anaesthesia 6 - sedatives and tranquilisers 2 Flashcards
(24 cards)
alpha 2 receptors are mostly what?
inhibatory! bind an inhibatory G protein which inhibits cAMP. CAUSE LOWERD CA2+ INFLUX. and lowered neaurotrans. (some excitatory)
where would you find adrenoreceptors?
they bind catecholamines (NA) in the postsynaptic part of the SNS. they are GPCR and are either alpha or beta.
alpha 2 receptors are where?
presynapticcaly - block release of NA. therefore cause sedation effects. (negative feedback)
postsynaptic - cause vasodilation in arteries and veins (peripheral. due to increased camp. ) also found on fat cells, kidney, lipolysis etc.
3 classes of alpha 2 agonists? vary how? which is less selective.
-imadozoles (clonidine)
-oxazolines
-phenylthylamines. (xylazines)
vary in slectivity for alpha 1 and 2 receptors. xylazine is less selective.
how do imidazoline binding sites work?
they are similar to aplha 2 binding sites. bind alpha 2 ligands that are imidazolines (clonidine) or oxazolines but not phenylthyamines. (adrenaline/xylazine)
what are the effect of alpha 2 agonists on the cns? if dose too high?
sedation and anxiolysis due to inhibiton of NA release. non-selective drugs may cause them to be more anxious at high doses.
what are the effects on the cns of alpha 2 agonists?
analgesia + sedation ans anxiolysis. analgesia - especially visceral and acts at 3 locations: -brain -spinal cord -peripheral tissues
when opioids are not effective in relieveing pain then what could you use? routes?
could use alpha 2 agonists - block release of NA. there fore stop pain signals. can give extradural or intrathecal routes.
what is an anaesthetic sparing effect?
means when you use alpha 2 agonists then you can cut down on other drugs. 95% MAC (minimum alveolar concentration) . but if you need it to last long then may need to up it again?
when are they good for muscle relaxation?
alpha 2 agonists are good when used prior to ketamine anaesthesia.
what is the importance of the species variations with regards to alpha 2 agonists?
some are much more sensitive. eg. cattle are 10x more sensitive to xylazine than horses. pigs are relatively resistant!!
wht are the effects on the cvs?
vascular tone, bp and hr.
alpha 2 effects and also non0selective alpha 1 receptors.
vasoconstriction and hypertension (alpha 2)
vagus and bradycardia response (alpha 1) - slowed HR. due to baroreceptors - sense high pressure blood. this leads to hypotension and so hr is lowered and
what are the effects of alpha 2 agonists on respiration? main effect on sheep. ?
species and agent varation
mild depression of ventilatroy response
marked increase in airway resistance with xylazine in sheep.
effects on the GIT?
vomiting, and reduced motility. lowered salivation and reduced gastric secretion.
effecst on the endocrine system?
inhibit ADH - diuresis
inhibit insulin - hyperglycaemia
induce growth hormone
effect son the urogenital system?
uterine contraction. dont use xylazine if pregnant!!!
also does what to platelets?
induces aggregation - increase clotting.
xylazine? alpha 2 agonists. cows? horses? zoo animals? 24 hour rule?
clear 2% solution for inj in cattle as they are sensitive. used for pre-med prior to ketamine. barbituate induction.
10% in horses solution
or dry substance white powder for inj in horse/zoo animal.
+ a range of doses given for standing cattle but 24 hour rule - do not re-dose if inadequate
9wait 24 hours then start again)
xylazine in horses? cat/dog? when dont you use in cattle? excreted? good for horses? muscle relaxant?
i/v. duration of 20 minutes.
cat /dog? - licensed pre-med but reduce barbituate by 50%. (sparing)
iin cattle not in last month of pregnancy as causes uterus contraction.
good analgesia in colic and muscle relaxant before ketamine. excreted in urine.
detomidine? - alpha 2 agonist. in cattle and horses? what doe i do if pregnant?
clear liquid 10mg/ml. sedative/analgesic in horses.
used with opoids to improve sedation. pre-med for ketamine
i/m or i/v .
more potent than xylazine.
+ cattle it is equipotent!!
longer duration
more ataxia
slow electrical activity in uterus of preg cow.
romifidine? ‘sedivet’ what doesnt this one do? why is this good?
liquid 10mg/ml. sedative/aanalgesix in horses or pre-med.
i/v use
less ataxia
longer duration (3hours) not a muscle relaxant! - therefore can be used for clipping etc.
medetomidine? routes? which species? highly selective for? whenwouldnt you use it? what can reverse?
im, iv, sc, inj in dog/cat.
1mg/ml
potent and highly selective in alpha 2
duration up to 3 hours.
anaesthetic sparing agent.
dont use if cv disease. met in liver and excreted by kidney. vomit less common!
antisedan can reverse!
dexmedetomidine? for use in? effect? how do you dose? why is this a problem?
dog/cat. very ptoent. antiarrynthmic agent. short duration.
dose according to body surface so this is a problem if they are fat.
alpha 2 antagonists? eg? for use in?
antisedan. dog/cat given i/m. in a helathy animal good for short duration procedures.
