Anesthesiology Quiz 1 Drugs (AH) Flashcards
When would you give pre-medication depending on the route of administration?
IV: 5-10mins, IM: 15-45mins, PO: 60min (rarely used)
What are the major classes of drugs used for pre-medication?
Phenothiazines, Butyrophenones, Alpha2-adrenoceptor agonists, Benzodiazepines, Opiods, Anticholinergics, Ketamine, Other (antibiotics)
What phenothiazine is most commonly used?
Acepromazine
What receptors does Acepromazine act on?
Blocks D (dopmamine) receptors, Blocks A1-adenoreceptors
Acepromazine blocking the D receptors leads to what desirable effects?
Sedation (variable), Is also an antipsychotic
What effects are the result of Acepromazine’s action on the A1-adrenoceptors?
Vasodilation and hypotension. –> HR may slightly increase with a drop in BP
How is Acepromazine administered?
IV - onset up to 20mins. IM, SC - up to 45 mins. Oral: dogs-> tablets, horses –> paste
When do the effects of acepromazine peak?
40 mins
How is Acepromazine metabolized?
By the liver, slowly –> 4-6 hour duration
What are the effects of Acepromazine on the CVS?
vasodilation, hypotension +/- slight increase in HR, ↓ PCV (sequestration in spleen), chatecholamine induced arrythmias ↓, inhibits platelet aggregation
How does acepromazine effect excited animals?
excited animal –> epi release –> paradoxical vasodilation
What breed shouldn’t be given Acepromazine and why?
Boxers (esp in europe and california). It can induce bradycardia and collapse
What are the clinical uses for Acepromazine?
Pre-med in SA and horses, Combine with opiods/ alpha2-agonists, horses - avoid ataxia (decreases mm movement), PO - long term sedation
What are the contraindications for Acepromazine?
Boxers (esp in europe and california)–> It can induce bradycardia and collapse. Breeding Stallions. Animals with hypotension, anemia, bleeding disorders. Animals prone to seizures –> it may lower the theshold but not enough data.
Does Acepromazine have analgesic effects?
No
Does acepromazine induce vomiting?
No, it is an anti-emetic
What can acepromazine cause in horses?
Piokilothermia, priapism
What effect does Acepromazine have of the resp system?
minimal effects
What are the two Butyrophenones?
Droperidol = innovar-vet, Azaperone = stresnil, suicalm
Which other class of pre-med drugs are Butyrophenones similar to?
Phenothiazines
How is Azaperone used clinically?
Used in combination with ketamine for anaesthesia in aggressive pigs.
What are the major A2-adrenoceptor agonisis used in vet met and in what species are they used?
Romifadine - horses, Detomidine - horse/cattle, Medetomidine & Dexmedetomidine - SA and can be used in others, Xylazine - all
Clinical uses of Alpha2-adrenoceptor agonists?
Protent sedative and analgesic
On what receptors do Alpha-2 adrenoceptor agonists act?
Post-synaptic A1 and A2, Pre-synaptic A2
What effects do a2-adrenoceptor agaonists produce when acting on post synaptic A1 and A2?
Vasocontriction, vagal tone increase –> relex bradycardia
What effects do a2-adrenoceptor agonists produce when acting on post synaptic A2?
Decrease NE release and sypathetic tone, prolong braycardia
Rank selectivity of A2-adrenoceptor agonists from least to most selective
Xylazine < Detomidine < Romifidine < Medetomidine < Dexmedetomidine
How does selectiviy alter A2-adrenoceptor agonists effects?
Increases sedation and analgesic effects
Which last longer with A2-adrenoceptor agonists, sedation or analgesia?
Sedation
Do A2-adeno agonisist cause emesis?
yes
Why shouldn’t you use an A2-adeno agonist in a blocked male cat?
They inhibit ADH production –> diuresis
What effect do A2-adeno agonists have on Resp system?
depresses resparatory system at high doses
What species is senstitive to Xyalazine?
Ruminants
What can you give to counteract bradycardia with A2-adeno agonisists?
Atropine (carefully), but only in healthy animals. Atropine increases HR which fights against increased pressure –> exploded heart in compromised patient.
If you were worried about ataxia in horses, which A2-adeno agonist would you use?
Romifidine –> less ataxia in horses
CV effects of A2-adeno agonists?
Bradycardia/arrythmia (1* and 2* AV blocks), vasoconstriction followed by BP decrease, Pale MM, CO decreased
Horses may develop colic from A2-adeno agonists, why?
Decreases GI motility
What SE of A2-adeno agonists?
Vomiting ( bad for GDV), Decreases GI motility (Colic in horses), sheep –>Hypoxemia and pulmonary edema, Pregenant cows –> uterine contractions, Increased intercranial pressure (bad for head trauma), Startle response, Inhibition of insuline release –>
What are the three A2-antagonists?
Atipamezole, Yohimbine, and Tolazoline (only effective for xylazine)
How much Atipamezole should be used when reversing Met or Dex?
equal volumes
Off lable use for Atipamezole?
Use in horses and wildlife
How should Atipamezole be administered?
IM 5-10min, or very slowly via IV
List the main Benzodiazepines
Diazepam, Midazolam, Zolazepam( +tiletamine)
What effects do Benzodiazepines have on the CNS?
Enhanced GABA binding –> open Cl- channels –> decrease in CNS APs.
what does the decreased CNS activity produced by Benzodiazepines produce?
Anti-anxiety effects, anti-convulsant, decreased ICP, Amnesia
Do Benzodiazepines produce analgesia?
no
what are the effects on CV and Resp for Benzodiazepines?
CV: no depression, Resp: mild dose related resp. depression
Clinical uses of Benzodiazepines?
Sedation of sick, pediatric, or geriatric patients (won’t produce enough sedation in healthy patients), Combo with other drugs to reduce amount of other drugs needed, Anti-convulsants
Which is the better drug, midazolam or diazepam and why?
Midazolam is better: Water soluble –> IM injection, no active metabolites –> less cummulative, shorter acting time but 2X as potent. Diazepam: reacts with light, not water soluble –> IV only (painful), 2 active metabolites, absorbs to plastic
Benzodiazepine antagonist?
Flumazenil
What type of antagonist is Flumazenil?
Competative antagonist –> reversal is reversable
Indications for Flumazenil?
Benzo overdose, prolonged sedation, equine recovery
Name a centrally acting mm relaxant used mostly in LA?
Guaifenesin
What are the CV/ Resp effects of Guaifenesin>
minimal depression for both. (mm without resp depression = good)
What other drugs are often combined with Guaifenesin when it is given in horses?
Thiopental or Ketamin
How is Guaifenesin administered?
IV only. Takes a large volume –> TIVA with Ketamine and Xylazine
SE of Guaifenesin?
Hemolysis and thrombophlebitis
What group of drugs are considered the “gold standard” for analgesia?
Opioids
What receptors do Opiods act on and what is the resulting effect?
μ (OP3) - analgesia, moisis, eupphoria, resp. depression, inhibition of gut motility. κ (OP2) - analgesia, sedation, miosis. Δ (OP1) - analgesia, resp. depression
Where are Opiod receptors found?
all over, increased in areas of injury
Opiod CNS effects?
Analgesia, Dogs - mild sedation, antitussive, Cats/Horses- excitement and increased locomotor activity, Cats - hyperthermia, Dogs/Cats - nausea/vomiting,
What do opioids depress?
respiration, GI motility, HR with high doses
Which opioids release histamine?
Morphine and Meperidine IV –> hypotension and reflex tachycardia
Which opioids cause emesis?
Morphine, hydromorphone, ocymorphone
Which opiods are unlikely to cause emesis?
Butorphanol, buprenorphine, meperidine, methadone, fentanyl
How is morphine used?
As a baseline analgesic for severe pain
Morphine in cats?
Slow elimination and causes euphoria/disphoria in cats
Methadone has what additional MOA?
NMDA antagonism –> additional analgesic mechanism
What route of admin should you avoid with Meperidine and why?
No IV use - histamine release
Is Meperidine short or long acting?
short
Does Meperidine cause emesis?
unlikely
Uses for Fentanyl?
CRI for surgery, intraoperative bolus, rapid onsetsetitive if IV or IM, rapid sequnce induction
How long does a fentanyl patch last for?
72 hours about
What can you do if a fentanyl patch isn’t providing enough analgesia?
Add another M agonist
How do you prepare a patient for a fentanyl patch?
shave but don’t scrub - you need the oils in the skin for absorption.
Why are fentanyl patches useful?
Long duration
What are the drawbacks to using fentanyl patches?
variable time to onset, variable plasma conc., poor alternative to opioid CRI, potential for abuse (by owners)
Remifentanil is indicated in what type of patient?
Patients with liver problems. Metabolized by plasma esterases instead of hepatic
How long does Remifentanil last?
3-4mins, ultra short acting. Give something about 20mins before stopping so keep analgesia going
Buprenorphine acts on what receptors as an agonist?
Partial M agonist
Buprenorphine timing?
slow onset, long duration of action 4-6h
SE of buprenorphine?
minimal
Burorphanol receptors?
M antagonist, K agonist
What is butorphanol good for?
Only a weak analgesic but good sedation and antitussive with minimal SE
List 3 opioid antagonists
Naloxone and Naltrexone (complete), Butorphanol (partial)
Which opiod is most commonly used in horses?
Butorphanol
What behavioral modification can occure in unsedated horses as a result of IV administered opioids?
box walking
What does Neuroleptoanalgesia mean?
Sedative + opioid
What is neuroleptoanalagesia used for?
Preanesthetic medication (ace + morphine), restraint for minor procedures
List 4 anticholinergic agents used in pre-med
Atropine, Glycopyrrolate, Scopolamine (Hyoscine)
What is the main use for anticholinergic agents?
for treatment of bradycardia caused by vagal stimulation (brought on by opioids)
Effects of Anticholinergics?
increased HR, Reduce salivation, Reduce gut motility (colic), Dilate pupils (–> panic in horse/cat), Relax bronchial smm.
Which anticholinergic crosses the BBB?
Atropine
Which anticholinergic is preffered for rabbits? Why?
Glycopyrrolate. Rabbits have atropine esterase –> very short acting.
Dosages for atropine differ in what spp?
Ruminants need a very high dose
Which anticholinergic produces and initial drop in HR when given IV?
Atropine
Indications for injectable anaesthetics?
Induction of general anesthesia, maintenance of anesthesia (CRI/Bolus), Balanced anesthesia, TIVA, to provide sedation (sm amount of propofol)
What are some of the most important characteristics of an ideal inj. anesthetic?
Rapid onset, high lipid solubility –> crosses BBB, no accumulation –> rapid recovery, high therapeutic index, no active metabolites, no endocrinologic effect, min CV/resp depression, no pain on injection.
How do you calculate a dose for an obese patient?
Use ideal weight
List 3 barbituates and what they are used for
Thiopental - induction in SA (short acting), Pentobarbital - euthanasia, Phenobarbital - long acting, anticonvulsant
How do you reconstitute thiopental
with sterile water. Forms a very alkaline solution and can be extremely irritating to tissues.
What is the only way to admin thiopental?
via IV cath. Necrosis if perivascular
What must you do before admin or thiopental?
remove LRS and flush. LRS + thiopental –> precipitate.
Main indications for Thiopental?
Anesthesia in SA, induction in horses when combined with guaifenesin –> reduced ataxia, bolus during maintenance in horses (emergency for when horse is waking up)
contraindications for Thiopental?
Patients with hepatic Dz, Greyhouds (can’t metabolize), neontal/ pregnant animals, cachexic animals, spenectomy. Not used for maintenance due to accumulation.
Which inj. Anesthetic is most commonly used?
Propofol
What about the way propofol is prepared makes it less economical?
Propofol is prepared with soy and egg products –> bact growth –> discard after 24 hours (new formula lasts 28 days)
Is propofol a tissue irritant?
no
Clinical uses for propofol?
Induction (short acting) in dogs and cats, can be used in sm. Ruminants but usually not approved.
When using propofol, what do you need to be ready to do?
be ready to intubate and ventilate.
Propofol CVS/Resp
CVS - hypotension Resp - depression, apnea.
Does propofol provide analgesia?
no
Effects on CNS?
anticonvulsant and neuroprotectant
Propofol and cats?
Not a good idea. Reduced capacity for glucuronidation –> prolonged recovery. Toxic injury to feline HB –> blood issues
contraindications for Propofol?
hypovolemic patients, HF, hyperlibidemia and pancreatitis, cats (avoid repeated)
Can you use propofol for CRI or TIVA?
Yes, minimal accumulation. Suppliment with O2 during repeated doses or TIVA
SE during induction for propofol?
excitatory signs
What is the main drawback to the classic prep of etomidate?
Perivascular injection causes necrosis and phlebitis
What are the drawbacks to lipid emulsion prep of Etomidate?
promotes bact. Growth–> discard w/I 24 hrs
Etomidate CNS stuff?
Quickly penetrates BBB, max CNS conc. within 1min
Clinical use of Etomidate?
Anesthesia induction in high risk patients. Ideal induction agent for compromised patients (shock patients)
What animals should not receive Etomidate?
animals with adrenal issues. Horses and Cattle
How should etomidate be administered?
Pain on injection. Use combo of fentanyl, diazepan, etomidate via IV cath.
Why isn’t etomidate used often in vet med?
expensive, rough indcution, inhibits adrenocortical fnx, hemolysis and hematuria reported, painful upon injection
What is Alfaxalone?
It is a neuroactive steroid
MOA of alfaxalone?
Hypnosis and mm relax via GABAa
Admin of Alfaxalone?
Perivascular injection not painful, no necrosis (pH=7), IV or IM via slow injection. Use premed and analgesic
Uses for Alfaxalone?
Indcution and TIVA for dogs and cats.
Does Alfaxalone provide analgesia?
no
CVS/Resp for alfaxalone?
Hypotension (not as bad as propofol), relex tachycardia. Min resp depression.
Alfaxalone SE in cats?
Myoclonus and poisthotonus during recovery
Admin of Ketamine
IV, IM, SQ, Rectal, Epidural. Never given alone.
What happens if you inject Ketamine perivascularly?
Pain! (pH 2-3) But no necrosis
Clinical Uses for Ketamine?
Indcution in many spp. especially in zoo animals, short maintencance, CRI in subanesthetic doses for analgesia, Never use alone.
Pros of Ketamine?
Analgesia, amnesia, hypnosis. Different routes of admin. Sympathetic stimulation, Min resp depression, bronchodilation
Cons of Ketamine?
Muscle rigidity, Pain on injection, Emergence psychomimetic reactions
How should you store Ketamine?
Away from light and heat. Otherwise it is stable
Onset of action for Ketamine?
IV- 30-90sec, IM - 10-15min
MOA of Ketamine?
NMDA = most improtant receptor –> antagonism in brain and spinal cord. Other receptor sites: opioid, cholinergic, adrenergic, GABAa
What is the active metabolit of Ketamine?
Norketamine
Does Ketamine accumulate?
Yes
Ketamine CVS?
Unique! Increases in HR BP and CO. Also direct myocardial depression, but stimulatory effects normally predominate.
Ketamine CNS
increases ICP, may elicit seizures, swallow and cough reflexes are retained, increases IOP, no eye rotaion –> use eye ointment
Does Ketamine have analgesic properties/?
Yes, profound somatic analgesia –> orthopedic pain
Besides the BBB, what other barrier does Ketamine cross and what effect does it have when it does?
Placental barier –> decrease in puppy vigor
Contraindications for Ketamine?
CV Dz patients, heptic/renal insufficiency, hyperhyerosis (high BP Dz), Neuro problems & head trauma, Caesarean section, increased IOP.
Pros of S(+) Ketamine?
Only need 1/2 dose, longer and stronger analgesia, decreased agitation, disorientation and anxiety, faster recover, suggestive of myocardial and neuronal protection
How is Tiletamine sold?
As a combo with Zolazepam
What is the main difference between ketamine/BZD and Tiletamine?
Tiletamine is longer acting
What is recovery like with Tiletamine?
Rough and long. Zolazepam wears off first –> mm rigidity, excitations and seizures
Tiletamine clinical use?
Indcution for many species.
Admin of Tiletamine?
IV/IM (painful)
Which pre-med drugs provide analgesia?
A2-agonists, opioids
Which pre-med drugs do not provide analgesia?
Acepromazine, Benzodiazepines, Guaifenesin
Which inj. anesthetics do not provide analgesia?
Propofol, Etomidate, Alfaxalone?
Which drugs have minimal CV/Resp effects?
Resp only: Alfacalone, Ketamine. Both: Acepromazine,BDZ (@ clinical dose), Guaifenesin, Opiods (dose dep), Etomidate (dose dep).
Which drugs are anti-convulstant
Benzodiazepines, Phenobarbital, Thiopental
Which drugs decrease GI motility?
A2-agonists, Opioids
