Snakes and snakebites in South Africa

There's always much published about the management of snakebites especially in South Africa with some proponents saying that the identification of snakes is not important as the syndromic management will suffice for the management of envenomation syndromes. Others argue that knowing one or two of the more dangerous snakes in South Africa is important as they do have clinical relevance.

From a wilderness emergency medicine perspective, there is probably no actual role for giving snakebite anti-venom in the field, due to the many logistical problems with the anti-venom itself, as well as the very real risk of anaphylaxis, although, in very remote areas with a crashing envenomation patient one might certainly consider giving it if appropriate resuscitation equipment and skills are available.

In any event, the identification of the snake that caused the envenomation is important as it determines the urgency to evacuate the casualty from the field. Therefore, clinical wilderness emergency medicine relevant points of note in snake envenomation syndromes are the following:

• Fang morphology
• Venom chemistry
• Snake types
• Clinical syndromes
• Management

Snakes are described as either front-fanged or back-fanged in SA, with the front-fanged further sub-divided as front hinged-fanged or front fixed-fanged. The front hinged-fanged are the viperidae (adders) and the front fixed-fanged are the elapidae (mambas and cobras). The back-fanged are the colubridae (boomslang and vine snake). The clinical relevance of this is on the depth of penetration into the tissues affected which determines the rapidity of onset of symptoms.

Previously, snakes were described as having neurotoxic, cytotoxic, haemotoxic and myotoxic venom, but studies have actually shown that venom chemistry is very complex with venoms containing varied types of proteins and other biologically reactive substances, with the effects of the venom dependent on the predominant chemical present. This predominant chemical and its resultant effects have paved the way for describing the envenomation as a syndrome or symptom complex which is managed appropriately.

The snakes themselves are classed as elapids (mambas and cobras) with the cobras sub-divided into spitting and non-spitting cobras. The mambas are predominantly neurotoxic in effects, whilst the cobras show a combination of neurotoxicity and cytotoxicity. The viperidae in SA are adders which show a predominantly cytotoxic reaction. The colubrids are predominantly haemotoxic.

The envenomation syndromes have been largely described as:

• Painful progressive swelling
• Progressive paralysis
• Bleeding abnormality

and more recently as:

• Neurotoxic with a cytotoxic component
• Cytotoxic with a neurotoxic component
• Cytotoxic with a haemotoxic component
• Predominantly haemotoxic
• Localised painful or painless swelling

First aid in the field involves applying a firm crepe bandage for the entire length of the limb involved, without the use of tourniquets or sucking the victim's wounds, and the application of splintage and keeping the patient immobilised.

The further management involves an assessment of the situation in the field and deciding on whether this patient needs to be extracted from the field by litter or carry, or requires a rapid extraction by aeromedical or other means. The use of anti-venom is definitely strongly discouraged in the field, unless strongly indicated due to envenomation sydrome and delay in extraction, and the availability of skills and resources to resuscitate the patient with advanced life support if necessary.

Check out this puff adder in captivity @ http://youtu.be/f_nCbHi6oKw