6. Scorpion Sting

Quick Recap

Toxicology System, Protocol 6/8.

1. Definition & Epidemiology

Scorpion envenomation, most clinically significant with medically important species (e.g., Indian red scorpion Mesobuthus tamulus, various Centruroides, Tityus, and Leiurus species depending on region) causes a syndrome driven by massive, sustained autonomic (catecholamine) storm — the venom acts on voltage-gated sodium channels, causing prolonged neuronal depolarization and uncontrolled release of both sympathetic and parasympathetic neurotransmitters. Children and the elderly are at higher risk of severe/life-threatening envenomation given lower physiologic reserve relative to a similar venom dose.

2. Pathophysiology — The Autonomic Storm

Venom-induced sodium channel activation causes massive catecholamine (epinephrine/norepinephrine) AND acetylcholine release, producing a biphasic or mixed autonomic picture: an initial CHOLINERGIC phase (sweating, salivation, vomiting, bradycardia) often followed by or overlapping with a dominant, more clinically dangerous SYMPATHETIC/catecholamine phase (hypertension, tachycardia, and — critically — acute cardiogenic pulmonary edema and myocarditis-like myocardial injury from catecholamine-induced cardiotoxicity, analogous mechanistically to stress cardiomyopathy/Takotsubo physiology). The cardiopulmonary complications, not the local sting itself, are the primary drivers of scorpion-sting mortality.

3. Clinical Presentation

Local: immediate, severe, disproportionate pain at the sting site (often the most prominent early symptom, out of proportion to visible local findings — unlike snakebite, local tissue necrosis/swelling is typically minimal).

Systemic (autonomic storm manifestations): restlessness, sweating, hypersalivation, vomiting (early cholinergic-predominant phase); hypertension, tachycardia (or occasionally bradycardia), cold extremities, and in severe cases acute pulmonary edema, cardiogenic/myocarditis-pattern shock, and encephalopathy/seizures.

Pediatric presentation caution: young children may present atypically — irritability, vomiting, and respiratory distress may be the dominant findings rather than clearly localizable pain complaints, given communication limitations — maintain a high index of suspicion for systemic envenomation severity in any child with a witnessed or suspected scorpion sting and new cardiorespiratory symptoms.

4. Immediate Stabilization (ABCDE)

Airway/Breathing: monitor closely for evolving pulmonary edema — a scorpion-sting patient can deteriorate from mild local pain to acute respiratory failure within hours as the catecholamine-driven cardiopulmonary phase develops; apply standard pulmonary edema/ARDS-pattern respiratory support (see Acute Heart Failure and ARDS protocols) if this occurs, including lung-protective ventilation if intubation is required.

Circulation — the central management target:

• Prazosin (alpha-1 adrenergic antagonist) is considered FIRST-LINE, DISEASE-MODIFYING therapy in regions/species where evidence supports it (notably Indian red scorpion envenomation) — directly counters the alpha-adrenergic-mediated vasoconstriction and afterload surge driving the cardiopulmonary complications, rather than merely treating symptoms
• Typical dosing: prazosin 30 mcg/kg PO, repeated every 3 hours until signs of sympathetic overactivity resolve (tachycardia, hypertension, cold extremities improving), individualized to clinical response and local protocol
• Antivenom availability and evidence for benefit vary substantially by region/species — where a specific, validated antivenom exists for the local scorpion species, administer per regional/toxicology guidance; unlike snakebite antivenom, scorpion antivenom evidence for improving hard outcomes is less consistently established across all species, and prazosin/supportive care carries more of the therapeutic weight in several well-studied envenomation patterns
• Manage hypertension/tachycardia of the sympathetic phase with the prazosin-based approach above rather than reflexive beta-blockade — unopposed beta-blockade risks worsening the alpha-mediated vasoconstriction/afterload (a parallel caution to the unopposed-alpha principle already established for catecholamine excess states in the Hypertensive Emergencies protocol, Cardiovascular System)
• Treat evolving cardiogenic shock/pulmonary edema per standard Acute Heart Failure principles (see that protocol, Cardiovascular System) — cautious diuresis/afterload reduction once the picture is clearer, inotropic support if myocardial depression dominates over pure vasoconstriction
• Atropine for significant symptomatic bradycardia/excessive cholinergic-phase secretions, analogous to (though generally at lower intensity than) the organophosphate poisoning approach

Checklist:

5. Investigations

ECG (arrhythmia, ischemia-pattern changes from catecholamine-mediated myocardial injury), troponin (myocardial injury marker, given the myocarditis-like cardiotoxicity mechanism), echocardiogram if cardiogenic shock/pulmonary edema develops (assess EF, regional wall motion — may show a stress-cardiomyopathy-like pattern), CXR (pulmonary edema), electrolytes and glucose, continuous pulse oximetry.

6. Organ Support

Respiratory support (oxygen, NIV, or invasive ventilation) for pulmonary edema/respiratory failure; cardiovascular support (afterload reduction once volume status clarified, inotropes if myocardial depression dominates) per Acute Heart Failure protocol principles; standard ICU supportive care; continuous cardiac monitoring throughout the acute autonomic storm window.

7. Consultation Matrix

8. Monitoring Framework

Continuous cardiac and respiratory monitoring through the acute autonomic storm window (typically the first 24-48 hours carry the highest cardiopulmonary complication risk), serial troponin/ECG if cardiac involvement suspected, serial vital signs tracking the transition from cholinergic-predominant to sympathetic-predominant phase, respiratory status surveillance for evolving pulmonary edema.

9. Complications

Acute cardiogenic pulmonary edema, myocarditis-pattern cardiac injury/cardiogenic shock, arrhythmia, encephalopathy/seizures (severe systemic envenomation), respiratory failure. Prevention: early prazosin initiation to counter the alpha-adrenergic surge, avoiding unopposed beta-blockade, close monitoring through the highest-risk early window, heightened pediatric vigilance. Rescue: standard cardiogenic shock/pulmonary edema management, mechanical ventilation for respiratory failure, species-specific antivenom where available and evidence-supported.

10. Escalation & De-escalation

Escalate: evolving pulmonary edema or cardiogenic shock -> full Acute Heart Failure/Cardiogenic Shock protocol management, ICU-level respiratory support.

De-escalate: sympathetic overactivity signs resolving on prazosin, stable cardiorespiratory status through the high-risk window -> wean monitoring intensity, transition to standard observation, discontinue prazosin per clinical resolution.

11. ICU Discharge Criteria

Hemodynamically and respiratory stable through the acute autonomic storm window, no ongoing cardiac dysfunction/troponin trending down if elevated, local pain controlled, no evidence of ongoing systemic envenomation effect.

12. Documentation & Medicolegal Checklist

13. Key Guidelines

Regional/WHO-affiliated scorpion envenomation management guidelines vary by geography given species-specific venom differences — consult local toxicology/poison control protocols for the specific regional scorpion species involved.

14. Controversies

The evidence base for prazosin's benefit, while well-studied for certain species (notably Indian red scorpion), does not generalize uniformly across all medically significant scorpion species worldwide, and management approach should be tailored to regional experience. Scorpion antivenom's efficacy and availability vary substantially by region and species, with less consistent outcome evidence than snake antivenom, leaving genuine practice variation in whether and when to use it.

15. References

1. General toxicology and envenomation principles applied from the shared framework in Toxicology (Snake Envenomation, general poisoning approach). Washington Manual of Critical Care, 4th ed, 2025 (Ch. 36).
2. Chaudhry D, et al. Snakebite (envenomation general principles, ICU Protocols framework structure adapted). ICU Protocols: A Step-wise Approach, 2nd ed. Springer; 2020 (Ch. 16, and Appendix D syllabus reference to Envenomation as a distinct ICU training topic).
3. Bawaskar HS, Bawaskar PH. Scorpion sting: update. J Assoc Physicians India. 2012;60:46-55.
4. Chippaux JP. Emerging options for the management of scorpion stings. Drug Des Devel Ther. 2012;6:165-173.

See also: Acute Heart Failure and Cardiogenic Shock (Cardiovascular System) for the cardiopulmonary complication management framework; Snakebite (Toxicology System) for the parallel envenomation-management approach in this system.