Venomous snake bites are rarely encountered, yet they are a frequently tested topic in Emergency Medicine. Luckily, in North America, there are only two broad categories of venomous snake bites that we need to know how to manage.
In the United States, 98% of reported venomous snake bites come from snakes in the crotalid family, otherwise known as pit vipers. Pit vipers that are found in the U.S. include rattlesnakes, cottonmouths (also known as water moccasins), and copperheads. Bites from these snakes cause immediate-onset symptoms and leave noticeable bite marks. This may account for the higher reporting of bites. The other 2% of venomous snake bites reported in the U.S. come from elapids, otherwise known as coral snakes, which we will review in a subsequent post.
This article aims to review prehospital care of crotalid snake bites, possible clinical manifestations in the ED, management of symptoms, indications and dosing for antivenom, and disposition.
CROTALID SNAKE EPIDEMIOLOGY
From Gwaltney-Brant SM, Dunayer E, Youssef H. Chapter 58 – Terrestrial Zootoxins. Veterinary Toxicology. 3rd Ed. 2018. 781-801. Print.
PREHOSPITAL MANAGEMENT
Prehospital management is essentially the same for all venomous snake bites and is focused on preventing the spread of venom.
DO:
- Stay calm
- Immobilize the bitten body part
- Splint the affected limbs/joints in extension
- Remove constricting clothing and accessories
- Mark the bite site and any swelling/erythema
- Immediately transport to the closest hospital that stocks antivenom.
DO NOT:
- Attempt to suck the venom out
- Attempt to catch or kill the snake
- Apply pressure dressings or tourniquets.
EMERGENCY DEPARTMENT MANAGEMENT
Once in the hospital, a thorough history and physical should be conducted to guide management. The Poison Control Center should be contacted for all suspected snake bites.
| Clinical Effect | Treatment | Antivenom |
| Pain | Opioids, acetaminophen
Avoid NSAIDs |
If refractory |
| Wound Care | Update tetanus
No antibiotics |
Yes |
| Anaphylaxis | Epinephrine, antihistamines, corticosteroids | Not helpful |
| Distributive Shock | Epinephrine (first-line) | Yes |
| Compartment Syndrome | Fasciotomy as last resort after measuring pressures | Yes |
| Coagulopathy | Blood products as last resort for severe anemia | Yes |
| Rhabdomyloysis | IV fluids | Yes |
Lab Studies:
- CBC
- PT/PTT
- Fibrinogen
- CMP
- CK
- Urine
Antivenoms:
- FabAV aka CroFab
- Initial dose: 4-6 vials; if in shock or active hemorrhage: 8-12 vials
- Maintenance: 2 vials q6 x3
- If known allergy, pre-treat before giving
- If allergy develops, treat supportively and continue antivenom
- Pregnancy Category C (but still give to pregnant patients)
- Pediatrics: same dosing
- F(ab’)2 aka Anavip
- Initial dose: 10 vials over 1 hour (repeat if no response)
- Observe 18 hrs
- Second dose: 4 vials (if symptoms recur)
DISPOSITION
- Admit: anyone who receives antivenom
- Observation: 8-12 hrs
- Symptomatic: repeat labs q4-6 hours and prior to discharge
- Asymptomatic: repeat labs just prior to discharge
Here is a clinical pathway by EM Practice that is a useful overview:
From Sheikh S, Lefferts P. Emergency Department Management of North American Snake Envenomations. EM Practice. 2018;20(9).
Resources:
- Ahmed SM, Ahmed M, Nadeem A, et al. Emergency treatment of a snake bite: Pearls from literature. J Emerg Trauma Shock 2008;1:97.
- Brown SA, Seifert SA, Rayburn WF. Management of envenomations during pregnancy. Clin Toxicol (Phila). 2013;51(1):3-15.
- Bush SP, Ruha AM, Seifert SA, Morgan DL, Lewis BJ, Arnold TC, et al. Comparison of F(ab’)2 versus Fab antivenom for pit viper envenomation: a prospective, blinded, multicenter, randomized clinical trial. Clin Toxicol (Phila). 2015 Jan. 53 (1):37-45.
- Cumpston KL. Is there a role for fasciotomy in Crotalinae envenomations in North America? Clin Toxicol (Phila). 2011;49(5):351-365.
- Darracq MA, Cantrell FL, Klauk B, Thornton SL. A chance to cut is not always a chance to cure- fasciotomy in the treatment of rattlesnake envenomation: A retrospective poison center study. Toxicon. 2015 Jul. 101:23-6.
- Kanaan N, Ray J, Stewart M, et al. Wilderness Medical Society Practice Guidelines for the Treatment of Pitviper Envenomations in the United States and Canada. Wilderness Environ Med. 2015;26(4):472-487
- Lavonas E, Ruha A, Banner W, et al. Unified treatment algorithm for the management of crotaline snakebite in the United States: results of an evidence-informed consensus workshop. BMC Emerg Med. 2011;11:2
- Mowry JB, Spyker DA, Brooks DE, et al. 2015 Annual Report of the American Association of Poison Control Centers’ National Poison Data System (NPDS): 33rd annual report. Clin Toxicol (Phila). 2016;54(10):924-1109.
- Ruha et al. Epidemiology, Clinical Course, and Management of Snakebites in the North American Snake Bite Registry. J Med Toxicol. 2017;13(4):309-320.
- Schaeffer TH, Khatri V, Reifler LM, et al J. Incidence of immediate hypersensitivity reaction and serum sickness following administration of Crotalidae polyvalent immune Fab antivenom: a meta-analysis. Acad Emerg Med. 2012;19(2):121-131.
- Sheikh S, Lefferts P. Emergency Department Management of North American Snake Envenomations. EM Practice. 2018;20(9)
- Spiller HA, Bosse GM, Ryan ML. Use of antivenom for snakebites reported to United States poison centers. Am J Emerg Med. 2010;28(7):780-785.
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