Premedication (Garcia) Flashcards
Acepromazine
- Potent sedative and anxiolytic
- categorized as an antipsychotic, used for schizophrenia in people
- anti-emetic
- Anti-arrythmic properties
- Dec dose requirement of other drugs
- blocks domaminergic effects in brain
- enhances analgesia of opioids
- blocks domaminergic effects in brain
- don’t give to boxers
- unless used previously without problems
- NON-REVERSABLE
Why premed?
- Humane: minimize stress
- May decrease other drugs: Synergism
- injectibles
- inhalents
Example of synergism
- Sedatives + opiods
- sedative can inc analgesic affect of opiods (phenothiazines: ace)
Neuroleptic def
- Major sedative (also described as antipsychotics)
- Cause deep sedation
- Acepromazine
- alpha-2s
Analgesics
- opioids
Neuroleptoanalgesia
- sedative + opioids
Drug selection
- Species
- Age
- Physical status (ASA)
- Animal behavior and attitude
- Procedure
- Duratio of precedure
- Experience with drugs used
Anticholinergic drugs
- atropine sulfate
- glycopyrrolate
About anticholinergics
- Blocks acetylcholine on muscarinic receptors only in central and peripheral nervous system
- inhibits parasympathetic nerve impulses
- Uses
- respiratory disorders
- sinus bradycardia due to hypersensitive vagus nerve
- dizziness/motion sickness
Main effect of anticholinergics
tachycardia
Primary use of atropine
treat bradycardia
Unwanted effect of anticholinergics
- block the feedback receptor for acetylcholine causing a surge in release of acetylcholine
- Causes initial worsening of bradycardia before an inc in heart rate
- Causes AV block on EKG (some P waves without QRS)
Giving Atropine dosage info
- ALWAYS GIVE FULL DOSE
- because if not you will just get that initial acetylcholine surge without the tachycardia you were going for
- Can commonly inc HR 2x to 3x
*If you only give partial dose and get bradycardia, go ahead and give full dose
*If tx of full dose doesn’t fix bradycardia can give epinephrine
Epinephrine
- adrenergic agonist (inc sympathetic tone)
- will inc heart rate
- BUT ALSO severe vasoconstriction/hypertension
Opiods commonly cause
- bradycardia
Other side effects of anticholinergics
- dec vagal influence on HR
- dec secretions (salivary secretions)
- Bronchial dilation
- inc anatomical and physiologic dead space
- dec GI motor and secretorya activity
Ketamine
- sympathomimetic
- causes tachycardia
- some people combine ketamine plus atropine (Garcia doesn’t like)
Ruminants and muscarinic blockers
- Ruminants have lots of salivary secretions and atropine can clog up trachea
Horses and anti-muscarinics
may cause colic, use carefully
Atropine sulfate
- Tertiary amine molecule
- High lipid solubility
- easily crosses BBB and Placental barrier
- should see effect in 2 minutes
- reported sedation in people, not animals…
*some prefer glycopyrrolate in preggos
Glycopyrrolate
- Synthetic quaternary ammonium molecule
- Low lipid solubility
- Does not cross BBB and placenta
- No effects on CNS
- Same peripheral effects as atropine, slower onset, lasts longer
*USE ATROPINE WHEN SHIT HITS FAN
*Maybe less inc in HR than atropin
Major tranquilizers
- Phenothiazines
- Acepromazine (cheap and reliable)
- Butyrophenones
- Droperidol
- Azaperone
Hit by car dog sequelae
- will have inc circulating catecholamines => inc arrhymogenicity
- ace can protect from arrhythmias but some gray zones
acepromazine side effects
- alpha-antagonist
- severe vasodilation & bradycardia (maybe don’t give to Hit by car)
- cardiac depression
- decreases adherance of platelets
- peripheral alpha-2 adrenergic blockade
- relaxation of vascular smooth muscle
- don’t give to DCM patients
- persistent or permanent penile paralysis
- 1/10,000 in horses
Droperidol and azaperone
- preferred to ace in pigs
Type of Opioids
- mu-agonist
- Partial mu-agonist
- K agonist - mu antagonists
- antagonists
mu agonists
- Drug examples
- morphine
- fentanyl
- methadone
- Causes
- respiratory depression (test question)
- vomiting
- bradycardia
- decreased GI motility
- Linear relationship to response
partial mu-agonist
- drug example
- buprenorphine
- Ceiling effect
- can start reversing effects at high doses
k agonist - mu antagonist
- Drug examples
- butorphanol
- nalbuphine
- sometimes used to reverse complete agonists respiratory depression while maintaining some analgesia
opioid antagonists
- naloxone
- naltrexone
Mu receptors cause the most
- analgesia
- side-effects: limiting factor
-
respiratory depression (test question)
- causes a lot of death in people
- vomiting
- bradycardia
- decreased GI motility
-
respiratory depression (test question)
- Linear relationship to response
Morphine IM
- Sometimes used to make animals puke when they eat a ton of food
- morphine will almost ALWAYS make an animal barf
*after first dose opioids are an ati-emetic
*apomorphine will cause vomiting
If an anticholinergic does not reverse a bradycardia think….
hypothermia
Potency is…
- dose related
- nothing to do with strength of analgesia
How do we pick opioids
Side effects and duration
Histamine release as result of morphine and noperadine
can get hypotension, vasodilation, urticaria
Methadone is an ……….. antagonist
NMDA
Buprenorphine is very…..
- long lasting
- moderate pain relief
- good for cats because of oral bioavalability
- poor oral bioavailability in dogs
- binds strongly to receptor
Butorphanol
- good sedative
- mild to moderate analgesia
- can reverse mu receptor agonism
Benzodiazepines
- anterograde amnesia
- GABA agonist
- hypothalamus
- Midbrain
- Hippocampus
- Medulla
- Spinal cord
Diazepam
- anxiolytic
- muscle relaxant
- anticonvulsant effect
- rapidly crosses BBB and placental barrier
- minimal cardiovascular effects
- dec BP and CO
- Propylene glycol is base of this drug
- high lipid solubility => not friendly, and hurts => don’t give IM
Diazepam often used with ……
ketamine
Ketamine + Diazepam (propylene glycol vehicle)
- safe
- opioids will precipitate with propylene glycol
- propylene glycol hurts IM
Midazolam
- Water soluble
- becomes lipid soluble at pH > 4
- Can be given IM
- More potent, shorter acting than Diazepam
- Crosses BBB and placental barrier
*Can mix with any opioids in syringe
Zolazepam
- most potent benzo used in vetmed
- available only in Telazol
- anticonvulsant and muscle relaxant
- least apt to cause CNS depression
Reversal for benzos
- Flumazenil
- competitive antagonist of benzo receptor
- very weak agonist effect
- no anxiety with reversal
alpha 2 adrenergic agonists
about……
- anxiolytic
- sedative and muscle relaxant
- analgesia
- dec ADH release = inc urinary output
- dec insulin release
- hypertension followed by hypotension
- reflex bradycardia
*reversal exists
alpha 2 adrenergic agonist
cardiovascular effects
- dec HR
- hypertension
- dec sympathetic tone
- dec CO
- dec myocardial contractility
- dec HR
- inc then dec BP
Don’t give alpha-2s to
- sick dogs
- especially cardiovascularly sick dogs
Good drug to use with xylazine
- atropine
Do not trocharize …….?! dogs with…..
Only with…..
dexmetatomidine
Xylazine
Xylazine
- Less selective for alpha-2 receptors
- Dirty: has alpha-1 effects too
- More ataxia
- shorter duration
- 2nd degree AV block….?
Detomidine
- Not very selective for alpha-2s
- Profound sedation compared to xylazine
- Ataxia
- large animal
Romifidine
- Still not very selective
- good sedation
- less ataxia
- large animal
- used for recovery
Dexmedetomidine
- most selective
- profound sedation
- may intubate some dogs
- quick acting
*causes vasoconstriction give in big muscle….? Quads
Reversals for non-selective alpha-2s
- Tolazoline
- Yohimbine
- Give only SC or IM
- May be given IV to Large animals
Reversals
alpha-2 selective drugs
- antipamizole for dexmetatomidine
- give only SC or IM
- May be given IV to large animals
Guaifenesin
- central muscle relaxant
- different from NMB
- Used as adjuvant in large animal induction
- Smothes induction and decreases injectable dose
- disrupts transmission at spinal cord and brain stem
- inc RR and dec tidal vol
- min vent unchanged
Ketamine and alfaxolone
- can be used as premed to cause chemical restraint
- higher doses than used IV
- used in difficult patients
