1/3/2018 1 WHAT’S NEW IN ANESTHESIA/ ANALGESIA? LYSA PAM POSNER, DVM, DACVAA PROFESSOR OF ANESTHESIOLOGY 1-2018 CREDIBILITY FACTOR? BS Biochemistry DVM 8 yrs DACVAA Faculty 2005 Faculty Anesthesiology Residency PLAN? • Introduce new products • Introduce new ways to use established products ANALGESICS REVIEW OF PAIN PATHWAY CLASSIC 3-NEURON CHAIN MODEL OF NOCICEPTIVE PROCESSING (SOMATIC)
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What’s New in Anesthesia and Analgesia 2018 · NMDA ANTAGONISTS • Ketamine: side effects – Anesthetic doses • 5mg/kg induction dose • Increased CV work • Hallucinations
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W H AT ’ S N E W I N A N E S T H E S I A / A N A L G E S I A ?
LY S A P A M P O S N E R , D V M , D A C V A A
P R O F E S S O R O F A N E S T H E S I O L O G Y
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CREDIBILITY FACTOR?
BS Biochemistry DVM 8 yrs
DACVAA Faculty 2005Faculty
Anesthesiology Residency
PLAN?
• Introduce new products
• Introduce new ways to use established products
A N A LG E S I C S
R E V I E W O F PA I N PAT H W AY
CLASSIC 3-NEURON CHAIN MODEL OF NOCICEPTIVE PROCESSING (SOMATIC)
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Ganong; physiology
PERIPHERAL SENSITIZATION
CENTRAL SENSITIZATION / WIND-UP
• Dorsal horn of the spinal cord• Extreme or repeated activation• Mediated by glutamate
• Results in– Decreased threshold
– Expansion of receptive field
– Increased spontaneous firing
– Hyperalgesia/allodynia
– Spontaneous pain
PERCEPTION
• Must reach cortex to be perceived as pain
• If patient is unconscious/ anesthetized, they won’t “feel” pain but the entire pathway may be activated
• When consciousness returns, pain pathway will be in full activation
– With less descending modulation
L O C A L A N E S T H E T I C S
LOCAL ANESTHETICS
– Mechanism of action
• Sodium channels propagate action potential
• Local anesthetics block sodium channel
– Routes of administration
• Perineural
• IV
• Dermal
– Species Differences
• Sensitivity to toxicity
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LOCAL ANESTHETIC UPDATES: LIDOCAINE PATCHES
• Lidocaine Patches
– Little to no systemic absorption (dogs/cats)
– CAN be cut to size/area wanted
– Should be replaced daily
– Potential uses
• IVDD, bone pain, inflammatory
LOCAL ANESTHETIC UPDATES: LIDOCAINE CRI IN DOGS
• IV lidocaine in DOGS
• Systemic analgesia
• Antiinflammatory
• GI Prokinetic
• Dose of IV lidocaine in dogs:
– Loading: 1.0 mg/kg
– CRI: 25 mcg/kg/min
LOCAL ANESTHETIC UPDATE: NOCITA
• Long acting local anesthetic– Extended-release bupivacaine technology
– Multivesicular liposomes
• 72 hr duration
• Labeled for dogs following CCL surgery
• Dosage – 5.3 mg/kg (0.4 mL/kg)
– Infiltration injection into the tissue layers
• No data on perineural administration
– At the time of incisional closure
• Very effective
• Expensive
• Short shelf life once opened– Labeled for 4 hr once opened
LOCAL ANESTHETIC UPDATE: NOCITA
• Off label use
– Amputations
– Orthopedics (besided CCL)
– Soft tissue procedures
– Cats
• Caution?
– Infected wounds
– Patients with immune disturbances
N M D A A N TA G O N I S T S
DISSOCIATIVE ANESTHETICSK E TA M I N E / T I L E TA M I N E / P H E N C Y C L I D I N EA M A N TA D I N E
•NMDA (N-methyl-D-aspartate) antagonists
–NMDA receptors are excitatory receptors
•Dissociative anesthetic
–Thalamo-cortical and limbic systems
–Altered consciousness (at anesthetic doses)
–Catalepsy (at anesthetic doses)
–Amnesia (at anesthetic doses)
–Analgesia –at subanesthetic doses
•Ketamine
–Approved for use in cats and primates
•Tiletamine (part of the combination Telazol)
–Telazol approved for cats and dogs
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NMDA RECEPTOR ANTAGONISTS PAIN PATHWAYDORSAL HORN OF SPINAL CORD
• Dorsal horn of spinal cord
– Opioid receptors
– Alpha-2 receptors
– NMDA receptors
• Central sensitization
– Wind-up pain
NMDA ANTAGONISTS
• Mechanism of action– Antagonize activation of NMDA receptor
with glutamate at dorsal horn of spinal cord
– With extended inactivation can interrupt central sensitization
• >24 hr (days? weeks?)
– Ketamine, amantadine
– Chronic pain/ wounds/ burns
– Amputations
DISSOCIATIVES: WHAT’S NEW?
•At least 24 hr CRI needed to “break” windup cycle (in humans)
– Unclear how long dogs/cats
– Induction dose unlikely enough
• Injectable ketamine CRI
– At least 24 hr is recommended to alter/ prevent windup
•Oral amantadine
– At least 2-3 week trial
– Can use with NSAIDs, gabapentin, opioids, etc
NMDA ANTAGONISTS
• Ketamine: side effects– Anesthetic doses
• 5mg/kg induction dose
• Increased CV work
• Hallucinations/ behavioral effects
– Analgesic doses—few side effects• 5-10 mcg/kg/min (ketamine)