Scorpion Sting (Envenomation) Management

Fig. Common Centruroides scorpion - Andrews' Diseases of the Skin

1. Background

2. Clinically Important Species

• Harrison's Principles of Internal Medicine 22E (2025), p. 3778

3. Venom Composition

• Neurotoxins - act on preganglionic/postganglionic terminals and muscle end-plates; keep sodium channels open
• Hemolysins, hemorrhagins, proteinases
• Phospholipase A, leucocytolysins, coagulins
• PC Dikshit Textbook of Forensic Medicine and Toxicology

4. Clinical Features

Local (most species)

• Immediate sharp burning pain at the sting site
• Erythema, edema, paresthesia, hyperesthesia
• "Tap test" - tapping the sting site exacerbates pain (classic for Centruroides)
• Minimal or no visible wound in many neurotoxic species

Systemic - Neurotoxic (Centruroides)

• Paresthesia spreading from the sting site
• Restlessness, profuse salivation, lacrimation, rhinorrhea
• Abnormal roving eye movements (classic), blurred vision, slurred speech
• Muscle twitching/jerking (may mimic seizure)
• Tachycardia, arrhythmias, hypertension, hyperthermia
• Rhabdomyolysis, acidosis
• Fatal respiratory arrest possible in children and the elderly

Systemic - Adrenergic Surge (Middle East, India, Brazil species)

• Hypertensive crisis
• Pulmonary edema (cardiogenic + non-cardiogenic)
• Myocardial damage, arrhythmias

Cytotoxic (H. lepturus)

• Minimal symptoms at first, then pain and hemolysis after 24 hours
• Hemoglobinuria, acute kidney injury

5. Grading (Simplified)

6. Management

6a. All Stings - First Aid

• Keep the patient calm and reassured; minimize movement
• Pressure dressing + cold packs over the sting site (reduces venom absorption)
• Do NOT suck out venom, apply tourniquets improperly, or use unproven treatments
• Immobilize the affected limb at or below heart level

6b. Mild Envenomation (Local Pain Only)

• Ice packs, oral analgesics (NSAIDs/paracetamol), oral antihistamines
• Can be managed at home with clear return precautions
• Instruct patient to return if cranial nerve or neuromuscular dysfunction develops

6c. Moderate-to-Severe Envenomation (Systemic Symptoms)

• Continuous IV midazolam infusion - reduces agitation and involuntary movements; preferred over opiates (which risk respiratory compromise)
• Benzodiazepines are the mainstay for neuromuscular hyperexcitability

• Prazosin (post-synaptic alpha-blocker) - especially effective in Indian red scorpion envenomation; counteracts catecholamine surge
  • Pediatric dose: 30 mcg/kg/dose orally or via NG tube; first repeat at 3 hours, then every 6 hours until recovery
• Nifedipine, nitroprusside, or hydralazine are alternatives
• A 2025 RCT (PMID 39953590) studied antivenom + prazosin combination vs. antivenom alone

• Bradydysrhythmia: Atropine
• Tachyarrhythmias: Managed per arrhythmia type

• Airway vigilance - severe Centruroides spasm can cause respiratory arrest
• Intubation and mechanical ventilation if respiratory compromise

• Local infiltration of lidocaine (lignocaine) around the sting site for pain relief
• Systemic opioids with close respiratory monitoring if needed

6d. Antivenom

• Antivenom is the most effective intervention when available and matched to the species
• Reduces or eliminates deaths in severe envenomation
• Indications: moderate-to-severe systemic symptoms refractory to analgesics and benzodiazepines
• Pre-medicate before antivenom: IV diphenhydramine + steroids; keep epinephrine at bedside (risk of anaphylaxis)
• Anascorp (Centruroides antivenom) - FDA-approved in the US; initial dose typically 3 vials IV, repeated every 30-60 minutes; up to 8 vials may be needed in severe cases
• Antivenom for many species remains controversial due to variable efficacy and adverse reactions

6e. Drugs to AVOID

• Lytic cocktail (pethidine + promethazine + chlorpromazine) - little efficacy
• Steroids - can worsen cardiac complications
• Antihistamines alone - insufficient for systemic effects
• Calcium channel blockers - negative inotropic effect, worsen cardiac outcomes
• Diuretics - can worsen hemodynamics
• Beta-blockers - harmful in catecholamine-mediated toxidrome

7. Special Populations

8. Disposition

9. Prevention

• Shake out shoes, clothing, and bedding before use in endemic areas
• Wear gloves when moving rocks, wood, or debris
• Use a flashlight when walking outdoors at night
• Seal cracks and gaps in buildings

Recent Evidence Note

• Harrison's Principles of Internal Medicine, 22nd Ed. (2025), pp. 3778-3779
• Andrews' Diseases of the Skin - Clinical Dermatology
• PC Dikshit Textbook of Forensic Medicine and Toxicology
• UN DHMOSH Guidance for Prevention & Management of Scorpion Stings (2024)
• Joint Trauma System CPG: Global Spider and Scorpion Envenomation Management (2021)