Dissociative anesthetics/barbiturates/non-barbiturates Flashcards
What is general anesthesia?
a drug induced CNS depression resulting in unconsciousness in which the patient cannot be aroused by painful stimuli, and sensory, motor, and autonomic reflex functions are attenuated.
What is dissociative anesthesia?
drug induced dissociation of the thalamocortical and limbic systems resulting in a catatonic state. Sensory input is dissociated from perception.
What is the MOA for dissociative anesthetics?
non-competitive NMDA receptor antagonist. It inhibits activation by glutamate of ligand gated ion channels.
NMDA antagonists affect what pathway of nociception?
modulation
Why do you have to be cautious with dissociative anesthetics in cats?
because they have the most renal excretion
How long does recovery from dissociative anesthetics take?
2-10 hours.
What are the CNS effects of dissociative anesthetics?
there’s a dual effect of depression of the thalamocortical system and activation of the limbic system which leads to dissociation. Catalepsy is also seen, and pharyngeal and laryngeal reflexes are maintained. Can see somatic analgesia at sub-anesthetic doses
T/F: you can give ketamine on its own as an anesthetic agent.
False
T/F: dissociative anesthetics cause myocardial depression.
True. However, net effect is CV stimulation
Why are dissociative anesthetics not recommended for craniotomy or ocular surgery?
Because they increase intracranial and intraocular pressure.
Why are dissociative anesthetics good for asthmatic patients?
they cause bronchodilation.
T/F: dissociative anesthetics can cause respiratory depression at large doses
True
This drug is a schedule III non-narcotic controlled drug that should not be used alone as an analgesic, but is known to have opioid-sparing capabilities when used at sub-anesthetic doses with opioids
Ketamine
What 3 drugs when used together to induce anesthesia are known as “kitty magic”?
ketamine + buprenorphine + dexmedetomidine
What does the triple dip in large animals consist of? What is it a form of?
guaifenesin + xylazene + ketamine. It is a form of total intravenous anesthesia
T/F: ketamine can serve as an anti-inflammatory
True
Why should you lubricate eyes when using ketamine?
because eyes remain open and the blink reflex may be delayed for hours
When is ketamine contraindicated?
renal disease or failure in cats
About how long does it take for ketamine to reach peak drug concentration?
1 hour
What is the MOA of GABA agonists?
they potentiate GABAa receptors. This results in sedation and hypnosis.
Which GABA mechanism is the cause of anti-convulsant and sedative effects?
GABA dependent mechanism.
which GABA mechanism can result in anesthesia?
GABA independent mechanism
Would you administer barbiturates IM or SC? Why or why not?
No because they can cause tissue damage.
Where are barbiturates metabolized?
They are metabolized by hydroxylation in the liver, but thiobarbiturates can also be inactivated in the brain and the kidney.
T/F: barbiturates are enzyme inducers
True
Are barbiturates good analgesics?
No, unless anesthetized.
Why are barbiturates sometimes used for head trauma?
because they decrease brain metabolism and are neuroprotective.
Why do you typically see hypotension with barbiturate use, and what can this hypotension cause?
hypotension is mainly seen because of cardiac depression, and it can cause reflex tachycardia
what can thiobarbiturates do to the myocardium?
they can sensitize it to catecholamine induced arrhythmias.
What can barbiturates do to the respiratory system and who is more sensitive to these effects?
they can cause respiiratory depression, especially at anesthetic doses. Cats are more sensitive to this. Important to intubate and monitor so as to not cause death.
When should Propoflo be discarded?
within 24 hours of use.
What is special about Propoflo 28?
it has benzyl alcohol as a preservative and is stable for 28 days after opening. Can’t be used in cats
How is propofol administered? How long does it act?
administered IV only. Has a very short duration, so ideal for CRI
T/F: propofol is metabolized in the liver only
False. It has extrahepatic metabolism as well
Can propofol function as an analgesic?
Although it does cause CNS depression, it is not an analgesic.
What can happen if propofol is administered rapidly?
can cause apnea
T/F: alfaxalone is a neurosteroid that binds to GABAa and other steroid receptors.
False. It is specific to GABAa only.
Can alfaxalone be administered IM?
Yes, but it is off label to do so
What can be seen during induction when using alfaxalone?
myoclonus. This can also be seen upon recovery when administered by non-IV routes
Does etomidate have an analgesic effect?
No
How does etomidate work?
it depresses the CNS by enhancing GABA
What effects does etomidate have on cortisol?
it inhibits the synthesis of cortisol by inhibiting the initial steps in the adrenal gland
Can propfol and alfaxalone function as anticonvulsants?
yes
