Paper I
Question
Rationale for the use of adrenaline along with local anesthetics.
Answer
Adrenaline is added to local anaesthetics because its α1-mediated vasoconstriction reduces blood flow at the injection site. This: (1) delays systemic absorption of the local anaesthetic, prolonging its duration of action locally, (2) reduces the risk of systemic toxicity by keeping peak plasma concentrations lower, and (3) produces a relatively bloodless field, useful for minor surgical procedures. (It must be avoided in end-artery regions — fingers, toes, nose, ears, penis — due to risk of ischaemic necrosis.)