Test 2: 16 case 2 Flashcards
what are 4 common injectable anesthetics
Phenols (Propofol)
Steroids (Alfaxalone)
Imidazoles (Etomidate)
Cyclohexanones (Ketamine, Tiletamine)-
pheonols, steroids and imidazole: increase time GABA A channel is open= ↑ inhibitory effect
cyclohexanones- ketamine: dissociative- block NMDA(glutamate) receptor→ decrease excitatory activity → intense analgesia, light sleep, amnesia and catalepsy
how do phenols, steroids and imidazole work?
increase time GABA A channel is open= ↑ inhibitory effect
synergism with benzodiazepines (that allow GABA to bind easier to GABA A channel
Phenols (Propofol)
Steroids (Alfaxalone)
Imidazoles (Etomidate)
how do dissociative anesthetics work
cyclohexanones- ketamine: dissociative
block NMDA(glutamate) receptor→ decrease excitatory activity → intense analgesia, light sleep, amnesia and catalepsy
why do injectable anesthetics wear off so quickly?
redistribution into other areas of the body
— can cause transient central excitatory effects during induction
propofol/etomidate
— can cause transient central exciatory effect during recovery
alfaxalone
ketamine, tiletamine (dissociative anesthetics)
— can cause muscle rigidity and hyperreflexia upon induction
dissociative anesthetics
(ketamine, tiletamine)
injectable anesthetics will do what to respiratory system
↓ tidal volume
↓ respiratory rate
propofol:
↓ RR, bronchodilation, ↓ swallow reflex,
↓ BP, no effect on HR
Alfaxalone:
↓ RR (less then propofol) ↓ swallow reflex
lesser CV effects then propofol- safe in shocky pts
Etomidate:
no/minimal effect on RR or CV
Ketamine:
apneustic breathing, bronchdilation
CV indirect stimulent: ↑ HR, CO, MAP in healthy but in sick direct inotropic and vasodilatory effect
in general injectable anesthetics will do what to CV system
cause hypotension
negative inotropic effect and direct vasodilation
propofol:
↓ RR, bronchodilation, ↓ swallow reflex,
↓ BP, no effect on HR
Alfaxalone:
↓ RR (less then propofol) ↓ swallow reflex
lesser CV effects then propofol- safe in shocky pts
Etomidate:
no/minimal effect on RR or CV
Ketamine:
apneustic breathing, bronchdilation
CV indirect stimulent: ↑ HR, CO, MAP in healthy but in sick direct negative inotropic and vasodilatory effect
what are the advantages of alfaxalone and ketamine in comparision to propofol?
- water soluble, can give IM- easier to give to angry animal
- less respiratory depressent
- less CV depressent
- Ketamine has some antinocicpetive (pain relief) activty
in anemic cats — injectable anesthetic should not be used
propofol- cats can not metabolize propofol in their liver, leads to heinz bodies formation
etomidate- should not be used in anemic animals- causes decreased adrenal steroid genesis which can lead to hemolysis
why should etomidate not be used in anemic pts
causes decreased adrenal steroid genesis which can lead to hemolysis
what are unique features of etomidate?
- extremely rapid induction < 20 secs
- decrease in CBF → direct cerebral vasoconstriction
- none or minimal Resp and CV effects
- extrahepatic metabolism (plasma ester hydrolysis- can be used in liver failure pts
- lowest plasma albumin binding (76%)- not effected by low albumin
Bad things
- inhibit adrenal steroid production (11β hydroxylase)
inhalent drugs with high or low B/G coefficients can change induction faster
low
sevoflurane and desflurane can be adjusted faster then isoflurane
risks associated with inhalant anesthetics
hypoventilation → resp acidemia
V/Q mixmatch → hypoxemia
Hypotension- tissue hypoperfusion, cardiac arrhythmia, muscle weakness
Vasodilation
inhibit ANS- negative inotropic effect, inhibit autonomic CV reflexes
increases stress hormone release
how to reduce risk factors of inhaled anesthetics
balanced anesthesia
use many drugs that work in different ways to reduce overall dose of each med
different agent and technique for each element:
- hypnosis and amnesia
- analgesia
- muscle relaxation
- absence of somatic or autonomic responses to noxious stimulation
low dose — can be given to prevent dysphoria post op
acepromazine(D2 antagonism- sedative/tranquilizer) /dexmedetomidine
dysphoria from opioids- use butorphanol (partial μ opioid) to block some opioid receptors
what can you use for premed of young healthy dog for TPLO
Can use many options:
- Opioid ± acepromazine (D2 antagonist)
- Opioid ± dexmedetomidine (⍺2 agonist)
- Systemic NSAIDs (implication of giving this drug pre-op rather than post-op)
- Opiods: Oxymorphone, hydromorphone, morphine, methadone
goals of premed
Sedation/ anxiolysis
Reduce induction/ maintenance agent doses
why use TIVA over inhalant
Both are valid options, but an inhalant anesthetic-based maintenance is certainly cheaper and more convenient
TIVA- pt are faster to ambulate after surgery, need less anesthetics
what drugs/protocols are most appropriate from young healthy dog for TPLO
- Propofol or alfaxalone ± midazolam 0.2 mg/kg to effect, followed by isoflurane/sevoflurane in oxygen ± air
- Propofol or alfaxalone ± midazolam 0.2 mg/kg to effect, followed by propofol and alfaxalone CRI, respectively
- Ketamine 4 - 5 mg/kg + midazolam 0.2 mg/kg IV, followed by isoflurane/sevoflurane in oxygen ± air
which drugs should you not use for induction for TPLO of young healthy pup
Etomidate for induction of anesthesia
Telazol for induction of anesthesia
Volatile anesthetics for induction of anesthesia
how to control nociception intraoperatively for TPLO
- Lumbosacral epidural anesthesia/analgesia
◦ Morphine 0.1 - 0.3 mg/kg
◦ Ropivacaine 0.25 % - Femoral & sciatic nerve block with 0.5 % bupi- or ropivacaine
- Fentanyl, Sufentanil or Alfentanil CRI
what drugs for 2yo cat declaw
- Local anesthesia with bupivacaine 0.25 - 0.5 %
- Systemic buprenorphine or oxymorphone or methadone or other opioid
- Systemic dexmedetomiding
what drugs are not effective for analgesia of 2 yo cat with declaw scheduled.
*NSAIDS as sole analgesic intervention
* IV lidocaine or IV ketamine
which inhalant anesthetic could be optimal for induction of anesthesia for cat declaw
propofol or alfaxalone +/- midazolam
ketamine+ midazolem 0.2 mh/kg IV, followed by isoflurane/seroflurane in O2
which inhalant anesthetic is optimal for cat declaw
seroflurane
why use sevoflurane in cats for declaw
sevo is faster in onset of diease
- less irritant for the airways
