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4 Cards in this Set
- Front
- Back
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what is the clinical use of local anaesthetics |
memonic???
topical/local infiltration/ instillation / intervenous regional using tourniquet/ peripheral nerve blocks/ epidural block/systemic |
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describe the MOA of the local anaeathetics give the physiology behind it as well. describe what susceptibility means in relation to LAs |
Na channel blockers, which prevents initiation and conduction of an AP.
the normal resting membrane potential of a cell is -60 to -90 mV. If a cell becomes stimulated it may stimulate an AP if its depolarisation is great enough. this happens due to opening of voltage gated Na channels and repolarisation happens when these channels are inactiveted quickly along with the delayed opening of the voltage gated K channels.
local anaesthetics are weak bases ( equation - BH+--> B+H+) and the Na channels are either open, closed or inactivated. Some LAs prefere to use open channels called the 'use dependant' pathway so if the axon is being used the LA will be more effectve.
small myelinated and unmyelinated fibres are more 'susceptible' than motor neurones |
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describe the pharmacokinetics of the LAs ( distribution, speed of onset, duration and potency, elimination) |
weak bases ( BH+-->B+H+) so inflammed acidic tissue may be resistant ( pH dependant ). To avoid this bicarbonate may be added to increase the pH.
The speed of onset is related to the degree of ionisation.
the duration is realted to the amount of protein binding and adrenaline may be given to increase duration by causing vasconstriction.
potency is related to lipid solubility.
ester linked = shorted half life due to elimination via cholinesterases in the plasma whereas amide lined have a longer half life as they are eliminated in the liver. |
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describe the side effects of the Local anaesthetics and when are they more likly to be seen |
most likly to be seen in an overdose or accidential IV administration.
side effects: CNS- at 1st stimulation which causes convulsions and later depression which causes a coma and death ! CVS- depression , decreased contractility and heart rate and peripheral vasodilation |
