Anesthesiology Quiz 1 Part 2

kelseyfmeyer's version from 2015-09-08 16:56

Premedication: Alpha-2 agonists, Alpha-2 antagonists

Question Answer
name the 5 alpha-2 adrenoceptor agonistsxylazine, medetomidine/demedetomidine, detomidine, romifidine
is xylazine a alpha-2 AGONIST or ANTAGONIST? (blocker or not?)AGONIST!! POTENTIATES, NOT BLOCKS (dont confuse with acepromazine causing some A-1 blocking)
which species can you use xylazine in?almost all species
which species can you use medetomidine and dexmedetomidine in?small animal, but is used in many others (small animals, longer words)
which species can you use detomidine in?horses and cattle (bigger animals with the shorter word)
which species can you use romifidine in?primarily in horses
MOA of Alpha-2 agonists? (where are a1/a2 receptors located?)(alpha 1 is primarily post synaptic and in the periphery(only in pharm does 1 come "post"). alpha 2 is pre and post synaptic, and primairly in the CNS). The alpha-2 agonists can work on both the postsynaptic a-1 and a-2 receptors and presynaptic a2 receptors
Alpha-2 agonists--> what are the effects if a a-2agonist works on the postsynaptic a1 and a2 receptors?vasoconstriction (remember bc ace is a blocker and causes dilation) and vagal tone increases--> reflex bradycardia
Alpha-2 agonists--> what are the effects if a a-2agonist works on the presynaptic a-2 receptors?NE release decreases, and sympathetic tone decreases, leading to prolonged braycardia (working on the post synaptic a1 and a2 also produce bradycardia) (PRE-pare for bradycardia by reducing things)
do drugs with a higher alpha-1 or alpha-2 agonizing produce more sedation and analgesia? what does the other receptor result in?a-2 are better for sedation/analgesia (prolly why the category is called A-2 agonists). the A-1 receptors mediate the SIDE EFFECTS, of bradycardia, arrythmias, and startle response
what are the side effects of working on (agonizing) a A-1 receptor?bradycardia, arrythmias, startle response
Rank the alpha-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 a-2 agonists... sedation or analgesia?Sedation lasts be careful (of course the crapper option that might result in pain is the answer!)
central effects--> what is sedation like with the a2 agonists?sedation is dose-dependent
do a2 agonists provide analgesia?YES!! including potent VISCERAL analgesia!!
central effects--> do a2 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 cause respiratory depression (look out!)
central effects--> are a2 agonists antiemetics?NO, they can cause emesis in cats and dogs. (ACE is the antiemetic)
central effects--> how might a2 agonists affect fluid balance?A2s can inhibit ADH, leading to diuresis
*CV effects--> what effects do a-2 agonists have on the heart? (rate, rhythm, output, the vessels of the body?)*THIS IS THE PROB WITH THESE DRUGS!* Bradycardia (potentiated by the A1 and A2 receptors, yikes) AND bradyarrythmias (1st and 2nd degree AV block...makes sense, heart is going so slow just starts dropping beats), there is a initial vasoconstriction (as mediated by the postsynaptic receptors), but thereafter a decrease in blood pressure . Due to the constriction, you'll see pale MMs. All of this combined leads to a DEC CO!!!
the biggest problem with a2 agonists is..their CV effects, esp. the severe bradycardia and bradyarrythmias
how do a2 agonists affect the GI of large animals vs small animals?Small animals: vomiting. Large animals: Decreased GI motility (go figure, basically opposite)
do A2 agonists affect the resp system?resp depression is dose dependent (minimal though)
what is something you should know about A2 agonists and sheep?hypoxemia and pulmonary edema in sheep
what a specific repro.-related use of a2 agonists with cattle?they can cause uterine contractions, allowing you to induce abortion in the last trimester
what is an unwanted response/reflex which a2 agonists can cause?startle response (sudden arousal)
how do a2 agonists affect blood sugar?a2s inhibit insulin release which can lead to hyperglycemia
caution with ruminants and a certain a2 agonist?rumis are VERY sensitive (like 10xs so) to xylazine
a2 agonists cause marked bradycardia. What might be used to treat this?anticholinergics (she put a bunch of ??? next to this)
detomidine has a drug reaction with a certain type of drug in horses. What's that?detomidine with interact with potentiated sulfonamides in horses!!
why do we like romifidine in horses?less ataxia. Because 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 below their withers while standing
what is used to reverse medetomidine/dexmedetomidine?Atipamezole
what is used to reverse xylazine? (2)yohimbine, tolazoline
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. Though if the procedure is long, then you might need a little less)
can you use atipamezole to reverse other a2 agonists?it CAN reverse all a2 agonist agents, but the proper doses are not always established and it would be off label in horses and 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 WITH ATIPAMZOLE?IT REVERSES ANALGESIA TOO! so only use if needed, and titrate to effect if possible

Premedication: Benzodiazepines+Antagonists, Guaifenesin

Question Answer
what are the three benzodiazepines?diazepam, midazolam, zolazepam*(only used with tiletamine)
what is the MOA of benzodiazepines?enhance GABA binding activity --> open Cl- channels, inhibition of action potentials within the CNS (remember, GABA is an inhibitory receptor)
**do benzodiazepines provide sedation?Ehhhhh... it is unreliable. paradoxial reaction in healthy adult animals (great sedative for the very young, very old or very sick though)
how do benzos interact with other CNS depressants?synergistic
**do benzos cause muscle relaxation? caveat to this?YES, they are centrally acting muscle relaxants, which means you should NOT USE IN CONSCIOUS HORSES (both guai and benzos are mm relaxants and are gentle on CV and resp, and this is why they were lumped together)
what should you know about seizures and benzos?ANTICONVULSANT, -and- decreases intracranial pressure
do benzos provide analgesia?NO!!
how do benzos affect the CV system?no or minimal 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 no/minimal effects on the CV system and 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 with ketamine/tiletamine to offset the muscle rigidity caused by them
what are the three major uses for benzos?(1) TREAT/PREVENT convusions (2) in drug combos (premed or coinduction) (3) sedation in pediatric/geriatric/sick animals (not healthy adults!!!)
which benzo is water soluble? which isnt?Midazolam IS water soluable (pH dependent). Diazepam is NOT water soluble (diluted in propylene glycol)
which benzo is stable in solution, and which reacts with 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... and 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 (can be IV too I'm pretty sure)
which benzo has good absorption when given IM?midazolam (diazepam is IV ONLY and 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 AND midazolam are highly protein bound
which benzo is the shorter acting BUT MORE POTENT (2x) one?midazolam is both more short acting and 2xs as strong as 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 required)helpful in equine recovery, it us 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
what is the metabolism for flumazenil like? (what is flumazenil?)(benzodiazepine antagonist) it is metabolized in the liver, so there is short duration of effect (may require redosing) (weirdo antagonist which can reverse reverse and 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 with the benzos which also mm relax, even tho guai doesnt really fit in with anything)
what is sedation with guaifenesin like?NO SEDATION. JUST MM RELAXANT. cannot use as anesthetic agent
which animals are 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 REQUIRED!
how does guaifenesin affect the respiratory system? CV system?only minimal resp. depression. Also only minimal CV depression (dec BP, inc HR) think about how arteries/diaphragm are made of mm and guai is a mm relaxant, but guai is gentle enough to be used as an expectorant.
does guaifenesin provide analgesia?NO!!!
what are the two major clinical uses for guaifenesin?(1) anesthesia induction in large animals- when combined with thiopental or ketamine (2) triple drip in horses for TIVA (in combination with ketamine and xylazine) (long notes said try not to exceed 1hr of infusion due to concerns of mm weakness and ataxia upon recovery)
why do we like to use guaifenesin in combination therapy?it decreases need for anesthetic, and has less CV and resp effects
what is the max duration of anesthesia with guaifenesin (in combination I'm assuming)1-1.5 hours
what are the two major adverse effects of guaifenesin?hemolysis (in concentrations >5%(long notes said 10%) ), and thrombophlebitis (might get your snot out, but it wants blood for it)
why shouldnt you use guaifenisen 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 guaifenisen?reportedly narrow (narrow, but when used right, gentle on the CV and resp systems)

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