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Pharm 1 - Injectable Anesthetics

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hpaul2's version from 2017-04-06 17:25

Basics

Question Answer
What are the 5 classes in injectables?Barbiturates
Dissociatives
Propofol
Neuropeptides
Etomidate/Medetomidate
Speed of induction is based on what two main things (& examples)?(1) Drug characteristics (lipid solubility, size, protein binding, ionization)
(2) Patient factors (acid/base status, PP conc, CO)
What are the receptors the 5 classes work on?All of them are GABA agonists EXCEPT Dissociatives, those are NMDA antagonists
What are the three main uses of injectable anesthetics?Induction, maintenance, & TIVA (total intravenous anesthesia)
What is the class of Injectable anesthetics which provides analgesia?Dissociatives (maybe Neurosteroids?)
Advantages of injectables? (7)(1) Rapid control of airway (prevent aspiration)
(2) Upper airway exam/sx
(3) Rapid control & reduction in CNS activity
(4) Less stressful (TIVA-total intravenous anesthesia)
(5) Better recoveries (TIVA)
(6) CV stability
(7) Improved stability of cerebral autoreg
Disadvantages of injectables? (4)(1) Lg vol distribution
(2) Recovery has redistribution & metabolism to contend with
(3) More difficult to regulate anesthetic depth (Propofol easier b/c short 1/2 life)
(4) Potential for human abuse
How do Injectable anesthetics affect the heart?<3 Stability
What do Injectable anesthetics do to the bronchi? Blood vessels?Dilate
What is the associated benefit of the effect of Injectable anesthetics on the bronchi?Dilate, so rarely need to intubate, & you can do work on the upper airway (barbs might cause laryngeal spasm tho)
Which drugs are hard to regulate? Easy to regulate?Most are hard to regulate, except propafol
What does a high protein binding do to the volume of distribution?LOWERS it (stays stuck on proteins, so cant be active)
How do the drugs which work on GABA do their effects?Leave the GABA channel open longer, decreased disassociation rate (more Cl- gets through) (barb= both, propophol= dissociation)
Which class(s) is not safe for use in head trauma?Dissociatives
Heart-friendly anesthetics?Dissociatives are best, & Etomidate has minimal effects (safe for congestive heart failure)
Which classes provide mm relaxation?Propophol (decreased laryngeal reflexes), Barbiturates (laryngeal spasms), Neurosteroids
Which classes do not provide mm relaxation?Dissociatives, Etomidate
What are the respiratory friendly classes?Neurosteroids (best) > Etomidate (minimal effects) > Dissociatives (slight resp. depression)
Which Barbiturate is commonly used as an anticonvulsant?Phenobarbital
Which drug is used as euthanasia?Pentobarbital
Which has high plasma protein binding? Low?High = Etomidate. Low = Neuropeptides
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Barbiturates

Question Answer
What are the two kinds of barbiturates?Thiobarbituates & Oxybarbituates
Name the Thiobarbituates?Thiopental , Thiamylal
Name the Oxybarbiturates?Phenobarbital, Pentobarbital, Methohexital
Do Barbiturates provide analgesia?No
Where are Barbiturates metabolized/excreted?Liver, kidney
What happens to metabolism if the dog is fat? Skinny?BOTH are LONGER. (Fat= lipophilic drug stays in fat —> redistribution. Skinny= drug doesn’t leave blood —> returns to brain)
What is the duration of action of thios and oxys and whyThio= shorter (more lipophilic), oxy= longer (less lipophillic)
What is the shortest acting Barbiturate?Methohexital (even though it’s an oxy!)
Thio vs oxy - induction, recovery, & duration of actionThio= quick induction/recovery, short duration; Oxy= slow induction/recovery, longer duration
What part of the brain do barbiturates affectReticular activating system (RAS)
What are the CNS effects of barbituratesdecreased cerebral blood flow, O2 consumption, & intracranial pressure
What effect does methohexital have on the CNSexcitement of epileptic foci
What are the CV effects of barbituratesdecreased stroke volume/contractility, hypotension (mild),
What are the resp. effects of barbituratescentral resp. depression, decreased reflexes to ↓O2/↑CO2
What are the muscular effects of barbituratesmuscle relaxation, increased reflexes (laryngeal spasms)
What are the kidney effects of barbituratesdecreased blood flow & GFR
What are the effects of barbiturates on fetus/neonatescross placenta, more active in neonates (pH)
What are the misc. effects of barbiturateshypothermia, splenic sequestration of RBCs (both b/c slowed metabolism)
What are the contraindications of barbituratesCompromised dogs, uremia, pregnancy
What are the two stages of recovery from barbiturates1) regain consciousness = redistribution from high to moderately perfused tissues 2) full recovery = redistribution to fat
How are barbiturates metabolizedliver - CYP450
What dog species are more effected by barbiturates and whysighthounds (greyhounds), deficient oxidative enzymes (breaks down thios)
How are ruminants affected differently by barbituratesregurgitate (so intubate), ‘pink tooth,’ metabolized pentobarbital 8x faster than dogs
How are pigs affected differently by barbituratesprolonged recovery from thiopental (fat)
How are horses affected differently by barbituratesthiopental excitation/incoordination, leg flextion, methohexital excitation during induction/recovery
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Propofol

Question Answer
Does Propofol provide analgesia?No
How does Propofol affect preg animals?CAN cross the placental barrier, but short acting - no clinical consequences
How does Propofol affect the GABA channel?Decreases disassociation rate
What are the indications of Propofol? (5)(1) Induction of general anesthesia
(2) Short term sedation
(3) long term sedation
(4) Maintenance of anesthesia
(5) Treatment of status epilepticus
Which indications of Propofol are provided via CRILong term sedation & maintenance of anesthesia
What are the effects of Propofol on intracranial pressure?Decrease
Respiratory effects of Propofol?CAUSES APNEA
Effects of Propofol on muscles? Notable muscle group?Muscle relaxation! Suppresses laryngeal reflex! (Risk of aspiration)
How does Propofol affect greyhounds?Slower recovery because of a small Vd
How does Propofol affect old dogs?Slower clearance (old liver & kidney)
Where is Propofol metabolized? Excreted?In the liver & IN THE LUNGS excreted in kidney
How does Propofol affect cats?Oxidative injuries
How well do horses recover from Propofol?Usually a smooth recovery (may show excitement upon induction after sedation w/ an α-2 agonist.)
How does Propofol affect birds?Sig. respiratory depression in red tailed hawks & great horned owls
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Dissociatives

Question Answer
Receptor action of Dissociatives?NMDA antagonist
Do Dissociatives provide analgesia?YES!
Do Dissociatives provide mm relaxation?No
How do Dissociatives affect cerebral blood flow?Increase - NO USE IN CONCUSSIONS
How do Dissociatives affect the CV system?GOOD TO USE in HEART PTs!
What are the Dissociative drugs?Ketamine & Tileamine
How do Dissociatives affect cats? (Metabolism-wise)Cat given ketamine will EXCRETE A STILL-ACTIVE compound, norketamine, which is 10-30% active. This is bc they can't glucoronidate
What is telazol?A 50/50 mix of Tiletamine (Dissociative) & Zolazepam (a Benzodiazepine)
How does Telazol affect cats & pigs? (Proportion of ingredients effectiveness)Zolazepam > Tiletamine (benzo aka GABA= more pronounced)
How does Telazol affect dogs & horses? (Proportion of the two components)Tiletamine > Zolazepam (NMDA aka Dissociatives = more pronounced)
How do Dissociatives affect (large) cats?LARGE CATS AKA TIGERS take DAYS to recover & it might kill them.
How do Dissociatives affect rabbits?Renal death in ONLY New Zealand white rabbits
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Etomidate/Metomidate

Question Answer
How does Etomidate affect the CV system?Maintains hemodynamic stability, heart failure friendly
How does Etomidate affect the resp system?Minimal resp effects
Describe the therapeutic index of Etomidate, what does this mean?It’s large, so it's a safer drug
Describe how the molecule of Etomidate affects its function?ONLY THE RIGHT enantiomer is active
Does Etomidate provide analgesia?No
How does Etomidate affect cerebral blood flow/ IC pressure?Cerebral friendly, safe to use in head trauma
How safe is Etomidate in the long term?DONT USE long term because it reduces cortisol production
Describe the plasma protein binding of Etomidate75% bound
What is the Vd of Etomidate?Large
Describe the recovery of Etomidate in terms of other classesSimilar to Thiopental (a Thiobarbiturate), but slower recovery compared to Propofol (Propofol leaves system faster)
How does Etomidate affect cats?Can get clinical hemolysis (causes fragility of RBCs)
How does Etomidate affect dogs?They can get hemolysis after CRI
When do you use Metomidate?Anesthetize fishies
Is Etomidate painful?Can cause pain after injection, but this is most likely bc of other components of the injection, not the drug itself
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Neurosteroids

Question Answer
What is the receptor Neurosteroids work on?GABA
What are the Neurosteroids (drugs)?Alphaxalone, Alphadolone (lone alphas on steroids)
Do Neurosteroids provide analgesia?Maybe
What are the combination drugs of Neurosteroids?Althesin & Saffan
What animals do you use Neurosteroids on?Cats & dogs
How do you administer Neurosteroids?IM or IV
How do Neurosteroids affect cerebral blood flow?Decrease, safe to use in head trauma
How do Neurosteroids affect resp fxn?Preserve it :)
How can Neurosteroids cause tissue damage?Perivascular admin will damage tissues
Do Neurosteroids provide mm relaxation?Yeah, good mm relax (ironic that a steroid could cause relaxation-- also ironic that it doesnt care about PP binding)
How much do Neurosteroids plasma protein bind?Not extensively at all
How do Neurosteroids affect cats?Theyre relaxed after 10 seconds
What happens w/ prolonged use of Neurosteroids?Decrease duration of action (tachyphylaxis?)
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