bleeding from recent wounds (including fang marks, venepunctures etc) and from old partly-healed wounds
spontaneous systemic bleeding - from gums, epistaxis, bleeding into the tears, haemoptysis, haematemesis, rectal bleeding or melaena, haematuria, vaginal bleeding, bleeding into the skin (petechiae, purpura, ecchymoses) and mucosae (eg conjunctivae), intracranial haemorrhage..
General symtoms (3)
Neurological (Elapidae, Russell’s viper): Drowsiness, paraesthesiae, abnormalities of taste and smell, “heavy” eyelids, ptosis, external ophthalmoplegia, paralysis of facial muscles and other muscles innervated by the cranial nerves, aphonia, difficulty in swallowing secretions, respiratory and generalised flaccid paralysis
Pressure immobilisation is recommended for bites by neurotoxic elapid snakes, including sea snakes but should not be used for viper bites because of the danger of increasing the local effects of the necrotic venom.
20WBCT
Few ml of fresh venous blood placed in a NEW, CLEAN, DRY, GLASS test tube
Left undisturbed for 20mn
Gently tilted to 45° and examined
If it has remained liquid: consumption coagulopathy ASV required
Clotted: ASV not necessary (at this stage)
Criteria for giving ASV
ASV’s only role is to bneutralize unbound free flowing venom
Premedication with hydrocortsisone, anti-histamine or Sc adrenaline: only for the first dose, efficacy unproven
Treatment of adverse raction
Usually within 20mn from start of ASV
Drug of choice = Adrenaline, 0.5 mg IM, to be repeated if symptoms donot improve within 15mn
100 mg hydrocortisone + 25 mg Promethazine IM / 10 mg chlorphenimarine IV
Types of ASV available
Liquid ASV (NIH)
Lyophilized (imported from India)
Liquid ASV requires no reconstitution but pb of cold chain
Lyophylized ASV no refrigeration needed but 1h required for reconstitution with distilled water
Dose of ASV (1)
Depending on the amount of venom injected by the snake
Cobra and Russel’s viper 60mg
Krait inject less venom but neurological symptoms similar to Cobra
Each ASV vial neutralizes 6mg of Cobra and Russel’s viper venom
Initial dose 8-10 vials (NIH/indian ASV same neutalzing capacity)
Dose of ASV (2)
Saw scaled viper (Echis carnatus, smaller, found in India) bite around 15 mg of venom
Larger saw scaled viper (Echis sochureki) found in Pakistan: no studies
Indian ASV made with Echis carinatus venom only (15 vials required to restore coagulation on average)
Local experience in Sindh: higher requirements (25+ vials)
? Efficacy of Indian ASV on Echis sochureki
NIH ASV produced with SSV from Sindh
NIH ASV guideline
In all cases other than confirmed SSV bite, use 8-10 vials
If confirmed SSV
give 4 vials if 20WBCT un coagulable
monitor coagulation and repeat ASV 6 hourly
Check series of patient
if 50-60% restore their coagulation, 4 vials is the correct starting dose
If 10-20% restore their coagulation after 6 hours increase the starting dose to all patients by one vial and monitor
Administration
Over 1 hour maximum
IV injection or continuous infusion
SC, IM, around bite site : no
Repeat doses
ASV should be given as late as blood is demonstrated incoagulable on 20WBCT performed 6 hourly (time required by the liver to restore clotting factors)
Neurotoxic:atient reviewed 1 hour after initial dose:
if worsening, give 2nd dose of ASV
if not worsened, review again after 2 hours, if not improved, give 2nd dose of ASV
After 2 doses, ASV should be stopped, nor role for very large dose in neurotoxic bites
Neostigmine
Cobra venom is a post synaptic neurotoxin and blocks the nicotinic receptor causing acetylcholine to be unable to bind
Neostigmine prolongs the life of acetylcholine by inhibiting cholinesterase, increasing the likelywood of acetylcholine binding with unblocked receptor
Baseline test: single breath count, time upward gaze
Neurotoxic envinemation requiring longer term mechnaical ventilation
Surgical cases requiring debridement of necrotic tissue
Transport
Viperine envenimation: give ASV then 6 hours before the next dose provides time to transport the patient
Neurotoxic: need for mechanical ventilatory support ? Inability to perform neck lift suggests imminent respiratory failure
Transportation of the patient: NPA + bag mask ventilation
Prevention (1)
Education ! Know your local snakes, know the sort of places where they like to live and hide, know at what times of year, at what times of day/night or in what kinds of weather they are most likely to be active.
Try to wear proper shoes or boots and long trousers, especially when walking in the dark or in undergrowth.
Prevention (2)
Use a light (torch, flashlight or lamp) when walking at night.
Avoid snakes as far as possible, including snakes performing for snake charmers. Never handle, threaten or attack a snake and never intentionally trap or corner a snake in an enclosed space.
If at all possible, try to avoid sleeping on the ground.
Keep young children away from areas known to be snake-infested.
Avoid or take great care handling dead snakes, or snakes that appear to be dead.
Prevention (3)
Avoid having rubble, rubbish, termite mounds or domestic animals close to human dwellings, as all of these attract snakes.
Frequently check houses for snakes and, if possible, avoid types of house construction that will provide snakes with hiding places (eg thatched rooves with open eaves, mud and straw walls with large cracks and cavities, large unsealed spaces beneath floorboards).
To prevent sea snake bites, fishermen should avoid touching sea snakes caught in nets and on lines. The head and tail are not easily distinguishable. There is a risk of bites to bathers and those washing clothes in muddy water of estuaries, river mouths and some coastlines.
