Scorpion Stings

Pathophysiology & Venom Dynamics

Venom Components and Ion Channel Effects

• Neurotoxic peptides: The most dangerous part of scorpion venom (mainly from the family Buthidae, such as Centruroides and Androctonus). The black scorpion Heterometrus, common in Vietnam, belongs to the family Scorpionidae (not Buthidae) and has much weaker venom.
  • Sodium channel effects (alpha and beta toxins): They slow the inactivation of voltage-gated sodium channels (VGSCs), causing prolonged depolarization of nerve cell membranes.
  • Potassium channel effects: They block potassium channels and prevent repolarization, so sensory and autonomic nerve fibers fire continuously and uncontrollably.
• Enzymes and chemical mediators: Hyaluronidase (which helps venom spread through tissue very quickly), phospholipase A2, histamine, serotonin, and bradykinin irritate local pain receptors and make blood vessels leakier.

Autonomic Storm

Continuous stimulation of the sympathetic and parasympathetic nervous systems floods the blood with catecholamines (epinephrine, norepinephrine) and acetylcholine, leading to:

• Sympathetic overdrive: Sudden high blood pressure, rapid heart rate, peripheral vasoconstriction, heavy sweating, high blood sugar, and myocardial strain causing acute pulmonary edema.
• Parasympathetic overdrive: Excess salivation, tearing, bronchospasm, slow heart rate, vomiting, and secondary low blood pressure.

Clinical Features by Severity Grade

Grade 1 (Local Skin Involvement Only):

• Severe local pain: Intense burning pain right after the sting, far worse than what the visible wound would suggest.
• Minimal skin findings: The stung area is only slightly red or not red at all, with little swelling (except with Hemiscorpius lepturus, which causes skin necrosis).
• Positive tap test: Lightly tapping the sting site with a finger triggers a sharp, jolting pain like an electric shock.

Grade 2 (Spread Along Peripheral Nerves): Pain and abnormal sensations (numbness, crawling, burning) spread through the whole stung limb or along the course of a nerve.

Grade 3 (Neuromuscular or Autonomic Dysfunction):

• Neuromuscular signs: Scattered muscle twitching, facial twitching, roving eye movements (nystagmus), difficulty swallowing, and slurred speech.
• Autonomic signs: Drooling, profuse sweating, high blood pressure, and painful persistent erection (priapism) in males.

Grade 4 (Multi-Organ Failure and Systemic Catecholamine Storm): Acute pulmonary edema (coughing up pink froth, gasping), acute heart failure, toxic shock, severe arrhythmias, generalized seizures, and delirium.

Emergency Care and Initial Management at Haute-Derma

Step 1: Reception and Essential First Aid

• Clean the wound: Wash gently with chlorhexidine or povidone-iodine antiseptic.
• Immobilize the limb: Splint the stung limb below heart level to slow the spread of venom through the blood and lymph.
• Cold therapy: Apply an ice pack for 15–20 minutes every hour. Cold constricts small vessels, slows venom absorption, and dampens pain signals.
• Important warning: Never apply a tight tourniquet, cut the wound, squeeze it, or try to suck out the venom.

Step 2: Assess and Grade Systemic Symptoms

• We screen for signs of central nervous system toxicity and autonomic dysfunction (drooling, muscle twitching, rapid heart rate, shortness of breath). Patients with grade 3–4 symptoms must be transferred immediately to intensive care (ICU).

Medical Treatment and Recovery Management at Haute-Derma

Stopping Severe Pain and Reducing Inflammation

• Local nerve block: Infiltration around the sting or a block of the supplying nerve with lidocaine 1% (without epinephrine) or bupivacaine 0.25%. This is the most effective way to stop the severe pain of a scorpion sting.
• Oral or injected systemic pain relief: Acetaminophen (paracetamol) combined with an NSAID (ibuprofen 400 mg or ketorolac). Avoid morphine and other opioids if there is respiratory depression or autonomic dysfunction.
• Antihistamines and corticosteroids: A medium-potency corticosteroid cream (hydrocortisone butyrate) and an oral H1 antihistamine (levocetirizine 5 mg/day) help reduce abnormal sensations and post-inflammatory itching and burning.

Specific Therapy and Control of Catecholamine Storm (in an Emergency Facility)

• Scorpion antivenom: Indicated for grade 3 and 4 envenomation. It neutralizes circulating venom and rapidly reverses neurological symptoms.
• Autonomic control: Prazosin (an α1-adrenergic blocker) is used to counter vasoconstriction, lower blood pressure, and prevent acute pulmonary edema from the catecholamine storm.

Recovery and Skin Care After a Sting

• Tetanus prevention: Tetanus vaccine or tetanus antitoxin (TAT) prophylaxis is mandatory.
• Preventing hyperpigmentation and restoring sensation: A moisturizer with ceramides and niacinamide, plus oral vitamin B complex (B1, B6, B12), supports repair of the myelin sheath of small nerve fibers and reduces the lingering numbness and abnormal sensations after a scorpion sting.