Envenomation Emergencies:

Definition/Etiology:

Envenomation is the exposure to a poison or toxin resulting from a bite or sting from an animal such as a snake, scorpion, spider, or insect, or from marine life. I mean just think about the word. Venom is a poison secreted by an animal and transmitted by biting or stinging. Envenom means to poison. So now you know.

Snakes account for thousands of bites each year but only 10-15% are actually fatal. There are two types of snakes we are concerned about: Elaapidae and Viperidae. We will get into which is which.

We also have insect bites, from which the most concerning reaction is anaphylaxis.

Pathophysiology:

So, the symptoms seen from snake envenomations are mainly due to the toxic components in their venom. The type of venom is different from species to species and can vary significantly from localized tissue destruction to profound coagulopathies. The effect on humans is related to both the potency and the volume of the toxin released during the snake bite.

Random fun fact: The venom released by the inland Taipan snake from Australia is the most potent in the world with a lethal dose of only 0.01 mg/kg with an average envenomation of 44 mg. Their envenomations have greater than 80% mortality. So, yea….don’t play with these. Do you guys remember the Croc Hunter, Steve Irwin, you know the guy who got killed by a stingray. Well, he actually found one of these guys and it kissed him on the face. Thanks, but no thanks.

Clinical Presentation:

Let’s talk about snake bites first. With the Elapidae (or coral snake), there is little to no reaction. If you gotta get bit, go with these. Viperidae on the other hand, can be a huuuuge problem. The venom from these snakes can be hemotoxic, neurotoxic and cardiotoxic.

With the hemotoxicity, you will see petechiae, anemia, hemolysis, coagulopathies, and DIC.

With the neurotoxicity, you will get periorbital paresthesias, pain or numbness at the injury site, constricted pupils, diplopia, muscle twitching in the mouth, face, and affected extremity, difficulty speaking, confusion, weakness, seizures, and paralysis.

Cardiotoxicity can cause tachycardia, hypotension, shock, cardiac arrest.

Understand that all of these signs and symptoms are progressive depending on the amount of envenomation and how long it has been since the bite.

With insect bites, likes bees, wasps, ants and such, (which collectively are referred to as hymenoptera), reactions can include local irritation at the sting site, anaphylactic reactions, and a delayed reaction as a serum sickness-like syndrome up to 2 weeks later. Toxic reactions are unusual, and most reactions occur secondary to allergens.

Collaborative Management:

For all envenomation injuries, we need to provide supportive care as indicated.

• Remove all constricting clothing.
• With snake bites, immobilize the involved area at or below the level of the heart. Any thoughts why? Right, we want to keep it dependent, keep the venom where it is. If we raise up the extremity for example, we promote blood flow to the heart and can bring that venom right to the core, maybe not the best idea.
• Get labs, CBC, CMP Coags, Type and cross, d-dimer. Do not use tourniquets, constrictive bands, or wound suction. Evidence shows that these measures don’t help and may actually make things worse. The days of “sucking out the poison” are past us. Sorry.
• Clean the wound, treat for pain, and determine the need for antivenin. We don’t use antivenin for mild or resolving symptoms. We give it if we see progression of symptoms. Keep in mind that antivenins are specific to the type of snake involved. Any questions here, call poison control or your local snake bite center.
• Antivenin should be given within 4 hours of exposure.
• With the hymenoptera bites, treat as we would any sting. For localized reactions, let’s scrape out that stinger. I don’t think I have to tell you guys that we should not use tweezers to remove a stinger…why? Don’t want to squeeze any more venom into our patients. Find that old credit card you don’t need any more, or, as I have seen many of my docs do, apparently you can use your hospital ID. Please don’t do that!
• For more severe reactions, like anaphylaxis, treat accordingly. I’m not going to get into anaphylaxis treatment here, just don’t forget your Epi!

Evaluation | Patient Monitoring | Education:

In evaluating these patients, our primary goal is improvement of symptoms. Whatever the envenomation, our goal is to either stop the spread or treat the current symptoms. If we see a reversal of symptoms and a return to baseline, we did our job well.

Monitoring for any of the severe reactions is standard, cardiac monitor, O2, BP. And yes, anyone showing any sort of envenomation needs to be on a monitor.

As far as education goes, well…with snake bites….don’t play with snakes. I don’t know how much more we can say here.

With the stings, it’s important to know if this is a known allergy or a new one. Either way, you might want to make sure they have an Epi pen or at least a prescription for one, and if they haven’t used one before, please show them how.

Linchpins: (Key Points)

• Coral vs King – Coral, red, yellow and black bands – red on yellow, kill a fellow
• Antivenin
• Scrape it
• No Heart – keep venom away from core