Question
Briefly describe Adrenaline. Advantage of combining Adrenaline with Lignocaine. Mention the sites where this combination is contraindicated. (4+3+1)
Answer
a) Adrenaline A direct-acting sympathomimetic acting on alpha-1, beta-1, and beta-2 receptors. Actions: alpha-1 — vasoconstriction; beta-1 — increased heart rate and contractility; beta-2 — bronchodilation and vasodilation in skeletal muscle. Uses: anaphylactic shock (drug of choice), cardiac arrest, added to local anesthetics, superficial bleeding control. Adverse effects: anxiety, tremor, palpitations, arrhythmias, hypertension (risk of cerebral hemorrhage), can precipitate angina in ischemic heart disease.
b) Advantage of combining adrenaline with lignocaine Adrenaline’s alpha-1-mediated vasoconstriction at the injection site reduces local blood flow, which slows systemic absorption of lignocaine — this prolongs the duration of local anesthetic action, reduces peak plasma lignocaine concentration (lowering systemic toxicity risk), and reduces bleeding at the site, improving the surgical field.
c) Sites where this combination is contraindicated End-arterial areas with limited collateral circulation — fingers, toes, nose, ear, and penis — where unopposed vasoconstriction risks ischemic necrosis of the tissue.