Scorpion Sting

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

Overview

Medically Important Species

• Harrison's 22E; Andrews' Diseases of the Skin

Venom Composition

• Neurotoxins - act on preganglionic and postganglionic nerve terminals and muscle endplates; keep sodium channels open, causing sustained neuronal excitation
• Hemolysins
• Agglutinins
• Hemorrhagins
• Proteinases
• Phospholipase A
• Leucocytolysins
• Coagulins
• Cholesterol and lecithin
• PC Dikshit Textbook of Forensic Medicine & Toxicology

Clinical Features

Local Effects

• Immediate sharp, severe burning pain at the sting site
• Red wheal with a central hole (single puncture mark - distinguishes from snake bite which has two holes)
• Variable local edema and erythema (may be minimal or absent with neurotoxic species)
• Tap test: hyperesthesia accentuated by tapping on the affected area - characteristic of C. sculpturatus
• Paresthesia, numbness, and hyperesthesia spreading from the site
• Wound necrosis is NOT typical for most species; delayed necrosis occurs with H. lepturus

Systemic - Neurotoxic (Centruroides and others)

• Restlessness, agitation, involuntary movements
• Cranial nerve dysfunction: blurred vision, roving/abnormal eye movements ("roving eye movements"), slurred speech, dysphagia, drooling, rhinorrhea
• Profuse salivation, lacrimation, diaphoresis
• Nausea and vomiting
• Muscle twitching, jerking, shaking (can mimic seizures), opisthotonos
• Peripheral skeletal muscle hyperexcitability and fasciculations
• Tachycardia, arrhythmias
• Hypertension
• Hyperthermia
• Rhabdomyolysis and acidosis
• Respiratory arrest - most common cause of death in children and elderly
• Symptoms peak at ~5 hours, subside within 1-2 days; pain and paresthesia may persist for weeks

Systemic - Cardiovascular (Androctonus, Leiurus, Mesobuthus, Tityus serrulatus)

• Massive endogenous catecholamine release
• Hypertensive crisis
• Cardiac arrhythmias
• Pulmonary edema
• Myocardial damage
• ST and T wave changes on ECG

Systemic - Cytotoxic (Hemiscorpius lepturus, Iran)

• Relatively asymptomatic initially
• Pain, hemolysis, and tissue necrosis after day 1
• Hemoglobinuria
• Acute kidney injury

Other

• Acute pancreatitis: Tityus trinitatis (Trinidad)
• CNS toxicity: Parabuthus and Buthotus (South Africa)
• Fever, chills, headache, giddiness
• Muscular cramps and convulsions, unconsciousness
• Paresis and muscular weakness persisting for ~1 week
• Death in children: primarily from pulmonary edema and respiratory depression
• Harrison's 22E; Rosen's Emergency Medicine; Andrews' Dermatology; Dikshit Forensic Medicine

Grading of Envenomation (North American Centruroides)

• Rosen's Emergency Medicine

Management

First Aid (Prehospital)

• Apply ice pack/cold compress to the sting site (reduces venom absorption and pain)
• Keep patient calm
• Transport to hospital
• Obtain history of sting circumstances and description/photo of scorpion (do NOT delay transport to capture it)
• Pressure dressing may reduce venom absorption

Emergency Department - Local / Mild (Grade 1-2)

• Local wound care
• Analgesics (oral)
• Antihistamines
• Tetanus prophylaxis if not current
• Grade 1-2: can potentially be managed at home with return precautions for cranial nerve or neuromuscular symptoms
• Local infiltration with lignocaine relieves pain

Emergency Department - Severe (Grade 3-4 / Systemic)

• Antivenom - most effective intervention overall
• Midazolam (continuous IV infusion) - reduces agitation and involuntary movements; monitor for respiratory depression
• Sedatives/opiates require close monitoring due to respiratory compromise risk
• Hypertension / pulmonary edema: nifedipine, nitroprusside, hydralazine, or prazosin
• Bradydysrhythmia: atropine
• Atropine sulfate also used to prevent pulmonary edema
• IV calcium gluconate (10 mL of 10% solution) for muscular cramps
• IV dextrose-saline + glucocorticoids IM for shock
• Airway management - especially for laryngeal edema, secretion management, respiratory arrest risk

Antivenom Specifics

• Anascorp (Centruroides [scorpion] immune F[ab']₂, equine-derived): FDA-approved for C. sculpturatus
  • Indicated for Grade 3 and Grade 4 envenomations
  • Initial dose: 3 vials IV as soon as possible after envenomation
  • Additional 1 vial IV every 30-60 minutes as needed
  • Rapidly reverses cranial nerve dysfunction and muscular symptoms
  • Not considered essential life-saving in adults (supportive care often sufficient); more critical in children
• Commercially prepared antivenins available in several countries for other dangerous species
• Antiarrhythmics, antiadrenergic agents, vasodilators, and calcium channel blockers may be required for cardiovascular toxicity
• Antivenin for Leiurus quinquestriatus, Androctonus, Tityus species available in respective endemic countries
• Harrison's 22E; Rosen's Emergency Medicine; Andrews' Dermatology; Dikshit Forensic Medicine

Key Distinguishing Points

• Scorpion sting mark: single hole in the center of reddened area (vs. snake bite = two holes; vs. spider bite = may have different appearance)
• Most scorpion stings worldwide are benign and self-limited; dangerous species are geographically restricted
• Pediatric patients are at highest risk for severe/fatal outcomes
• "Tap test" positive (hyperesthesia on tapping) = hallmark of C. sculpturatus envenomation
• Muscle twitching can mimic seizures - distinguish by lack of EEG changes
• Allergic reactions to venom can also occur