Scorpion Sting
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Direct answer
The sting of the Indian red scorpion (Mesobuthus tamulus, synonym Hottentotta tamulus) — the medically important species across Maharashtra, Karnataka, Tamil Nadu and the Andhra coast — injects venom whose alpha-toxin delays inactivation of neuronal sodium channels, firing an autonomic storm: an initial cholinergic phase of vomiting, sweating, salivation, abdominal pain, priapism and bradycardia, followed by the dangerous adrenergic phase of hypertension, pulmonary oedema, tachycardia and venom-induced myocarditis with cardiogenic shock. Management is graded — local pain at grade one, autonomic features at grade two, pulmonary oedema or shock at grade three — with prazosin as the specific Indian answer: an alpha-1 blocker given orally (about 30 micrograms per kilogram per dose, 1 mg in adults, repeated), after vomiting has settled, which reverses the adrenergic phase; dobutamine supports cardiogenic shock, and intensive care with oxygen and ventilation serves the worst cases.
What you must remember
- Species and mechanism: Mesobuthus tamulus venom toxins bind voltage-gated sodium channels, prolonging their opening — transmitter release from both parasympathetic and sympathetic terminals, endogenous catecholamine surge, and a myocarditis that behaves like prolonged adrenergic stimulation.
- The two-phase exam pattern: cholinergic first — vomiting, sweating, salivation, lacrimation, abdominal colic, priapism (a much-tested sign), bradycardia; adrenergic next — hypertension, tachycardia, peripheral vasoconstriction, acute pulmonary oedema and, in the fulminant case, hypotension from myocarditis.
- Prazosin protocol: 1 mg orally in adults (30 micrograms per kilogram in children) once vomiting has stopped, repeated after a few hours if needed and continued two to three times daily for a day or two — it blocks alpha-1 receptors, relieves preload and afterload, and resolves the pulmonary oedema of the adrenergic phase; administration during active vomiting risks aspiration.
- Cardiac care: venom-induced myocarditis with raised troponin and reduced ejection fraction — dobutamine infusion is the inotrope of choice in shock with pulmonary oedema (fluids are dangerous); refractory cases have used nitroprusside or clonidine for hypertension.
- What not to do: no fluids boluses in pulmonary oedema phase, no beta-blockers as monotherapy (unopposed alpha vasoconstriction), no sedatives masking evolving envenomation; local ice and analgesia suffice for pain.
- Antivenom reality: a commercial scorpion antivenom exists in India but efficacy evidence is weak and availability patchy — the exam answer remains prazosin and graded supportive care, with antivenom not standard.
- Epidemiology: stings peak in the summer monsoon months when scorpions shelter in footwear, firewood and construction material; children carry higher mortality from myocarditis, and coastal Konkan and western-ghats districts report seasonal case loads.
Dusk in a Konkan village
A nine-year-old is stung on the toe at dusk while barefoot in a Konkan village; within thirty minutes she vomits, sweats profusely and has marked priapism with a heart rate of 52 — grade two envenomation in the cholinergic phase. Step one triages to a facility with cardiac monitoring: the cholinergic phase of mild cases may pass, but children deserve observation for the adrenergic switch. Step two watches for the transition over the next hours: blood pressure climbing, tachycardia, and crackles on auscultation would announce grade three. Step three gives prazosin 30 micrograms per kilogram orally once vomiting has stopped, repeating per protocol as the storm resolves — priapism fades first, blood pressure settles. Step four escalates for the worst case: oxygen, upright positioning, dobutamine for shock with pulmonary oedema, and intensive care for myocarditis. Discharge instructions — footwear at night, shaking out clothes and firewood — prevent more cases than pharmacology.
Priapism, fluids and timing
The priapism sign is the classic missed clue — among Indian children stung by the red scorpion it is almost pathognomonic of the cholinergic phase, yet candidates read past it to arrive at "anaphylaxis". The second slip is timing prazosin during vomiting, courting aspiration; the protocol waits for the stomach to settle. Third, the fluid reflex: a child in shock gets a bolus — but in scorpion myocarditis with pulmonary oedema, that bolus kills, and dobutamine is the answer. Finally, atropine for the early bradycardia is used only for symptomatic bradycardia or excessive secretions per protocols — reflexive repeated atropinisation risks masking progression and worsening the later hypertension.
Frequently asked questions
Which scorpion species is medically important in India?
Mesobuthus tamulus, the Indian red scorpion, whose alpha-toxins prolong sodium-channel opening and trigger a dual autonomic storm.
Why is priapism significant in a stung child?
It is a hallmark of the cholinergic phase of severe envenomation, from parasympathetic overactivity, and marks the patient for observation of the adrenergic phase.
What is the role of prazosin?
An alpha-1 blocker, about 30 micrograms per kilogram orally (1 mg in adults) once vomiting has settled, repeated as needed — it specifically reverses the adrenergic phase and its pulmonary oedema.
Why are fluid boluses dangerous in severe scorpion envenomation?
Venom-induced myocarditis with pulmonary oedema makes the circulation volume-intolerant; dobutamine supports the pump without flooding the lungs.
Is scorpion antivenom standard treatment in India?
No — available but with weak evidence and limited availability; graded supportive care with prazosin remains the standard answer.