Local experts, addressing a session on neuro toxicity at the annual Critical Care Conference in Gqeberha this week, have advised against the use of tourniquets when treating snakebite victims, saying it could lead to circulatory damage and threaten the loss of the affected limb.
The conference also heard that national supplies of polyvalent anti-venom vials dropped – by 90% at one stage – last year. This is according to an expert in the treatment of snakebite envenomation, Professor Andreas Engelbrecht, head of Emergency Medicine at Steve Biko Academic Hospital, writes Chris Bateman for MedicalBrief.
This was due to a combination of load shedding and generator problems at the South African Vaccine Producers (SAVP) plant, a subsidiary of the National Health Laboratory Service (NHLS) at Edenvale – affecting both production and storage. At the same time, the SPCA temporarily stopped them from using horses for creating anti-venom serum. An SPCA inspection reportedly showed the horses not to be in optimal condition, with insufficient food, rest and sub-standard stabling, he explained.
Co-hosting a session on neuro toxicity at the conference, he and snake handler/conservationist Mark Marshal said that last year SA averaged 100 puff-adder bites per month.
“We were down to 1 000 polyvalent vials at one stage when the country probably needs a back-up stock of some 10 000,” Engelbrecht revealed.
The expert snake duo held an audience of critical care specialists and allied healthcare professionals spellbound, respectively handling and identifying highly venomous snakes and discussing the optimal hospital treatment of their respective bites.
Engelbrecht said there were ‘about 10’ snakes for which the polyvalent serum was effective, excluding the boomslang, (whose often-deadly bite or scratch results in copious bleeding and requires a dedicated mono-valent serum), the night adder, vine snake, garter snake and skaapsteker – all less venomous.
Engelbrecht said one study of his local snakebite patients revealed that most victims were bitten on the hands, and to a lesser extent the arms, almost certainly due to consciously handling or touching snakes. Far fewer people were bitten on the legs or torso, except for victims of the Mozambican Spitting Cobra, (or Mfezi).
Engelbrecht advised his colleagues to treat patients symptomatically when the snake had not been conclusively identified, the close monitoring of physiological symptoms providing therapeutic clues as to what type of envenomation they had suffered.
“Be careful of the venom rush when removing a tourniquet. Don’t pull it off or loosen it too suddenly because the patient can suddenly go into arrest,” he warned.
Both he and Marshal advised against tourniquets because they caused circulatory damage and threatened the loss of the affected limb. They recommended pressure bandages instead.
Admitting a patient for observation had a single purpose; to see, in the initial stages whether they were developing neurotoxic syndrome. Respiration had to be closely monitored and blood gases measured.
“The medico-legal pitfall is to put a patient in a normal ward and hope they’re OK. They’re often discovered dead the next day,” he warned. Neurotoxicity was, “sneaky; it’s sometimes not fully developed in the beginning. If you see fang marks you should admit kids for at least 24 hours. With adults if there are no symptoms after 12 hours, then they probably won’t develop,” he said.
Engelbrecht echoed the advice of top South African herpetologists, who recommend high doses of anti-venom once the bite is correctly classified.
A one-time medical snakebite adviser to the SAVP, Dr Darryl Wood, of Ngwelezana Tertiary Hospital in Empangeni, probably the country’s leading snakebite referral centre and top snake ‘’hotspot’’ region, has compiled a national snakebite treatment guideline. Wood saw an average of 2-300 snakebite victims annually. Most of them were victims of either the nocturnal Mozambican Spitting Cobra or Puff Adder, both of them predominantly cytotoxic (tissue-destroying poison).
Wood followed in the footsteps of respected herpetologist and medical doctor, the late Dr Roger Blaylock (a Zimbabwean medical doctor who worked at the nearby Eshowe Hospital) and based his PhD on an analysis of snake bite data in KwaZulu-Natal. He is head of the Emergency Medicine Department at Ngwelezana Hospital.
Wood’s biggest take-home message to anyone involved with a snake bite is to get the victim to a hospital as soon as possible; “please, no tourniquets, sucking, burning, or electrocuting of wounds, or visits to traditional healers. Only a herpetologist who knows he’s been bitten by a mamba or similar neurotoxic snake will know how to apply a tourniquet. If you try this with a puff adder or other cytotoxic bite you will destroy that limb’’.
Wood said immobilising and elevating the affected limb to the level of the heart, providing pain relief, and getting the patient to the hospital were top priorities.
“Don’t do all kinds of weird and wonderful things. If you can positively ID the snake great, but we follow the syndromic approach and find species-identification notoriously unreliable,’ he added.
He said many doctors made the mistake of injecting just 2-3 vials of anti-venom and labelled this ‘’homeopathic’’.
“We start with about five vials, see how the patient is responding and then give another five – it’s an active dynamic process’’. He stressed that the risk of an anaphylactic reaction to the anti-venom stood at 30-40% with children generally presenting with more severe symptoms and a posing a higher anaphylactic risk.
“The appropriate use of anti-venom is where we’re at on the research barrier at present – when you do use it, you have to give enough. The decision to give anti-venom is a very difficult one, especially with swelling. We’ve published a scoring system as part of the guidelines,” he said.
Engelbrecht and Marshal encouraged doctors to network, consult the national snake bite advisory group, the African Snakebite Institute, or the Tygerberg Poison Centre in Cape Town.
Engelbrecht said every referral hospital should ensure they had enough useable antivenom stocks – which had a two-to-three-year shelf life.
Hospital Snakebite Management – presentation by Professor Andreas Engelbrecht