Flashcards in CAL - sedation, premedication and induction of anaesthetics Deck (59)
Name 5 alpha-2 agonists
Which alpha-2 agonist has the longest effect?
Romifidine (analgesic properties questioned)
What effects does medetomidine have?
Very powerful sedative, hypnotic and analgesic. Its effect may be enhanced by combining with an opioid (butorphanol)
What can be used to revere the sedative and other actions of alpha -2 agonists?
Alpha-2-antagonists such as Atipamezole, Yohimbine, Tolazoline and Idazoxan
How do alpha-2-antagonists work?
Act at both pre- and post-junctional sites on noradrenergic nerves centrally and peripherally. Wide ranging effects.
Via which route are alpha-2agonists strong analgesics?
What is the biphasic BP response of alpha-2 agonists?
Transient (5-15 min) hypertension, (due to vasoconstriction) followed by prolonged (but very slight) hypotension
What are the 2 main side effects of alpha -2 agonists
bradycardia and fall in CO
Why is emesis common in small animals soon after alpha-2 agonist administration?
CRTZ stimulation. Gut motility then almost totally ceases.
What skin reactions occur with alpha-2 agonists?
Sweating common in the horse. Piloerection may occur with very high doses. Occasional 'anaphylactic' skin plaques - most commonly with romifidine.
Where are alpha-2 agonists metabolised?
T/F animals given alpha 2 agonists may respond violently to some stimuli, especially touch
True - this effect can be reduced by combining with opioids as low doses of opioids are synergistic
What drug interactions might occur with alpha-2 agonists?
- some ABs (potentiated sulphonamides)
What should you be aware of when giving ruminants alpha-2 agonists?
severe respiratory depression possible --> hypoxia
What are the contra-indications for alpha-2 agonists?
- ABSOLUTE CI - urinary obstruction
- PARTIAL CI - myocardial disease, liver/renal failure, pulmonary disease, pregnancy, DM, hypovolaemia
What drugs are excellent for determining a colic's response to analgesia
Alpha 2 agonists (partly because they inhibit gut motility)
List some examples of benzodiazepines
What is an antagonist to benzodiazepines?
Flumazenil and Sarmazenil
How do benzodiazepines work?
Agonists at several CNS sites for BZ1/, BZ2 sites on the GABA-A-R causing increased chloride conduction. No effect on peripheral receptors of this type due to no benzodiazepine binding site.
Indications for benzodiazepines
Reduce anxiety, taming effects, behavioural changes and relaxation of skeletal muscle (spinal effect), stimulate appetite (IV administration in cats).
Highly lipid soluble, therefore rapidly cross BBB. Converted to active metabolites in liver, which may have much longer half-life than parent compounds, so that circulating concentrations of the latter may not be predictive of duration of action.
Benzodiazepine side effects
- minimal CVRS effects, even high doses
- may be synergistic with many anaesthetic agents in causing respiratory depression
What is a risk when injecting benzodiazepines?
some formulations cause thrombophlebitis and pain on injection (midazolam is water soluble and can be given IV or IM and is NOT painful on injection)
What is the main anaesthetic use of benzodiazepines?
in combination with opioids or ketamine or as part of an anaesthetic induction protocol
T/F: phenothiazine and butyrophenones have many similarities.
True - they are typical tranquilizer drugs
What is an example of a phenothiazine?
Name 3 examples of butyrophenones
Name an antagonist to acepromazine (ACP)
There is not antagonist - if serious hypotension occurs whilst giving ACP, treat with IV fluids.
Why shouldn't you give adrenaline with acepromazine (ACP)?
ACP causes alpha-1 adrenergic blockage so adrenaline may stimulate an unopposed beta-2 adrenergic receptor action. This effect will increase vasodilation and so hypertension may worsen.