Part 2: In-hospital Management
So you’ve been admitted to the hospital following a snakebite. If you have any signs of an envenomation, you need to be monitored for at least 12 to 24 hours.
If you have a minimal envenomation, treatment with antivenom may be unnecessary. Of course, it’s essential to monitor for any progression to something more significant.
If you have an envenomation that is more-than-minimal, you should be treated with antivenom. Hopefully the first dose was already administered in the emergency department. If not, hopefully your treating physicians will start it as soon as possible.
So what happens next?
The team caring for you should continue elevating the affected extremity. As mentioned previously, elevation is really helpful. I would argue that it’s second only to antivenom in improving outcomes.
You need good pain control. We initially start with intravenous opioids, but at some point, we need to transition to oral analgesics, because you won’t go home with an IV. The good news is that elevation and appropriate treatment with CroFab® can reduce total opioid requirements.
Maintenance CroFab® dosing consists of two vials every six hours for three doses. In some circumstances, when there is a physician with snakebite expertise who can frequently reassess the patient at the bedside, one or more maintenance doses may not be needed. In the absence of such an expert, maintenance dosing is recommended.
I suggest consulting physical therapy and occupational therapy early in the hospitalization. For lower extremity bites, you need to learn to ambulate and transfer without bearing weight on the affected limb. Patients with upper extremity bites may need assistance performing skills one-handed, especially if the envenomation affected the dominant hand. Physical therapy and occupational therapy can also teach you how to do the important range-of-motion exercises to prevent atrophy and contractures.
As I mentioned in a previous blog, prophylactic antibiotics are unnecessary. Snake envenomation is rarely associated with infection. Less than 1% of the time in one large study out of the University of Arizona. Prophylactic antibiotics confer no benefit, and unnecessary antibiotics can lead to side effects and contribute to antibiotic resistance. Antibiotics should be reserved for documented infection, which is fortunately rare in snakebite.
Similarly, surgical intervention is rarely necessary following snake envenomation. If a surgeon comes to see you, you can be civil to him or her. Even charming. But do not let anyone cut into you without a compelling reason. There will almost never be one.
In the absence of an allergy to the antivenom (rare) or the snake envenomation itself (also rare), there’s no direct benefit from corticosteroids or diphenhydramine (Benadryl).
Most snakebite patients can be discharged within 24 hours. My criteria for discharge include:
- No ongoing systemic toxicity from the envenomation
- Any hematologic laboratory abnormalities have corrected or are at least trending in the correct direction
- Pain is controlled with oral medication
- I DON’T want my patients to bear weight on the affected limb prior to discharge. If someone asks you to do that, just say no!
I also give my patients the following instructions for home care:
- Keep the affected limb elevated as much as possible. But do the range of motion exercises!
- Do not bear weight until it is no longer painful to do so (typically 5 – 7 days if you are treated with antivenom. Often longer in patients who go untreated)
- No prolonged icepacks or cold packs to the affected extremity
- Follow up in 2 – 3 days with a physician with snakebite expertise. Assessment of the local damage is essential, and repeat bloodwork may be needed
- Return to the emergency department for worsening symptoms or other concerns
Dr. Greene is a paid consultant for BTG International Inc.
Spencer Greene, MD, MS, FACEP, FACMT, FAACT, FAAEM is a board-certified medical toxicologist and emergency physician. He currently serves as the Director of Toxicology and an attending emergency physician at HCA Houston Healthcare-Kingwood. He is a Clinical Professor at the University of Houston College of Medicine. Dr. Greene is a recognized expert in the management of snake envenomation in the US. He has treated more than 1000 snakebites at the bedside and has authored more than 50 scholarly articles and book chapters. He has also served as the course director for the Houston Venom Conference since 2013.
CroFab® Crotalidae Polyvalent Immune Fab (Ovine) is a sheep-derived antivenin indicated for the management of adult and pediatric patients with North American crotalid envenomation. The term crotalid is used to describe the Crotalinae subfamily (formerly known as Crotalidae) of venomous snakes which includes rattlesnakes, copperheads and cottonmouths/water moccasins.
IMPORTANT SAFETY INFORMATION
Do not administer CroFab® to patients with a known history of hypersensitivity to any of its components, or to papaya or papain unless the benefits outweigh the risks and appropriate management for anaphylactic reactions is readily available.
WARNINGS AND PRECAUTIONS
Coagulopathy: In clinical trials, recurrent coagulopathy (the return of a coagulation abnormality after it has been successfully treated with antivenin), characterized by decreased fibrinogen, decreased platelets, and elevated prothrombin time, occurred in approximately half of the patients studied; one patient required re-hospitalization and additional antivenin administration. Recurrent coagulopathy may persist for 1 to 2 weeks or more. Patients who experience coagulopathy due to snakebite should be monitored for recurrent coagulopathy for up to 1 week or longer. During this period, the physician should carefully assess the need for re-treatment with CroFab® and use of any type of anticoagulant or anti-platelet drug.
Hypersensitivity Reactions: Severe hypersensitivity reactions may occur with CroFab®. In case of acute hypersensitivity reactions, including anaphylaxis and anaphylactoid reactions, discontinue infusion and institute appropriate emergency treatment. Patients allergic to papain, chymopapain, other papaya extracts, or the pineapple enzyme bromelain may also have an allergic reaction to CroFab®. Follow-up all patients for signs and symptoms of delayed allergic reactions or serum sickness (e.g., rash, fever, myalgia, arthralgia).
The most common adverse reactions (incidence ≥ 5% of subjects) reported in the clinical studies were urticaria, rash, nausea, pruritus and back pain. Adverse reactions involving the skin and appendages (primarily rash, urticaria, and pruritus) were reported in 12 of the 42 patients. Two patients had a severe allergic reaction (severe hives and a severe rash and pruritus) following treatment and one patient discontinued CroFab® due to an allergic reaction. Recurrent coagulopathy due to envenomation and requiring additional treatment may occur.
Please see full Prescribing Information.