Scorpion Sting (Envenomation) Management

Overview

Of ~40 scorpion species in the US, only the bark scorpion (Centruroides sculpturatus/C. exilicauda) of the Southwest produces potentially lethal venom. Globally, dangerous species include Androctonus, Leiurus, Buthus, and Tityus genera. The venom mechanism involves neurotoxins that keep sodium channels open, leading to a hyperexcitatory toxidrome. (Harrison's, p. 13100)

Clinical Presentation

Local (most stings — non-lethal species)

Pain, erythema, swelling at the sting site
Paresthesia and hyperesthesia
Tap test positive: pain accentuated by tapping the affected area

Systemic (neurotoxic — Centruroides and dangerous species)

System	Features
Neurological	Restlessness, agitation, blurred vision, abnormal eye movements, slurred speech
Autonomic	Profuse salivation, lacrimation, rhinorrhea, diaphoresis, nausea/vomiting
Neuromuscular	Muscle twitching, jerking, shaking (may mimic seizure)
Cardiovascular	Tachycardia, arrhythmias, hypertension
Metabolic	Hyperthermia, rhabdomyolysis, acidosis

Symptoms typically progress to maximal severity within hours.

Severity Grading (Centruroides)

Grade	Features
I	Local pain/paresthesia at sting site only
II	Pain/paresthesia remote from sting site
III	Cranial nerve dysfunction OR skeletal neuromuscular dysfunction
IV	Both cranial nerve AND skeletal neuromuscular dysfunction

Management

1. Initial Assessment

Identify the species if possible — determines treatment intensity
Check for signs of cranial-nerve or neuromuscular dysfunction
Grade severity

2. Mild Envenomation (Grade I–II / non-lethal species)

Can be managed at home or with brief ED observation
Ice packs to the sting site
Oral analgesics (NSAIDs/acetaminophen)
Antihistamines for local allergic reaction
Instructions to return if systemic symptoms develop

3. Moderate–Severe Envenomation (Grade III–IV)

Hospital admission and the following measures: (Harrison's, p. 13101)

General measures:

Keep patient calm; apply pressure dressings and cold packs to sting site to decrease venom absorption
IV access; continuous monitoring (ECG, SpO₂)

Sedation / Neuromuscular agitation:

Midazolam (IV infusion) — first-line agent to control agitation, flailing, and involuntary movements
⚠️ Close monitoring required: risk of respiratory arrest with benzodiazepines or opioids in patients with neuromuscular symptoms
Avoid opioids if possible (can worsen respiratory depression)

Antivenom:

Indicated for Grade III–IV or severe systemic envenomation
Centruroides immune F(ab')₂ (Anascorp) — FDA-approved for C. sculpturatus; administered IV; can rapidly reverse neurotoxic symptoms
Aggressive supportive care + antivenom together can reduce or eliminate deaths from severe envenomations
Pretreat with antihistamines to reduce anaphylaxis risk

Cardiovascular:

Hypertension: treat with antihypertensives (vasodilators; avoid beta-blockers alone due to unopposed alpha effects)
Arrhythmias: standard ACLS protocols

Respiratory:

Intubation and mechanical ventilation if respiratory failure or inability to handle secretions

Other:

Rhabdomyolysis: aggressive IV fluids, monitor creatinine/CK, urine output
Monitor for acidosis and correct electrolytes

Special Considerations

Population	Consideration
Children	Higher risk of severe envenomation due to smaller body mass; lower threshold for antivenom
Elderly	Increased risk of cardiovascular complications
Pregnant	Antivenom generally considered safe; maternal stabilization takes priority

Disposition

Severity	Disposition
Grade I	Home with return precautions
Grade II	ED observation 4–6 hours; discharge if stable
Grade III–IV	Admit; ICU if respiratory or cardiovascular compromise

Key Pearls

Do NOT apply tourniquets — venom spreads via lymphatics/nerves, not vascular
The tap test helps distinguish Centruroides envenomation from other causes
Muscle jerking ≠ seizure — EEG is typically normal; treat with benzodiazepines, not anticonvulsants
Most US bark scorpion stings in healthy adults are managed supportively; antivenom is reserved for severe or pediatric cases

(Harrison's Principles of Internal Medicine, 21st Ed., pp. 13100–13101)

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