II. Epidemiology

  1. Worldwide Incidence of Scorpion bite: 1.2 Million/year (3,250 deaths/year)

III. Background

  1. Scorpions are Arachnids with venomous Stingers in their tails
  2. Scorpions tend to hide in crevices, shoes

IV. Mechanism: Toxicity

  1. Envenomation is via the tip of the Scorpion tail
  2. Toxicity findings are specific to the Scorpion species
  3. Most Scorpions cause only self-limited, local reactions
    1. Of more than 2000 Scorpion species, only 25 are considered dangerous to humans
    2. Even with venomous Scorpion Stings, 95% of stings are dry without Envenomation
    3. However, a threatened Scorpion may inject up to twice as much venom
    4. In North America, Centruroides Scorpions are the most dangerous to humans
  4. Centruroides Scorpion Stings may result in severe Envenomation (5% of cases)
    1. Arizona Bark Scorpion (Centruroides sculpturatus) venom is a Neurotoxin
    2. Striped Bark Scorpion (Centruroides vittatus) is also a Neurotoxin, but less harmful than sculpturatus

V. Types: Centruroides

  1. Arizona Bark Scorpion (Centruroides sculpturatus)
    1. Yellow to brown Scorpions, primarily found in the southwestern United States
    2. Subnuclear tooth at the base of the Stinger
    3. Much more potentially dangerous than the Striped Bark Scorpion
  2. Striped Bark Scorpion (Centruroides vittatus)
    1. Black stripes on thorax

VI. Symptoms

  1. Immediate burning pain at site of sting (typically on an extremity)
  2. Local or regional hyperesthesia for varying period

VII. Signs

  1. Local reaction (Scorpion other than C. sculpturatus)
    1. Erythema
    2. Edema
    3. Ecchymosis
  2. Tap test (Suggests C. sculpturatus sting)
    1. Administer sharp tap at wound site
    2. Positive
      1. Patient experiences significant pain
      2. Abruptly withdraws wound site
  3. Centruroides sculpturatus reaction
    1. Muscle spasm or Tetany
    2. Excessive Salivation
    3. Rapid Tongue movement
    4. Fever
    5. Tachycardia
    6. Nystagmus
    7. Blurred Vision
    8. Slurred speech
    9. Respiratory distress or Wheezing
    10. Cranial Nerve dysfunction (e.g. roving eye movement)
    11. CNS hyperstimulation
    12. Seizures
    13. Cardiogenic Shock
    14. Pulmonary Edema

VIII. Exam

  1. Sting site evaluation
  2. Thorough Neurologic Exam including Cranial Nerve exam

IX. Grading: Envenomation

  1. Grade 1
    1. Pain and Paresthesias at localized site of sting
  2. Grade 2
    1. Pain and Paresthesias at remote site from bite (as well as meeting Grade 1 Criteria)
  3. Grade 3
    1. Meets criteria for Grade 2 sting AND
    2. ONE of the following neurologic criteria
      1. Cranial Nerve Involvement (e.g. Nystagmus, Dysarthria, Dysphagia, Drooling)
      2. Skeletal neuromuscular involvement (e.g. writhing, Fasciculations, jerking, Tetany)
      3. Autonomic signs (Salivation, Vomiting, bronchospasm, diaphoresis, Tachycardia)
  4. Grade 4
    1. All findings of Grade 3 Envenomation are present (Cranial Nerve AND skeletal neuromuscular)

X. Labs: Grade 3 and 4 Envenomations

XI. Course

  1. General
    1. In the U.S., no fatal Scorpion Stings have been reported since 1960s
    2. However worldwide, Scorpion Stings may still be lethal
      1. Tunisia sees 100 deaths/year due to Androctonus, Buthus and Leiurus Scorpion Stings
      2. Brazil sees 121 deaths/year (outnumbering fatal Snake Bites)
  2. Centruroides sculpturatus (U.S.)
    1. Infants <1 years: Fatal reactions are not uncommon
    2. Child <5 years: Potentially life threatening reactions
    3. Adults: Variable reactions but rarely fatal (elderly may be at higher risk)

XII. Management: General

  1. First aid and general measures
    1. Clean bite site with soap and water
    2. Ice or cool compress to wound site
    3. Elevation of affected part
    4. Tourniquets are not recommended for the affected, stung limb
    5. Avoid home remedies (e.g. Garlic)
  2. General Medical Approach
    1. Immediate medical attention for children
    2. Try to identify the Scorpion type that caused the bite
    3. Consult poison control
    4. Tetanus Vaccine as needed
  3. Symptomatic therapy
    1. Antihistamines
    2. Corticosteroids
    3. Consider Regoinal Anesthesia
    4. Analgesics
      1. NSAIDs
      2. Acetaminophen
      3. Opioids are often needed
        1. Avoid Morphine if antivenom planned (increases Histamine release with risk of Anaphylaxis)
        2. Fentanyl is preferred Opioid in Scorpion Stings
  4. Disposition
    1. Observe Grade 1 cases for at least 4 hours
    2. Observe Grade 2 cases at least 4 hours and until symptoms are controlled or improving
    3. Admit Grade 3 and 4 Envenomations to ICU (see below)

XIII. Management: Severe Envenomation (Grade 3 and 4 Envenomation)

  1. Consult poison control
  2. Admit to Intensive Care Unit
  3. Arizona Bark Scorpion (Centruroides sculpturatus) Equine Antivenom
    1. Indicated for Grade 3 or Grade 4 Envenomations, refractory to supportive care
    2. Typical dose 3 vials IV (at up to $5000 per vial)
    3. Reduces length of severity of symptoms (most effective if <4 hours from sting)
    4. Antivenom is a risk for Hypersensitivity including Serum Sickness and Anaphylaxis (uncommon)
  4. Observe closely
    1. ABC Management
      1. Respiratory depression
      2. Adequate ventilation
      3. Maintain Oxygen Saturation >92%
    2. CNS Hyperstimulation
    3. Seizures
    4. Severe Hypertension
      1. Consider Prazosin or vasodilator
    5. Manage Cardiogenic Shock (e.g. BiPaP, nitrates, Diuretics)
    6. ParenteralAnalgesics
    7. Parenteral Benzodiazepines for Muscle spasticity

XIV. Complications: Severe Envenomation

XV. References

  1. (2021) Presc Lett 28(7): 40
  2. Cowling and Ferreri (2019) Crit Dec Emerg Med 33(2): 17-25
  3. Cowling and Lowes (2024) Crit Dec Emerg Med 38(1): 4-13
  4. Herness (2022) Am Fam Physician 106(2): 137-47 [PubMed]

Images: Related links to external sites (from Bing)

Related Studies