Analgesia Flashcards
Define: Analgesia
Absence of awareness of pain
Define: Pain
An unpleasant sensory & emotional experience associated with actual or potential tissue damage
*Untreated pain leads to patient suffering & prolongs recovery from surgery
Define: Nociception
The nerve cells involved in the detection of actual or potential tissue injury (pain) by the central nervous system
What are the 4 stages of pain perception?
- Transduction
- Transmission
- Modulation
- Perception
Transduction refers to?
- Tissue injury from physical trauma including burns/chemical burns
- Transformation of noxious thermal, chemical, or mechanical stimuli into action potentials by peripheral A-Delta & C fibers
*Essentially once you get hurt pain receptors are notified & nerve fibers send the pain response to the spinal cord/brain
A Delta Nerve Fibers are found & are generally used in response to what type of pain?
- Found Joints & Skin
- Sharp Distinct Pain
C Nerve Fibers are found where & are used in response to what type of pain?
- Found: Internal Organs especially the abdominal cavity
- Dull achy throbbing pain
Transmission refers to what?
Conduction of sensory electrical impulse to the spinal cord.
*When the pain response moves through to the spinal cord
Modulation
Neurons in the spinal cord amplify or suppress the sensory impulse received from the peripheral nociceptors
Perception
Sensory impulse is transmitted to the brain where it is processed & recognized as pain
Multimodal Analgesia
Using a combination of analgesic drugs, each with a different mechanism of action to control different pain
Pain may be classified as?
- Adaptive Pain
- Maladaptive Pain
Adaptive Pain
Is the normal sensory response caused by tissue damage/injury & inflammation
*Acute & Chronic
Maladaptive Pain
- Results from physical changes that occur in the normal spinal cord & brain if adaptive pain is not managed appropriately
Increased nociceptor sensitivity can lead to?
Increase nociceptor stimuli caused by non-noxious stimuli
Define:
HyperalgesiaIncreased sensitive to noxious stimuli
Allodynia
Pain produced by non-noxious stimuli
Windup
CNS hypersensitive to noxious & non-noxious stimuli
Somatic Pain
Arising from skin, sc tissue, muscles, bones & joints
Visceral Pain
C fibers transmit this pain
Arising from internal organs
Neuropathic Pain
Pain arising from direct damage to peripheral nerves or the spinal cord
Acute Pain
Typically adaptive pain
Sudden onset w/ short duration
Chronic Pain
Slow onset w/ longer lasting effect
Preemptive Analgesia
◦ Administration of an analgesic before tissue damage occurs or the patient has awareness of pain
◦ Reduces the analgesic requirements as well as how long the patient will need analgesics for pain control
◦ Opioids
◦ Alpha 2 Agonists
◦ Local Anesthestics
◦ Nonsteroidal Anti-Inflammatory Drugs (NSAIDS)
Postoperative Analgesia:
◦ Administration of analgesic agents for a few hours to a few days following surgery
◦ Repeated doses of oral or parenteral analgesic agents may need to be administered over an extended period of time
◦ Opioids
◦ NSAIDs
◦ Local Anesthestics
◦ Ketamine
◦ Alpha-2 Agonists
What common anagelsia drugs are administered by CRI?
- Diazepam
- Dobutamine
- Dopamine
Why are CRI’s becoming more popular?
◦ Provides stable plane of analgesia
◦ No peaks or troughs
◦ Lower drug dosage delivered ay any point in time
◦ Greater control over drug administration
What analgesics drugs can be used for CRI’s?
- Opioids - Morphine & Fentanyl
- Lidocaine *Pain relief abdominal surgery
- Ketamine *Maladaptive pain
- Alpha-2 Agonist *Dexmedetomidine - helps w/ restlessness after surgery
What are common opioids used for moderate to severe pain control?
- Morphine
- Oxymorphone
- Hydromorphone
- Fentanyl
What are common opioids used for mild to moderate pain control?
- Buprenorphine
- Butorphanol
- Meperidine
- Nalbuphine
Morphine works by?
Binding mU & Kappa receptors
Morphine is most commonly used in what species?
- Dogs
- Cats
- Horses
Morphine can be administered what route?
- IV
- IM
- SC
- Epidural
- By Mouth
Morphine side effects?
- Dysphoria *Cats & Horses
- Salivation
- Vomiting
- Defection
- Panting *Dogs
- Bradycardia
- Colic in Horses
- Respiratory Depression
- Histamine Release *IV
- Excessive sedation
What opioid is prescribed when a strong pain relief is need that has a longer lasting affect?
Oxymorphone & Hydromorphone
Oxymorphone & Hydromorphone bind with what receptors?
MU
If you need to give a large dose of an opioid via IV what drug has a lower chance of a histamine release?
Oxymorphone & Hydromorphone
Buprenorphine is a partial?
MU receptor agonist
*Binds with the receptors but the effects aren’t as prominent as a drug that binds completely with the mU receptor
Butorphanol is what type of receptor?
Kappa receptor agonist
Butorphanol is used to?
reverse the mU receptor analgesia drug effects
Ketamine is
◦ Dissociate Anesthetic
◦ Block the N-methyl-D-aspartate (NMDA) receptors that are in the spinal cord
◦ Used for animals experiencing chronic pain with no relief from other drugs
◦ Windup: Increased pain hypersensitivity
◦ Can be prescribed with opiods which will address the pain & the ketamine with prevent the maladaptive pain that can develope after a painful surgical procedure
◦ Administration
‣ SQ in small doses to chronic pain patients
‣ IV - CRI
• Nonsteroidal Anti-Inflammatory Drugs (NSAIDS)
◦ Acts as an anti-inflammatory to help relieve pain & decrease inflammation
◦ All relieve somatic pain control
◦ Some visceral pain relief
◦ Adverse effects:
‣ GI issues
‣ Renal/Kidney issues
◦ Do NOT use in combination w/ glucocorticoids
• Local Anesthetics
◦
Prevent transduction & transmission of pain impulses
◦ This is the only drugs that affects transmission of the nerve pain response/impulses
◦ Short duration of action - the affects do not last a long time
◦ Potential for toxicity with repeated doses
◦ Most commonly administered in clinic versus sending home
• Alpha 2 Agonists
•
◦ Provide good analgesia properties
◦ Use is limited by 3 factors:
‣ 1: Short duration of effect
‣ 2: Profound sedative effect
‣ 3: Potential adverse effects on the respiratory & Cardiovascular systems
◦ Best analgesia is through CRI in hospital
◦ Animals must have a healthy cardiovascular system before administration
Tramadol
◦
•
Nonopiate drug
◦ Stimulates the mU receptor
◦ Decreased use in vet med due - as other drugs have greateer analgesia effects
‣ Study shows that it does not provide good analgesia in animals
◦ Administration:
‣ PO (By Mouth) for continuation of pain management at home
Gabapentin
Mechanism of Action:
‣ Not well understood
‣ Appears to decrease secretion of excitatory neurotransmitters
• Norepinephrine
• Substance P
◦ Reduces windup pain
◦ Used for chronic pain management in dogs & cats
◦ Also used for refractory seizures & sedation in dogs & cats
◦ Used to treat arthritis
◦ Used in cats for spicy cats at vet visits
‣ 1 dose the night before & another dose 2-3 hours before appt
◦ Can be prescribed in Dogs but it’s more common to prescribe Trazodone
‣ Can prescribe Gabapentin & Trazodone to dogs for behavioral issue
• Amantadine
A NMDA receptor antagonist similar to
Ketamine
◦ Reduced windup pain
◦ Used for chronic pain management in dogs & cats
Glucocorticoids
◦ Provide analgesia by reducing inflammation
◦ Do not use in combination with a n NSAID
