Pre-Meds Flashcards
What does the preanesthetic assessment include?
- identification
- signalment
- history
- blood panel
- ASA status
- type of procedure and duration
- physical exam and temp assessments
What is the ASA classification system and how many categories are there ?
its a fast assessment of the patient’s overall health
I) normal
II) mild systematic dz
III) severe systematic dz
IV) severe systematic dz that threatens life
V)moribund patient not expected to survive 24hrs
E) emergency (mostly used in human med)
what do you have to do in order to prep the patient ?
- correct fixable problems (ex: hypoglycemia)
- assess degree of pain
- fasting
are fasting protocols the same for pediatric vs adults vs geriatric patients
no
a bunch of reasons to use pre anesthetics
- calm patient/ chemical restraint
- reduce total dose of anesthetic induction + maintenance
- provides ANALGESIA
- prevents BRADYCARDIA
- reduces salivation and airway secretions
- improves recovery, less delirium
Preanesthetic drug subgroups (6)
1) anticholinergics
2) tranquilizers
3) muscle relaxants
4) dissociative
5) neuro active steroids
6) sedative/ analgesics
what do anticholinergics do?
- used to inhibit excessive parasympathetic activity
- works at muscarinic receptors to clock the action of acetylcholine
-hint: remember that cholinergics mimic Ach
anticholinergics indications (3)
1) concurrent use with a drug that promotes vagal tone (opioids)
2) performing surgery in areas of high vagal activity
3) individual patients that have high vagal tone or reliance on heart rate to maintain cardiac output
anticholinergics are NOT recommended for …. (3)
1) do not use to “dry up” airway
2) promote arrhythmia formation
3) tachycardia results in increased myocardial O2 demand (so I guess don’t use it to promote tachycardia?)
what are the 2 anticholinergics that we use and their main differences ?
1) Atropine : faster onset + shorter duration, induces tachycardia, more arrhythmogenic, less expensive, crosses BBB and placental barrier
2) Glycopyrrolate : slower onset + longer duration, less tachycardia and arrhythmias, $, does NOT cross those 2 barriers, give to pregnant patients!
which tranquilizer do we use an what is its mechanism?
acepromazone : reticular activating system to produce CNS depression, antagonize dopamine receptors within CNS, and cause blockade of peripheral alpha-1 adrenoceptors and vasodilation
acepromazine details
- tranquilizer
- slow onset, long duration
- dose dependent effect
- NO reversal agent
- minimal muscle relaxation and NO analgesia
- peripheral vasodilation, anti thermo regulation, anti emetic, anti arrhythmic, anti histaminic
acepromazine in boxers and stallions
boxers: some strains have intense vasovagal reaction at normal doses
stallions : may show permanent or transient penile paralysis
Muscle relaxants : benzodiazepines
- poor sedation in healthy animals, good on geriatric/neonatal/ pediatric
- controlled substance (duh ?)
- minimal cardio - respiratory depression
- potent anticonvulsant
- useful sedative or augment others (works well with opioids) in debilitated animal
what is the reversal agent for benzodiazepines ?
flumazenil
what are the two benzodiazepines we use and their differences
1) diazepam : oily propylene glycol formulation (painful IM), less $, AVOID IN LIVER FAILURE, precipitates when mixed with other drugs except ketamine
2) midazolam: water soluble, does not precipitate when mixed with other drugs, safer in liver failure, $$
what is the one drug that does not cause diazepam to precipitate when mixed with it
ketamine
muscle relaxant: guaifenesin (GG)
- used in conjugation with ketamine in horses, small ruminants, and camelids
- NO reversal, unlike benzodiazepines
- requires large volume and irritating when administered perivascular
- mild sedation
- acts on the internuncial neurons of the spinal cord
what is the “triple drip” in horses
GG + ketamine + xylazine
dissociatives
- stimulate sympathetic tone, increases HR and RR
- painful IM injection due to low pH
- causes delirium, uncoordination, focalization, agitation
- induces muscle rigidity, salivation, anyway secretions
- controlled substance
what other drugs do we combine dissociatives with for better sedation ? (3)
benzodiazepines
alpha 2 agonists
opioids
dissociative mechanism
- acts on glutamate binding sites, NMDA and non NMDA receptors
- potentiates GABA inhibition
- antagonism of NMDA receptor causes amnesiac and psychosensory effects, analgesia, neutoprotection
somatic vs visceral analgesia of dissociatives
- superior somatic
- less visceral
what are the 2 dissociatives that we use?
1) Ketamine
2) Tiletamine (in Telazol)
Vicky the notes you’re looking for:
(Tiletamine and Zolazepam are in the bottle of Telazol. Zolazepam combats the muscle rigidity that tiletamine (all dissociatives) profuce. Note that because dogs will metabolize the zolazepam faster than the tiletamine in the dose they will not recover as smooth as cats will)
neuroactive steroid mechanism
- enhances interaction of GABA receptor complex to produce anesthesia and muscle relaxation
- analogue of progesterone
what is the neuroactive steroid that we use
alfaxalone :
- AVOID in large dogs due to large volume
- fast onset, short duration
- respiratory depression, hypotension, mild increase in HR
- safer for cats with hypertrophic cardiomyopathy
T/F : alfaxalone is safer for cats with hypertrophic cardiomyopathy
TRUE
sedative/ analgesics : alpha 2 agonist
- blocks alpha 2 receptors and inhibits norepinephrine release, leasing to sedation
- NOT a controlled substance
types of alpha 2 agonists
1) romifidine
2) detomidine
3) clonidine
4) xylazine
5) dex-medetomidine
alpha 2 agonists on the heart
- increases vagal tone leading to AV block
- dec. HR -> dec. CO, BP(BP increases after time however) and can lower threshold for dysrhythmias
- Cardiovascular side effects are dose dependent
- respiratory depression, hypoinsulinemia, hyperglycemia, reduce GI motility, hypothermia, vomiting (especially cats), sweating, inc. intensity of uterine contractions
Alpha 2 agonists are more potent the more selective they are to the alpha 2 receptor. The more potent the less volume of drug is needed to produce effect. What is the order of potency of the alpha 2 agonists?
Dex(medetomidine)»_space;> Romifidine»_space; Detomidine > Clonidine > Xylazine
Which animals are more sensitive to alpha 2 agonists?
Ruminants especially, small lab animals are the least sensitive
alpha 2 reversal agent?
Yohimbine or Tolazoline for Xylazine.
Atipamezole for everything
using alpha 2s with horses?
Detomidine CRI for standing procedures. Can use Romifidine, xylazine, detomidine, dex for premed. MAC sparing effect on inhalants, Good for smooth recoveries.
Most of the alpha 2 ags can be used for small animals and horses except _______ cannot be used in dogs.
detomidine
opioids mechanism of action
inhibits pain transmission at the dorsal horn of the spinal cord. they activate descending inhibitory pathways.
opioid receptors
mu, kappa, delta G protein receptors.
Partial agonists have a __________ effect that plateaus at a lower level of effect than full agonists.
dose dependent
How long do they last? morphine, hydromorphone, methadone? butorphanol? buprenorphine? fentanyl? naloxone?
2-4 hrs 1-2 hrs 8 h 15-30 min 30-45 min
Side-effects of Opioids?
bradycardia, vomiting, histamine release, hyperthermia in cats, dysphoria
pure mu agonists cause
excitement and inhibition of GI activity
for ASA I/II use:
Ace + Opioid +/- Dex
for ASA III/IV/V/E, pediatrics or geriatrics use:
Benzodiazepines + Opioid +/- Atropine
Crazy cat, what do you want to knock it down with?
Alfaxalone + Opioid
Ideal pre-meds for horses?
Alpha 2 + Opioid
2 month puppy in for a spay?
Diazepam + Opioid
Horse getting a cyptorchidectomy could get ___ which we normally wouldnt give to horses.
Acepromazine
