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Sunday, January 21, 2024
Snake Awareness:
Quoting: Rob Timmings of ECT4Health ....“3000 bites are reported annually. 80% of these are from people trying catch or kill them! 300-500 hospitalisations and 2-3 deaths annually.”
Rob’s article on Facebook recently is well worth a read and definitely gained praise and appreciation for enlightening all and sundry of the vagaries where interfering with venomous snakes ends in disaster. It was well written and easy to digest and certainly his advice is a must-read for those contemplating the great outdoors.
As stated by Rob, the average time to death from snakebite, and we are talking averages, is somewhere between 4 and 12 hours depending on a range of factors, species, weight, age allergies and severity of the bite.
It is important that everyone contemplating outdoor activities, including rural dwellers, refresh their strategic plans stranding's in remote locations, bushfire, floods and emergency response for venomous snakebite.
Of the genus of snakes that historically have been known to harm us here in Tasmania, tigers and copperheads are the snakes of interest and the focus of this narrative, and to a lesser degree White-Lipped Snake, commonly referred to as the Whip snake.
Snake venom is made up of large proteins. Being a protein, it's unstable and eventually subject to decay if not refrigerated or freeze dried when harvested; however it remains virulent when injected into a bite victim in most instances.
When a snake injects a quantity of venom, the venom enters the body via the adipose tissue and finds its way into our body’s lymphatic system. This is a network of fine vessels running through the dermis carrying a clear fluid called lymph. Lymph consists of a cocktail of antigen fighting defensive cells, made up of B and T-lymphocyte cells and so does not usually enter directly into the vascular system.
As with everything, including snakebite, nothing is impossible, and on rare occasions venom can enter directly into the vascular system via an intravenous bite. Although rare, I have attended a bite recipient who suffered this experience.
In this instance the systemic response was acute and potentially life threatening, requiring above the recommended dose of anti-venom for a tiger snake, prescribed as essential to stabilise the patient (ten ampules = 30,000 units) were administered. That said, under most circumstances venom travels via the lymphatic system, not directly into the blood stream.
Unlike blood, lymph is not pumped by the heart but rather courses through the body by physical movement especially of the arms and legs where most bites occur. Walking for example moves lymph, and running moves it faster. Therefore if envenomated the venom will eventually find its way into the vascular system after passing through lymph nodes.
Under normal circumstances, the movement of lymph throughout our bodies is essential to our wellbeing. It fights antigens and toxins and certainly maintains the body’s defence against infection from wounds and skin breaches, such as cuts and abrasions. This is part of our body’s natural immune response against invading bacterial and viral infection.
Within the complexity of the network our immune response cells lymphocytes are part of the defence mechanism that consist of two types of immune cells, B cells and T cells. In loose terms, B cells attach themselves to antigens and seek out an immune response to a known invader and T cells set out to destroy it.
The B cells can be likened to an index system where a known response is stored and identified. When an antigen is recognised, it gives rise to the production of large plasma cells which will go on to produce antibodies. An antibody will match the antigen like matching pieces of a jigsaw puzzle. Whenever the matching parts interlock they are marked for destruction.
Because B cells are unable to penetrate cells, the markers allow for T cells to recognise and contribute to the destruction of antigens. T cells are programmed to remember and destroy antigens. T lymphocytes or T cells contribute to the immune system by directing and regulating the immune response. When stimulated by the antigenic material presented by the macrophages, the T cells make lymphokines that signal other cells. Other T lymphocytes are able to destroy targeted cells on direct contact.
Macrophages are the body's first line of defence and play many roles. A macrophage is the first cell to recognise and engulf foreign substances (antigens). Macrophages disassemble these substances into smaller proteins and present them to the T lymphocytes. Remember T cells are programmed to recognise, respond to and remember antigens. Macrophages produce substances called cytokines that help to regulate the activity of lymphocytes.
Accordingly a person’s metabolic rate will also determine the rate of the flow of lymph. Larger framed or obese individuals won’t move lymph as efficiently as a lightweight person with a fast metabolism, resulting in overweight people taking longer to present with a systemic response. In cases where pathology returns a positive result to warrant advanced treatment protocols and anti-venom, a longer period of observation and blood tests may be required to return a positive result.
Lymph eventually converges with blood via lymph nodes through two large vessels connected to veins at the base of the neck. So when a bite occurs, the lymphatic system is compromised and inundated by a chemical cocktail that overwhelms our normal immune response. This eventually conveys the toxins into the general circulatory system where it can cause mayhem with muscle function and body chemistry.
For this reason the first and most important emergency response to snakebite is to remain calm and cease all movement. Remember, keeping immobile slows the transmission of venom from the bite site into the trunk where it can have devastating consequences if left untreated.
Back in the 1980s the pressure immobilisation method of treating snakebite was introduced in Australia. Immobilisation is the first essential part of first aid; however the application of an elasticised bandage about 100mm wide compliments the effect of arresting the movement of lymph. The bandage is applied with enough pressure to compress the lymphatic vessels and hold the venom in situ until the patient can be clinically managed in hospital.
The bandage is applied to the entire length of the bitten limb as tight as would be applied for a sprain, not too tight to effect circulation of blood to the limb, but enough to flatten lymphatic vessels.
The technique I prefer is a derivation of the St John's method:
1. Starting at the extremities of the bitten limb, apply a firm bandage in small increments until you are over the bite site, then continue in wider winds until either the elbow or knee is reached then continue back down the limb until the bandage is expended.
2. Start the second bandage from either the armpit or groin and work down the limb overlapping the first bandage by one bandage width, then exhaust the bandage back up the limb.
3. Where appropriate, especially with children, apply a splint to restrict movement and monitor the patient for any signs of nausea, headache or extreme lethargy. Remember that hypotension (low blood pressure) can be symptomatic of anaphylaxis or shock. Apply CPR if necessary and roll the patient onto their side in the recovery position and clear the airways.
Bite recipients should be questioned re tingly fingers or toes and any blue discolouration of the bandaged limb. Capillary return is a technique that can be used to test whether or not the bandage has been applied with too much vigour. Simply squeeze the tips of either fingers or toes which will turn white when pressure is applied, then observe that the pink colour returns when the pressure is released. If the extremity remains white you may need to loosen the bandage just a little. If the bandage has been applied in two parts, then it’s best to do each bandage separately.
There is no need to remove clothing, all bandages are applied over shirts or pants. Any quilted garments may need to be taken into consideration when applying first aid and compensate where appropriate the firmness and effectiveness of the bandage.
Forget all previous snakebite lore such as cutting or incising and attempting to suck the venom out. A tourniquet is dangerous and can result in the loss of a limb if left on too long, so refrain from using this method.
The treatment protocols have gone through an evolutionary change over the last few years. An assay of the bite site previously determining the monovalent anti-venom requirement and so it hasn’t been necessary to identify the snake, one of the reasons not to wash the bite site; however with the advent of polyvalent anti-venom given in higher doses, assures cross protection for all 5 most widely prevalent Australian snakes on the dangerous snake list, Taipans, Brown snakes, Tiger snakes, Death Adders and Black snakes,
Anti-venom is delivered intravenously in solution in the prescribed amount over a defined period and adjusted according to the systemic response, along with hydra-cortisone, adrenalin and steroids or whatever medications are required for presenting side effects.
In recorded history, there are differing effects from the variety of snakes that we have to deal with. Not all bites will have a local response and so the bite may go unnoticed in the short term, however some case histories reflect on severe local pain being amongst the first indicator of snakebite.
Coagulopathy defects are early symptoms of an envenomation, followed by a range of conditions such as headache, vomiting, abdominal pain, muscle pain, rapid heart beat (tachycardia) and muscle paralysis. Rhabdomyolysis which is a rapid release of protein particles resulting from the myolytic response caused by the effects of venom on striated muscle, poses a severe threat to long term health if left untreated.
On occasion patients may be put on dialysis to bypass kidney function and remove protein particles to avoid the onset of tubular necrosis of the kidneys and other vital organs, possibly resulting in permanent kidney damage that may end with renal failure as a result of severe rhabdomyolysis.
We associate muscle dysfunction and paralysis with snakebite; and although a major consideration if first aid is delivered effectively and efficiently the systemic response can be isolated from the bitten limb before it has a chance to effect vital organs such as heart lungs and diaphragm. The neurotoxins attack the motor end plates at the neuromuscular junction by inhibiting acetylcholine transmission the fluid that triggers muscle function.
For this reason it’s important to monitor breathing and give assistance where appropriate using CPR if breathing becomes difficult.
Local damage at the bite site can result in a necrotic lesion and tissue damage. In some snakebites, severe muscle pain in the limb can be experienced and days later the bite site can break down forming a nasty painful wound, sometimes causing scarring or even the loss of fingers.
Under normal circumstances the treatment of snakebite is fast and the majority of bite recipients make a complete recovery, Though in one case, prolonged undetected envenoming resulted in the loss of peripheral vision and acquired brain impairment.
Dry bites are quite common; however all bites should be treated as viable until proven otherwise by a qualified medical practitioner. To help prevent incidents of snakebite, appropriate dress sense is advised. Often gaiters or leggings are worn to alleviate the risk of snakebite. My suggestion would be to wear them to keep out grass seeds, but don’t encumber yourselves with the mistaken reason of snake protection.
Shorts are probably not wise when actively snake hunting; however a large part of the population prefer them when bushwalking. Thick woollen socks may provide limited protection but long trousers will afford better results.
Inclosed shoes or walking boots will protect feet far better than sandals or thongs. As a rule in Australia our snake’s fangs rarely exceed 3mm therefore the likelihood of a fang inflicting a well dressed pair of legs would be rare. Bare legs on the other hand, when in the great outdoors, maybe a compromise worthy of more thought.
Also leaving your snakebite bandages in the car glovebox is not a good idea. Have them in a dedicated pocket of your backpack and advise fellow travellers where they can be found. Your bandages should be prominent in your safety strategy when out walking, even in well inhabited parks bordering bushland. The minute or two taken to apply them can save lives, either yours or someone accompanying you.
Clinical Management:
The onset of symptoms may take a while, and may only be detected by either a blood or urine test. If any of the following symptoms present, (see below) take appropriate action to manage the condition of the victim.
Systemic reaction to tiger snakebite
less than an hour after snakebite:
• Headache
• Vomiting
• Transient hypotension (low blood pressure), associated with confusion or unconsciousness
• Diplopia (double vision).
Keep airways clear and monitor breathing. Monitor for shock. In the event, raise patient’s legs and lower head if the skin is clammy and pallor, these symptoms are a possible indicator of hypotension (shock).
1 to 3 hours after the bite,
usually less than an hour after snakebite:
• Headache
• Vomiting
• Transient hypotension (low blood pressure), associated with confusion or unconsciousness
• Diplopia (double vision).
Apply CPR if necessary.
More than 3 hours after bite:
• Paralysis of large muscles of limbs.
• Progressive loss of respiratory muscle function.
• Peripheral circulatory failure, hypoxia (blood oxygen deficiency) and cyanosis (bluish appearance mainly around the lips).
• Myolysis (muscle destruction leading to protein release into the circulatory system).
• Myoglobinuria, (dark urine) evidenced by the effects of toxins found in Tasmanian snake venom degrading muscle cells and releasing protein (rhabdomyolysis) which, after passing through the kidneys, may cause tubular necrosis leading to potentially fatal acute renal failure. Urine may appear black due to myoglobin (an iron and oxygen-binding protein found in the muscle tissue) being present.
Monitor conscious status, apply CPR if breathing ceases and seek immediate emergency assistance.
Always carry at least two 10 –12cm elasticised sports bandages whenever in areas where snakes are likely to be found.
(Referenced from ‘Australian Animal Toxins’ by Straun Sutherland)
For further information contact Reptile Rescue Incorporated TAS. 0499 116 690
Tuesday, October 24, 2023
Clinical Management
The onset of symptoms may take a while, and may only be detected by either a blood or urine test. If any of the following symptoms present, (see below) take appropriate action to manage the condition of the victim.
Systemic reaction to tiger snakebite.
Less than an hour after snakebite:
• Headache
• Vomiting
• Transient hypotension (low blood pressure), associated with confusion or unconsciousness
• Diplopia (double vision).
Keep airways clear and monitor breathing. Monitor for shock. In the event, raise patient’s legs and lower head if the skin is clammy and pallor, these symptoms are a possible indicator of hypotension (shock).
1 to 3 hours after the bite:
• Paralysis of cranial nerves, e.g. ptosis, (eyelid dysfunction) dysphagia, (difficulty swallowing) dysphasia (speech impairment) diplopia (double vision).
• Abdominal pain, increasing confusion.
• Hemoglobinuria (reddish urine, caused by the presence of blood cells).
• Haemorrhage (bleeding from snakebite wound).
• Hypertension (high blood pressure) and tachycardia (rapid heart beat).
Apply CPR if necessary.
More than 3 hours after bite:
• Paralysis of large muscles of limbs.
• Progressive loss of respiratory muscle function.
• Peripheral circulatory failure, hypoxia (blood oxygen deficiency), and cyanosis (bluish appearance mainly around the lips).
• Myolysis (muscle destruction leading to protein release into the circulatory system).
• Myoglobinuria, (dark urine) evidenced by the effects of toxins found in Tasmanian snake venom, degrading muscle cells and releasing protein (rhabdomyolysis) which, after passing through the kidneys may cause tubular necrosis leading to potentially fatal acute renal failure. Urine may appear black due to myoglobin (an iron- and oxygen-binding protein found in the muscle tissue) being present.
Monitor conscious status, apply CPR if breathing ceases and seek immediate emergency assistance.
Always carry at least two 10 –12cm elasticised sports bandages whenever in areas where snakes are likely to be found.
(Referenced from ‘Australian Animal Toxins’ by Straun Sutherland) For more information:
go to http://reptilerescueaustralia.blogspot.com/
First Aid and Clinical Management of Snakebite.
Snakebite may or may not present with a local reaction. Depending on the severity of the bite and volume of venom, a snakebite victim may not feel local pain.
Generally most bites are fleeting and may not be effective, these occurrences are called dry bites, where a snake doesn’t inject venom; however where a snake bites and holds, venom usually will be injected and pain at the bite site experienced.
Observation of the bite site may show steady bleeding from the effects of anti-clotting activity found in snake venom. At this point it is critical that first aid be applied as a matter of urgency.
The most common route for envenoming is via the lymphatic system, a fine network of vessels that transport a clear fluid called lymph. Containing T-cells, lymph is the body’s frontline defence mechanism where antigen, a substance or molecule that, when introduced into the body, triggers the production of an antibody by the immune system, which will then kill or neutralize the antigen that is recognized as a foreign and potentially harmful invader, usually derived from a cut or similar injury, including venom.
Lymph is not pumped around the body by the heart, but rather by muscle movement, that is why immobilisation is important when applying first aid for snakebite.
Less likely is an intravenous bite directly to a blood vessel; however these can occur and are considered far more serious than lymphatic infusion.
Whenever conducting any outdoor activity such as hiking, fishing, wood cutting etc, a pair of 10 –12cm elasticised broad bandages should bean essential addition to your kit. In the event of a sprain they will prove effective; however where snakebite occurs they may save your life.
Important: Any suspected bite must be treated as positive until determined otherwise. First aid must be applied fast and effectively and medical assistance sought as a matter of urgency.
In the case of a bite to the limb, apply a pressure bandage, starting at the extremities and working up the limb until either the elbow or knee is reached, then work back down until all the bandage is used. The second bandage is started at the armpit or groin working down and overlapping the first bandage by one bandage width.
The bandage should be as firm as if applied for a sprain (about 55mm Hg). Cover the entire limb with the tips of toes or fingers exposed. The patient should be either sitting or preferably laying down, and where appropriate a splint applied especially when children are bitten to ensure the limb is immobile.
Monitor the patient and remain vigilant should their condition deteriorate, and treat for shock when or if necessary. If a patient loses consciousness, roll the victim into the recovery position and ensure the airways are clear, if breathing ceases, apply CPR until medical personnel can assume responsibility.
Where possible, notify the nearest emergency facility or hospital as to the nature of the emergency, and condition of the patient. This will allow emergency staff to be ready to respond upon arrival at the medical centre.
If you are able, stay on the line so that medical advice can be given should the bite recipient’s condition worsen.
Do not give fluids or food, and definitely no alcohol; small occasional sips of water only.
Warning! Do not wash the wound and do not attempt to catch or kill the snake. Monovalent tiger snake anti-venom gives cross protection for all Tasmanian snakes.
Example of bandaged limb.
Wednesday, October 18, 2023
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