SNAKE BITES

Snakebites can cause local effects (swelling, redness, laceration) and in case of poisonous snakes, local and systemic effects caused by envenomation. More than 50% of bites are “dry” i.e. no envenomation occurs, and most bites are from non-venomous snakes.

In the event that poison is injected, the effect depends on the type of venom, quantity, location of the bite and size and general condition of the victim.

Cause

  • Common poisonous snakes in Uganda: puff adder, Gabon viper, black and green mambas, boomslang and several cobras

Clinical features

  • Puncture wounds, pain, swelling, discoloration
If cytotoxic venom
  • Extensive local damage with swelling, pain, regional lymphadenopathy – starting 10-30 minutes after the bite
If neurotoxic venom (e.g. green and black mamba)
  • Weakness and paralysis of skeletal and respiratory muscles (drooping eyelids, difficulty in swallowing, double vision, slurred speech, difficulty in breathing) – starting 15-30 minutes after the bite
  • Excessive sweating and salivation
If hemotoxic venom
  • Bleeding, oozing from the site, bloody blisters
  • Haematuria, haematemesis – even after some days

Investigations

  • Whole blood clotting test at arrival and every 4-6 hours for the first day: put 2-5 ml of blood in a dry tube and observe after 30 minutes: if incomplete or no clotting, it indicates coagulation abnormalities

Management

  • Wash site with a lot of clean water
  • Wipe away excess venom
  • Assess skin for fang penetration
  • If there is a wound, clean it with a lot of clean water
If signs of fang penetration
  • Apply firm crepe bandage to entire limb to ensure constant pressure (except if cytotoxic)
  • Immobilise limb with a splint
  • Analgesic e.g. paracetamol (avoid aspirin)
  • If no signs and symptoms for 6-8 hours: most likely bite without envenomation
  • Observation for 12-24 hours recommended
  • Tetanus toxoid (TT) IM 0.5 ml if not previously immunised in the last 10 years
If local necrosis develops
  • Remove blisters, clean and dress daily, debride after lesions stabilise (minimum 15 days)
Venom in eyes
  • Irrigate eyes with plenty of water
  • Cover with eye pads
Criteria for referral for administration of antivenom
  • Signs of systemic poisoning (paralysis, respiratory difficulty, bleeding)
  • Spreading local damage:
    • Swelling of hand or foot (site of most bites) within 1 hour of bite
    • Swelling of elbow or knee within 3 hours of bite
    • Swelling of groin or chest at any time
    • Significant swelling of head or neck
  • Antivenom sera polyvalent (E & C Africa)
    • Check package insert for IV dosage details.Ensure the solution is clear and check that patient has no history of allergy
Antibiotics
  • Indicated only if wound is infected

Caution

  • Do not apply a tourniquet
  • Do not squeeze or incise the wound
  • Do not attempt to suck the venom out