ASI Newsletter - January 2020 

First Aid for Snakebite – Tourniquets and Pressure Bandages

" First-aid: most of the familiar methods for first-aid treatment of snakebite, both western and "traditional/herbal", have been found to result in more harm (risk) than good (benefit) and should be firmly discouraged" ~ Prof. David Warrel, Emeritus Professor of Tropical Medicine, University of Oxford, United Kingdom. 

Much has been said about first aid for snakebite over the years, and several books have been published on the subject. With the rise of social media, the endless old wives’ tales, myths, and general bad advice on the topic has progressed these into believable advice, which is willingly shared on a number of Facebook pages.

I am close to finishing off a revised edition of my popular book, “A Complete Guide to Snakes of Southern Africa”, and have been studying the literature and discussing first aid for snakebite with a number of experts in the field of snakebite treatment, as well as experienced people in the field of first aid treatment. The current book was first published in 2004, and is now more than 15 years old.

I recently completed a Basic Life Support instructor’s course with Neil Kelham, Vice-Chairman National Faculty of the Resuscitation Council of Southern Africa.  One of the first things he told us was to forget about how we did CPR and rescue breathing in the past – things have changed. To some degree we can say the same about first aid for snakebite.

The most important thing to do in the event of a snakebite is to get the patient to the closest medical facility urgently and safely. The first choice is always the closest hospital that has a trauma unit, but this is not always possible.

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At the African Snakebite Institute, we are inundated with calls and emails asking what hospitals carry antivenom. Nobody knows, as a hospital may obtain antivenom today, use it tonight and never replace it. But that is not the big issue. When someone is bitten by a highly venomous snake, the biggest danger is that the person may die from a lack of oxygen. In Black Mamba or Cape Cobra bites, the victim may have trouble with breathing well within an hour. If you can get such a patient to a medical facility, they should be able to assist-breathe the patient, either with a ventilator, a bag valve mask reserve, or at worse, with mouth-to-mouth resuscitation. Such assistance could well be life-saving.

Well over 90% of all serious snakebites in Southern Africa are from snakes with potent cytotoxic venom – with the Mozambique Spitting Cobra, Puff Adder, Rhombic Night Adder and the Stiletto Snake being the main culprits. In such bites there is very little that the first aider can do, as cytotoxic venom causes severe pain and swelling that spreads slowly and may result in blistering and tissue damage. Such a patient needs to be taken to a medical facility, as the early administration of antivenom, if required, will reduce the extent of tissue damage. Bear in mind that only one out of ten snakebite patients that are hospitalised require and receive antivenom.

Boomslang bites are rare and their venom affects the blood clotting mechanism. In a known boomslang bite, do not apply any bandages and get the patient to a medical facility.

If you are dealing with a snakebite with immediate pain and swelling, loosen tight clothing, remove rings and bracelets and avoid all bandages. While transporting the patient you can slightly elevate the affected limb – just above the heart. It has little effect on the outcome of such a bite but will bring pain relief.

The life-threatening bites are from snakes with predominantly neurotoxic venom, and in southern Africa the main culprits are the Black Mamba and Cape Cobra. Other cobras like the Snouted Cobra and Forest Cobra have neurotoxins in their venom, but usually have their fair share of cytotoxins as well and the onset of symptoms is not that dramatic.

Very soon after a bite from a Black Mamba or Cape Cobra, patients often mention numbness of the lips, a metallic taste in the mouth, difficulty with swallowing, nausea and excessive sweating. As they become progressively weaker, ptosis (droopy eye lids), dilated pupils and difficulty swallowing may be seen. The breathing becomes heavier and heavier until the patient stops breathing.

First aid for such a bite firstly involves getting the patient to the nearest medical facility as soon as possible.

Pressure Pad

In a confirmed Black Mamba or Cape Cobra bite on a limb one can immediately put a pressure pad on the bite or just above it towards the heart. Such a pad could consist of a piece of cotton wool and should be bandaged as tightly as one would a sprained ankle. Such a pressure pad may trap the venom in that area and delay the rate at which it spreads and does damage. Experiments on pressure pads have been done for more than 40 years and with good results, but this form of first aid has had little appeal and for no good reason.

Pressure pad applied to a bite on a leg.

Pressure Immobilisation

The initial idea of pressure bandages for neurotoxic envenomation came about in the late 70s when Dr. Sutherland from Australia experimented with pressure bandages. His hypothesis was that initially, most of the venom is absorbed through the lymphatic system, and by putting pressure on lymphatics, he demonstrated that venom absorption and subsequent symptoms were delayed. While pressure immobilisation is now used throughout the world, no recent studies have been done and some scientists are sceptical.

Application of a Smart Pressure Bandage, stretching the rectangles to squares to apply around 60mmHg. 

The biggest problem with pressure immobilisation is that a specific pressure is required for such bandages to have any effect – around 50 – 70 mmHg – and achieving that pressure is no easy task. Having said that, we now have bandages with rectangles printed on them, and when the bandage is stretched so that the rectangles become squares, and applied so, the correct amount of pressure is achieved. The pressure then averages around 60 mmHg. One always starts wrapping the bandage on the site of the bite and then the limb is wrapped towards the heart. Once applied, the patient must be kept as still as possible as muscle movement stimulates the lymphatics.

Limb wrapped from the bite site towards the heart. 

Pressure bandages should not be applied in cases of cytotoxic or haemotoxic envenomation. Once applied, leave the bandage in place until the patient reaches a medical centre.

Arterial Tourniquets

Arterial tourniquets can be extremely dangerous and are not recommended for snakebite. Sadly, most rural people immediately apply a tourniquet after a snakebite using a belt, shoelace, clothing or even fence wire, and in many cases such tourniquets do a great deal of damage. Patients have lost limbs and others have died because of tourniquets.

Watt, et al. (1988) recommend the use of arterial tourniquets for Philippine Cobra (Naja naja philippiensis) bites in cases where the snake was positively identified. In a small study they demonstrated that tourniquets delayed the onset of serious envenomation. Amaral et al. (1998) studied the effectiveness of tourniquets for South American Rattlesnake (Crotalus durissus) bites and the conclusion was that tourniquets are ineffective and should not be used.

At an international congress in the 90s, R.D.G. Theakston mentioned that the use of tourniquets in first aid for snakebite remains highly controversial, and he summed up some of the published research:

HO et al. (1986) did extensive research in Thailand using EIA (enzyme immunoassay) for testing the efficiency of tourniquets in six patients after being bitten by Malayan Pit Vipers, and there were no significant differences in envenomation before and after releasing tourniquets. Khin Ohn Lwin et al. (1984) demonstrated no significant differences in admission venom levels in 20 victims of Russel’s Viper envenomation. Pugh and Theakston (1987) reported a case of Echis carinatus envenomation in Nigeria where the victim had an arterial tourniquet on for 48 hours. After admission to hospital his coagulopathy and haemorrhage were corrected with antivenom, but he died 6 days later due to pulmonary thromboembolism preceded by thrombophlebitis and gas gangrene. Leopold (1957) reported failure of arterial tourniquets in rabbits injected with Eastern Diamondback Rattlesnake venom while Sutherland (1979) stated that neither immobilisation nor tourniquets alone will prevent the spread of venom.

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Fairley (1929) and Christensen (1969) reported that arterial tourniquets prolonged the survival time of animals injected with elapid and Russell’s Viper venom. Other studies in patients, not animals, showed that tourniquets were ineffective in preventing systemic envenomation by Echis carinatus, Russel’s Viper and Cobras (Reid, 1964). The few studies involving the use of EIA, however, show that tourniquets do not appear to be useful in delaying venom absorption, although there is some evidence from individual cases that they may occasionally be beneficial if applied and managed correctly.

There is definite evidence that incorrectly applied and managed tourniquets are dangerous, especially in cases of local necrosis where a tourniquet may result in the confining of venom locally. Theakston conclude by saying that at present, arterial tourniquets are contraindicated in first aid treatment of snakebite.

In South Africa it is common for snakebite victims from rural areas to arrive at hospital with a tourniquet. This is a problem at some of the busiest snakebite treating hospitals, as such tourniquets often do serious damage. In Snakes and Snakebite by Visser and Chapman (1978), they discuss arterial tourniquets with a disclaimer that they can be ‘dangerous first aid’. They go further and state that ‘it must be released for a few seconds every fifteen minutes’. Mention is made that in surgery an arterial tourniquet can remain on for up to one-and-a half to two hours.

In A Complete Guide to Snakes of Southern Africa (2004) I say the following: “Avoid tourniquets: Unless the source of a bite is a Cape Cobra or Black Mamba, avoid using a tourniquet. In such instances an arterial tourniquet may well be lifesaving, especially when proper medical help is hours away. The tourniquet should not be left on for more than 15 to 30 minutes (or at the very most an hour) at a time without being loosened for a few seconds. In any event it should not be left on for more than one-and-a-half-hours. Tourniquets can cause severe damage and should only be resorted to if absolutely necessary.”

More recently, in Snakes and Snakebite in Southern Africa (2014) I say the following: “Do not apply a tourniquet. Snake venom is absorbed initially by the lymphatic system, not through the blood system. Tourniquets may concentrate the venom at the site of the bite, especially with cytotoxic bites, and can promote necrosis and cause severe tissue damage. A tourniquet may even result in the need to amputate if left on for too long.”

Prof. David Warrell, the world leader when it comes to treating snakebites, in the World Health Organisation Snakebite Protocol (2010) says this about tourniquets – “Traditional tight (arterial) tourniquets are not recommended. To be effective, these had to be applied around the upper part of the limb so tightly that the peripheral pulse gets occluded. This method can be extremely painful and very dangerous if the tourniquet was left on for too long (more than about 40 minutes), as the limb might be damaged by ischaemia. Tourniquets have caused many gangrenous limbs.”

Having said all of the above, there is little in the literature showing that arterial tourniquets are a good choice of first aid in snakebite except for advice shared on Facebook or written in self-published notes. There is no doubt that arterial tourniquets may be useful and even lifesaving in Black Mamba or Cape Cobra bites, if far from a medical facility, but can also be extremely dangerous and even lead to loss of limbs or fatalities. (Dr. George Oosthuizen, chief surgeon, Ngwelezane Hospital – pers comm; Dr. Colin Tilbury – pers comm, Dr. G. Muller, Tygerberg Poison Centre – pers comm).

A further problem is that one is now teaching the use of arterial tourniquets to members of the public, when Cape Cobras and Black Mambas account for very few bites on humans. In a five year survey of 879 snakebite cases in Zululand where patients were hospitalised, there were five bites resulting in neurological symptoms and all five victims survived (Darryl Wood, et al – S.Afr. Med. J 2009, 99: 814 – 818).

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I recently approached Prof. David Warrrell, Emeritus Professor of Tropical Medicine, University of Oxford, UK, again to discuss the use of arterial tourniquets as a first aid measure for snakebites and he replied as follows:

“Arterial (tight) tourniquets applied at pressures above systolic blood pressure are far too dangerous ever to be recommended as I have made clear in all my publications. If applied at sufficient pressure to the upper arm or thigh where there is no interosseous blood supply, they can cause total ischaemia distally with a high risk of gangrene after as little as 30 minutes.”

So, for now, when addressing members of the public including farmers, housewives, hikers, fishermen, outdoor enthusiasts and the like – and I do reach a very large audience – I will not be recommending the use of an arterial tourniquet for a snakebite.

Assist-breathing

Snakebite victims that die soon after a bite, do so as a result of a lack of breathing. It is of utmost importance to assist-breathe such patient, hopefully while on the way to a hospital. If you are far from the nearest medical facility, consider getting to a medical doctor who has training in how to assist-breathe a patient, or meet an ambulance halfway – they are manned by paramedics who are trained to give mouth-to-mouth resuscitation or to use a pocket mask, bag valve mask rerserve, or ventilator.

Pocket Masks

A simple one-way pocket mask to assist breathe a patient.

This simple and inexpensive device seals well over the mouth and nose of an adult and if inverted can also be used on an infant. It has a one-way valve to protect the rescue breather from ingesting bodily fluids and in adults you will give one breath every six seconds. In children, one breath is required every five seconds, and in infants one in every four seconds. It is a slow breath given over one second and just enough air to give a chest rise – no more. Continue rescue breathing until you reach a medical facility. 

The correct seal of the pocket mask

Bag Valve Mask Reserve

This is by far the best form of rescue breathing in a remote setting, but is ideally a two-person operation with one person sitting behind the patient and getting a good seal over the mouth and nose while the second person gently squeezes the bag to get a chest rise at the same rate mentioned in the previous paragraph.

Bag Valve Mask Reserves are the best form of rescue breathing, but ideally require two people to opporate. 

Always bear in mind that most snakebite fatalities occur when patients stop breathing. By getting them to a medical facility quickly and providing rescue breathing there is a very good chance that such a patient will survive.

Our latest video on the Stiletto Snake is now online! Check it out here.