- sedative via dopamine antagonism - anti-emetic - a1 antagonism = vasodilation and anti-arrhytmic - anti-histamine - penile priapism

Anaesthesia - drugs Flashcards by Ella Townsend

What anaesthetic agents can be used in food animals?

ketamine
thiopental
isoflurane

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Injectable anaesthetic agents

propofol
alfaxalone
ketamine
thiopental
etomidate

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what injectable agents can you use for long term maintainance?

propofol

alflaxalone

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what inhalational agents are available today?

isoflurane
sevoflurane
desflurane
N2O

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what are some considerations with isoflurane and sevoflurane?

very vasodilatory

secoflurane may be nephrotoxic

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considerations with desflurane

expensive

irritant

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considerations of nitrous oxide

cant reach anaesthesia with it alone
very insoluble
switch it off before end of procedure and put on 100% O2 as can get diffusion hypoxia as it rapidly diffuses into lungs (as insoluble in blood) as end of anaesthesia and decreases oxygen pressure

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what anaesthetic agent doesnt cause dose-dependant CVs and resp depression?

ketamine as causes catecholamine release which counteracts it

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what is TIVA and PIVA?

total / partial IV anaesthetic

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advantages and disadvantages of intermittent IV maintenance

simple, less equipment

- swinging plane of anaesthesia, side effects when really deep

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advantages and disadvantages of continuous IV maintenance?

need a syringe driver
can control with a computer
need to know minimum infusion rate (MRI) where 50% dont respond to stimuli

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How is inhalational agent concentration affected by vessel richness of tissues?

Vessel rich tissues will reach higher concentrations and be removed faster than vessel poor tissues

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what is MAC?

minimum alveolar concentration - needed to prevent movement to a painful sitmuli in 50% of animals

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what MAC is aimed for?

1.25 - 1.5 xMAC

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what can decrease MAC?

hypothermia
young / old
hypoxia
hypotension
CVs depressants
pregnancy

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what can increase MAC?

hyperthermia
healthy and young ish
excitation

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What do neuromuscular blocking agents do? What considerations do you need?

inhibit ACH binding at NMJ so the AP isnt propogated to the muscle

cause relaxation of all skeletal muscles
must be able to IPPV as cant breathe
hard to monitor as cant asses reflexes
use nerve stimulator to measure effect of block
antagonise with ACHe and anticholinergic agent to prevent bradycardia from high ACH at muscarinic receptors

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How is potency related to MAC?

potency = 1/MAC

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What are the 4 classes of premed?

phenothiazines
butyrphenones
benzodiazepine
a2 agonists

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what is the main phenothiazine?

acepromazine (ACP)

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what does ACP do?

sedative via dopamine antagonism
anti-emetic
a1 antagonism = vasodilation and anti-arrhytmic
anti-histamine
penile priapism

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how long does ACP take to work and how long does it last?

20-30 mins to work
4-6 hours duration
IM or IV

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when is ACP contradicted?

brachycephalic
hypotensive
boxers
breeding stallions
intradermal skin testing
organophosphates (be careful is poisoned)

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what does ACP potentiate?

opioids
local A
GA

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how much does ACP affect the respiratory system?

not much unless very sick

what is Azaperone?

butyrphenones | -pig sedative

what are the pharmokinetics of azaperone?

- deep IM - dose related sedation - 30 mins of quietness to effect - 2-3 hr duration

what are some examples of benzodiazepines?

- diazepam / valium - midazolam / hypnovel - diazemuls

what do benzodiazepines do?

- potentiate GABA - muscle relaxation - anti convulsant - variable sedative effect - appetite stimulant in cats - minimal CVS / resp depression

what is the pharmacokinetics of benzodiazepines?

- good in very old/young/sick - irritant - absorbed onto plastic so dont draw up early - rapid onset and short duration - IV

what benzodiazepine can be given IM?

midazolam and diazemuls

what benzodiazepine is inhibited by erythromycin?

miadazolam / hypnovel

when are benzodiazepines contraindicated?

- long term in cats as can cause hepatic failure - hepatic encephalopathy - very excited / aggressive patient

what are some a2 agonists?

xylazine detomidine / domosedan romifidine / sedivet medetomidine (domitor)and dexmetomidine

what do a2 agonists do?

- muscle relaxation - initial hypertension from a1 effects post synaptically then get normo/hypo tension - bradycardia from herpertension - resp depression - vomiting - inhibit ADH and insulin - uterine contraction

which a2 can be used in horses?

romifidine / sedivet detomidine / domosedan xylazine

how long do a2 agonists work for?

about 2 hrs

why do we pre-med?

- help and potentiate anaesthetics - relieve anxiety - analgesia - less anaesthetic dose so less anaesthesia side effects - smoother induction and recovery

what is a tranquiliser?

reduce anxiety but no dullness

what is a sedative?

reduce anxiety and cause drowsiness

what is a hypnotic?

anaesthesia inducing

what is a benzodiazepine antagonist?

flumazanil / sarmazenil

what is a a2 antagonist?

atipamezole yolimbine tolazoine

what do anti-chollinergic drugs do?

``` increase HR decrease salivation decrease gut motility dilate pupil relax bronchi ``` atropine, glycopyrollate, hyoscine

how do we estimate the brain concentration of inhaled agents?

alveoli conc = brain conc

what happens with more soluble agents?

- more in the blood so less in lungs / brain - longer induction and recovery as takes time to saturate blood first before pressure builds up in brain and lungs - more soluble = higher gas partition coefficient

what are 5 induction agents?

``` propofol propofol plus alfaxalone ketamine thiopentone / thiopental ```

what class is propofol?

phenol

what can propofol be used for?

induction, maintenance, TIVA

what induction agent has less cardiopulmonary depression?

alfaxalone

what induction agent cause CV stimulation?

ketamine - hypertension and tachycardia

what is an advantage of propofol plus over normal propofol?

28d shelf life compared to 1 d shelf life

which induction agent causes reflexes to remain?

ketamine

how is propofol given?

IV slowly to effect

what cant you use propofol plus for that you can use propfol for?

TIVA

what is the difference in propofol plus?

benzyl alcohol preservative (may cause toxicity)

what can alfaxalone be used for?

induction and maintenance | -rapid onset and short duration

what is a consideration of alfaxalone?

difficult recovery

what is ketamine used for?

induction and maintenance has analgesic effects *dont give alone as will be excitatory

what is an issue with thiopentone/thiopental?

no longer licensed irritant if extravascular cumulative in body fat so be careful slow metabolism

what is the issue with propofol in cats?

cats cant conjugate glucuronides and have problems metabolising triglycerides so have a very slow recovery and toxic if dose repeated

what is the triple combination used in aggressive cats?

ketamine + medetomidine + opioid | IM lasts 15 m

what is etomidate?

minimal CVS and RESP depression so good if very sick | -depresses adrenal function (low cortisol)

what combination is used for very sick patients?

opioid and benzodiazepine