Snakebites

T63.0 + (X20.99/W59.99)

DESCRIPTION

Of all the snake species found in South Africa, about 12% are considered to be potentially dangerous to humans. However, all snakebites should be considered dangerous until proven otherwise. In the majority of snakebite incidents, the offending snake is not identified.

South African poisonous snakes can be broadly divided into 3 groups according to the action of their venom although there is significant overlap of toxic effects in some snake venoms.

Cytotoxic venoms

  • Venom causes local tissue damage and destruction around the area of bite, including swelling, discolouration of the skin and blister formation.
  • Bite is painful and symptoms usually start within 10–30 minutes after the bite.
  • Examples include: Puff adder, Gaboon adder, Mozambique spitting cobras, other smaller adders and spitting cobra, stiletto snake, Rinkhals (cytotoxic as well as neurotoxic).

Neurotoxic venoms

  • Neurotoxic venom causes weakness, ptosis, drooling and dysphagia, pins and needles, sweating, blurred vision, hypotension and respiratory difficulty and paralysis of skeletal muscles and respiratory failure.
  • Bite is not as painful as cytotoxic venom bites.
  • Symptoms usually start in 15–30 minutes.
  • Examples include: Black and green mamba, non-spitting cobras (Cape, forest, snouted), Berg adder (neurotoxic as well as cytotoxic), Rinkhals (cytotoxic as well as neurotoxic)

Haemotoxic venoms

  • Venom affects the clotting of blood causing bleeding tendency that may present within hours or up to a few days after the bite.
    • Boomslang
    • Vine snake

Symptoms and signs of snakebite envenomation include:

Local

  • Fang marks with or without pain.
  • Swelling around the bite, which may be severe with discolouration of skin and/or blister formation.
  • Bleeding or oozing from bite site.

Note: the absence of fang marks does not exclude envenomation.

Systemic:

  • Nausea, vomiting.
  • Sweating, hypersalivation and hypotension.
  • Pins and needles.
  • Skeletal muscle weakness (descending paralysis), which may cause:
    • drooping eyelids
    • difficulty in swallowing
    • double vision
    • difficulty in breathing
  • Shock.
  • Rarely bleeding(epistaxis, haematuria, haematemesis or haemoptysis).

CAUTION
Do not apply a tourniquet.
Do not apply a restrictive bandage to the head, neck or trunk.
Do not squeeze or incise the wound.
Do not attempt to suck the venom out.


GENERAL MEASURES

Emergency treatment

  • Remove clothing from site of the bite and rings if an extremity bite.
  • Clean the wound thoroughly with chlorhexidine 0.05%, aqueous solution.
  • Be prepared to support ventilation in neurotoxic bites as this can be life-saving.
  • To prevent spread to vital organs, immediately apply a wide crepe bandage firmly from just above the bite site up to 10–15 cm proximal to the bite site. Apply no tighter than for a sprained ankle.
  • Immobilise the affected limb with a splint or sling.
  • Obtain an accurate history e.g. time of the bite, type of snake.
  • If the snake is unidentified, observe for 6–24 hours with repeated examinations.
  • Absence of symptoms and signs for 6–8 hours usually indicates a harmless bite.
  • For neurotoxic bites only:
    • As this may be life-saving, support ventilation as required.
    • To prevent spread to vital organs: immediately apply a wide crepe bandage firmly from distal to the bite site up to 10–15 cm proximal to the bite site. Apply no tighter than for a sprained ankle.

MEDICINE TREATMENT

Venom in the eyes: S05.9 + (X20.99)

Irrigate the eye thoroughly for 15–20 minutes with water or sodium chloride, 0.9%.

  • Tetracaine 1%, drops (if available), instil 1 drop into the affected eye(s) before irrigation.

LoEIII

Refer the patient.

Pain:

Note: The use of NSAIDs is not recommended due to the antiplatelet effect and the potential danger of renal failure in a hypotensive patient.

LoE:III

Shock:

Treat if present. See Shock

Tetanus prophylaxis: Z23.5

If not previously immunised within the last 5 years:

  • Tetanus toxoid (TT), IM, 0.5 mL.

Note:

  • The majority of patients do not need and should not be given antivenom.
  • Adverse reactions to antivenom (including anaphylaxis) are common and may be severe.
  • The dose of antivenom is the same for adults and children.
  • Polyvalent antivenom does NOT include antivenom for Berg adders or Stiletto snakes. Management for these snakebites is symptomatic and supportive only.
  • Antibiotics are seldom needed, except for secondary infection.

LoEIII [23]

Criteria for antivenom administration

All patients with systemic signs and symptoms or severe spreading local tissue damage should receive antivenom.

  • signs of neurotoxicity.
  • Positively identified puff adder, Gaboon adder, Mozambique spitting cobra or rinkhals bites AND evidence of entire severe progressive cytotoxicity.
  • Unidentified snakebites and evidence of severe progressive cytotoxicity envenomation, i.e.:
    • swelling of whole hand/ or foot within 1 hour
    • swelling to the knee or elbow <6 hours
    • swelling of the whole limb < 12 hours
    • swelling progression >2.5cm per hour
    • a threatened airway - due to swelling
    • evidence of complication, e.g. compartment syndrome

LoEIII [24]

REFERRAL

  • All patients with bites or likely bites even if puncture marks are not seen. If possible, take the dead snake to the referral centre for identification. Referral centre will determine if antivenom is indicated.
  • If patient presents at the clinic with their own antivenom, contact the secondary level hospital for advice. (antivenom should be given as soon as possible, however administration may be considered even as late as 48-72 hours after the bite, if there is continued clinical deterioration indicating ongoing venom activity).

South African Vaccine Producers (SAVP):

Office hours: (011) 386 6062/6063/6078

After hours: (011) 386 6000 or 071 680 9897