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Intro to Anesthesiology > Anesthetic Induction > Flashcards

Anesthetic Induction Flashcards

1
Q

Anesthetic induction components

A
  • sleep induction
  • skeletal muscle relaxation
  • loss of reflexes
  • endotracheal intubation
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2
Q

_____ is necessary for all patients undergoing inhalant anesthesia, or to give patient oxygen

A

Endotracheal intubation

  • need to lose laryngeal reflexes
  • may go nasally in large animals
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3
Q

Anesthetic induction

A

Safely transfers a patient from a state of conscious sedation to a chemically induced coma
- ultimate goal = controlled anesthesia!!

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4
Q

How do we judge an animal is at stage 3 anesthesia?

A

Loss of righting reflex

- NOT surgical plane

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5
Q

Surgical plane

A

Patient will not respond or respond minimally to surgical procedures

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6
Q

Stages of anesthesia

A
  • stage 1: analgesia
  • stage 2: disinhibition
  • stage 3: surgical anesthesia
  • stage 4: medullary depression
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7
Q

Eyes are _____ during anesthesia

A

Medially ventrally rotated

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8
Q

Stress ______ epinephrine levels

A

Increases

  • elevated sympathetic tone
  • epinephrine is arrhythmogenic
  • fight or flight
  • poor inductions = poor recoveries
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9
Q

Induction drugs

A

Most have low therapeutic index (narrow safety margins)

- give to effect, until the animal is unconscious and can be intubated

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10
Q

“To effect”

A

Decrease in laryngeal effect to intubate

- not done in horses/wildlife –> give full amount of drug

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11
Q

Ideal anesthetic agent

A
  • smooth loss of consciousness
  • analgesia and relaxation
  • wide safety margin
  • not controlled
  • minimal to no metabolism
  • inexpensive
  • doesn’t exist
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12
Q

GABAa agonists

A

Work similarly to endogenous GABA in the brain to induce a sleep state

  • propofol
  • etomidate
  • alfaxalone
  • thiopental
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13
Q

NMDA antagonists

A
  • ketamine

- telazol

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14
Q

Opioids

A

Used in patients that are very sick

- very depressed patients do not need a lot to enter sleepy state

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15
Q

Thiopental

A

Ultra short acting barbiturate

  • rapid 30 sec onset
  • rapid tissue redistribution
  • rapid recovery 15-30 min
  • bind to GABAa receptor and enhance GABA effect (low doses) and directly stimulates (high doses) = increased chloride current and hyperpolarization
  • reduces CMRO2, ICP, and CBF but preserves CPP due to greater drop in ICP than MAP
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16
Q

Thiopental - side effects

A
  • respiratory depression
  • arrhythmias, hypotension
  • controlled substance (3)
  • no analgesia
  • rough and prolonger recoveries in sighthounds (cumulative)
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17
Q

Propofol

A

Substituted isoproylphenol (soy lecithin base)

  • hypnotic: enhances GABA inhibition, mild NMDA inhibition
  • no analgesia
  • extra hepatic metabolism (can still be used in liver failure patients)
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18
Q

Propofol - action

A
  • onset of action IV: 10-30 sec

- duration: 3-7 min

19
Q

Propofol emulsion

A

Alkylphenol relatively insoluble

  • emulsion containing soybean oil, glycerol and purified egg phosphatide
  • pH is 7.0-8.5 (bacterial growth will occur if contaminated)
20
Q

Propofol - pros

A
  • excellent relaxation
  • non-cumulative
  • useful in sighthounds due to minimal body fat
  • crosses placenta but clears rapidly from neonatal circulation (drug of choice for C sections)
21
Q

Propofol 28

A
  • less expensive
  • old version no preservative - promotes bacterial growth
  • 2% benzyl alcohol
  • significant respiratory depression
  • no analgesia
22
Q

Propofol side effects

A
  • cardiovascular: vasodilation –> hypotension, bradycardia, impaired baroreceptor response
  • pulmonary: decrease RR and tidal volume, apnea
  • excitation at induction
23
Q

Propofol - metabolism

A

Both hepatic and extra-hepatic metabolism

  • extensive and rapid tissue redistribution
  • cats: every day dosing leads to hemolysis, lethargy, anorexia
  • cats have prolonged recovery after single dose if sick
24
Q

Propofol/ketamine mix

A

Reduced dose of each

  • 50:50 mix in same syringe
  • rapid, reliable, effective, chemically stable, bacteriostatic
25
Q

Propofol - technique

A

Slow IV

  • over 30-60 seconds
  • too fast: apnea, cyanosis, bradycardia
  • flow by O2
26
Q

Alfaxalone

A

Neuroactive steroid

  • progesterone derivative
  • cyclodextrin
  • enhances GABA inhibition
  • no analgesia
  • non-cumulative
27
Q

Alfaxalone side effects

A
  • cardiovascular: decreased hr and bp in cat, increased hr, no change in bp
  • pulmonary: decreased rr and tidal volume
  • excitation at recovery
28
Q

Ketamine and tiletamine

A

NMDA antagonists

  • dose dependent restraint to anesthesia
  • onset: 60 sec after IV, 5-10 min after IM, SC
  • useful in many species
  • NOT recommended in cats with HCM!!
  • DEA class 3
29
Q

Ketamine

A

Common, wide safety margin

  • inexpensive
  • IM, SQ, IV, rectally, orally
  • DEA 3 (highly addictive)
30
Q

Single use ketamine

A
  • long lasting motor effects after IM
  • poor relaxation alone, add tranquilizer
  • inadequate analgesia for acute pain with single dose, add analgesic drug +/- CRI
31
Q

Ketamine combinations

A

Versatile drug = IM, SC, slowly IV to effect in small animals

  • do not titrate in large animals
  • combine with benzo
  • light sedation –> general anesthesia
  • free ranging wildlife
32
Q

Telazol

A

Combo of tiletamine HCL (NMDA antagonist) and zolazepam HCl

  • high doses lead to prolonged recovery
  • commonly mixed with alpha2-agonists and ketamine for injectable anesthesia
33
Q

Etomidate

A

GABAa agonist

  • non-barbiturate sedative hypnotic injectable anesthetic agent
  • clinical use = cardiac animals
34
Q

Etomidate - technique

A
  • give slow IV, titrate
  • administer with IV fluids to decrease pain
  • patient must be well sedated before use!!!
  • minimal effects on cardiovascular
  • respiratory function maintainedd
  • expensive
  • not controlled
  • rapid onset, short duration
35
Q

Etomidate - method of action

A

Propylene glycol diluent

  • myoclonus: use tranquilizers to minimize
  • suppresses adrenocortical steroidogenesis
  • avoid in Addisonian and immune compromised and extremely sick animals!
36
Q

Opioid combinations

A
  • useful in debilitated dogs
  • unreliable induction in other species
  • cardiovascular stability
  • reversible
  • used most often in sick patients!! (fentanyl, remi-fentanyl)
37
Q

Opioid combo - technique

A

Must give slowly!!

  • quiet environment, prone to dysphoria
  • may produce bradycardia
  • hydromorphone, fentanyl, methadone+diazepam or midazolam (IV)
38
Q

Guaifenesin

A

Centrally-acting muscle relaxant

  • used as anesthetic adjunct in large animals
  • large volumes required (induction dose 55 mg/kg IV)
  • very irritating, accidental perivascular injection (will slough)
39
Q

Inhalational agents for anesthetic induction

A

Iso, sevo, desflurane

  • useful after premed or alone
  • not good for adult large animals
  • not to be used routinely
40
Q

Inhalational agents

A

Caution in stressed animals (high epinephrine levels)

  • environmental pollution
  • slow onset, excitation likely (stage 2 anesthesia)
  • mask or chamber
41
Q

Chamber induction

A

Small animals/exotics

  • small, really upset patients
  • high O2 flow rates
  • high inhalant concentrations
  • monitor closely until animal becomes recumbent
  • remove from chamber and continue delivery via mask
42
Q

Chamber induction technique

A

Easy, single agent

  • wasteful and causes pollution
  • no ready access to animal in case of emergency
  • prolonged excitation phase (stage 2)
43
Q

Mask induction

A

Common in pocket pets, birds/exotics

  • neonate and pediatrics
  • ideal in neonates, very young patients
  • tight fitting mask
  • restraint often necessary
44
Q

What to do first after anesthetic induction?

A
  • intubate
  • connect breathing system
  • turn on vaporizer
  • check vital signs: airway, breathing, circulation

Intro to Anesthesiology (10 decks)

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