Lets talk Lets talk aboutabout Pain PainBrian DaubsBrian Daubs

Surgery ResidentSurgery ResidentVeterinary Specialists of South FloridaVeterinary Specialists of South Florida

Cooper City, FLCooper City, FL

Painful??Painful??

Pathway overviewPathway overviewPainful stimuli causesPainful stimuli causes Disruption of phospholipid membraneDisruption of phospholipid membrane

Creates inflammation via arachidonic acid cascadeCreates inflammation via arachidonic acid cascade

Metabolites of AA cascade activate afferent fibersMetabolites of AA cascade activate afferent fibers Direct activation of afferent fibers (a-delta and C Direct activation of afferent fibers (a-delta and C

fibers)fibers)

These afferent nerves synapse in the dorsal These afferent nerves synapse in the dorsal horn of the grey matterhorn of the grey matter

The impulse travels up ascending pathways and The impulse travels up ascending pathways and terminate by synapsing in somatosensory cortexterminate by synapsing in somatosensory cortex

Activation of the pain pathway causesActivation of the pain pathway causes

Release of numerous intracellular substancesRelease of numerous intracellular substances Hydrogen, potassium ions, serotonin, Hydrogen, potassium ions, serotonin,

histamine, prostaglandins, bradykinin, histamine, prostaglandins, bradykinin, substance P, acetylcholine, and many others.substance P, acetylcholine, and many others.

Bradykinin, potassium, and sP directly activate Bradykinin, potassium, and sP directly activate nociceptorsnociceptors

Prostaglandins sensitize the nociceptors Prostaglandins sensitize the nociceptors facilitating depolarization.facilitating depolarization.

Activation of the pain pathway can cause Activation of the pain pathway can cause

Increased heart rate, stroke volume, cardiac oxygen Increased heart rate, stroke volume, cardiac oxygen consumption, may cause arrhythmiasconsumption, may cause arrhythmiasShockShockIleusIleusReduced urinary outputReduced urinary outputHypo or hyperventilationHypo or hyperventilationWind up of both peripheral and central nociceptorsWind up of both peripheral and central nociceptorsIncreased release of cortisol, ACTH, Glucagon, cAMP, Increased release of cortisol, ACTH, Glucagon, cAMP, ADH, growth hormone, renin, and other catabolically ADH, growth hormone, renin, and other catabolically active hormonesactive hormonesNegative energy balance leading to immunosuppressionNegative energy balance leading to immunosuppression

Arachidonic acid cascadeArachidonic acid cascade

Arachidonic acid cascadeArachidonic acid cascade

NSAIDs mechanism of actionNSAIDs mechanism of action

Ketofen (ketoprofen) – cox 1and cox 2 inhibitionKetofen (ketoprofen) – cox 1and cox 2 inhibitionBanamine (flunixin meglumine) - cox 1and cox 2 Banamine (flunixin meglumine) - cox 1and cox 2 inhibitioninhibitionFeldene (piroxicam) – unknown probably cox Feldene (piroxicam) – unknown probably cox 1and cox 2 inhibition1and cox 2 inhibitionRimadyl (carprofen)- cox 2 preferential Rimadyl (carprofen)- cox 2 preferential Metacam (meloxicam) – cox 2 preferentialMetacam (meloxicam) – cox 2 preferential Deramaxx (deracoxib)- cox 2 selectiveDeramaxx (deracoxib)- cox 2 selectiveEtoGesic (etodolac) - cox 2 selectiveEtoGesic (etodolac) - cox 2 selectivePrevicox (firocoxib) - cox 2 selectivePrevicox (firocoxib) - cox 2 selective

Nerve blocks and epiduralNerve blocks and epidural

Local or regional- lidocaine, bupivacaine Local or regional- lidocaine, bupivacaine or ropivacaine blocksor ropivacaine blocks Mechanism of action – Na channel blockadeMechanism of action – Na channel blockade

Consider lidocaine patch Consider lidocaine patch

Epidural- allows delivery of a Epidural- allows delivery of a µ receptor µ receptor agonist, bupivacaine, alpha 2 agonists, or agonist, bupivacaine, alpha 2 agonists, or ketamine.ketamine.

OpioidsOpioids

µ and k- high concentration in CNS, may be µ and k- high concentration in CNS, may be present outside the CNSpresent outside the CNS

µ agonist- morphine, hydromorphone, µ agonist- morphine, hydromorphone, oxymorphoneoxymorphone, fentanyl, meperidine, tramadol, fentanyl, meperidine, tramadol

Partial µ agonist- buprenorphine has a higher Partial µ agonist- buprenorphine has a higher affinity for the µ receptor than the pure µ affinity for the µ receptor than the pure µ agonists. agonists.

µ antagonist- butorphanol and naloxoneµ antagonist- butorphanol and naloxone

k agonist - butorphanolk agonist - butorphanol

Alpha 2 agonistsAlpha 2 agonists

Alpha 2 agonists bind to receptors in the Alpha 2 agonists bind to receptors in the CNS and in other tissues leading to CNS and in other tissues leading to sedation, peripheral vasoconstriction, sedation, peripheral vasoconstriction, bradycardia, respiratory depression, bradycardia, respiratory depression, diuresis, muscle relaxationdiuresis, muscle relaxation

and analgesiaand analgesia..

Multimodal pain managementMultimodal pain management

Use a combination of pain medications Use a combination of pain medications with different MOA to treat painwith different MOA to treat pain This allows a reduced dose for all medication This allows a reduced dose for all medication

and less detrimental side effectand less detrimental side effect

5 modalities we can treat pain with are 5 modalities we can treat pain with are NSAIDs, the caines, opioids, NMDA NSAIDs, the caines, opioids, NMDA antagonists, and alpha 2antagonists, and alpha 2’’ss

Wind up or HyperalgesiaWind up or Hyperalgesia

Wind up can occur after one episode of Wind up can occur after one episode of acute pain or more commonly occurs after acute pain or more commonly occurs after chronic pain.chronic pain. Suspect substance P at NK-1 receptors are Suspect substance P at NK-1 receptors are

involveinvolve Suspect glutamate at NMDA receptors are Suspect glutamate at NMDA receptors are

involve.involve.

Best treatment is preemptive analgesiaBest treatment is preemptive analgesiaGabapentin and ketamine may helpGabapentin and ketamine may help

Preemptive analgesiaPreemptive analgesia

The preventative medicine of painThe preventative medicine of pain

Blocking the pain pathways before any Blocking the pain pathways before any tissue injury will decrease the dose and tissue injury will decrease the dose and frequency of analgesics after tissue injury.frequency of analgesics after tissue injury. Also decreases the amount of inhalant Also decreases the amount of inhalant

anesthesia needed anesthesia needed Provides a quicker return to normal functionProvides a quicker return to normal function Decreases cost to the clientDecreases cost to the client

CRI, IM, IVCRI, IM, IV

1 2 3 4 5 6 7 8 9 10 11 12S1

0

1

2

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5

Time

[Drug]

Assessing the painful patientAssessing the painful patient

Most reliable indicators areMost reliable indicators are Heart rateHeart rate Blood pressureBlood pressure Respiratory rateRespiratory rate

More subjective parameters are More subjective parameters are VocalizationVocalization AppearanceAppearance Activity or restlessnessActivity or restlessness

Take em out to pee!Take em out to pee!

Painful ??Painful ??

Prayer positionPrayer position

Prayer positionPrayer position

Case reviewCase review

Princess a 4 mo female spayed mix breed Princess a 4 mo female spayed mix breed was trapped in a house fire. Stabilized and was trapped in a house fire. Stabilized and treated for smoke inhalation by the treated for smoke inhalation by the emergency group. No significant burns emergency group. No significant burns were present at that time. were present at that time. At the first recheck a fluid pocket was At the first recheck a fluid pocket was present over her back, penrose drains present over her back, penrose drains were placedwere placedPain meds: Deramaxx and tramadolPain meds: Deramaxx and tramadol

Second recheckSecond recheck

Princess was hospitalized due to Princess was hospitalized due to the progressive burn lesionthe progressive burn lesion

Pain managementPain managementDay 1 pain managementDay 1 pain management

oral morphine Gabapentin, and Deramaxx. oral morphine Gabapentin, and Deramaxx.

Day 2Day 2 Continued oral morphine Gabapentin, Deramaxx and added 3 CRIContinued oral morphine Gabapentin, Deramaxx and added 3 CRI’’s of lidocaine, ketamine, s of lidocaine, ketamine,

and domitor and domitor

Day 3Day 3 Continued Gabapentin and Deramaxx and addedContinued Gabapentin and Deramaxx and added fent cri at 5 mcg/kg/hrfent cri at 5 mcg/kg/hr lidocaine cri at 25 mcg/kg/minlidocaine cri at 25 mcg/kg/min ketamine cri at 2 mcg/ kg/ minketamine cri at 2 mcg/ kg/ min domitor cri at 1.2 mcg/kg/ hr domitor cri at 1.2 mcg/kg/ hr

Day 7Day 7 Continued Gabapentin and Deramaxx…Continued Gabapentin and Deramaxx… fent cri at 12 mcg/kg/hrfent cri at 12 mcg/kg/hr lidocaine cri at 35 mcg/kg/minlidocaine cri at 35 mcg/kg/min ketamine cri at 4 mcg/ kg/ minketamine cri at 4 mcg/ kg/ min domitor cri at 8 mcg/kg/ hr domitor cri at 8 mcg/kg/ hr

DebridementDebridement

Hospitalization continuedHospitalization continued

On day 8 On day 8 All the CRIAll the CRI’’s were discontinued except a cri of s were discontinued except a cri of

fentanyl at 4 mcg/kg/hr.fentanyl at 4 mcg/kg/hr.

On day 9 discharged to owners for On day 9 discharged to owners for bandage changes every 3 days for the bandage changes every 3 days for the next 3 weeksnext 3 weeks

At home pain medsAt home pain meds Gabapentin and DeramaxxGabapentin and Deramaxx

discharge discharge

Pre opPre op

Post opPost op

Perioperative pain managementPerioperative pain management

Fentanyl CRI, hydromorphone premedFentanyl CRI, hydromorphone premed

Sent home on tramadol and DeramaxxSent home on tramadol and Deramaxx

RecheckRecheck

CatsCats

Tend to get a temperature spike after Tend to get a temperature spike after hydromorphone, fentanyl, and other drugs at hydromorphone, fentanyl, and other drugs at anesthesia, adjust opioid dose based on pupil anesthesia, adjust opioid dose based on pupil sizesizeTend to handle oxymorphone with less Tend to handle oxymorphone with less temperature variation and less dysphoria (no temperature variation and less dysphoria (no data to support this) data to support this) NSAIDS are fine in young healthy cats use low NSAIDS are fine in young healthy cats use low end of dose and discontinue after 5 daysend of dose and discontinue after 5 daysCats are sensitive to the cains, avoid CRI. Cats are sensitive to the cains, avoid CRI. Epidurals, local blocks, and chest tube infusions Epidurals, local blocks, and chest tube infusions are fine.are fine.

NSAID Doses dogsNSAID Doses dogs

Ketofen (ketoprofen) – 2mg/kg im/sq onceKetofen (ketoprofen) – 2mg/kg im/sq onceFeldene (piroxicam) –0.3 mg/kg po sid Feldene (piroxicam) –0.3 mg/kg po sid Rimadyl (carprofen)-2.2 mg/kg bid or 4.4 Rimadyl (carprofen)-2.2 mg/kg bid or 4.4 mg/kg po sidmg/kg po sidMetacam (meloxicam) – 0.1 mg/kg po sidMetacam (meloxicam) – 0.1 mg/kg po sid Deramaxx (deracoxib)-1-2 mg/kg po sidDeramaxx (deracoxib)-1-2 mg/kg po sidEtoGesic (etodolac) -10 mg/kg po sidEtoGesic (etodolac) -10 mg/kg po sidPrevicox (firocoxib) -5 mg/kg po sidPrevicox (firocoxib) -5 mg/kg po sid

CRI dosesCRI doses

Fentanyl -2-10 mcg/kg/hr (up to 45 Fentanyl -2-10 mcg/kg/hr (up to 45 mcg/kg/hr for anesthesia)mcg/kg/hr for anesthesia) Load with 3 mcg/kg ivLoad with 3 mcg/kg iv

Morphine 0.12-0.36 mg/kg/hrMorphine 0.12-0.36 mg/kg/hr Load with 0.5 mg/kg imLoad with 0.5 mg/kg im

Lidocaine 0.6 3 mg/kg/hrLidocaine 0.6 3 mg/kg/hr

Ketamine 0.12-1.2 mg/kg/hrKetamine 0.12-1.2 mg/kg/hr Load with 0.25 mg/kgLoad with 0.25 mg/kg

CRI dosesCRI doses

Butorphanol 0.04 - 0.1 mg/kg/hr Butorphanol 0.04 - 0.1 mg/kg/hr Load 0.1 mg/kgLoad 0.1 mg/kg

Hydromorphone- 0.01-0.04 mg/kg/hrHydromorphone- 0.01-0.04 mg/kg/hr Load 0.02 mg/kgLoad 0.02 mg/kg

Medatomidine 1-10 mcg/kg/hrMedatomidine 1-10 mcg/kg/hr

Questions ??Questions ??

ReferencesReferences

1.1. Robinson E, Graham L, Quant J. Pain Robinson E, Graham L, Quant J. Pain management. In: Anesthesia and critical management. In: Anesthesia and critical medicine, St. Paul, MN: 2003medicine, St. Paul, MN: 2003

2.2. Plumb D. Veterinary drug handbook 5Plumb D. Veterinary drug handbook 5 thth edition. edition. Ames, IA: Blackwell, 2005.Ames, IA: Blackwell, 2005.

3.3. Thurmon J, Tranquilli W, Benson G. Thurmon J, Tranquilli W, Benson G. Veterinary Anesthesia 3Veterinary Anesthesia 3rdrd ed. Philadelphia, ed. Philadelphia, PA:1996.PA:1996.

4.4. Quant J, Lee J, Powell L. Analgesia in Quant J, Lee J, Powell L. Analgesia in critically ill patients. Compendium of critically ill patients. Compendium of continuing education for veterinarians, 2005; continuing education for veterinarians, 2005; June 433-446.June 433-446.