All LA’s are weak bases,so sodium bicarbonate speeds up the action of LA’s by increasing the unionized form.
LA’s act by blocking voltage gated sodium channels.
Vasoconstrictors like adrenaline prolong duration of action and decrease systemic toxicity.
Thin unmyelinated fibers are blocked first and thick myelinated fibres are blocked last.
Order of blockade is B, C ,Adelta,Aalpha, Abeta.
Autonomic>Sensory>Motor
Temperature(cold first)>Pain>Touch
Chlorprocaine is CI in spinal anaesthesia.
Dibucaine is most potent,longest acting and most toxic LA.
Bupivacaine is best for regional block,but it is the most cardiotoxic so should not be used in Biers block.
Prilocaine is most suitable for Biers block.
Lignocaine and Bupivacaine are used for spinal anaesthesia
Adrenaline should not be combined with LA’s when used on organs with end arteries(fingers,toes etc.)
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