Neurotoxic Snake Bite Management

1. Relevant Snake Species (Neurotoxic)

• Asia: Cobras (Naja spp.), Kraits (Bungarus spp.)
• Australia/New Guinea: Tiger snakes (Notechis), Brown snakes (Pseudonaja), Taipans (Oxyuranus), Death adders (Acanthophis)
• Americas: Coral snakes (Micrurus fulvius, M. tener)
• Africa: Mambas (Dendroaspis), African cobras

2. Pathophysiology of Neurotoxins

• Bradley & Daroff's Neurology in Clinical Practice, p. 2790
• Tintinalli's Emergency Medicine, p. 1402

3. Clinical Features

• Ptosis (often first sign)
• Ophthalmoplegia / diplopia
• Loss of facial expression
• Dysarthria, dysphonia
• Dysphagia (bulbar paralysis)
• Salivation, nausea, vomiting
• Fixed and constricted pupils
• Progressive respiratory muscle weakness
• Respiratory paralysis - the immediate cause of death

• Australian elapids: coagulopathy (prothrombin conversion), rhabdomyolysis
• Brown snake: rapid collapse, cardiac arrest, renal failure
• Cobras: local necrosis may be prominent
• Kraits: rhabdomyolysis possible
• "Spitting cobras": venom ophthalmia (corneal injury) if spit into eye - does NOT cause systemic envenomation

• Tintinalli's Emergency Medicine, p. 1402-1403

4. Pre-Hospital First Aid

• Pressure immobilization bandage (PIB): Wrap elastic bandage firmly over the bite site, then extend to cover the entire limb (similar pressure to a sprain bandage - firm, not tourniquet-tight)
• Splint the limb - immobilization is as important as bandaging; even walking hastens systemic absorption via lymphatics
• Do NOT use tourniquets
• For trunk bites: apply firm pressure without restricting breathing

• More nuanced - if spitting cobra (causes local tissue damage) or unidentified snake, PIB may worsen local necrosis
• Weigh risk of increased local damage vs. benefit of preventing neurotoxicity spread
• If likely snake does NOT include neurotoxic species: splint alone, omit pressure bandage
• If neurotoxic species suspected: PIB is appropriate
• Tintinalli's Emergency Medicine, p. 1403

5. Emergency Department Management

A. Initial Resuscitation

• Airway is the priority - monitor closely for signs of respiratory failure
• Serial pulmonary function testing: inspiratory pressure, vital capacity
• Have early plans for intubation and mechanical ventilation - prolonged ventilatory support may be required
• Establish IV access; isotonic fluids for hypotension; vasopressors if needed
• Maintain pressure bandage until antivenom is infusing, then remove to allow antivenom to reach envenomated area

B. Diagnostic Workup

• Baseline bloods: PT/INR, aPTT, d-dimer, fibrinogen, FDPs, CBC with platelets, BMP (electrolytes, creatinine), creatine kinase, myoglobin, urinalysis
• Repeat at 1 hour after first aid removal, then at 6 and 12 hours (earlier if deterioration occurs)
• Look for: coagulopathy, rhabdomyolysis, renal impairment, hyponatremia, hemolytic-uremic syndrome
• In Australia: Snake Venom Detection Kit (SVDK) on bite site or urine can identify venom immunotype to guide monovalent antivenom selection - but a positive result alone does NOT mandate antivenom (high dry bite rate)

C. Antivenom - The Definitive Treatment

• Give antivenom as early as possible - antivenom is most effective before toxin binds irreversibly
• Presynaptic toxins (e.g., beta-bungarotoxin) are poorly reversed once bound; postsynaptic toxins (alpha-neurotoxins) are variably reversible
• Indications: any neurological signs, coagulopathy, or significant systemic envenomation
• Pregnancy is not a contraindication

• Give 3-5 vials of anti-venin (M. fulvius) IV immediately in confirmed bites, even before symptoms appear - effects can develop hours later and may not be reversible once present
• Additional doses for progressive symptoms
• Sonoran coral snake (Micuroides euryxanthus): bites are mild, antivenom not usually needed

• Monovalent or polyvalent antivenom depending on species identification
• Give immediately when indicated; adequate doses to improve coagulation values and neurological signs

D. Antivenom Administration Precautions

• Pre-treat with H1 and H2 antihistamines
• Have epinephrine immediately available for anaphylaxis
• Monitor for serum sickness (fever, rash, arthralgias) 1-2 weeks later - treat with prednisone 1 mg/kg/day tapered over 1-2 weeks

E. Anticholinesterase Trial (Neostigmine)

• For postsynaptic neurotoxicity (alpha-neurotoxins): a trial of neostigmine (cholinesterase inhibitor) + atropine (to block muscarinic side effects) may partially reverse weakness
• Works on the same principle as myasthenia gravis treatment
• Not effective for presynaptic toxins (beta-bungarotoxins from kraits, taipan); may even transiently worsen symptoms in mixed-venom envenomation
• A recent 2025 study (PMID 41343543) examined protective effects of anticholinergic and anticholinesterase agents against Bungarus multicinctus venom

F. Supportive Care

• Mechanical ventilation for respiratory failure - may be required for days to weeks
• Wound care: clean, assess for tetanus, antibiotics only if signs of infection (prophylactic antibiotics not routinely indicated)
• Do NOT give steroids (not effective; potentially harmful) - reserve only for allergic reactions or serum sickness
• Monitor for compartment syndrome (rare with elapids, more common with vipers)

6. Disposition

• Coral snakebite: always admit for observation - symptoms can be delayed 12+ hours
• Monitor with serial neuro exams, pulmonary function parameters
• Discharge when symptoms resolve, patient ambulatory; arrange outpatient follow-up for serum sickness monitoring

7. Venom Ophthalmia (Spitting Cobras)

• Irrigate eye copiously with water or saline immediately
• Topical anesthetics for pain relief
• Check for corneal ulceration; treat as chemical burn
• Systemic envenomation does NOT occur via this route

Summary Algorithm

Neurotoxic snakebite suspected
    |
    v
First aid: PIB + immobilization (if neurotoxic elapid likely)
    |
    v
Transport to ED
    |
    v
Airway/respiratory assessment (most critical)
Serial neuro exam: ptosis, diplopia, bulbar function
Baseline labs (coag, CK, renal, FBC)
    |
    v
Any symptoms or confirmed bite (coral snake)?
    YES --> Antivenom immediately (species-appropriate)
    NO  --> Observe ≥8 hours
    |
    v
Respiratory failure? --> Intubate; prolonged ventilation
    |
    v
Postsynaptic toxin? --> Trial neostigmine + atropine
    |
    v
Monitor for coagulopathy, rhabdomyolysis, renal failure
Serum sickness follow-up at 1-2 weeks

• Tintinalli's Emergency Medicine: A Comprehensive Study, Chapter 212-213, pp. 1400-1404
• Bradley and Daroff's Neurology in Clinical Practice, pp. 2789-2790

Recent evidence note: A 2025 study (PMID 41343543, PLoS NTD) examined anticholinergic and anticholinesterase agents specifically against Bungarus multicinctus (krait) venom - highlights ongoing research into adjunct pharmacological management. Core management principles remain antivenom-centered.