Scorpion Sting

Epidemiology

  • Incidence: >1 million scorpion stings occur worldwide annually
    • Most Cases are Minor with Only Localized Pain and Minimal Systemic Involvement
    • Only 10% of Scorpion Stings Result in Severe Systemic Envenomation
  • Age: most severe envenomation cases occur in children

Taxonomy

  • Buthidae Family: scorpions from this family account for most clinically serious scorpion stings
    • Genus Centruroides: North America/Central America
    • Genus Tityus: South America
    • Genus Leiurus: near East/Middle East
    • Genus Androctonus or Buthus: North Africa
    • Genus Mesobuthus: Asia (especially India)
    • Genus Parabuthus: South Africa
  • Liochlidae Family
    • Hemiscorpius Lepturus: endemic in areas of Iran

Physiology

Stinger Apparatus

  • Scorpions Have a Venom Gland-Containing Stinger (Telson) in Their Tail (Terminal Segment)

Scorpion Venom

  • General Comments: contains small peptide toxins which target ion channels in mammals and insects
  • α-Toxins: bind to mammalian voltage-gated sodium channel -> inhibits inactivation of the channel, resulting in prolonged depolarization and neuronal excitaton
    • Sympathetic Excitation: contributes to complications such as myocardial infarction, pulmonary edema, and cardiogenic shock
    • Parasympathetic Excitation: usually occur soon after the sting, are generally less severe, but may contribute to respiratory impairment
    • Induction of Massive Endogenous Catecholamine Release (Epinephrine, Norepinephrine): contributes to complications such as myocardial infarction, pulmonary edema, and cardiogenic shock
      • Catecholamine-Induced Myocarditis and Myocardial Ischemia: may complicate severe androctonus/buthus/mesobuthus/tityus envenomations
      • Myocardial Ischemia (Due to Coronary Vasoconstriction)
    • Induction of Release of Vasoactive Peptide Hormones (Neuropeptide Y, Endothelin)
    • Possible Direct Effect of the Toxin on the Myocardium: which contributes to cardiac dysfunction
  • Other Toxins: act on potassium and calcium channels
    • These toxins appear to be less importan tin human envenomations

Physiologic Effects

Time Course of Cardiovascular Effects

  • Initial Increase in Cardiac Output and Blood Pressure, Followed by Decreased Left Ventricular Function and Hypotension

Parasympathetic/Cholinergic Effects (see Cholinergic Intoxication, [[Cholinergic Intoxication]])

  • General Comments: tend to occur early
  • Bronchorrhea (see Bronchorrhea, [[Bronchorrhea]])
  • Bronchospasm (see Obstructive Lung Disease, [[Obstructive Lung Disease]])
  • Diaphoresis (see xxxx, [[xxxx]])
  • Diarrhea (see xxxx, [[xxxx]])
  • Hypersalivation (see xxxx, [[xxxx]])
  • Hypotension (see xxxx, [[xxxx]])
  • Lacrimation (see xxxx, [[xxxx]])
  • Miosis (see xxxx, [[xxxx]])
  • Priapism (see xxxx, [[xxxx]])
  • Sinus Bradycardia (see Sinus Bradycardia, [[Sinus Bradycardia]])
  • Vomiting (see xxxx, [[xxxx]])

Sympathetic Effects

  • General Comments: tend to persist because of the release of catecholamines
  • Agitation
  • Hyperglycemia
  • Hypertension
  • Hyperthermia
  • Mydriasis
  • Restlessness
  • Tachycardia

Neuromuscular Excitation (Characteristic of Centruroides Envenomations)

  • General Comments: due to direct effects of toxin on neuronal sodium channels in somatic and cranial nervous system
    • Central nervous system effects are uncommon, as the toxins cannot cross the blood-brain barrier
  • Muscle Spasms
  • Oculomotor Abnormalities
  • Paralysis
  • Uncoordinated Neuromuscular Activity
  • Visual Disturbances

Clinical Manifestations-Centruroides Exilicauda (Sculpuratus) Envenomation

General Comments

  • Epidemiology: adults are more commonly envenomated, but children are more likely to develop severe illness
  • Centruroides Suffusus Envenomation is Clinically Similar
  • Onset of Symptoms: symptoms begin immediately and progress to maximum severity within 5 hrs
    • Infants can reach peak severity of symptoms within 15-30 min
  • Duration of Symptoms: variable (based on age of victim and grade of envenomation)
    • Grade III/IV Envenomations: symptoms usually abate within 9-30 hrs without antivenom therapy (although pain/parasthesias may persist for up to 2 wks)
  • Presence of Intact Mental Status: this finding may be useful to rule out other intoxications where delirium is common (such as methamphetamine intoxication, phencyclidine intoxication, etc)

Grade I Envenomation

  • Local Pain/Parasthesias at Sting Site with No Local Inflammation (see Parasthesias, [[Parasthesias]])
    • Puncture Site is Usually Too Small to Be Seen
    • Angioedema (see Angioedema, [[Angioedema]]): may occur in some cases
    • Tap Test: gently tap the site (with patient looking away) -> this greatly exacerbates the pain (this is unique to envenomation by this scorpion species)

Grade II Envenomation

  • Local Pain/Parasthesias at Sting Site see Parasthesias, [[Parasthesias]])
    • Angioedema (see Angioedema, [[Angioedema]]): may occur in some cases
  • Remote Pain/Parasthesias (see Parasthesias, [[Parasthesias]])
    • May radiate proximally up the affected limb
    • May occur at more remote body sites or as generalized parasthesias
  • Unexplained Agitation/Crying: may occur in children
  • Hypertension (see Hypertension, [[Hypertension]]): common and occurs early in course

Grade III Envenomation

Either of the Following Neurologic Manifestations

  • Cranial Nerve Dysfunction
    • Abnormal Eye Movements: involuntary, conjugate, slow, roving
      • Chaotic, multi-directional conjugate saccades (resembling opsoclonus and unsustained primary positional nystagmus) may be seen in some cases
      • Patient may prefer to keep their eyes closed
    • Dysarthria (see Dysarthria, [[Dysarthria]])
    • Hypersalivation (see Hypersalivation, [[Hypersalivation]])
    • Tongue Fasciculations (see Fasciculations, [[Fasciculations]])
    • Blurred Vision (see Blurred Vision, [[Blurred Vision]])
  • Somatic Skeletal Neuromuscular Dysfunction
    • Agitation/Akathisia (Motor Restlessness) (see Akathisia, [[Akathisia]])
    • Emprosthotonos: tetanic forward flexion of the body (may be mistaken for seizures, although these movements are more undulating/writhing than seizure activity and patient remains alert)
    • Fasciculations (see Fasciculations, [[Fasciculations]])
    • Jerking of Extremities
    • Opisthotonos: arching of the back (may be mistaken for seizures, although these movements are more undulating/writhing than seizure activity and patient remains alert)
    • Shaking of Extremities (may be mistaken for seizures, although these movements are more undulating/writhing than seizure activity and patient remains alert)
  • Hypertension (see Hypertension, [[Hypertension]]): common and occurs early in course

Grade IV Envenomation

Both of the Following Neurologic Manifestations

  • Cranial Nerve Dysfunction
    • Abnormal Eye Movements: involuntary, conjugate, slow, roving
      • Chaotic, multi-directional conjugate saccades (resembling opsoclonus and unsustained primary positional nystagmus) may be seen in some cases
      • Patient may prefer to keep their eyes closed
    • Dysarthria (see Dysarthria, [[Dysarthria]])
    • Hypersalivation (see Hypersalivation, [[Hypersalivation]])
    • Tongue Fasciculations (see Fasciculations, [[Fasciculations]])
    • Blurred Vision (see Blurred Vision, [[Blurred Vision]])
  • Somatic Skeletal Neuromuscular Dysfunction
    • Agitation/Akathisia (Motor Restlessness) (see Akathisia, [[Akathisia]])
    • Emprosthotonos: tetanic forward flexion of the body (may be mistaken for seizures, although these movements are more undulating/writhing than seizure activity and patient remains alert)
    • Fasciculations (see Fasciculations, [[Fasciculations]])
    • Jerking of Extremities
    • Opisthotonos (see Opisthotonos, [[Opisthotonos]]): arching of the back (may be mistaken for seizures, although these movements are more undulating/writhing than seizure activity and patient remains alert)
    • Shaking of Extremities (may be mistaken for seizures, although these movements are more undulating/writhing than seizure activity and patient remains alert)

Cardiovascular Manifestations

  • Conduction Abnormalities: occur in 33-50% of severe envenomation cases (likely related to autonomic effects of toxins, with vagal effects or sympathetic stimulation)
    • Atrial Tachycardia
    • Bundle Branch Blocks: less common
    • ST Changes
    • T-Wave Inversion
    • Ventricular Extra Systoles
  • Hypotension (see Hypotension, [[Hypotension]])

Gastrointestinal Manifestations

  • Abdominal Pain (see Abdominal Pain, [[Abdominal Pain]]): common (due to cholinergic stimulation)
  • Acute Pancreatitis (see Acute Pancreatitis, [[Acute Pancreatitis]]): rarely occurs with Centruroides envenomation (in contrast to Tityus and Leiurus Quinquestriatus scorpion envenomations) and is typically transient
  • Diarrhea (see Diarrhea, [[Diarrhea]]): common (due to cholinergic stimulation)
  • Nausea/Vomiting (see Nausea and Vomiting, [[Nausea and Vomiting]]): common (due to cholinergic stimulation)

Pulmonary Manifestations

  • Acute Respiratory Failure (see Respiratory Failure, [[Respiratory Failure]])
    • Mechanisms: bronchospasm, increased bronchial secretions, and uncoordinated respiratory muscle activity
  • Pulmonary Edema (see Acute Lung Injury-ARDS, [[Acute Lung Injury-ARDS]])
  • Stridor (see Stridor, [[Stridor]])
  • Wheezing (see Obstructive Lung Disease, [[Obstructive Lung Disease]])

Other Manifestations


Clinical Manifestations-Centruroides Vittatus Envenomation

General Comments

  • Generally Less Severe Than Centruroides Exilicauda (Sculpuratus) and Centruroides Suffusus Envenomations

Neurologic Manifestations

  • Local Pain/Parasthesias at Sting Site (see Parasthesias, [[Parasthesias]])
  • Systemic Neurologic Manifestations: occur in 20% of cases

Other Manifestations

  • Local Bleeding at Sting Site
  • Local Erythema/Edema/Pruritus/Urticaria at Sting Site

Clinical Manifestations-Hemiscorpius Lepturus (Liochlidae Family) Envenomation

General Comments

  • Produces a Cytotoxic Syndrome: similar to that from Loxosceles (recluse) spider bite

Dermatologic Manifestations

  • Absence of Immediate Severe Pain at Sting Site
  • Erythema/Purpuric/Bullous Lesions at Sting Site: generally resolve
    • However, in 20% of cases, delayed necrosis occurs over a period of hours-days

Gastrointestinal Manifestations

Hematologic Manifestations

Renal Manifestations

Other Manifestations

  • Fever/Hyperthermia (see Fever, [[Fever]])
  • Minor Autonomic Effects

Treatment According to Clinical Grade/Class [MEDLINE]

Grade 1

  • Local Effects Only
    • Ibuprofen (see Ibuprofen, [[Ibuprofen]]): analgesic, anti-inflammatory and anti-pyretic
    • Acetaminophen (see Acetaminophen, [[Acetaminophen]]): analgesic, anti-inflammatory and anti-pyretic
    • Local Anesthesia: may be required for severe pain that is unresponsive to analgesics

Grade 2

  • Autonomic Excitation
    • Centruroides Antivenom: binds toxins and prevents them from reaching target site; increases rate of toxin elimination
    • Prazosin (see Prazosin, [[Prazosin]]): decreases systemic vascular resistance without affecting cardiac output or
      heart rate (or contributing to elevation of catecholamine levels)
  • Agitation/Anxiety

Grade 3

  • Pulmonary Edema
    • Centruroides Antivenom: binds toxins and prevents them from reaching target site; increases rate of toxin elimination
    • Prazosin (see Prazosin, [[Prazosin]]): decreases systemic vascular resistance without affecting cardiac output or heart rate (or contributing to elevation of catecholamine levels)
      • Dose: 0.5 mg PO q3hrs
      • Other vasodilators (hydralazine/captopril/nifedipine/nitroprusside/clonidine) have potential adverse effects (sympathetic stimulation, reflex tachycardia) and should be avoided
    • Intravenous Nitroglycerin (see Nitroglycerin, [[Nitroglycerin]]): decreases preload and afterload via arteriolar dilation and venodilation
    • ICU Admission
    • Non-Invasive/Invasive Mechanical Ventilation: as required
  • Hypotension/Cardiogenic Shock
    • Centruroides Antivenom: binds toxins and prevents them from reaching target site; increases rate of toxin elimination
      • However, the role of antivenom is less supported when severe systemic envenomation is well-established
    • Dobutamine (see Dobutamine, [[Dobutamine]]): positive inotrope
  • Severe Neuromuscular Excitation: associated with Centruroides envenomation
    • Centruroides Antivenom: binds toxins and prevents them from reaching target site; increases rate of toxin elimination
    • Intravenous Benzodiazepines (see Benzodiazepines, [[Benzodiazepines]])
  • Bradycardia
    • Atropine (see Atropine, [[Atropine]]): acts as muscarinic receptor blocker to decrease the cholinergic effects (bradycardia, early hypotension, and excessive sweating or salivation; however, iy can potentiate sympathetic effects, including hypertension)

Grade 4

  • Multi-Organ Failure (Coma/Seizures/End-Organ Damage Due to Hypotension)
    • Dobutamine (see Dobutamine, [[Dobutamine]]): positive inotrope
    • Intravenous Benzodiazepines (see Benzodiazepines, [[Benzodiazepines]])
    • Non-Invasive/Invasive Mechanical Ventilation: as required
    • Other Supportive Care

References

  • Scorpion envenomation. N Engl J Med 2014;371:457-463 [MEDLINE]