Snake bites

Two major classes of venomous snakes

Bite Symptoms

N.b. Fear may mimic systemic poisoning
Early Local: pain, and bleeding, swelling and tender lymph nodes
- this lets you know venom HAS been injected, LN puts you on guard
- Viper >> elapids
Early systemic: nausea, vomiting, collapse
- Vipers:
  - Bleeding (from gums), swelling, coagulopathy (activation-> consumption coagulopathy)
  - Swelling and ecchymosis tracking up lymphatics (foot bite can extend all the way up legs)
  - Coagulopathy
    - Early test: 20 Minute Whole Blood Clotting Test- take clean glass tube, leave for 20 minutes, look for clotting
    - Usual cause of death: intracranial hemorrhage
  - Hypotension: fluid shifts, haemorrhage, kinins, cardiotoxicity
- Elapids: neurotoxic
  - Pre-(e.g. taipan) and post-synaptic (e.g. Phillipine cobra), some have both
  - Initial ptosis then ophthalmoplegia
  - Bulbar weakness (pooling of secretions is cardinal sign)
  - Progressive weakness->respiratory failure due to diaphragmatic paralysis
  - N.b. Consciousness is NOT impaired

Diagnosis: dead snake can be useful, be suspicious based on history or physical, look for bite site + lymphadenopathy

Management: antivenom in systemic or severe local envenoming

Neurotoxic, shock, coagulopathy, renal failure, ?extensive blistering/swelling/bruising (up more than half the bitten limb- past elbow or knee)

Antivenom basics: envenom a horse, process serum somehow -> you’ve got antivenom!

Processing = safety = increased cost
Monospecific or mixed monospecific
Has to be appropriate to local snakes
Give slowly (20-30 minutes), have epinephrine on standby for allergic reaction (0.5-80% rates)
- Consider epi for prophylaxis (0.25mL epi 1:1000 SC) if staff limited or high reaction rates
Dose is same for adult as for child (based on venom dose, not weight-based)
Monitoring response
- Reversal of coagulopathy (may recur as some venoms are persistent)
- Monitoring of neurotoxicity
  - Good response for post-synaptic venom
  - Poor response for pre-synaptic venom (Death adder, Philippine cobra)
Availability crisis in Africa, importing of inappropriate antivenoms

Other supportive measures

Airway
Volume for hypotension
Tetanus (not routine antibiotics)
FFP can be used ONLY after antivenom if bleeding is still life threatening
Anticholinesterases: useful in some neurotoxic envenoming
- Increase acetylcholine at receptor endplate -> can overcome post-synaptic envenoming
- Edrophonium (Tensilon) as trial -> assess response w upward gaze and expiratory pressure
  - If good response, mainatin with loger acting drugs (neostigmine, pyridostigmine + atropine)

Complications

Compartment syndrome- Fasciotomy usually not indicated as true compartment syndrome is rare
Renal failure
- Direct nephrotoxic, hypotension, myoglobulin
- Can support with a few days of peritoneal dialysis

Training

Spitting Snakes

First Aid

Don’t Cowboy (cut and suck)
Cutting, suction, black stone, electric shock don’t work
Use of tourniquets can prevent lymphatic flow, hard to use, not generally recommended
Pressure immobilization
- Compression of lymphatics by crepe bandage (not arterial flow) and splinting of bitten limb
- Some anectodal evidence of effect
- May be harmful if necrotic venom -> potential concentration of venom at site

Prevention