Scorpion envenoming — DTM&H MCQ

Correct answer: A — Prazosin with supportive respiratory care where indicated

The correct answer is A, prazosin with supportive respiratory care where indicated. This child's presentation, vomiting, sweating, cold extremities, hypertension, pulmonary oedema and falling saturations, is the classic autonomic storm and cardiogenic pulmonary oedema seen with severe Indian red scorpion (Mesobuthus tamulus) envenoming, driven by a massive catecholamine surge. Prazosin, a post-synaptic alpha-1 blocker, directly counters this catecholamine-mediated vasoconstriction and afterload, reducing pulmonary oedema and improving survival in controlled trials from India. Oxygen, fluid restriction and ventilatory support are added as needed, but prazosin is the specific antidote-like intervention that addresses the underlying pathophysiology rather than just the hypoxia. Why the other options are wrong: C. Oral antihistamine as definitive therapy: Antihistamines address local histamine-mediated itching or urticaria, not the catecholamine-driven cardiovascular and pulmonary crisis; they have no role in reversing hypertension or pulmonary oedema. B. Incision and suction at the sting site: This outdated first-aid manoeuvre does not remove circulating venom once systemic autonomic toxicity has developed, and it risks local tissue damage and infection without altering outcome. D. High-dose corticosteroids as sole therapy: Steroids have no proven role in reversing scorpion venom-induced catecholamine excess or acute left ventricular failure, and using them alone would delay effective treatment. E. Rabies vaccine and immunoglobulin: This is a scorpion sting, not a mammalian bite, so there is no rabies exposure risk and this option is entirely irrelevant to the clinical scenario. Key point: In severe scorpion envenoming with autonomic storm and pulmonary oedema, prazosin (alpha-1 blockade) is the specific therapy that reverses venom-induced catecholamine excess, alongside supportive respiratory care.

Reference: Rodrigo C, Gnanathasan A. Management of scorpion envenoming: a systematic review and meta-analysis of controlled clinical trials. Systematic Reviews 2017;6:74. https://systematicreviewsjournal.biomedcentral.com/articles/10.1186/s13643-017-0469-8