processed and recognized as pain
*occurs in Thalamus
Pain & The Brain
Pain free region of the body
* no sensory nerves
Tissue Sensitivity to Pain
Degree of tissue sensitivity to pain is related to density of pain recepors present
Areas with High Density of Pain Receptors
- Skin
- Periosteum
- Joint capsule
- Muscle tendons
- Arterial walls
Area with Low Densitity of Pain Receptors
Visceral and Thoracic Organs
* few sensory nerves
* visceral pain vague, hard to localize
Cardinal Signs of Inflammation
- Pain
- Heat
- Redness
- Swelling
- Loss of function
Clinical Signs of Pain
- Increased HR and BP
- Peripheral vasoconstriction
- Pale MM
- Rapid breathing or panting
- Mydriasis
Perioperative Analgesia
- Provide analgesia surrounding time of surgery
- Multimodal Therapy & Preemptive Analgesia
Multimodal Therapy
- Treating more than one pain receptor site at same time*
- Prefered over using a single analgesic
- Lower dosages used
- Wide margin of safety
*using opioid and NSAID same time
“Wind up”
- CNS hypersensitivity
- Occurs with untreated, moderate-severe pain
“Wind up” Cause
Occurs when spinal cord neurons receive constant or longer term input from pain nerve fibers
* neurons become hypersensitive and hyperexcitable
NMDA
- N-methyl-D-aspartate
- Receptor that is activated in the spinal cord (hypersensitive)
Ketamine
And Wind-Up
- Prevent “wind up”
- Analgesic
- Block NMDA receptor
CRI
Constant Rate Infusion of analgesics
* method of treating constant pain
* IV drip to administer mixture of analgesics
* Can be added to bag of IV fluids
CRI Medications
- Morphine
- Ketamine
- Lidocaine
Opioids
- Analgesic
- Narcotics
Narcotics
Safety
Safest and most effective analgesic group available
Opiods
How They Work
Act at specific opioid receptors in CNS
* most activity in brain and spinal cord
Opioid Receptors
Categories
- Mu
- Kappa
- Sigma
- Delta
- Epsilon
Morphine
Agonist
- Mu agonist
- Produces very effective pain control
Buprenorphine
Agonist
- Mu agonist
- Not as effective as morphine
Agonists
Agonists stimulate the recepors for effect
Antagonists
Antagonists block opioid receptors for effect
* will act as a reversal agant*
EX: naloxone or nalorphine
Agonists and Antagonists
Mixed
Will stimulate some receptors and block other receptors
* allows for analgesia while reducing addiction potential
Butorphanol
Mixed Agonist/Antagonist Classifications
- kappa agonist
- mu antagonist
Butorphanol
Analgesic
- Will reverse analgesic effect of morphine
- Acts as an analgesic, but not as effective as morphine
Narcotics
Side Effects
- Panting
- Respiratory depression (in high doses)
- Bradycardia
- GI tract stimulation
Morphine
- Narcotic drug
- Analgesic with some sedation
- Should be given prior to painful event for greatest effect
Morphine
Excitement
Excitement associated with histamine release
Horses
* causes excitement when used without sedation
Cats
* causes excitement when used in high doses
Morphine
Side Effects
- Vomiting
- Bowel evacuation
- Bradycardia
Atropine or Glycopyrollate will lessen GI side effects
Fentanyl
- Mu agonist
- Synthetic opioid with 100x potency of morphine
Fentanyl
Patch
- Allows for TD administration for prolonged effect
- Needs to be on for 24 hours
- Provides about 72 hours of pain control
- Schedule II
Fentanyl
Recunyra
- Transdermal solution
- Applied to skin of the dorsal scapular area
- Will be absorbed
- One application = 4 days pain control
Hydromorphone
- Synthetic narcotic
- 5x better analgesic than morphine
- Mu agonist
- Can be combines with tranquilizer (Ace)
Torb
- Kappa agonist
- Will produce analgesia
- Not as effective as morphine
- Frequent redosing needed
- Mild-moderate pain
Buprenorphine
- Partial mu agonist
- Not as potent as morphine
- Longer duration than torb (8 hrs)
- Mild-moderate pain
Tramadol
- Synthetic derivative of codeine
- Controlled substance
- Mu agonist
- Will cause sedation
Tramadol
Pain Control
More effective in pain control than an NSAID
* may be used for longer, chronic pain (arthritis)
Narcotic
Reversals
- Nalorphine
- Naloxone
Nalorphine
- Reverses effects of opioids
- Very effective with morphine
- Schedule III drug
Naloxone
- Rapidly reverses the effects of opioids
- Not controlled
- Effective for reversing hydromorphone
Selective Nerve Blocks
- Non-narcotic analgesics
- Used to control pain and inflammation associated with arthritis
Ex: Carprofen (NSAID) for hip dysplasia
Dysplasia
Abnormal growth or development
Selective Nerve Blocks
Block What
Effect on peripheral tissues
* blocks production of COX-1 and COX-2
* reduces production of prostaglandin
COX-1
Relates to the production of mucus protective layer of stomach
* protects from formation of stomach ulcers
Plays an important role in the renal blood supply
COX-2
Produces prostaglandin associated with clinical signs of inflammation
Prostaglandins
Produced in the process of inflammation
* produce susbtances that stimulate sensory nerve cells
* causes sensation of pain
Salicylate Analgesics
- Asprin-type products
- Manage arthritis pain
- May cause GI irritation*
*monitor for vomiting
Salicylate
For Arthritis in Cats
May be used as long as administration is controlled
* not given more often than every 36-48 hours
* some NSAIDS are single use only*
*not to be repeated
Ex: Metacam
Carprofen
- Also called Rimadyl
- Reversible inhibitor of COX-2 with some COX-1 activity
Carprofen
Side Effects
Most Common Include
* vomiting
* anorexia
* lethargy
Onsior
Robenicoxib
- NSAID only approved for cats*
- Control of postoperative pain and inflammation
- Do not use with other NSAIDs or cortisones
- Max use is 3 days
*need to be greater than 5.5 lbs and 6 months of age
Onsior
Side Effects
- Vomiting
- Lethargy
- Polyuria / Polydipsia
Robenicoxib
Meloxicam
Metacam
Reversible inhibitor of COX-2 with some COX-1 activity
Meloxicam
Form and Use in cats
Injectable form approved for cats
* one time only administration
* other NSAID use is extra-label
Metacam
NSAIDs
Patient Caution
Use with caution in patients with:
* compromised renal function
* cardiac disease
* geriatrics
NSAIDs
Combinations
May be combined with opioids
* for severe pain
Do not combine with glucocorticoids
* high potential for gastric ulcers
NSAIDs
Use and Function
- Impare renal blood flow
- Used on healthy patients undergoing moderately painful procedures or experiencing moderate pain
NSAIDs
General Anesthesia Length
If surgery expected to last longer than 30 minutes:
* administer IV fluids
* will help preserve renal blood flow
Sucralfate
- Treatement of gastric ulcers related to NSAIDs
- Mucosal adherent that will protect ulcerated MM surface of stomach
Famotidine, Ranitidine, Cimetadine
- Help treat gastric ulcers related to NSAIDs
- Reduce acid production in the stomach
Misoprostil
- Help treat gastric ulcers from NSAIDs
- Promotes protective mucus layer in stomach
- Prostaglandin medication
- May induce labor
NSAIDs
with Cortisones
Should never be used together
* increased chance of gastric ulcers
* increases wound healing time after surgery
Local Anesthetics
Block selective nerves prior to or following surgery
* provide good pain relief
* block sodium movement across nerve cell membrane
Local Anesthetics
Side Effects
- Minimal
Local Anesthetics
Dental Procedures
Infraorbital nerve block used
Bupivicaine
- Local anesthetic
- Infiltrate intercostal nerves after thoracic surgery
- Lasts longer than lidocaine
Signs of Pain
- Abnormal Respiration
- Increased HR
- Aggression
- Lack of Grooming Behavior
If signs are confusing but surgery just happened, pain likely
Acute Short Term
Pain Treatment
Best treated with opioid analgesics
* May be combined with a tranquilizers
* May also be combined with NSAIDs
Chronic Long Term
Pain Treatment
Best treated with NSAIDs
* asprin may be used in cats*
*no more often than every 2nd day
Xylazine
- Alpha2 Adrenergic Agent
- Causes vasoconstriction*
- Good sedation and analgesic effect
- Reversed with yohimbine
*increases arterial BP = lower HR and reflex vascular hypotension
Dexdomitor
- Alpha2 Adrenergic Stimulator
- Good sedative and analgesic
- May be used in CRI prep*
* for somatic and visceral pain control
Dex Reversal
Reversed with antipamezole
Gabapentin
- Analgesic and Anticonvulsant
- Decreases release of excitatory neurotransmitters*
*norepinephrine
Gabapentin Use
- Control of chronic pain
- Reduce seizures in difficult cases
- Reduce anxiety
Gabapentin Side Effects
Seen in higher doses
* Sedation
* Ataxia
Antipyretic
Relieves fever
