Sting, Scorpion, Emergency Medicine

Basics

Description

Scorpion venom is neurotoxic:
- Sodium channels opening
- Prolonged firing of neurons
Autonomic, somatic, and cranial nerve excitation occurs.
Symptoms begin within minutes of bite.
Symptoms persist 1 " 72 hr.

Etiology

Centruroides species found in Southern US, Mexico, Central America, and Caribbean
Many other species in Asia, Africa, Israel, South America, and Middle East

Can be misdiagnosed as seizures, amphetamine poisoning, or meningitis
Higher mortality and severity of illness

Diagnosis

Signs and Symptoms

Onset within minutes, progressing to maximum severity in ’ Ό1 " 2 hr but may persist ≤48 " 72 hr.
Scorpion species determines symptomatology (Centruroides sculpturatus, aka Centruroides exilicauda or bark scorpion, is the only species in US causing symptoms).
Local tissue effects:
- No erythema
- Pain
- Hyperesthesia
Autonomic effects:
- Sympathetic symptoms:
  - Tachycardia
  - Hypertension
  - Hyperthermia
  - Pulmonary edema
  - Agitation
  - Perspiration
- Parasympathetic effects:
  - Hypotension
  - Bradycardia
  - Hypersalivation
Somatic effects:
- Involuntary muscle contractions
- Restlessness
Cranial nerve effects:
- Roving eye movements
- Blurred vision
- Nystagmus
- Tongue fasciculations
- Loss of pharyngeal muscle control

Essential Workup

Identification of scorpion species not needed if scorpion is native to US (see above).
Maintain high clinical suspicion in endemic areas
Assess envenomation grade severity:
- Grade I: Local pain and/or paresthesias at site
- Grade II: Local pain and/or paresthesias at a remote site
- Grade III: Either cranial/autonomic or somatic skeletal neuromuscular dysfunction
- Grade IV: Both cranial/autonomic and somatic skeletal muscle dysfunction

Diagnosis Tests & Interpretation

Lab

Grades I and II envenomations:
- None
Grades III and IV envenomations:
- BUN, creatinine
- Electrolytes
- UA
- CBC
Severely agitated patients:
- Creatine kinase
- Urine myoglobin
Severe respiratory distress:
ABGs

Imaging

Chest radiograph for respiratory symptoms
ECG for tachycardia

Differential Diagnosis

Snake, spider, insect envenomation
Tetanus
Diphtheria
Botulism
Overdose/dystonic reaction
Seizures
Infections

Treatment

Pre-Hospital

Evaluate ABCs
IV access

Initial Stabilization/Therapy

ABCs
Endotracheal intubation if necessary
IV
O2
Monitor

Ed Treatment/Procedures

Mild envenomations " grades I and II:
- Oral analgesics
- Tetanus prophylaxis
Severe envenomations " grades III and IV:
- Antivenom (Anascorp), expensive therapy
- Tetanus prophylaxis
- Hypertensive urgencies/emergencies (rare):
  - Standard therapy such as labetalol
- Hypotension:
  - IV fluid resuscitation and pressor therapy with dopamine
- Severe agitation:
  - Midazolam
- Treatment for rhabdomyolysis if present

Medication

Antivenom: Centruroides (scorpion) (Rx: Anascorp infuse 3 vials IV over 10 min); monitor for up to 60 min after completing infusion to determine if symptoms are resolved. Additional doses may be used if needed; infuse 1 vial at a time at 30 " 60 min intervals.
Dopamine: 2 " 5 Όg/kg/min IV; increase in 5 " 10 Όg/kg/min as needed
Midazolam: 1 " 2 mg (peds: 0.01 " 0.05 mg/kg) IV
Labetalol: 20 mg (peds: 0.3 " 1 mg/kg/dose) q10min
Fentanyl: 50 " 150 Όg (peds: 1 " 3 Όg/kg) IV
Tetanus toxoid: 0.5 mL IM (peds: Same dose)

Antivenom doses are the same in children because dosage is based on venom burden.

Follow-Up

Disposition

Admission Criteria

Grades III and IV envenomations require admission to ICU.
If antivenom is given with resolution of symptoms, observe for 1 " 2 hr if asymptomatic.

Discharge Criteria

Grades I and II envenomations after a short observation period (3 " 4 hr after sting occurred) for progression of symptoms
Grades III and IV envenomations given antivenom with resolution of symptoms can be discharged.
If patient received antivenom, discuss signs and symptoms of delayed serum sickness.
Discuss possibility of persistence of pain and paresthesias at site.
Encourage patient to return for progression of symptoms.

Toddlers are more likely to have early airway involvement.

Followup Recommendations

Primary care follow-up if antivenin given.

Pearls and Pitfalls

Maintain high index of suspicion for scorpion stings in endemic areas when patients present with typical symptoms.

Additional Reading

Boyer LV, Theodorou AA, Berg RA, et al. Antivenom for critically ill children with neurotoxicity from scorpion stings. N Engl J Med. 2009;360(20):2090 " 2098.
LoVecchio F, McBride C. Scorpion envenomations in young children in central Arizona. J Toxicol Clin Toxicol. 2003;41(7):937 " 940.
O 'Connor A, Ruha AM. Clinical course of bark scorpion envenomation managed without antivenom. J Med Toxicol. 2012;8(3):258 " 262.
Quan D. North American poisonous bites and stings Crit Care Clin. 2012;28(4):633 " 659.

Codes

ICD9

989.5 Toxic effect of venom

ICD10

T63.2X1A Toxic effect of venom of scorpion, accidental, init

SNOMED

217670007 poisoning due to scorpion venom (disorder)

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