small animal anaesthesia Flashcards
what are the four classes of sedatives?
APBB
1. Alpha-2-agonist
2. phenothiazines
3. Butyrophenones (not rly used)
4. Benzodiazepines
give an example of an A2-agonist and what are their properties
medetomidine, xylazine
sedation, analgesia, muscle relaxation.
cause vasoconstriction and reflex bradycardia.
increases urine production
Atipamezole=reversal agent
immediate onset
give an example of a phenothiazine and what is its properties
Acerpromazine
sedation, muscle relaxation but NO analgesia
vasodilator
20-40 min onset.
Used in patients with mitral valve disease, BOAS, URT disease, laryngeal paralysis.
very useful if nervous patient
give an example of a benzodiazepine and what are its properties
Diazepam, Midazolam, Dormazolam.
sedation, smooth muscle relaxationbut NO analgesia.
minimal side effects but unreliable sedation.
5 min onset IV
Flumazenil=reversal agent
What are the SIX analgesic classess
NO PLAN
1. NSAID’s
2. Opioids
3. Paracetamol
4. Local anaesthetic
5. Alpha-2-agonist
6. NMDA antagonist
What are the three opioids used in small animal
- Methadone
full mu agonist, painful procedures - Buprenorphine
partial mu agonist, moderatley painful procedures - Butorphanol
kappa agonist, mu ANTagonist, non painful procedures only sedation needed
What are the THREE induction agents used in SA
- Propofol
- Alfaxolone
- Ketamine
what are the properties of propofol and how is it metabolised
vasodilation, respiratory depression.
Recovery due to redistribution, hepatic metabolism.
*only give one dose to cats as very poor at propofol metabolisation (cause heinz body anemia)
*baroreflex abolished
what are the properties of alfaxolone and how is it metabolised
Vasodilation, respiratory depression, baro reflex intact.
recovery due to redistribution, hepatic metabolism.
*excitable recovery for noise sensitive individuals
what are the properties of ketamine and how is it metabolised
Dissociative anaesthesia
Muscle hypertonicity, maintenance of CN reflexes, tachycardic, vasoconstrictive.
Hepatic metabolism, urine excretion
What can be given to anxious patients prior to the appointment
gabapentin (dog/cat)
trazadone (dog)
give an example of a dog sedation protocol (no underlying CV disease present)
medetomidine
opioid
ketamine
(IM)
why is inclusion of a benzoidiazepine useful for nervous patients during some point of sedation
retrogade amnesic effects.
Wont be able to remember the traumatic trip to the vets. make future appointments easier
give an example of a cat sedation protocol (no underlying CV disease present)
medetomidine
opioid
ketamine
give an example of a cat sedation where CV disease present
alfaxolone
butorphanol
midazolam
what circuit would you use for dogs <10kg
Mapleson D
what is the normal ET CO2 level seen on capnograph?
35-45mmhg
normal for it to be in the 50s at first due to post induction apnoea
what does the capnograph tell us about respiration?
Peak below 40= hyperventilation
Peak above 70= hypoventilation
Lowest point never reaching 0= rebreathing
Jagged on inspiration= cardiac oscillations, not significant
Gradually declining peak= leak or dying
what is the minimum mean alveolar blood pressure required during anaesthesia?
Need mean arterial pressure (MAP) to be at 60 minimum as a pressure difference of 50 is needed to allow perfusion. The normal intracranial pressure is around 10, so need a MAP of 60 to ensure the brain is properly perfused.
what are the SIX agents used for maintiaining blood pressure
- Fluid boluses
- Medetomidine
- Dopamine
- Atropine
- Glycopyrrolate
- Dobutamine
At what rate would you give an anaesthetised patient a fluid bolus to maintain BP
10-20ml/kg/hr over a 15-20 minute period.
Don’t give if underlying CV compromise
How much medetomidine would you give during anaesthesia to maintain BP
1/4 dose to increase BP through vasoconstriction.
This wears off very quickly so only useful for short term
How is dopamine given to improve BP?
commonly given as an infusion via a syringe driver.
a vasoconstrictor at higher dose however not a positive ionotrope. Only give if heart rate is satisfactory
How does atropine increase BP
it is a parasympatholytic (inhibits rest and digest)
Causes vasoconstriction and increased heart rate
