Krait Snake Bite Management

The Snake - Key Facts

• Common krait (B. caeruleus, Chitti) - most common, found throughout India
• Banded krait (B. fasciatus, 1.5-2 m, jet black + yellow alternating bands)
• Black krait (B. niger) - North-East States, Sikkim, Bengal, Assam
• Sind krait (B. sindanus) - Rajasthan, Maharashtra, Bengal, UP, Bihar

Venom Composition and Mechanism

• Acts via pre-synaptic (beta-bungarotoxin) and post-synaptic (alpha-bungarotoxin) blockade at the neuromuscular junction
• Pre-synaptic toxin causes irreversible blockade - this is why krait envenomation responds poorly to neostigmine compared to cobra bites
• Unlike cobra venom (which produces convulsions AND paralysis), krait venom produces only muscular paralysis
• Key components: neurotoxin, phospholipase A (destroys phospholipids in nervous tissue), hyaluronidase (spreads venom), cholinesterase

Clinical Features

Local (Minimal)

• No significant local swelling - a key distinguishing feature from viper bites
• No burning pain at bite site (unlike cobra)
• Bite marks may be imperceptible - often discovered at night while sleeping
• Fang marks ~1.2 cm deep

Systemic (Neurotoxic - onset can be delayed 1-10 hours)

• Intense drowsiness and feeling of intoxication (more pronounced than cobra)
• Milder convulsions
• Progression of descending flaccid paralysis:
  1. Ptosis - earliest sign
  2. Ophthalmoplegia
  3. Paralysis of palate, jaw, tongue, larynx, neck
  4. Muscles of deglutition
  5. Chest muscles - respiratory paralysis (often terminal)
• Pupils remain reactive to light until terminal stages
• Deep tendon reflexes generally preserved until late
• Coma (variable onset)
• Albumin in urine
• Early warning symptoms: repeated vomiting, blurred vision, paraesthesiae around mouth, hyperacusis, headache, dizziness, vertigo, signs of autonomic hyperactivity

First Aid (Pre-Hospital)

1. Reassure the patient - fear and anxiety worsen prognosis
2. Immobilize the bitten limb - movement accelerates venom spread
3. Apply pressure-immobilization bandage - firm enough to occlude lymphatics but not venous drainage; one finger should fit between bandage and limb
4. Do NOT elevate the extremity (hastens systemic absorption)
5. Do NOT incise or suck the wound (venom absorbed almost instantly; causes bleeding and nerve injury)
6. Do NOT apply tourniquet (risk of avascular necrosis if left too long; for elapid/krait bites pressure bandage is preferred)
7. Do NOT cauterize (seals poison in tissues)
8. Do NOT apply cryotherapy
9. Do NOT give aspirin (bleeding risk)
10. Clean wound with soap and water or iodine; sterile dressing
11. Place patient in recovery position (lateral decubitus) to protect airway
12. Transport rapidly to hospital - do not waste time with first aid

Hospital Management

Assessment on Arrival

• If patient arrives 4-6 hours after bite with mild local swelling and no systemic symptoms - observe for 24 hours, monitor vital signs, cardiac system, and SpO2
• 20-minute whole blood clotting test (20WBCT): fresh venous blood in a clean dry glass tube, left undisturbed 20 minutes, gently tilted - if liquid, indicates viper bite (not applicable to krait, but useful to rule out concomitant viper envenomation)

Antivenom - Polyvalent Antisnake Venom (PAV)

• 0.45 mg dried common krait (B. caeruleus) venom
• 0.60 mg Indian cobra (Naja naja) venom
• 0.60 mg Russell's viper venom
• 0.45 mg saw-scaled viper venom

• Neurotoxicity, coma, hypotension, shock
• Bleeding/DIC, acute renal failure, rhabdomyolysis, ECG changes
• Local swelling involving >half the bitten limb within a few hours (without tourniquet)
• Rapid progression of local lesions within 30-60 minutes

• Do NOT give a test dose - poor predictor of anaphylaxis and may pre-sensitize the patient
• Lyophilized powder reconstituted with 10 mL distilled water, then diluted in 500 mL normal saline, infused over 1 hour
• Potency retained for ~5 years; half-life ~90 hours

Children receive the same dose as adults (venom load is the same; body weight does not reduce venom quantity)

• For neurotoxic poisoning: give a second dose of 10 vials after 1 hour
• Best given within 4 hours of bite; less effective after 8 hours; doubtful value after 24 hours (but still give if signs of active envenomation)

Managing Anaphylaxis to PAV

1. Stop PAV infusion immediately
2. Give adrenaline 0.5 mg IM (1:1000) for adults; 0.01 mg/kg for children
3. Hydrocortisone + antihistamine for longer-term protection
4. If no improvement after 10-15 min, give second dose of adrenaline
5. Once condition improves, restart antivenom infusion

Neostigmine-Atropine (Anticholinesterase) Test

• Atropine 0.6 mg IV (pediatric: 0.05 mg/kg) - given FIRST to block muscarinic side effects
• Then Neostigmine 1.5 mg IM (pediatric: 0.04 mg/kg)
• Repeated twice at 10-minute intervals
• If improvement: continue neostigmine 0.5 mg SC/IM every 30 minutes with 0.5 mg atropine before each injection

Important: A positive response (improvement of ptosis, breathing) indicates primarily post-synaptic blockade (cobra-type). Krait venom is predominantly pre-synaptic, so response to neostigmine is often absent or poor in pure krait envenomation.

Respiratory Support

• Mechanical ventilation is the most critical intervention for krait bite
• Respiratory failure from paralysis of respiratory muscles is the primary cause of death
• Endotracheal intubation and ventilatory support should be started before complete respiratory failure
• Monitor: SpO2, respiratory rate, ability to lift head (sag test)

Other Measures

Special Consideration: Delayed Presentation of Krait Bite

• Occurring at night while sleeping (nocturnal snake)
• Bite being painless - patient may not realize they were bitten
• Delayed onset of neurotoxicity (1-10 hours)
• Patient presenting with just drowsiness - often misdiagnosed as alcohol intoxication

Differences: Cobra vs Krait Envenomation

Recent Evidence

• A 2024 systematic review and meta-analysis (PMID: 38153416) confirmed that Indian polyvalent antivenom effectively neutralizes B. caeruleus venom, but noted heterogeneity in venom toxicity across regions and variation in antivenom neutralization potency - underscoring the need for region-specific antivenom development.
• A 2025 comprehensive review of kraits in the Indian subcontinent (PMID: 40374096) identified critical knowledge gaps in snakebite management among healthcare workers, highlighted the problem of dry bites from kraits (up to ~50% of bites), and emphasized the need for affordable, accessible treatment options. (Note: an erratum was published for this paper - PMID: 40897152.)