Anesthesiology - Quiz 1-2

pufexaxe's version from 2016-09-18 20:36

Pre-meds: α-2 agonists

Question Answer
Name the 5 α-2 adrenoceptor agonistsXylazine
Is Xylazine an α-2 AGONIST or ANTAGONIST? (Blocker or not?)AGONIST!! POTENTIATES, DOES NOT BLOCK (dont confuse w/ Acepromazine causing some α-1 blocking)
Which species can you use Xylazine in?Almost all species
Which species can you use Medetomidine & Dexmedetomidine in?Small animal, but is used in many others (small animals, longer words)
Which species can you use Detomidine in?Horses & cattle (bigger animals w/ the shorter word)
Which species can you use Romifidine in?Primarily in horses
MOA of α-2 agonists? (Where are α-1/ α-2 receptors located?)The α-2 agonists can work on both the postsynaptic α-1 & α-2 receptors & presynaptic α-2 receptors (α-1 is primarily post synaptic & in the periphery (only in pharm does 1 come "post"). α-2 is pre & post synaptic & primarily in the CNS)
α-2 agonists → what are the effects of an α-2 agonist on the postsynaptic α-1 & α-2 receptors?Vasoconstriction (remember bc Ace is a blocker & czs dilation) & ↑ vagal tone (↑ parasympathetic tone, ↓ sympathetic tone) → reflex bradycardia
α-2 agonists → what are the effects if an α-2 agonist works on the presynaptic α-2 receptors?↓ NE release & ↓ sympathetic tone (↑ parasympathetic/vagal tone)→ prolonged bradycardia (working on the post synaptic α-1 & α-2 also produce bradycardia) (PRE-pare for bradycardia by reducing things)
Do drugs w/ a higher α-1 or α-2 agonizing produce more sedation & analgesia? What does the other receptor result in?α-2s are better for sedation/analgesia (prolly why the category is called α-2 agonists). The α-1 receptors mediate the SIDE EFFECTS, of bradycardia, arrhythmias & startle response
What are the side effects of agonizing an α-1 receptor?Bradycardia
Startle response
Rank the α-2 agonist drugs from shortest acting to longest acting(Shortest) Xylazine < (Romifidine+Medetomidine+Dexmedetomidine) < Detomidine (longest acting) (lol it's reverse ABC order)
Which effect lasts longer from α-2 agonists... sedation or analgesia?Sedation lasts be careful
Central effects → what is sedation like w/ the α-2 agonists?Sedation is dose-dependent
Do α-2 agonists provide analgesia?YES!! Inclding potent VISCERAL analgesia!!
Central effects → do α-2 agonists provide analgesia? Do they affect muscles? Do they affect respiration?YES! (But remember the sedation effect lasts longer than the analgesic effect). They also provide mm relaxation (really only dissociatives don't, I think?). At higher doses, they can cz respiratory depression (look out!)
Central effects → are α-2 agonists antiemetics?NO, they can cz emesis in cats & dogs. (ACE is the antiemetic)
Central effects → how might α-2 agonists affect fluid balance?α-2s can inhibit ADH, leading to diuresis
*CV effects → what effects do α-2 agonists have on the heart? (Rate, rhythm, output, the vessels of the body?)*THIS IS THE PROB w/ THESE DRUGS!* Bradycardia (potentiared by the α-1 & α-2 receptors, yikes) & bradyarrythmias (1st & 2nd degree AV block...makes sense, heart is going so slow just starts dropping beats), there is an initial vasoconstriction (as mediated by the postsynaptic receptors), but thereafter a ↓ in blood pressure . Due to the constriction, you'll see pale MMs. All of this combined leads to a ↓ CO!!!
The biggest problem w/ α-2 agonists is...Their CV effects, esp. the severe bradycardia & bradyarrythmias
How do α-2 agonists affect the GI of large animals vs small animals?Small animals: Vomiting
Large animals: ↓ GI motility (go figure, basically opposite)
Do α-2 agonists affect the resp system?Resp depression is dose dependent (minimal tho)
What is something you should know about α-2 agonists & sheep?Cz hypoxemia & pulmonary edema in sheep
What a specific repro-related use of α-2 agonists w/ cattle?They can cz uterine contractions, allowing you to induce abortion in the last trimester
What is an unwanted response/reflex which α-2 agonists can cz?Startle response (sudden arousal)
How do α-2 agonists affect blood sugar?α-2s inhibit insulin release which can lead to hyperglycemia
Caution w/ ruminants & a certain α-2 agonist?Rumis are VERY sensitive (like 10x) to Xylazine
α-2 agonists cz marked bradycardia. What might be used to treat this?DO NOT USE Anticholinergics (she put a bunch of ??? next to this)
Detomidine has a drug rxn w/ a certain type of drug in horses. What's that?Detomidine interacts w/ potentiated sulfonamides in horses!!
Why do we like Romifidine in horses?Less ataxia (they're good enough at breaking their legs on their own)
How can you tell if a horse is sedated from a glance?Their head will be lower than their withers while standing
What is used to reverse Medetomidine/Dexmedetomidine?Atipamezole
What is used to reverse Xylazine? (2)Yohimbine
What dose of Atipamezole would you give to reverse Medetomidine/Dexmedetomidine?You'd give an equal amount! (If 0.2ml Medetomidine, then 0.2 Atipamezole, but if the procedure is long, then you might need a little less)
Can you use Atipamezole to reverse other α-2 agonists?It CAN reverse all α-2 agonist agents, but the proper doses are not always established & it would be off label in horses & wildlife
How can you administer Atipamezole?(1) Licensed for IM use, 5-10min for effect
(2) If given IV, give slowlllllyyy (if you dont IV slowly, you'll tip'em over the edge. Just do IM if youre not in a hurry)
WHAT IS THE BIG CAUTION w/ ATIPAMZOLE?IT REVERSES ANALGESIA TOO! So only use if needed & titrate to effect if possible

Premeds: Benzodiazepines, Guaifenesin

Question Answer
What are the 3 Benzodiazepines?Diazepam
Zolazepam* (only used w/ Tiletamine)
What is the MOA of Benzodiazepines?Enhance GABA binding activity → open Cl-channels, inhibition of action potentials w/in the CNS (remember, GABA is an inhibitory receptor)
**Do Benzodiazepines provide sedation?Ehhhhh... it is unreliable. Paradoxical rxn in healthy adult animals (great sedative for the very young, very old or very sick tho)
How do Benzos interact w/ other CNS depressants?Synergistic
**Do Benzos cz muscle relaxation? Caveat to this?YES, they are centrally acting muscle relaxants, which means you should NOT USE IN CONSCIOUS HORSES (both guai & Benzos are mm relaxants & are gentle on CV & resp & this is why they were lumped together)
What should you know about seizures & Benzos?ANTICONVULSANT & ↓ intracranial pressure
Do Benzos provide analgesia?NO!!
How do Benzos affect the CV system?Minimal to no cardiac depression at clinical doses :)
How do Benzos affect the resp. system?Mild dose-related resp. depression
How safe are Benzos?Theyre considered pretty safe due to minimal/no effects on the CV system & minimal effects on the resp. system (just like guai, which is why theyre lumped together)
Which drugs do we like to add Benzos to, to offset their (the not Benzos) side effects?Combine Benzos w/ Ketamine/Tiletamine to offset the muscle rigidity czd by dissociatives
What are the 3 major uses for Benzos?(1) TREAT/PREVENT convulsions
(2) In drug combos (premed or coinduction)
(3) Sedation in pediatric/geriatric/sick animals (not healthy adults!!! IT ONLY GIVES MUSCLE RELAXATION IN HEALTHY ADULTS)
Which Benzo is water soluble? Which isnt?Midazolam IS water soluble (pH dependent)
Diazepam is NOT water soluble (diluted in propylene glycol)
Which Benzo is stable in solution & which reacts w/ light/other drugs/ plastics?Diazepam is reactive
Midazolam is stable in solution
Which can you give CRI → Diazepam or Midazolam?Midazolam (remember, it is STABLE in solution! Also, no active metabolites, unlike Diaz. So it's less cumulative which is good for CRI)
Which Benzo might elicit pain upon IV admin?Diazepam... & this is the only route of admin for Diazepam! Bummer!
What are the routes of admin for Midazolam? Diazepam?Diazepam is given IV ONLY
Midazolam is well absorbed IM
Which Benzo has good absorption when given IM?Midazolam (Diazepam is IV ONLY & is burny)
Which Benzo has active metabolites?Diazepam is metabolized to 2 active metabolites. (Midazolam has no active metabolites so it is less cumulative)
Which Benzo is highly protein bound?TRICK QUESTION - Both Diazepam & Midazolam are highly protein bound
Which Benzo is the shorter acting BUT MORE POTENT (2x) one?Midazolam is both shorter acting & 2x more potent than Diazepam
What is the antagonist for Benzodiazepines?Flumazenil (& Sarmazenil, but she doesnt seem to care about this one)
When would you want to antagonize Benzodiazepines? (Usually rarely reqd)Helpful in equine recovery & is generally indicated in cases of prolonged sedation or in overdose
What kind of antagonist is Flumazenil?(Benzo antagonist) it is a COMPETITIVE antagonist, which means the reversal is reversible (ugh)
What is Flumazenil? What is the metabolism for Flumazenil like?Benzodiazepine antagonist it is metabolized in the liver, so there is short duration of effect (may require redosing) (weirdo antagonist which can reverse & is so short might need more dosing? weird.)
WHAT KINDA DRUG IS GUAIFENESIN?It is a centrally acting mm relaxant (which is why she lumped it in w/ the Benzos which also mm relax, even tho guai doesnt really fit in w/ anything)
What is sedation w/ Guaifenesin like?NO SEDATION. JUST MM RELAXANT. Cannot use as anesthetic agent
Which animals is Guaifenesin usually used on?Large animals
What is Guaifenesin usually used for?Mm relaxation, expectorant
How do you administer Guaifenesin? How much do you usually give (in general)IV USE ONLY! (Extravascular leads to necrosis) can be in ready-to-use for or a powder to be reconstituted (usually 5% solution in 5% dextrose). A LARGE VOLUME IS REQD!
How does Guaifenesin affect the respiratory system? CV system?Only minimal resp. depression. Also only minimal CV depression (↓ BP, ↑ HR) think about how arteries/diaphragm are made of mm & guai is a mm relaxant, but guai is gentle enough to be used as an expectorant.
Does Guaifenesin provide analgesia?NO!!!
What are the 2 major clinical uses for Guaifenesin?(1) Anesthesia induction in large animals-when combined w/ Thiopental or Ketamine
(2) Triple drip in horses for TIVA (in combination w/ Ketamine & Xylazine) (long notes said try not to exceed 1hr of infusion due to concerns of mm weakness & ataxia upon recovery)
Why do we like to use Guaifenesin in combination therapy?It ↓ need for anesthetic & has less CV & resp effects
What is the max duration of anesthesia w/ Guaifenesin (in combination I'm assuming)1-1.5 hours
What are the 2 major adverse effects of Guaifenesin?Hemolysis (in concentrations >5 %(long notes said 10%) )
Thrombophlebitis (might get your snot out, but it wants blood for it)
Why shouldnt you use Guaifenesin alone in horses?Only mm relaxation, so horse will panic as it feels its mm getting weaker before it falls down.
What is the margin of safety like for Guaifenesin?Reportedly narrow (narrow, but when used right, gentle on the CV & resp systems)

Premeds: Anticholinergic (antimuscarinic) (parasympatholytic) agents

Question Answer
What are the 3 anticholinergics?Atropine
Scopolamine (Hyoscine)
What is the MOA of Anticholinergics?Block acetylcholine (ACh) receptors of the parasympathic system (parasympatholytic, sympathomimetic)
How do Anticholinergics affect heart rate? How might this be useful?↑ heart rate, which is useful as it prevents or treats drug (opioid) induced bradycardia
How do Anticholinergics affect salivation?Reduce salivation (useful for Ketamine where you salivate too much) downside is that saliva becomes more viscous :(
How do Anticholinergics affect GI motility? What should you know about this?REDUCE gut motility, which can cz impacted colic in horses :(
How do Anticholinergics affect pupils & what clinical relevance does this have?Dilates pupils (Mydriasis), which spoils focus → cats & horses can panic
How do Anticholinergics affect the bronchioles?Relax bronchiole smooth mm → counteracts constriction
WHAT IS THE SUPER DUPER AWESOME THING WE WANNA USE ANTICHOLINERGICS THE MOST FOR?For Tx of bradycardia czd by vagal stimulation (remember what drugs ↑ vagal tone?)
What do you need to know about the pharmacokinetics of Atropine?Can cross BBB & placenta!!!
How does Atropine affect the HR?Although Anticholinergics ↑ heartrate, Atropine might have an initial ↓ in HR
Explain the major species differences in doses w/ AtropineHorses/cats/dogs are similar. You need HIGH doses for effect in rumis & rabbits have Atropine Esterase so it will be VERY short acting
Is Glycopyrrolate synthetic or natural? How does its pharmokinetics differ from Atropine's? What is it usually used for?Synthetic
Does NOT cross BBB
Explain what is happening here
Atropine has a steeper rise & resulting in an immediate ↑ in HR
Glyco is slower & lower