Envenomation (Snakes)

The protocol for Envenomation (Snakes):

Envenomation (Snake Bites)

 

Let’s break it down!



Nothing makes your sphincters clinch more than walking up on a snake…

Although the far majority of snakes are harmless, approximately 25% of snakes are identified as being venomous and pose a dangerous threat to soldiers working in austere environments. Globally, they’re quite problematic.  According to the World Health Organization, more than 5 million snakebites occur worldwide each year, resulting in 2.5 million envenomations and 81,000 to 138,000 deaths.  Because most venomous snakebites occur in developing countries with poorly developed health reporting systems and because many deaths occur before medical care can be provided, these numbers are likely underestimated.

Understanding the types of snakes is particularly important for management.  There are two broad classes of venomous snakes that you need to know: Crotalidae and Elapids.

  • Crotalidae: These are are your classic pit vipers.  They typically have a “triangular-shaped head” and are more common in North American and European countries.  They include rattlesnakes, water moccasins, copperheads, bushmaster, etc.  

Rattlesnakes - Grand Canyon National Park (U.S. National Park Service)

  • Elapids: These snakes generally have a flatter, rounder head that transitions with the body; most commonly found in Asia, Africa, South America, and the Middle East.  They include mambas, cobras, sea snakes, coral snakes, etc.  

The North American Coral Snake

 

 



Crotalidae

Bites from vipers are typically more localized.  The local area around these bites are usually more painful than elapids and cause more visual effects like erythema (redness), ecchymosis (bruising), and bleeding.  The severity of the bite depends on the snake.  A bite from a copperhead usually doesn’t cause any significant damage, but a bite from a something like a Bothrop viper progresses like this:

Evolution of Bothrops snakebite wounds in this study: (A) Foot ...

Elapids

Bites from elapid snakes are typically more systemic; causing nerve damage, paralysis, altered mental status, and hypotension.  This is what a bite from a cobra looks like in a patient:

 



1. If signs and symptoms of anaphylaxis present, treat per Anaphylaxis protocol

As a rule of thumb, any time a patient presents with any sort of envenomation from an animal, anaphylaxis should always be at the forefront of your mind.  Although it’s particularly rare for this to occur in snakebites, an anaphylactic reaction would certainly kill your patient first.  Signs and symptoms of anaphylaxis include respiratory distress, edema, hypotension, urticaria (hives), etc.

Popular hair product causes severe allergic reaction | 7NEWS.com.au

2. Treat per Pain Management protocol using narcotics.  Avoid NSAIDS!

Snakebites are painful, especially from snakes in the Crotalidae family.  The swelling and localized tissue necrosis definitely warrant narcotics like Morphine or Fentanyl.  NSAIDs like Ibuprofen and Ketorolac are generally avoided in these patients due to the risk of bleeding.

In the midst of a massive opioid crisis, hospitals are ...

3. Treat per Nausea/Vomiting protocol

Nausea and vomiting are common symptoms associated with snakebite envenomations.  Your best choices from the protocol would be Ondansetron (Zofran) or Promethazine (Phenergan). 

                                     Hospira 00409475503 - McKesson Medical-Surgical West Ward Pharmaceutical 00641608425 - McKesson Medical-Surgical



Minimize activity and place on a litter

One of our primary goals in the initial management of a snakebite is to reduce the amount of venom absorption in the body.  By minimizing activity, we’re preventing muscle contractions which reduces circulation and lowers systemic absorption of the venom.  

Start IV in unaffected extremity

IV access will be crucial for additional pain/nausea management, or fluid resuscitation if needed.  It should be done on the unaffected extremity so as not to risk having compromised access from the local swelling or necrosis. 

Monitor and record vital signs and extent of edema every 15-30min

Particularly important when making an evacuation decision.  Should be monitored for up to 4 hours.  Progressive signs of edema and soft blood pressure would warrant an Urgent evacuation

Give IV crystalloid for hypotension as necessary

Hemorrhage secondary to coagulopathy, fluid shifts in the affected limb, and systemic vasodilatory effects can all cause hypotension in these patients.  These patients would benefit from a bolus of normal saline or lactated ringers

Immobilize affected limb in a neutral position

Goes hand-in-hand with the concept of minimizing activity; immobilizing the affected limb will help discourage movement and ultimately reduce venom absorption.

Compression wrap (proximal to distal) may be helpful with an Elapidae (neurotoxic snake) but is not indicated for a Crotalidae (pit viper) bite.

This is a fairly controversial practice.  In Elapidae, their bites generally pose the greatest threat when the venom is absorbed systemically, causing neurotoxic symptoms as seen in the video earlier.  The idea behind using a compression bandage to wrap proximal-distal is to prevent the venom from moving from the lymphatic system and draining into the vital organs.  There hasn’t been any study that has definitively proved its effectiveness, but it’s generally regarded to be safe.

The video below shows the optimal pressure/immobilization strategy for snake bites:



Remember, most snakes are harmless.  Not every snake that bites you is going to have venom potent enough to require advanced care, and some won’t even be venomous at all.  But you still need to be on the lookout for things like anaphylaxis, or any signs/symptoms of severe envenomations.  These patients will require an Urgent evacuation, hopefully to a site that has antivenom to treat the worst cases.  

 

Good luck out there!

 

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