Temptation
Want to know what my biggest phobia is? When not to wash a wound? What toxicology problem the WHO calls a neglected tropical disease killing more than 100,000 people per year? Listen to find out!
This is the Pick Your Poison podcast. I’m your host Dr. JP and I’m here to share my passion for poisons in this interactive show. Will our patients survive this podcast? It’s up to you and the choices you make. Our episode today is called Temptation. Want to know what my biggest phobia is? When not to wash a wound? What toxicology problem the WHO calls a neglected tropical disease killing more than 100,000 people per year? Listen to find out!
Today's episode starts in the emergency department in the American southwest. You're trying to decide whether to eat a glazed or chocolate donut when you hear a loud commotion from the ambulance bay. It's not an ambulance, but rather someone in a car shouting for help. Often, this means a gunshot wound but not today. The driver is shouting and pointing at the man slumped in the passenger seat with his head lolling back.
You grab a stretcher and wheel it outside. The rest of your team pulls the patient from the car and moves him into your Critical Care room. The man is awake and holding his neck. He’s not talking. He makes gurgling sounds with every breath.
You move his hands away from his neck. The right side is extremely swollen, reddish purple in color. There are 2 side-by-side puncture wounds in the center of the affected area.
Uh oh.
Question number one. This wound is consistent with which injury?
a snakebite
b. Scorpion envenomation
c. bee stings
d. stonefish envenomation
The answer is A. Two puncture wounds next to each other is the classic pattern of a snakebite. The other exposures result in one puncture wound. Even if the patient sustained multiple stings, the punctures wouldn’t be lined up exactly parallel. The driver of the car, the man’s brother, confirms the patient was bitten by a snake 15 minutes prior to arrival. The men immediately jumped into the truck and raced to the hospital. The patient’s condition declined precipitously enroute.
The nurses hook the patient up to the cardiac monitor and start IVs in each arm. The swelling is progressing right in front of your eyes. I hope you’re ready, today’s questions are rapid fire because this is a rapid-fire type of case. Buckle up.
Question number two. What about this case is most concerning?
Determining what species of snake bit him
The risk of bleeding from the bite
The location of the bite
The answer in this case is C. The other aspects are important, but the location of the bite makes it an absolute life-threatening emergency. I hear some of you arguing we need to know the species of snake. Of course, it would be helpful. The truth is we don't always know in the emergency department, and we have to manage the patient, as usual, without all the necessary information. What we do know for a definite fact -- snake bites to the head and neck are extremely dangerous and associated with high mortality rates. Why? The patient makes a few more gurgling noises and grabs his neck again.
The sound of someone about to lose their airway, we need to act immediately. The problem is his neck is not only swelling on the outside, but thanks to the injection of venom from the snakes fangs, it’s also swelling on the inside. Like a throat swelling shut from anaphylactic shock, though totally different mechanism. He needs a breathing tube now, super stat, before the airway swells shut and you can’t pass it at all.
This kind of airway is every EM physician’s worst nightmare. You use the laryngoscope to look down the back of his throat, attempting to visualize the vocal cords. Everything is red and pink and swollen, none of the anatomy looks the way it's supposed to. It’s hard to keep a grip on the handle because your palms are sweaty. After several heart pounding seconds, you finally find the barely visible white vocal cords and squeeze the tube thru the narrow opening.
What if the patient arrived a few minutes later? If his airway already swelled shut? You’d have to do an emergency cricothyroidotomy, essentially cutting a hole in his neck to put a tube directly into the trachea. Even this would be difficult thanks to the swelling obscuring your landmarks.
We’ve secured the airway. I need a deep breath just thinking about this, even though it’s a fictional case. Question number three. What’s the next step?
A. Apply a tourniquet
B. administer Anti-Venom
C. apply suction to the wound to suck out the venom
D. a fasciotomy, call surgery to place incisions in the patient's neck to relieve the pressure
Answer is B. antivenom. More on the other answers in a bit.
We’ve secured his airway, but he could still die. Only 5 people a year die from snakebites in the US. We really don’t want him to be one of the statistics, so he needs antivenom. Did I hear you just ask how to give it when we don’t know what kind of snake bit him? Question #4. What should we do now?
ask the brother to describe the snake and see what local snakes fit the description
forget the description, ask the brother to go and try to find the snake and bring it back for identification
Treat empirically
Let’s first talk about snakes, then antivenom, then back to the answer to this question. About 25% of snakes are venomous. Hold here so I can clarify a toxicology pet peeve. The difference between poisonous and venomous. Poisons have to be ingested, inhaled or absorbed. Venom is injected by the wildlife. If you bite the animal and get sick, it’s poisonous. If it bites you and you get sick, it’s venomous.
We’re going to focus on North American snakes to prevent this episode from becoming several days long. There are 4 families of venomous snakes, of which 2 live in the US. We have elapids, usually coral snakes. The venom of these snakes is neurotoxic, causing weakness, paralysis and respiratory failure. The bites are minimal, because there’s significant tissue damage and the onset of toxicity can be delayed for up to 12 hours. Also, apparently when biting, coral snakes latch on and are difficult to get off. So this is another clue which I personally hope never to see. Our patient obviously wasn’t bitten by a coral snake.
The second family of venomous snakes in the US, the cause of most snake bites, the Viperidae family, specifically pit vipers, crotalids in Latin, like copperheads and rattlesnakes. Venom contains literally 100s of compounds. Composition of the venom varies with species of snake, location where the snake lives, its age and its diet. Crotalid venom effects are hemotoxic, cytotoxic and myotoxic. Meaning toxic to blood, cells and muscles, just to name the major effects. The rapid swelling of our patient’s neck is thanks to tissue damage. This is definitely a crotalid bite.
We know what kind of snake. What kind of antivenom? In this episode we get to discuss one of my favorite topics, new antidotes. For many years, we used Crofab for North American crotalid bites. It’s sheep derived and made from the pooled venom of 4 different kinds of North American crotalids. It’s a Fab antibody fragment, like another antidote digibind. It works well, except for one area. It doesn’t treat the hemotoxic effects effectively. Now we have a new antivenom, brand name Anavip. It was designed to treat the hematologic effects of venom more effectively. It’s also an antibody fragment, from horses, against the pooled venom of 2 North American crotalids.
Fortunately, we don’t need to determine what exact snake bit him because both antidotes work against all North American crotalids. Answering question #4, we don’t need the brother to describe or bring us the snake. It is not, I repeat it is not, recommended that someone try to catch the snake. Bystanders have been envenomated attempting to do so. Question 5. True or false. You can be envenomated by a dead snake?
True
False
Answer: A. True. Sometimes patients bring the head of a dead snake to the emergency department. Whatever you do, don’t touch it. The fangs have a spring mechanism that works even after they’re dead and decapitated. Touching the fang causes reflex venom release. In fact, someone was even envenomated by a freeze-dried rattlesnake sold as a souvenir at a national park. For some reason, they used the snake head as a tie-tack.
We do need to determine who needs antivenom, because believe it or not, it’s not everyone. About 25% of bites are what we call dry bites. The snake doesn’t inject any venom. The bite is to scare you to go away and leave them alone, rather than kill you. How can you tell a dry bite? Observation. If the bite swells up, the patient’s been envenomated. If you watch the bite for around 6-10 hours and it doesn’t change, it’s dry and the patient won’t require antivenom.
The answer to question 4 is C, empiric treatment with antivenom. Our patient clearly meets the criteria. You order 10 vials, the standard dose of Anavip over an hour. He’s admitted to the ICU.
As I mentioned, five people die a year in the US from snakebites, versus 130,000 per year worldwide. The WHO classifies snakebites as a neglected tropical disease. What accounts for this staggering difference? First, prevalence of snakes. In areas like India for example, there are tons of venomous snakes, and they live in close proximity to humans. Unlike the US southwest, where the snakes can generally avoid human interaction. Second, medical care and access to antivenom.
Third is the safety of the antivenom itself. Not all are as safe as CroFAb and Anavip. Venom is made by milking snakes, injecting small amounts into animals like horses or sheep, then obtaining antibodies from the exposed animal. Antibodies are Y shaped. The top part, the V-shapes, bind to the toxin. The lower part of the Y is strongly identified with the animal from which it came, and when injected into humans causes a very strong immune response. CroFab and Anavip consist of the top part of the antibody only, reducing the unwanted immune response and subsequent allergic reactions to a very low level. This isn’t always the case with antivenoms used outside the US.
Most acute, ie immediate, allergic reactions are mild, but anaphylaxis can occur. In a Sri Lankan study of patients treated with Indian manufactured antivenom, 43% had severe acute reactions to the antivenom itself, including altered mental status and low blood pressure. You can give test doses, and administer at slower rates, but you’re still dealing with an envenomation, so it’s an issue. Serum sickness, essentially a delayed reaction, occurs 5-10 days after exposure to any antivenom. It’s unclear how often it happens, estimates are all over the map.
Outside of location and access to care, elements increasing the risk of death, include bites to the head and neck. The venom affects threatens the airway as well as large, important blood vessels like your carotid artery and jugular vein. Intravascular injection of venom anywhere increases the risk, because it rapidly enters the circulation. All patients with crotalid bites are at risk for bleeding. Some have severe life-threatening bleeding like an intracranial hemorrhage or large gastrointestinal bleeding. Patients with severe envenomation, like our patient, may require an additional dose of anavip. While waiting, let’s discuss the incredible amount of lore and misinformation associated with snake bites and their treatment.
What should you do if you’re bitten by a snake. I’d probably scream bloody murder, then expire on the spot from a heart attack. I don’t recommend this approach, especially if you’re in the US. Take a deep breath, because you’re more likely to die from a bee sting then a snakebite. What else not to do after a snakebite could be its own episode.
We don’t use tourniquets, they can increase tissue damage and don’t improve outcomes. Of course, you can’t put a tourniquet on his neck anyway. What about a pressure dressing? No, not recommended in the US.
Should you cut it open and suck out the venom? Absolutely not. You won't reduce the risk of envenomation and you will introduce a lot of bacteria from your own mouth increasing the risk of infection. Don’t waste your money on suction devices, they don't work either. And please don't try to zap out the venom. The victim does not need to be electrocuted immediately following.
Since the dawn of time, pretty much, it appears treatment for snakebites was often worse than the bite itself. Ancient Egyptians cut them open to let the evil spirits out. Romans amputated the body part. In medieval times, a physician wrote the severed head of the snake should be applied to the wound as a plaster. American cowboys treated bites with a hot branding iron.
Washing the wound with soap and water to prevent infection is recommended, except in Australia, interestingly enough. Why? They use snake venom detection kids to help determine what type of venom the patient was exposed to and the presence or absence of venom. The tests aren’t perfect, but can be useful in treatment decisions. So cleaning the wound isn’t recommended until after testing.
I promised to tell you my biggest phobia. I share it with Indian Jones. You guessed it, snakes. Before I started my toxicology fellowship, I imagined hikers and gardeners attacked by vicious snakes with fangs dripping venom. Imagine my surprise when I learned 50% of bites occur on the upper extremities. Meaning it's not the misstep of an innocent hiker, but rather somebody trying to grab the snake. Legitimate bites is the term given to accidental bites, and illegitimate describes essentially provoked bites. The terminology is a little strange, but anyway, in the US, 75% of illegitimate bites occur in men. Alcohol is often involved. One well-known toxicologist said he'd seen one, single illegitimate bite in a woman saying, “Women are far too intelligent to go messing around.”
What happens if you’re in the US and are bitten by an exotic snake? A classic story is as follows. Doc, I was sitting in Central Park when I got bitten by a insert here the name of a rare and exotic species definitely not native to Central Park or Manhattan or even the US. First of all, foreign snakes are not lurking under the bushes and benches of Central Park, and even if they were, how did this person know the exact species of snake he- it’s always a he- was bitten by? Many hospitals in the US don’t have CroFab or Anavip. They certainly don’t have other antivenoms, and most of those aren’t approved for use in the US anyway. If you are working in an ER and this happens, call your local Poison Center immediately. Different poison centers have different protocols, often they'll reach out to places that might keep exotic anti-venoms, for example the zoo. Many zoos stock antivenom for the poisonous creatures in their care. Often, they will share with a nearby hospital. Finding the right antivenom, though is no guarantee. When the police investigate these incidents, rather than a snake loose in the park, usually they find the patient’s garage filled with illegally imported snakes.
You’ve probably heard about or seen on TV religious snake handlers. Frequently the pastors die from snake bites. I came across something even more bizarre during my research. So called, snake venom addiction. I'm not sure this meets criteria for a true addiction as a psychiatrist would define it. Nevertheless, it’s as hard to believe as it sounds. Patients, particularly in India where the case reports originate, go to dens or parties and raves where they are intentionally bitten with snakes. I have no idea what kinds of snakes are used or if there's actually any venom involved. The snakes are rapped on the head forcing them to bite, starting on a person’s pinky fingers or toes, progressing to ears, lips and even the tongue. Patients report feeling calm and relaxed afterwards. I don't have any further details on this though I am dying to know more. If you know something about it, please let me know.
While on this topic, let me mention there’s no convincing evidence of anyone developing immunity to snake venom. In fact, with re-exposure the risk might increase due to the risk of anaphylaxis.
There’s a long history of veneration of snakes not just in India, but around the world. Snakes are one of the oldest and widespread symbols found in Gilgamesh, the Bible, Aztec, native American, Hindu and Norse mythology just to name a few. They representing everything from evil, the underworld and death, to fertility, rebirth and eternity. The staff of Asclepius with a snake wrapped around it, is the symbol of medicine even in modern times. Derivates of snake venom are used in modern medicine in the blood pressure medicines captopril and enalapril and blood thinning medicines like tirobfiban.
Let’s check on our patient to see if we’ve achieved control with the antidote. What does this mean? Essentially, rapid progression of the swelling has stopped, no evidence of serious bleeding, or other major venom effects. He is still having swelling; it’s now extending down his arm. The ICU has consulted surgery to see about a fasciotomy. A fasciotomy is essentially slicing open an area to reduce the pressure from swelling. A good idea? Crotalid wounds look awful and surgeons love to operate. Nevertheless, the answer is almost always no. The best treatment for an elevated compartment pressure is more antivenom, so let’s order another dose.
I’ve said you’re more likely to die from a bee sting in the US than a snake bite. Not so worldwide. It’s estimated five million people a year are bitten, about 100,000 die. The sequalae, for survivors, can be severe. Many are left disabled or disfigured. Blindness may occur after ocular exposure. Renal failure is possible. Many suffer from PTSD and depression.
Two days later, the patient, amazingly, is awake and extubated. He tells you what happened during the camping trip with his brother. They found a rattlesnake under a rock. Thanks to a few too many beers, he decided to catch the snake for a closer look. He did catch it and held it up, when it struck him in the neck. The cardiac monitor shows his heart rate is 120 beats per minute and his blood pressure is high at 180/90. He’s very shaky.
Is this a side effect of the snakebite? Is he having an allergic reaction to Anavip? You ask him to stick out his tongue, noting fasciculations along the sides. Nope. This is alcohol withdrawal, another known side effect of snakebites. You leave the room and tell your ICU colleagues so they can start treatment. No word on the snakes’ status, but the patient recovers without sequalae, declining help for his alcohol use disorder and looking forward to future camping trips. This is a fictional case, as are all our cases, to protect the innocent. But it is based on real poisonings.
Last question in today’s podcast. What animal is both venomous and poisonous?
Scorpionfish
Blue-ringed octopus
Gila monsters
Keelback snake
Follow the Twitter and Instagram feeds both @pickpoison1 and you’ll see the answer when I post it. Remember, never try anything on this podcast at home or anywhere else.
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