Lecture 9: Induction drugs (Exam 2) Flashcards
(41 cards)
1
Q
What are the characteristics of the ideal injectable drug
A
- Provide reliable sedation, analgesia, & muscle relaxation
- Min changes in CV or respiratory fxn
- Small vol needed
- Wide safety index
- Rapid onset & short duration of action
- Reversible
- Non-cumulative
- Readily metabolized & excreted by the body
- Long shelf life (stable in heat & light)
- Inexpensive
- Ava on the market
- Low potential for human abuse (not a controlled substance)
2
Q
Fill out the table:
A
3
Q
Describe propofol
A
- Milky white oil in water emulsion
- No preservative (discard open vial w/in 6 hours)
4
Q
Describe propofol28
A
has benzyl alcohol preservative but only approved for dogs
5
Q
What is the MOA of propofol
A
Activates GABA(a) receptor -> increases Cl conduction & block Na channel -> hyperpolarization (brought in a lot of neg ions) -> CNS depression & loss of consciousness
6
Q
What are the pharmacokinetics of propofol
A
- Rapid distribution followed by a slower clearance phase
- Rapid hepatic metabolism & excretion by kidneys (not in cats or greyhounds)
7
Q
What are the pharmacodynamics of Propofol (CNS, CV, Resp, musculoskeletal, & fetal/neonatal)
A
- CNS - Decreases intracranial pressure & cerebral metabolism of oxygen (anticonvulsant effects so good for px w/ head trauma)
- CV - Decreases BP due to vasodilation
- Resp - Dose dep respiratory depression & transient apnea (often w/ cyanosis)
- Musculoskeletal - produced muscle relaxation (transient myoclonus can occur)
- Fetal/neonatal - cross placenta but is rapidly cleared from neonate
8
Q
What is the propofol species specific consideration for grey hounds
A
Need same dose for induction but the recovery time is longer
9
Q
What is the propofol species specific consideration for cats
A
- Caution w/ repeated daily use
- Don’t use propofol28 (can’t process the preservative really well)
10
Q
What is the propofol species specific consideration for horses
A
- not really used b/c excitation & vol/cost
- Can be used for CRI
11
Q
What is the propofol species specific consideration for swine
A
Does not induce malignant hyperthermia (good drug to use for them)
12
Q
What is the propofol species specific consideration for small ruminants
A
- Smooth rapid induction w/ a good recovery
- Possible cost considerations
13
Q
Describe the clinical scenario of propofol
A
- Give over 60 - 90 sec
- Swift induction (20 to 30 sec)
- Be ready to ventilate px
- Recover in 2 to 12 mins
- No analgesia
- Possible pain when injecting
14
Q
What is the characteristics dissociative anesthetics
A
Dissociation from thalamocortical (consciousness) & limbic (emotion & memory) systems to change awareness (decrease)
15
Q
What are the two most common dissociative anesthetics
A
- Ketamine
- Tiltamine
16
Q
What is the MoA of dissociative anesthetics
A
- Mainly: via antagonist effects @ NMDA receptors
- Others: AMPA, BDNF, opioid, etc receptors
- Interacts w/ voltage-gated Ca channels
17
Q
What are the PKs of dissociative anesthetics
A
- Water soluble (can give in multi different ways)
- Rapid onset
- Short duration
- Highly lipophilic (quickly crosses the BBB)
- Metabolized by the liver & excreted by the kidneys
18
Q
What are the PDs on the CNS or dissociative anesthetics
A
- Cataleptic state (not asleep but not responding to external stimuli)
- Can see emergency delirium (ataxia, hyper-reflexive, sensitive to touch, & increased motor activity)
19
Q
What are the PDs on the CV or dissociative anesthetics
A
- Direct neg cardia inotropic effects (usually overcomed by sympathomimetic effects)
- Increased BP, HR, cardiac output, myocardial oxygen req, & cardiac work
- Inhibition of NE reuptake (increased plasma catecholamines)
20
Q
What are the PDs on the resp sys or dissociative anesthetics
A
- Doesn’t cause sign resp depression
- Bronchial smooth muscle relaxant (bronchodilation & decreased airway resistance)
- “apneustic” resp pattern (prolonged inspiration & rel short expiratory time w/ several shallow breaths taken
- Increased salivation & respiratory tract secretion
21
Q
What are the PDs on the musculoskeletal sys or dissociative anesthetics
A
- Can cause muscle rigidity & even spont movements
- IOP can increase after admin (b/c of increased tone of extraocular muscles)
22
Q
What are the PDs on the Fetal/neonatal or dissociative anesthetics
A
- Crosses the placenta
- Can cause fetal depression
23
Q
What are some dissociative anesthetics species specific considerations for dogs
A
Combine ketamine w/ benzo for induction (can us a alpha 2 agonist or opiod)
24
Q
What are some dissociative anesthetics species specific considerations for cats
A
- Can spray into the mouth of fractious cats (can increase salivation)
- Caution w/ use of dissociative in tigers (seizure-like behavior possible)
- ketamine + alpha 2 agonist, benzo, &/or ace for IM
25
What are some dissociative anesthetics species specific considerations for horses
* Adequately sedate before induction
* Admin ketamine w/ benzo, alpha 2 agonist, or guaifenesin)
* Telazol inductions are smooth but recovery is rough
26
What are some dissociative anesthetics species specific considerations for ruminants
* ketamine + benzo/guaifenesin
* "ketamine stun" tech (sub anesthetic dose of ket & xylazine given to calves prior to castration
27
What are some dissociative anesthetics species specific considerations for swine
* Does not induce malignant hyperthermia
* Telazol has a slow calm recovery but not rec for pot belly pigs
28
Describe the clinical use of dissociative anesthetics
* Typically ketamine + benzo ( or a2 agonist)
* Ket can be given as CRI @ sub anesthetic doses to reduce inhalant req
* Not reversible
* Oral, ocular, & swallowing reflexes are still intact (nystagmus common)
* Use caution w/ px that have hepatic or renal dysfxn
* Scheule 3 controlled sub
* Telazol usually used in shelter med
29
Describe alfaxalone
* Older formulation was poorly water soluble & caused histamine release in dogs
* New formula w/ non-cremophor (no histamine release & better water solubility) & can give IM/IV
* No antimicrobial preservative
* P450 hepatic metabolism & elimination via kidneys & feces
30
What is the MOA of alfaxalone
Neuroactive steroid molecule that binds to GABA(A) receptor to increase Cl condution into the cell -> hyperpolarization of postsynaptic membrane -> CNS depression
31
What are the PDs of alfaxalone (CNS, CV, Resp, Musculoskeletal, & neonatal/fatal)
* CNS - Decreases CBF, ICP, & CMRO2
* CV - hemodynamic stability but can cause dose dep hypotension (b/c of vasodilation)
* Resp - dose dep respiratory depression &/or apnea
* MS - good muscle relaxation
* N/F - Crosses placenta & causes dose dep fetal depression
32
Describe the clinical use of alfaxalone
* No analgesia
* Used for induction but can also be used as CRI to maintain ax
* Used for px undergoing c-section
* Good induction for dogs that are a poor ax risk
* Can increase IOP in dogs
* No pain on IV injection
* Schedule IV controlled sub
* Transient paddling, excitement in cats, & vocalization in dogs may occur in recovery (rough recovery for horses)
33
Describe etomidate
* pH of 6.9
* Insoluble in water
* high osmolarity leads to adverse effects
34
What is the MOA of etomidate
Enhances action of GABA (inhibitory neurotransmitter) @ the GABA(A) receptor -> increased Cl conduction into cell -> hyperpolarization of postsynaptic neuron -> CNS depression & hypnosis
35
What are the PKs of etomidate
* Rapid penetration of brain (quick induction)
* Rapid redistribution to inactive tissue (fast recovery)
* Large therapeutic index
* Metabolism by liver & plasma esterases
* Excreted in urine
36
What are the PDs of etomidate (CNS, CV, Resp, Endocrine, MS, N/F)
* CNS - cerebroprotective effects (vasoconstriction of cerebral vessels, reduces CBF, & CMRO2) which leads to cerebral perfusion maintained & decrease in ICP occurs. Decreases IOP
* CV - Min to no change in HR, SV, CO, MAP, & CVP. Baroreceptor fxn & SNS response remain intact (hemodynamic stability)
* Resp - min effects
* Endo - Adrenocortical suppression for up to 5 to 6 H
* MS - myoclonus or tremors
* N/F - min effects
37
What is the clinical effects of etomidate
* Preferred induction agent for px w/ hemodynamic instability, increased ICP, or cirrhosis
* No analgesia
* Caution for px w/ addison's or highly stressed px
* Doesn't appear to be cumulative but not recommended as a CRI b/c of adrenocortical suppression & possible RBC damage
* Premed dose of benzo can decrease myoclonus
38
What are the side effects of etomidate
* Pain on injection
* Vomiting
* Excitement
* Cats - drooling/salivation & concern for IV hemolysis
39
When are mask/chamber inductions used
* Exotics
* Very aggressive px where injectable anesthetics are not possible
40
What should be noted about mask or chamber inductions
* Use caution b/c of exposure to personnel & potential to harm px
* They are not considered the standard of care in most situations
41
What are some other combos that can be used for induction
* Opioid induction (fent + benzo)
* Ket + propofol
* Guaifenesin + ket
* Guaifenesin + ket + xylazine
* Guaifenesin + thiopental
* Propofol + thiopental
* Ket + xylanzine
* Telazon + ket + xylazine/dexmed
* Ket + alfaxalone
