LA action Flashcards
when can local cross the nerve fibre membrane
when it is in non-ionised form
how does local enter the nerve and block transmission?
LA is in: ionised base.H+ form
they dissociate and unionised base can cross membrane to inside the fibre
base recombines with hydrogen inside the cell to become ionised again. now it can bind to the ion channel and block influx of Na+
what is the critical length?
length / number of nodes of ranvier needed to be blocked to block transmission
which are easier to block, larger or thinner nerve fibres?
thinner, as there are less Na channels to block.
what effects does local have on the body that aid / hinder its function?
increases blood flow, causes a shorter duration of time, hence why vasoconstrictor is added
increased protein binding due to slow diffusion into membrane, so longer duration of action and faster speed of action
increases lipid solubility due to aromatic ring so longer duration and stronger effect
lower the pKa = faster action
what are the benefits of adding epinephrine to the local anaesthesia?
prolong numbness due to constriction and less local leaves area
decreased toxicity as less opportunity for the local to enter the bloodstream
promote haemostasis due to the constriction of vessels
