Anesthesia Induction Agents Flashcards
(91 cards)
1
Q
thiopental, propofol, etomidate, and alfaxalone are all examples of what kinds of anesthetic agents?
A
hypnotic-sedatives
2
Q
ketamine and tiletamine are examples of what kind of sedatives?
A
dissociatives
3
Q
what are hypnotic-sedatives?
A
take you from a relaxed state to a sleep state
4
Q
what does CSU do before induction?
A
pre-oxygenates everything because of elevation
5
Q
what can happen if you don’t give thiopental in a bolus right away?
A
the animals can get excited, often is why a benzodiazepine will be administered as well to reduce it
6
Q
propofol is what type of drug
A
- alkyl (hindered) phenol
- sedative-hypnotic agent
- available w soybean oil and egg protein
7
Q
what is the shelf-life of propofol?
A
- 6-hour shelf life once the bottle is penetrated
- additional formulation is approved in US for dogs with benzyl alcohol added as a preservative
- this extends the shelf life to 28 days
^ termed multi-dose propofol
licensed for dogs, studied in cats
8
Q
how do you administer propofol?
A
5-8mg/kg IV, dog and cat
9
Q
what other drugs can be given with propofol? how does it affect dosage?
A
- premedication decreases dose required for dogs
- addition of benzodiazepines will reduce dose in dogs and cats
10
Q
what color of propofol bottle has an extended shelf life?
A
green: extended shelf life of 28 days
blue: normal bottle, shelf life of 6 hours
11
Q
what is the concentration of propofol?
A
10mg/mL
12
Q
if a 4kg cat is dosed of propofol at 6mg/kg, what is the volume administered?
A
2.4mL
13
Q
what does 1% propofol mean?
A
10mg/mL
14
Q
T/F: propofol doesn’t have any peri-vascular sloughing if given extravascularly
A
true
15
Q
pharmacokinetics of propofol
A
- rapid onset 20-30 sec, IV
- 95% protein bound
- rapidly redistributed
- rapid metabolic clearance: hepatic and extra hepatic
16
Q
can you give propofol as maintenance?
A
yes, can give as IV maintenance, esp in dogs
- want to limit use in cats to 30 minutes because they saturate the enzyme system so they can’t clear as fast, get a prolonged recovery
^ same with repeated day use; cats can get oxidative stress like heinz body anemia
17
Q
why would you want to give an analgesic with propofol for noxious procedures
A
propofol doesn’t have any analgesic properties
18
Q
T/F: propofol is a mild analgesic
A
false, has no analgesic properties, so want to give analgesics for noxious procedures
19
Q
central effects of propofol
A
- administered IV, range from light sedation to general anesthesia
- does NOT cause excitement when given slowly in small animals
^ what can influence excitement is when you give IV w no catheter or fluids running
20
Q
T/F: propofol can cause excitement upon IV injection
A
false, does not cause excitement when given SLOWLY, but can cause excitement with no catheter or fluids if given fast. typically doesn’t cause excitement though
21
Q
what other properties does propofol have other than sedation?
A
anticonvulsant
anti-emetic
21
Q
how does propofol influence ICP and CCP?
A
decreases intracranial pressure and cranial peripheral pressure
variable effects on IOP (intraocular pressure)
22
Q
what cardiovascular effects are seen with propofol?
A
- VASODILATION- pre-induction fluid bolus may be used, esp if pt fasted and not drinking bc want to counter the dehydration
- myocardial depression
- slow drug administration can reduce these side effects!!
23
Q
what respiratory effects can propofol induce?
A
- transient apnea common after induction dose. apnea can last a while esp if opioids given at same time
- slow drug administration will reduce!
- preoxygenation recommended- want lungs filled with O2 before induction and becoming apneic!
24
what are the indications for propofol?
- anesthesia induction for dogs, cats, small ruminants
- for short and minimally invasive procedures (with oxygen)- airway exam, rads, etc
- ok for use in patients with liver disease or neurological disease if CV stable
25
what about propofol use in patients with hyperthermic syndromes?
can be used, but want no inhalant exposure
- good for sighthounds as they get rigid and weird with thiopental
- good drug for c-sections; need to let mom clear it, let circulate to puppies and out and then take them out, so usually give them 5-10 minutes
25
what about propofol in horses?
- would take 100mL for a full dose in horse!
minis ok, foals ok
adult horse: even after premedications, will get excited and fall on floor. can mitigate by mixing it with ketamine but is scary
26
cautions with propofol?
- good growth medium! some practices refrigerate
- not to be subjected to extremes of temp (refrigeration) bc may come out of emulsion
27
how do you manage propofol-induced apnea when doing a laryngeal examination (assessing abduction of arytenoids)
want arytenoids to be symmetrical; need to be breathing to see this!
give a drug called doxopram: respiratory stimulant: if they do stop breathing, can give a little bit and they will start breathing as long as they are well-oxygenated
27
You see a mature, mixed breed F K9 with foot & pad laceration. Administer SC morphine, remove bandage to examine and determine you should anesthetize to further clean & suture this wound. Start IV fluids and check PCV/TP (26% and 5 g/dL). is propofol a good choice for anesthesia?
problem: PCV and TP both low. problem because propofol causes vasodilation. if an already low PCV/TP, best way to treat is fluids.
- don't use vasoconstrictors in small animals, fluids work fine
- if horse, use vasoconstrictor bc they are so much bigger
- alternatives: alfaxolone, ketamine/diazepam. if you don't have any, just give one induction agent slowly with a benzodiazepine to reduce the dose.
28
alfaxan/alfaxolone
neuro-active steroid with no gluco/mineralocorticoid actions at clinical doses
- another hypnotic-sedative
- made in cyclodestrin
- pH is iso-osmolar- 6.5-7: you don't have to dilute it!
29
MOA of alfaxan
inhibits propagation of action potentials by altering chloride ion flux thru the GABAa channel
30
alfaxan regulations
need to keep records on it! schedule IV drug- records needed. michael jackson overdosed on propofol. alfaxolone similar in properties so US put a lot of restrictions on it
now there is a formulation with preservatives which broadens its usefulness (longer shelf life)
31
what formulations of alfaxan exist?
- form with preservative added broadens its usefulness (longer shelf life)
- preservative free formulation in other countries, can keep in fridge up to 7 days but orgs detected after multiple punctures
cyclodextrin doesn't kill bacteria but also doesn't support growth
32
alfaxan usage
- licensed in dogs and cats in US
- experience and evaluation in other species for anesthesia induction and maintenance and pre-anesthesia sedation
33
how long does alfaxan last in animals?
- dogs: 9-18 mins
- cats: 25 mins
33
how do you administer alfaxan?
- IV
- 1-3mgkg in dogs, 2-5mg/kg in cats
these are AFTER premedication: use the low end of these ranges after animals are premedicated. if you give slowly can use less drug and lower apnea risk and excitement
- administer over 60 seconds, IV for better dose titration and to reduce the risk of apnea
34
how is alfaxan metabolized?
same as endogenous steroids, noncumulative
cat: glucor-sulfon
dog: oxid-glucor
35
how is induction and recovery with alfaxan?
- induction and recovery generally smooth but occasional twitching//paddling seen at induction
- quiet dark environment when recovering is desirable- uncontrolled recovery with hypersensitivity to stimuli may be observed
36
what animals are more likely to have a poor recovery from alfaxalone?
cats
37
T/F: alfaxan should be given with analgesics
true- has no analgesic properties!
38
why is alfaxalone good for feral cats?
can give IM for moderate to heavy sedation. can get them to sleep without a lot of cardiovascular compromise. downside is the volume: pretty big for a cat, so give other drugs with it
39
why do you want to give other drugs with alfaxalone when sedating a cat IM?
volume for IM injection in a cat is pretty big- 0.8-1.2mL.
efficacy is improved with concurrent use of an opioid or other sedative/tranquilizer
40
T/F: alfaxalone is licensed for IV and IM use in other domestic and exotic species
false, not licensed for but has been used
has graded dose dependent effects from sleep to general anesthesia
41
alfaxan cardiovascular effects
not studied in same depth
- increases heart rate IV but doesn't decrease vasomotor tone
- likely some myocardial depression
- unlike propofol, doesn't seem to cause vasodilation
42
what drug causes vasodilation: propofol or alfaxalone?
propofol
43
respiratory effects of alfaxolone
respiratory depressant (IV)
- can reduce incidence of apnea with slower drug administration
44
T/F: you will see less respiratory effects of alfaxan when given IM
true. depends on dose, but always watch them once you give it because there will be some that stop breathing
45
indications for alfaxan
- ok for sighthounds and c-sections
- likely ok for animals with mild-moderate cardiac disease
46
9 yr. MC Cavalier King Charles Spaniel with mitral regurgitation (B2) receiving pimobendan needs lipoma removal
Justify your choice of alfaxan (as opposed to propofol) to your boss who raises concern about the increased cost of alfaxalone over propofol
alfaxan doesn't cause vasodilation! don't want to fluid overload. if pt already in cardiac depression, etc would choose alfaxan > propofol
47
etomidate
- hypnotic-sedative
- imidazole derivative
- weak base
- in US, made in high concentration of propylene glycol. in other countries, looks more like propofol (very white)
- pH of 8.1
- hyperosmolar
48
what are advantages of etomidate?
- minimal cardiopulmonary depression
- transient decrease in HR and RR, may only be noted following administration
49
disadvantages of etomidate
- hemolysis, hematuria, pain on IV injection (propylene glycol)
^ hematuria because of osmolality: want to dilute or administer with fluids if you want to avoid these. if you really want it isosmol, would dilute 1-3 or 1-4 of your dosage
- myoclonus, vomiting
- expensive
50
how much would you need to dilute etomidate to make it iso-osmolar to plasma?
1-3 or 1-4 of your dosage
51
what are side effects of etomidate?
- hemolysis, hematuria, pain
- myoclonus, vomiting (minimized with premedication)
- adrenocortical suppression is a people issue
52
when is etomidate indicated?
- in patients with CNS/cardio/resp disease
ex: HBC with head trauma and pneumothorax. want to keep O2 low because intracranial pressure will increase and cause higher pressure
- etomidate good bc want to lower pressure but keep them breathing
- great choice in cats with HCM
prefer opioids in dogs with cardiac disease
53
what sedative is best for cats with HCM?
etomidate- no cardiovascular effects!
54
A cat received hydromorphone, etomidate and sevoflurane for CT of a nasal tumor. In recovery the cat is stargazing/looks opisthotonic. Is this concerning?
Yes- happens when etomidate is used in short procedures and the body hasn’t cleared it. Osmolality can result in this kind of manifestation. Usually only see these effects after short procedures
55
what are the dissociative anesthetic agents?
ketamine, tiletamine (GG lumped in)
56
ketamine
- weak base
- ketamine HCl: racemic mix of 2 isomers
- dissociative anesthetic
61
onset of ketamine
rapid onset IV: 30-45 sec
absorption is 93% 20 mins following IM administration
only 16% available 30. mins after oral administration
62
what is the difference of ketamine metabolism between dogs and cats?
dogs: N-demethylation to norketamine (10-20% activity), hydroxy-norketamine
cats: norketamine only: they only metabolize it to this, and is active so you will get a prolonged recovery in cats with renal failure
62
how does ketamine affect pressures?
increases ICP and IOP
63
why can cats with renal failure get a prolonged recovery with ketamine?
because they metabolize ketamine to norketamine only, which is active and if they are in renal failure it will circulate much longer as it needs excreted by the kidneys
64
ketamine central effects
- rigidity, muscle hypertonicity, seizure like behavior, hallucinations
- dissociative state
- scrambles neurons
often used intraoperatively to help with postoperative patients, brings elevated nervous system back down into a more normal responsiveness
65
how does ketamine affect CV function in compromised patients?
in a compromised patient or in one where sympathetic tone is reduced, myocardial contractility is depressed: decrease in BP, CO etc
if you don't have a sympathetic reserve, will decrease heart function
65
T/F: ketamine has analgesic properties
true, as an anesthetic and at sub-anesthetic doses
65
what are the CV effects of ketamine?
increases sympathetic tone: increases HR, BP, contractility
increases myocardial oxygen consumption
66
T/F: ketamine increases sympathetic tone
true
because of increased HR and vasomotor tone, myocardial oxygen need also goes up
67
what respiratory effects does ketamine cause?
- hypoventilation and hypoxemia
- increase RR if excitement seen
- increases tracheobronchial and salivary secretions
- bronchodilation
68
when is ketamine indicated
- healthy or mild to moderately compromised patient
- patient with bronchoconstriction or for bronchoscopy
- aggressive animals
69
cautions of ketamine
Stings when given IM so patient
may react violently
Patients with intracranial disease or history of seizures
Cats in renal failure
- DONT USE IN PATIENTS WITH HIGH HYPERTENSIVE EPISODES LIKE HYPERTHYROIDISM OR CARDIAC DISEASE
69
T/F: ketamine is okay to use in patients with cardiac disease as long as it is mild
FALSE do not use with restrictive or hypertrophic cardiac disease
increase in myocardial work is undesirable and may cause death
70
guaifenesin
- GG, glycerol guiacolate etc
- muscle relaxant used as adjunct with anesthesia induction agents in large animals species
- works at interneurons in spinal cord at level of brainstem
71
how do you give guaifenesin?
- IV! such a large volume needed
dose 50-100mg/kg
72
guaifenesin side effects
- results in significant ataxia and some mental quieting
- toxicity at 200mg/kg
- results in rigidity, then apnea
73
what is telazol
tiletamine (dissociative)
zolazepam (benzodiazepine)
only way these 2 drugs come; don't come individually
74
how is tiletamine-zolazepam available
- available in powder form, has to be reconstituted
- each mL contains 50mg of each compound, or *100mg of the combination**
- refrigeration recommended
75
how do you dose telazol
- based on the combination
- intra-animal! as long as its in the pet it will work
- rapid onset via any route
76
opioids
- many drugs
- typically reserved for dogs with cardiovascular compromise!
- IV administration in cats and horses can result in excitement
76
when would you use telazol?
to provide heavy sedation or to induce anesthesia
use when safe handling not possible
77
cautions of telazol
- duration is dose dependent and prolonged sedation and ataxia reported
- behavioral changes in exotic cats
- nephrotoxicity in rabbits maybe?
78
for IV induction, what type of opioids do you not want to choose?
want to pick ones that don't cause histamine release!
79
what opioids don't cause histamine release?
fentanyl, morphine, methadone
80
what is the main side effect of opioids?
bradycardia
81
what are indications for opioids?
- cardiovascular safety
- analgesia
- when reversal of effects is important
82
cautions when using opioids
- respiratory depression
- excitement and noise sensitivity
- slow induction up to a minute, can get excitement
- intubation conditions not ideal
83
what are the 2 safest cardiovascular drugs for sedation?
1. opioids
2. etomidate
choose opioids > etomidate unless some specific reason because etomidate causes adrenocortical suppression
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