anesthesia- induction

what is induction?

the process of transitioning a patient from a conscious state to a state of general anesthesia

induction drugs are administered how?

IV (with catheters)

the induction drugs are dose-effect, so how do we administer the drugs?

slowly, with IV catheter, until the palpebral reflex is gone- if the patient still has it, we must use more drug, and cannot intubate until it is fully gone

how do we check to see if the patient is conscious/unconscious?

check the palpebral reflex

this is the first reflex to come back and the last to go away in CNS depression.

can we intubate a conscious patient?

no!- they must be fully unconscious (without palpebral reflex) to be able to intubate

how is O2 provided to the patient?

with a mask

do induction drugs have their role in analgesia, muscle relaxation, or immobility-unconsciousness-hypnosis?

immobility-unconsciousness-hypnosis

what is the MOA of most induction drugs?

they target the GABA receptor, which inhibits the synapse between neurons, allowing CNS inhibition/depression.

what are the 3 main effects of induction drugs on the animal?

CNS depression

Respiratory depression

Cardiovascular depression

must we provide O2 to a patient with induction drugs?

YES, because inductors depress the respiratory system. we provide O2 with a mask.

what is different about the intubation of a horse?

-we first put a hard tube in the mouth to protect the intubation tube from the horse's teeth.

-we do not need a laryngoscope because the esophageal sphincter is so strong and will not allow the tube to be inserted here

induction drugs can accumulate where in the body?

muscles

fat

other tissues

is it possible to administer induction drugs another route than IV?

yes, but we must increase the dose

are induction drugs metabolized?

yes, in the liver

what are the 5 induction drugs we use in veterinary medicine?

1. Thiopental

2. Propofol

3. Alfaxalone

4. Etomidate

5. Ketamine

thiopental is used for what?

anesthesia in equine (rescue agent if they wake up during surgery)

euthanasia in small animals

how long is the duration of action of Thiopental?

5-10 min

what is the dosage form that thiopental is available to us in?

powder- we mix it with saline

what are the problems with using Thiopental in anesthesia?

it accumulates after the second dose, so it not good for maintenance.

there is a long recovery

if we are operating on a horse and it wakes up during the procedure, what drug might we use as a rescue agent?

thiopental

what drug is used to euthanize small animals?

thiopental

how do we administer thiopental?

IV

it is available as a powder that we mix with saline

the most commonly used induction agent in small animals is...

propofol

what is propofol used for?

most commonly used induction drug in small animals

rescue sedation

anesthesia maintenance (TIVA) in dogs (not cats)

propofol is administered by...

IV (slowly)

what drug do we use for anesthetic maintenance in dogs?

propofol

(not used as maintenance in cats)

what is the duration of action of propofol?

15-20 min

what is Propofol plus?

propofol + benzyl alcohol (as a preservative)

lasts 28 days

without preservatives, propofol lasts _______ in storage (time)

24 hours

propofol is NOT used in what animals?

Diabetes

pancreatic disease

what is dangerous about propofol in cats?

multiple doses can cause Heinz body anemia

alfaxalone is a ________derivative

progesterone

the duration of action of Alfaxalone is...

15 min

how do we administer Alfaxalone?

IM/IV

what is Alfaxalone used for?

complete anesthesia with TIVA (mostly in cats)

rescue sedation in minor procedures

which drug gives a good complete anesthesia with TIVA in cats?

alfaxalone

what drug can be used in minor procedures as a rescue sedation?

alfaxalone

alfaxalone is not safe for animals with...

liver disease

what side effects might Propofol cause?

severe respiratory depression if administered too fast

painful perivascular administration

heinz body anemia in cats if multiple doses

seizure-like activity

what are the disadvantages of Alfaxalone?

expensive

not good for animals with hepatic disease

Alfaxalone is good for what type of animals?

cats, aggressive animals

etomidate is a ____ derivative

imidazole

what inductor drug is the best for an animal with cardic disease?

etomidate

is etomidate commonly used?

no

is propofol commonly used?

yes, it is the most common inductor in small animals

etomidate's action lasts ________ (time)

3-8 min

how do we administer etomidate?

IV

what are the side effects of Etomidate?

very irritant (can cause anemia)

muscle rigidity

adrenal suppression (so depresses the immune system)

painful injection

we must combine Etomidate with what other drug?

a benzodiazepine, because etomidate causes muscle rigidity

which inductor drug can suppress the adrenal glands, and therefore depress the immune system?

Etomidate

Ketamine is used for...

premedication OR co-induction

in horses, co-induction

in small animals, sedative for aggressive animals, analgesia, co-inductor

what is the MOA of ketamine?

MNDA antagonist

can we use ketamine with TIVA?

yes

can we use Etomidate with TIVA?

NO- because it causes cortisol suppression

can we use propofol with TIVA?

yes- but not in cats

can we use alfaxalone with TIVA (total intravenous anesthesia)?

yes, in cats

what are the disadvantages of ketamine?

accumulation, so poor recovery (dysphoria)

muscle rigidity

apnea (IV)

does ketamine accumulate in the body?

yes

does etomidate accumulate in the body?

NO- there is a fast recovery

does Alfaxalone accumulate in the body?

NO

most induction drugs work by _______, but ______ is a MNDA antagonist

GABA agonists; ketamine

does thiopental provide analgesia?

no

which induction drug also provides analgesia?

ketamine

which induction drugs accumulate in the body, so have a slower/more complicated recovery?

Thiopental

Ketamine

how can we administer Alfaxalone?

IV, IM

which induction drugs can be also administered intramuscularly (IM)?

alfaxalone

ketamine

thiopental is used as a rescue agent for what species?

horses

which drug is a good choice of inductor for aggressive animals and cats?

Alfaxalone

do induction drugs have a short or long duration of action?

very short- max 20 min