Injectable Anesthetics Flashcards
List dissociative anesthetics
- Ketamine
- Tiletamine
List the barbiturates
- Thiobarbiturates
-Thiopental - Oxybarbiturates
-Phenobarbital
-Pentobarbital (Euthasol)
List the non-barbiturates
- Propofol
- Alfaxalone
- Etomidate
What stages are involved in inducing anesthesia?
Stage 1 + 2
- Analgesia - no pain still conscious
- Excitement phase - Loss of consciousness and voluntary control
MOA for dissociative anesthetics?
Non-competitive NMDA antagonists
-Binds irreversibly! (No reversal)
(Ketamine, Tiletamine)
Where do dissociative anesthetics work on the pain pathway?
Modulation
(Ketamine, Tiletamine)
Amantadine, Ketamine, and Tiletamine all have the MOA. Why is amantadine not in the class of dissociative anesthetics?
- Amantadine is given PO and does not cross BBB
- Ketamine and Tiletamine are injectable anesthetics that cross BBB causing dissociation
Similarities: All are NMDA antagonists and have analgesic properties (neuropathic pain)
What route of administration can Ketamine and Tiletamine be given?
Usually IV, can be given IM
What is false about Ketamine and Tiletamine?
A. Decent transmucosal bioavailability
B. Caution with pre-existing renal disease
C. Has a long duration of action
D. Blocks glutamate by irreversibly binding to NMDA receptors
C. Has a long duration of action
Only has anesthetic effects for ~30 mins
Recovery is long
Main effects of Ketamine and Tiletamine on the CNS?
- Depression of thalamocortical system (sensory perception)
- Activation of limbic system (dissociation)
- Anesthesia and amnesia through CNS stimulation and catalepsy
What level of anesthesia can be reached when using Ketamine alone?
Only Stage 1 + 2
consciousness not completely lost when used alone
What drugs are used to counteract the catalepsy that occurs when using Ketamine?
Used with a muscle relaxant (Benzos)
- Diazepam
- Midazolam
- Alprazolam
What is catalepsy?
CNS stimulation, seen with ketamine use
- Muscle tone maintained to hypertonic
- Pharyngeal and laryngeal reflexes maintained
- Eyes open, mydriasis
- Light and sound sensitivity
Ketamine at subanesthetic doses has analgesic properties which work better for ___________ (visceral/somatic) pain
Somatic
Main effects of ketamine on the CV system?
- Cardiovascular stimulation
- Increased sympathetic tone (Positive inotropic)
- Increased CO, HR, CVP
- Increased cerebral blood flow
- Increased intracranial and intraocular pressure (ICP and IOP)
Main effects of Ketamine on the respiratory system?
- Safe respiratory profile
- Bronchodilation (good for asthmatic patients)
What body systems are most at risk when using ketamine?
- Cardiovascular system
- CNS
can cause CV and CNS stimulation
What drugs are in kitty magic?
Ketamine + Dexdom + Buprenorphine
- Ketamine for dissociation/unconsciousness
- Dex for sedation and pain
- Bup for pain
When would ketamine be used alone?
Rarely
- Chemical restraint and anesthesia for minor procedures
Ketamine and Tiletamine are the only induction agents for anesthesia with _______ properties
Analgesic
Which injectable anesthetics are GABA receptor agonists?
Barbiturates and non-barbiturates
Barbiturates
1. Thiopental
2. Pentobarbital
3. Phenobarbital
Non-Barbiturates
4. Propofol
5. Alfaxalone
6. Etomidate
Barbituates and non-barbituates main clinical uses?
- Anesthetic induction (stage 1 + 2)
- Sedation
- Emergency anticonvulsant (anti-seizure)
- Total IV anesthesia (TIVA)
How are barbituates most commonly administered?
IV
What needs to be considered when using barbituates over time rather than just a single dose?
Enzyme Inducers
Esp Phenobarbital
over time will lead to quicker metabolism of the drug, also drug/drug interactions
How is recovery time of barbituates effected from patient to patient?
Thin/emaciated animals recover slowly, sleepier/sedated for longer
Thiopental can be inactivated by the ___________
Brain and kidney
What adverse effects are seen with barbiturates?
- Respiratory depression, apnea Most common cause of death
- CNS depression
- Hypotension, which may cause reflex tachycardia
Should barbiturates be used adjunct therapy for cases of head trauma?
Yes, decreases ICP and decreases brain metabolism
Which animal is most sensitive to respiratory depression when given barbiturates and non-barbiturates?
Cats
What is the most common cause of death when using a barbiturate/non-barbiturate?
Respiratory depression
____________ is an ultra short acting GABA receptor agonist
Thiopental
Which of the following injectable anesthetics is not available in the USA or Canada?
Thiopental
What is thiopental used for?
Anesthetic induction
Which injectable anesthetic is used for humane euthanasia?
Pentobarbital (oxybarbiturate)
What drug should be used in adjunct to a barbiturate in a euthanasia procedure?
Pentobarbital + neuroleptic/sedative
Pentobarbital + Propofol
allows for a smooth euthanasia and limits the effects of excitement during stage 2 of anesthesia
MOA of propofol?
GABA agonist
How is propofol administered?
IV only
Onset of action and duration of action for propofol?
Fast onset, short duration
Why is propofol part of a euthanasia procedure?
Rapid, smooth, excitement-free anesthetic induction prior to admin of pentobarbital
Propofol given repeatedly over 5 days can have adverse effects in ________
Cats - Heinz body anemia
Effects of propofol on the muscle?
- Decreased laryngeal reflexes
- Myoclonic movements during induction, good muscle relaxation after induction
Which barbiturate is prohibited for use in food animals?
Pentobarbital
Which of the following barbiturates/non-barbiturates are labeled for use in dogs only?
Propofol
heinz body anemia in cats
Extravasation of propofol after IV induction can cause ________
Abscesses/ tissue damage
Which of the following GABA agonistscan be administered IV or IM?
Alfaxalone
_________ is classified as a neurosteroid, although it has no clinical steroidal effects
Alfaxalone
Propofol has similar adverse side effects as _________
Alfaxalone
Which of the following injectable anesthetics is indicated for use in patients with cardiac disease?
Etomidate
Minimal CV effects
What is the main contraindication when using Etomidate?
Contraindicated in hypoadrenocorticism (Addisons dz)
Inhibits cortisol synthesis
True or False, unlike propofol and alfaxalone, Etomidate has analgesic effects when used alone
FALSE
all have no analgesic effects when used alone
Which of the following non-barbiturates have the most to least CV side effects?
Propofol > Alfaxalone > Etomidate
Why is pre-oxygenation important when planning to use barbiturates/non-barbiturates?
Reduce risk of respiratory depression and apnea on induction
Which injectable anesthetics can be used as an anticonvulsant?
Propofol and Alfaxalone (non-barbiturates)
Phenobarbital (oxybarbiturate)
