Injectable Anesthetics Flashcards
What are the 4 stages in general anesthesia?
Analgesia
-> Conscious
-> Reduced pain sensation
Excitement
-> Unconscious
-> Modern anesthesia
–> Designed to shorten / eliminate this stage
Surgical anesthesia
Medullary depression
-> Deep depression of CNS
Why are IA so hydrophobic?
Cross BBB
Is the distribution of IA “perfusion - dependent” or “permeability - dependent”?
Perfusion - dependent
Is anesthetic effect terminated by “metabolism” or “redistribution”?
Redistribution
Is elimination of IA or IH generally faster?
IH
Provide 3 example of barbiturates with for ultra short lasting, and 1 for short lasting and long lasting effects
Ultra short
- Thiopental
- Thiamylal
- Methohexital
Short acting
- Pentobarbital
Long lasting
- Phenobarbital
Is Thiopental, Thiamylal or Methohexital the fastest acting?
Methohexital
What is the post synaptic receptor that Barbiturates binds to?
GABA(A)
Which Barbiturate is used for Anticonsulvant?
Phenobarbital
Does Barbiturates cause respiratory depression or cardiac depression?
Both
What are 4 advantages of ultra short - acting Barbiturates?
Cheap
Rapid administration
Minimal equipment required
Rapid induction & recovery
-> After a SINGLE dose
Why happens after repeated injections of Barbiturates?
Accumulation in fat tissue
-> Slow metabolism
–> Drug hangover
—> Prolonged recovery
What are 4 adverse effects of Barbiturates?
Local irritation
-> Perivascular tissue necrosis
–> Barbiturate ( weak acid ) is mixed w/ NaOH
—> Sodium barbiturate = pH
Low safety margin (<2)
-> Respiratory depression
–> Can cause death
—> Used for euthanasia for lab animals though
Low doses cause excitement
-> Chances : Methohexital > Thiopental
Significant depression
-> CNS
-> Respiratory
-> Cardiovascular
What are the two reasons we would choose Thiobarbiturate induction?
Animals w/
-> Seizure history
-> Raised intracranial pressure
What are the two reason we would avoid using thiopental in “greyhounds”?
Deficient in oxidative enzymes
-> for drug metabolism
Recovery takes 2 - 4 times compared to other dog breeds
What are the reason we would avoid using thiopental in “sighthounds”?
Lean breeds
-> No fat storage
–> No redistribution
–> Prolonged effect
What should we use for greyhounds and sighthounds if thiopental is avoided?
Methohexital
-> Rapid distribution
-> Rapid metabolism
-> Quick recovery
What is one example of pre meds used for large animals?
Guaifenesin
-> Glyceryl Guaiacolate
What is the 2 reasons to use Guaifenesin w/ Barbiturates for large animals?
Reduce Barbiturates doses
Less side effects
Which barbiturate should be avoided for horse and cats anesthesia w/o prior sedation?
Thiopental
-> May cause excitation
Which barbiturate is recommended for lean dogs but not for horses?
Methohexital
What is the 2 pharmacological effects for Guaifenesin?
Skeletal muscle relaxant
-> Central acting
Expectorant
-> Aids in removing mucus
Is Propofol a ( barbiturate / non - barbiturate ) & ( dissociative / non - dissociative ) IA agent?
Non - barbiturate
Non - dissociative
What is Propofol similar to? Why? ( 4 reasons )
Thiobarbiturate
-> GABA
-> Rapid onset
-> [Cardiovascular & Respiratory depression]
-> Large doses induces apnea
What are the 7 (= =) advantages for Propofol?
Rapid hepatic & lungs metabolism
-> [Used for both induction & maintenance]
Suitable for outpatient procedure
Recovery quality»_space;> Thiopental
No perivascular tissue irritation
-> Though small pain injection causes local pain
–> Large veins recommended
Maintenance of anesthesia
-> When IH is not possible
–> Much movement needed during the procedure
Minimal effects on Babiesssss
Excellent muscle relaxation
What are the 7 (= = again?) disadvantages / cautions for Propofol?
No analgesia effect
Expensive
Bad for cats
-> Oxidative damage to RBC
–> Repeated use may result in Heinz body
—> Heinz body : Deposition of denatured hemoglobin from RBC
Septicemia
-> If badly stored
–> Ingredients favors bacterial growth
Bad for horse
-> May cause excitement
Cardiovascular & respiratory depression
-> Slow administration is recommended
-> Pre med is recommended
–> Reduce dosage of induction agent
Overdose
-> Treatment is similar to Thiopental
Other than Thiobarbiturate, what else is extremely similar to Propofol?
Etomidate
( “H”e took my date )
What is so similar about Propofol & Etomidate?
Non - barbiturate
Non - dissociative
Rapid onset
Respiratory depression & Apnea
No perivascular tissue injection
Rapid hepatic metabolism
No analgesic effect
Expensive
Induction of anesthesia
- Dogs
- Cats
- Humans
What is the advantage of Etomidate compared to Propofol & Barbiturates?
Less cardiovascular depression
What are the disadvantages of Etomidate?
[Hemolysis & Hematuria]
-> Dogs
-> Cats
–> Not popular in veterinary medicine
[No analgesic effect]
[May cause serious adrenal suppression]
Pain upon injection
Expensive
Is Ketamine & Tiletamine “dissociative” or “non - dissociative”?
Dissociative
Which receptors does Ketamine binds to?
Is it a (competitive / non-competitive) (agonist / antagonist)?
Non - competitive antagonists
-> Glutamate NMDA receptors
Does Ketamine stimulate “sympathetic” or “parasympathetic” with clinical doses?
Sympathetic
-> Cardiovascular stimulation
Does large doses of Ketamine cause cardiovascular depression or stimulation?
Cardiovascular depression
-> Hypotension
What are two classes of Glutamate receptors?
Metabotropic
-> G protein
Ionotropic
-> Ligand - gated ion channel
What are two types of Glutamate Ionotropic receptors?
And their functions ( Ion permeability )?
AMPA
-> Na+ & K+ permeable
-> Ca++ limited
NMDA
-> Highly Ca++ permeable
–> 20 : 1 : 1 ( Ca++ : Na+ : K+ )
Does Ketamine have ‘Fast’ or ‘Slow’ elimination rate?
Slow elimination rate
-> Several days
List 5 characteristic of Dissociative Anesthesia ( Cataleptic State )
Strong analgesia
Unaware of the environment
Eyes open
Increased muscle tone
-> Moves limbs
-> Occasional seizure
Increased salivation & lacrimation
Which hepatic enzyme is used for Ketamine metabolism?
Cytochrome P450
What is norketamine?
Why do we have to be cautious about it?
Norketamine
-> Metabolite of Ketamine
–> 10 - 30% of Ketamine effects
Cats always have impaired renal function
-> Slower elimination of Norketamine
–> Prolonged effect
What are 2 advantages of Dissociatives?
Less respiratory depression
-> compared to Thiopental & Propofol
Can be administered
-> IV
-> IM***
–> Used for intractable animals
Why are pre meds used with Ketamine?
What are pre meds used w/ Ketamine
- in Dogs
- in Horses
- in Large animals
What are pre med used w/ Tiletamine?
Choices : Guaifenesin, Diazepam, Xylazine, Detomidine, Medetomidine, Midazolam, Zolazepam
To prevent involuntary movement
Dogs
-> Diazepam
-> Midazolam
-> Medetomidine
Horses
-> Xylazine
-> Detomidine
Large animals
-> Guaifenesin
Tiletamine
-> Zolazepam
Match the following
Guaifenesin
Diazepam CNS sedative (minor tranquilizer)
Xylazine
Detomidine Alpha2 - agonist (tranquilizer)
Medetomidine
Midazolam CNS sedative + muscle relaxant
Zolazepam
CNS sedative (minor tranquilizer)
->Diazepam
-> Midazolam
-> Zolazepam
Alpha2 - agonist (tranquilizer)
-> Medetomidine
-> Xylazine
-> Detomidine
CNS sedative + muscle relaxant
-> Guaifenesin
Can Ketamine used in food - producing animals?
No
Why shouldn’t we use dissociative anesthetics as single agents for horses?
Delirium during recovery
What is the difference of Thiopental, Propofol, Etomidate & Ketamine? ( Increase, Decrease, Remains the same )
- CBF ( Cerebral blood flow )
- ICP ( Intracranial pressure )
- MAP ( Mean arterial pressure )
- HR ( Heart rate )
- CO ( Cardiac output )
- RR ( Respiratory rate )
- MV ( Minute ventilation )
CBF
-> Only Ketamine increases
ICP
-> Only Ketamine increases
MAP
-> Etomidate remains the same
-> Ketamine increases
HR
-> Propofol & Etomidate remains the same
-> Ketamine increases
CO
-> Etomidate remains the same
-> Ketamine increases
RR
-> Only Ketamine remains the same
MV
-> Only ketamine remains the same
What is the 2 Steroidal anesthetics?
Althesin
Saffan
What are the difference between Althesin and Saffan?
THEY ARE EXACTLY THE SAME, IDIOT
What is the two type of steroids in Althesin / Saffan?
Alphaxalone
Alphadolone
Which receptor does Althesin acts on?
Is it ‘agonist’ or ‘antagonist’?
GABA(A)
-> Agonists
Is Althesin short or long acting?
Short acting
What are the injection methods for Althesin?
IV
IM
Is Althesin used for anesthetic induction or maintenance?
Induction
- Most animals
Maintenance
- Cats
Why was the old formulation of steroidal anesthetics withdrawn from the market?
Severe anaphylactic reactions
-> caused by vehicle : Cremophor EL
–> causes Histamine release
Why is Steroidal anesthetic back on da market?
Different vehicle used
-> Cyclodextran
