PRINCIPLES OF PAIN MANAGEMENT & ANALGESIA

1. PRINCIPLES OF PAIN MANAGEMENT & ANALGESIA “thERE IS NO COMING TO CONSCIOUSNESS WITHOUT PAIN.” -CARL JUNG

2. PRINCIPLES OF PAIN & ANALGESIA • WHAT IS PAIN? • An unpleasant sensory or emotional experience associated with actual or potential tissue damage • Pain results when nerve cells in the skin or deep tissues, called _______________, detect a noxious stimulus • 2 types of sensory neurons that detect and transmit pain • _________________(large, myelinated) • Transmit sharp, discrete pain signals that allow the patient to localize the source of pain. • transmits somatic pain • _________________(small, nonmyelinated) • Transmit dull, aching, throbbing pain that cannot be easily localized • transmits somatic & visceral pain (visceral pain is only transmitted by C fibers)

3. PRINCIPLES OF PAIN & ANALGESIA • THE PAIN PATHWAY • _________________: transformation of noxious thermal, chemical, or mechanical stimuli into electrical signals called action potentials by A-delta & C fibers • _________________: these sensory impulses are then conducted to the spinal cord • _________________: in the spinal cord where the A-delta & C fibers terminate, the impulses can be altered by other neurons, which either amplify or suppress them. • _________________: the impulses are transmitted to the brain, where they are processed and recognized.

4. THE PHYSIOLOGY OF PAIN

5. PRINCIPLES OF PAIN & ANALGESIA • WHAT IS PAIN? • __________ arises from the skin, soft tissues, muscles, bones, or joints • Easily localized through stabbing, throbbing, or aching • ___________arises from internal organs • not easily localized and is characterized by cramping or burning • ____________term used to describe the pain that is felt in a body part other than where the actual pain stimulus is coming from

6. PRINCIPLES OF PAIN & ANALGESIA • WHAT IS PAIN? • ______________ is increased sensitivity to a stimulus • _______________arises from direct damage to peripheral nerves or the spinal cord. • May be shooting, sharp, or tingling • _____________or stump pain is sensation or pain arising from the missing body part • Pain can also be classified according to onset and duration • ________ pain has an abrupt onset and a relatively short duration of action. *Effectively treated with analgesic drugs • ________ pain has a slow onset, and duration of several months to years. *May be unresponsive to drug therapy

7. PRINCIPLES OF PAIN & ANALGESIA • MYTHS ABOUT PAIN IN ANIMALS • Consider how some people without medical backgrounds may view the animal’s response to pain

8. PRINCIPLES OF PAIN & ANALGESIA • THE 5 FREEDOMS OF ACCEPTABLE ANIMAL WELFARE • Freedom from hunger • Freedom from physical and thermal discomfort • Freedom from pain, injury, & disease • Freedom to express normal behavior • Freedom from fear and distress

9. PRINCIPLES OF PAIN & ANALGESIA WHAT ABOUT OUR ANIMAL PATIENTS AND/OR OUR JOBS COULD MAKE MONITORING FOR PAIN and ADMINISTERING ANALGESICS DIFFICULT?

10. PRINCIPLES OF PAIN & ANALGESIA • MONITORING SIGNS OF PAIN • Consider how we as humans display pain vs. how our animal patients display pain. Write some ways you can monitor for pain in animals. • 3 TYPES OF BEHAVIORS ASSOICIATED W/PAIN IN ANIMALS

11. PRINCIPLES OF PAIN & ANALGESIA • PAIN ASSESSMENT • The measurement of pain is important to: • Pain scales • Based on observer’s assessment of patient’s spontaneous behaviors, and behaviors on handling, interaction, and manipulation, & maybe physiologic parameters. • Pain scores should be reassessed regularly and preferably by the same person to minimize observer variation.

12. PRINCIPLES OF PAIN & ANALGESIA PAIN ASSESSMENT TOOLS: Simple descriptive scale

13. PRINCIPLES OF PAIN & ANALGESIA PAIN ASSESSMENT TOOLS: Numeric rating scales

14. PRINCIPLES OF PAIN & ANALGESIA PAIN ASSESSMENT TOOLS: Visual analogue scale

15. PAIN ASSESSMENT TOOLS: Comprehensive scales

16. PRINCIPLES OF PAIN & ANALGESIA • CONSEQUENCES OF UNTREATED PAIN • Consider the long term effects of untreated pain

17. PRINCIPLES OF PAIN & ANALGESIA PHYSIOLOGICAL SIGNS OF PAIN

18. PRINCIPLES OF PAIN & ANALGESIA • WHAT IS ANALGESIA? • ___________ is the absence of the awareness of pain, achieved through the use of drugs or other modes of therapy. It applies to the relief of pain without the loss of consciousness. • WHAT ARE THE GOALS FOR PAIN CONTROL? • Control pain at every stage of treatment • to administer analgesics before the patient has an awareness of pain. This is known as ____________________. • Decreases the analgesic requirements • Decreases CNS sensitization • To prevent __________ an event caused by a buildup of chemical mediators that intensify the pain response

19. PRINCIPLES OF PAIN & ANALGESIA • METHODS OF PAIN CONTROL WITHOUT MEDS • _______________ are endogenous compounds produced by the pituitary gland and the hypothalamus that bind to opioid receptors during situations of trauma or stress. They resemble opiates in their ability to provide pain relief and a feeling of well-being. “natural pain reliever” • Nursing care: • Other therapies to control pain:

20. PRINCIPLES OF PAIN & ANALGESIA • METHODS OF PAIN CONTROL USING MEDS • OPIOIDS • NSAIDS • OTHERS: alpha-2 agonists,ketamine, steroids • LOCAL ANESTHETICS

21. METHODS OF PAIN CONTROL USING MEDS OPIOIDS

22. OPIOIDS • MODE OF ACTION: • Acts on 4 different receptors in the brain and spinal cord • _______ • _______ • _______ • Sigma(only cause hallucination, euphoria/dysphoria) • An opioid agent may act as an _______ (stimulating agent) or __________ (blocking agent) at each receptor • Some opioid agents are considered _________________________in that they block one type of receptor and stimulate another or _______________in that they only partially stimulate some opioid receptors • Binding to these receptors can result in a number of effects: • ANALGESIA • Respiratory depression • Sedation • Dysphoria • And others,…

23. OPIOIDS • REVERSIBILITY • One major advantage of opioids is their reversibility with pure antagonists such as ______________, which is the most effective • Naloxone competitively binds to opioid receptors • It is also possible to use a mixed agonist/antagonist such as BUTORPHANOL or a partial agonist such as BUPRENORPHINE to reverse the effects of the pure agonists • CONTROLLED

24. OPIOIDS • MORPHINE: a FULL AGONIST (stimulates all 4 receptors) • Great for moderate to severe pain • Produces significant sedation • cardiovascular & respiratory depression • SIDE EFFECT/CAUTIONS: • Can cause excitement in cats (use lower doses) • Often results in ______________ due to its effects on the CRTZ • Give slowly IV otherwise severe __________________release can lead to hypotension and pruritis • Other FULL AGONISTS include oxymorphone, hydromorphone, and fentanyl

25. OPIOIDS • FENTANYL: a FULL AGONIST (stimulates all 4 receptors) • the injectable has a rapid onset of action and short duration of action. Onset of action: 2 min; duration of effect: 20-30 min • commonly used as a _____________ skin patch • Fentanyl is slowly absorbed through the skin and may take 4-12 hrs in cats, and 12-24 hrs in dogs to reach therapeutic levels • See pg 230 in your book, Procedure 7-1 for instructions on placing a fentanyl patch.

26. OPIOIDS • BUPRENORPHINE: partial agonist of the mu receptor(aka bupi, buprenex) • Delayed onset of action, (40 min IM) but longer duration of action than other opioids – ___________ • Best used for mild to moderate pain • The injectable product is effectively given to cats _____________________ (applied to the gingiva, under the tongue, in cheek pouch) • Can be used to reverse the effects of pure agonists, while maintaining some analgesic effect. Not as effective as naloxone • THIS DRUG IS PART OF THE VTI PROTOCOL FOR DOGS & CATS*

27. OPIOIDS • BUTORPHANOL: mixed agonist(kappa,sigma)/antagonist (mu)(aka torb, torbugesic) • Best used for mild to moderate pain; and is commonly used as a ________________ • Can be used to reverse the effects of pure agonists. Not as effective as naloxone • Commonly combined with a sedative such as dexmedetomidine or acepromazine • MIXING AN OPIOID & SEDATIVE IS KNOWN AS _____________________

28. OPIOIDS • TRAMADOL: a non-opiate drug that has agonist activity at the mu receptor • Oral tablets • Useful post-operative pain med in dogs and cats • Not currently controlled

29. METHODS OF PAIN CONTROL USING MEDS NSAIDS

30. NSAIDS • MECHANISM OF ACTION: • Inhibits the synthesis of prostaglandins by blocking the enzyme cyclooxygenase ( aka COX-1 & COX-2) • ______ leads to the production of beneficial prostaglandins • ________ leads to the production of harmful prostaglandins that are present during tissue damage and inflammation.

31. NSAIDS • BENEFITS OF NSAIDS: • No strict record keeping • Little abuse potential • Effective when given orally • No sedative, cardiovascular, or respiratory effects • Antipyretic effects • SIDE EFFECTS/CAUTIONS: • GI upset/GI ulcers due to inhibition of __________ • DO NOT USE CONCURRENTLY w/ ___________ • ______ toxicity due to inhibition of PGE2 • hepatic toxicity • Inhibits platelet aggregation due to blockage of ______________

32. NSAIDS • RIMADYL (carprofen) • Approved for use in DOGS ONLY! • Oral(chewable tablets) and injectable forms available • Less likely to cause side effects mentioned previously due to its COX-2 selectivity • Common uses: • Post-operative pain relief • Pain relief from osteoarthritis and other musculoskeletal injuries • PART OF THE CANINE POST-OP PAIN CONTROL PROTOCOL AT VTI

33. NSAIDS • METACAM (meloxicam) • Approved for use in dogs and cats • COX-2 selective • Oral and injectable formulations available • PART OF FELINE POST-OP PAIN CONTROL PROTOCOL AT VTI

34. METHODS OF PAIN CONTROL USING MEDS OTHERS: ALPHA-2 AGONISTS KETAMINE

35. ALPHA-2 AGONISTS & KETAMINE • ALPHA-2 AGONISTS (ex: dexdomitor, xylazine) • Short duration of action (~90 minutes) • Also causes profound sedation, bradycardia • Commonly combined with butorphanol • Reversible (analgesic effects are reversed as well) • KETAMINE • Works by antagonizing ____________receptors in the spinal cord • Blocking NMDA receptors prevents central sensitization & windup • Effective for _________analgesia, but limited visceral analgesia • Duration of action is short 30min

36. METHODS OF PAIN CONTROL USING MEDS LOCAL ANESTHETICS

37. LOCAL ANESTHETICS • WHAT IS LOCAL ANESTHESIA/ANALGESIA? • The use of a chemical agent on sensory neurons to produce a disruption of nerve impulse transmission, leading to temporary loss of sensation

38. LOCAL ANESTHETICS • CHARACTERISTICS OF LOCAL ANESTHETICS • Exert their effects on neurons in the peripheral nervous system and spinal cord that control pain, heat, cold, & pressure • Relatively few effects of the cardiovascular and respiratory systems • Exert their effects in the area closest to the site of injection • Not normally transferred across the placenta • Safe for c-sections

39. LOCAL ANESTHETICS • ROUTES OF ADMINISTRATION • TOPICAL: must penetrate the epidermis to reach the dermis where the peripheral nerves are located • Sprayed on intact skin for superficial procedures such as skin biopsies (ex: ethyl chloride) • Creams can also be applied to desensitize skin for superficial minor procedures (ex: lidocaine/prilocaine) • Splash blocks refer to the use of sprays or anesthetic soaked gauze sponges on open wounds or surgical sites • Applied through a chest tube in patients having thoracic surgery • Should be done when patient is awake • Absorbed through the mucous membranes (larynx, eye, urethra) • Short duration of action and less pain relief when compared to other routes of administration of local anesthetics

40. LOCAL ANESTHETICS • ROUTES OF ADMINISTRATION: • INFILTRATION(injection): • Local anesthetic can be injected subcutaneously, intradermally, or between muscle planes • Ideally the site of injection is clipped and cleaned • Small needle (23-25 gauge) used to prevent tissue damage • Test efficacy by pricking the site with a needle • Do not inject into infected or inflamed tissues • Some local anesthetic drugs are combined with epinephrine • Epinephrine causes vasoconstriction which decreases rate of absorption and prolonging effect • It also decreases the amount of drug entering the circulation, decreasing chances of toxicity. • CAUTION AROUND AN INCISION OR ON EXTREMITIES AND WITH PATIENTS WITH CV ABNORMALITIES

41. LOCAL ANESTHETICS • ROUTES OF ADMINISTRATION • _________ BLOCKS: Injection of a local anesthetic in the proximity of a specific nerve to desensitize a specific anatomic location. Location of target nerve must be known and palpated if possible. • Lameness exams in horses • Cornual blocks for dehorning cattle • Dental blocks in dogs and cats • Infiltration of nerves during amputation of a limb • Declawing cats • May take 15-20 minutes for absorption • Nerve blocks include ________ blocks and ______ blocks

42. Cornual blocks for dehorning cattle THIS NERVE BLOCK IS ALSO A RING BLOCK

43. Dental blocks for tooth extractions Maxillary Nerve block via The infraorbital foramen

44. NERVE BLOCKS Nerve blocks help pinpoint areas of pain Paravertebral block THESE ARE EXAMPLES OF LINE BLOCKS

45. NERVE BLOCKS THIS NERVE BLOCK IS ALSO A RING BLOCK

46. LOCAL ANESTHETICS • ROUTES OF ADMINISTRATION • NERVE BLOCKS • LINE BLOCKS: continuous line of local anesthetics placed SQ in an area served by numerous small nerves • The needle is inserted along the line of infiltration and the anesthetic is injected as the needle is withdrawn • If placed encircling an anatomic part, it is called a RING BLOCK • _________________: injecting local anesthetics directly into a joint usually after surgery of the joint, immediately after closure of the joint capsule

47. LOCAL ANESTHETICS • ROUTES OF ADMINISTRATION • ____________: blockage of sensory and motor nerves in the rear, abdomen, pelvis, tail, hind limbs, and perineum • Anesthetist must be familiar with the anatomy of the terminal spinal cord and lumbosacral vertebrae Epidural space Dura mater arachnoid Subarachnoid space w/CSF Pia mater Spinal cord

48. LOCAL ANESTHETICS EPIDURALS http://www.youtube.com/watch?v=zmwvMHZG_5g

49. SIDE EFFECTS OF LOCAL ANESTHETICS • Allergy • Rash or hives in the area • Systemic toxicity • Sedation, nausea, restlessness, hyperexcitability, seizures, respiratory suppression, coma • Infection (esp. w/epidurals) • Cranial infiltration of an epidural may cause serious toxicity, respiratory suppression • death

50. METHODS OF PAIN CONTROL • Combining drugs from different categories (multi-modal therapy, balanced analgesia) is more beneficial than using high doses of one medication. • Pain is alleviated via different pathways