II. Indications: Venomous Snake Bite
- Unstable SnakeBite patient
- All eastern Coral Snake bites
- Clinical worsening in SnakeBite patient
- Progressive local swelling and Ecchymosis at bite
- Coagulopathy
- Hypotension
- Mental status changes
III. Efficacy
- Effective if given within 24 hours of bite
- Most beneficial if given within 4 hours of bite
IV. Contraindications
- Positive Skin Test for Horse Serum Sensitivity
- Mild pit viper bite
V. Preparations
- Pit vipers (Rattlesnake, Cottonmouth, Copperhead)
- Equine-derived Snake Antivenin (horse derived)
- Antivenin Crotalidae Polyvalent (ACP)
- Ovine-derived Snake Antivenin (CroFab)
- Equine-derived Snake Antivenin (horse derived)
- Eastern coral Snake Antivenin (Micrurus fulvius)
- Required in all Coral Snake bite cases
VI. Protocol
- Start reconstituting antivenin on patients ER arrival
- Requires 60 minutes to prepare
- Consider Skin Test for Horse Serum Sensitivity
- Controversial due to lack of efficacy
- Only advantage may be a medicolegal one
- Consider Premedication for Allergy Prevention
- Be prepared for Anaphylaxis
- Administer antivenin
- Depending on severity may require more than 25 vials (typically 8-12 vials for life threatening bite reactions)
- Dosing is per recommendations of poison control and local herpetologists
- Protocols vary for ACP, CroFab, and Coral antivenin
- Antivenin doses are the same for children and adults
- Give 4-6 vials in 250 ml Normal Saline over 1 hour for any of the following findings
- Advancing swelling (mark margins, and repeat hourly until stops advancing)
- Platelet Count <100
- Fibrinogen <100
- Maintenance dosing (typically 2 vials every 6 hours)
- Consult with poison control
- May not be recommended by toxicologists (despite package inserts)
- Monitoring
- See Snake Bite for monitoring
- Monitor labs at baseline (see above), one hour after antivenom, and then every 6 hours until stable
- Monitor for Anaphylaxis and anaphylactoid reactions
- Recheck at 48 to 72 hours for repeat CBC, Fibrinogen (for hematologic toxicity)
- References
- Swadron and Nordt in Herbert (2016) EM:Rap 16(5): 15
- Depending on severity may require more than 25 vials (typically 8-12 vials for life threatening bite reactions)
-
Rattlesnake hand bites are associated with risk of hand dysfunction
- CroFab 6 vials (based on expert opinion)
- Most protocols follow antivenom with Prednisone 40-60 mg orally daily for 5 days
- Consult with poison control
VII. Adverse Effects
- Serum Sickness
- Severe allergy or Anaphylaxis
- ACP: 23 to 56% Allergic Reaction rate
- CroFab: 14.3% Allergic Reaction and none severe
- Some studies quote CroFab adverse reaction rates 0.5 to 5%
VIII. Disadvantages
- CroFab is very expensive
- Cost to hospital is over $1,000 per vial
- Typical 12 vial course with hospital mark-up pricing is over $100,000
IX. Resources (Antivenin sources)
- Arizona Poison and Drug Information Center
- Exotic Snake Antivenins
- Phone: 520-626-6016
- American Zoo and Aquarium Association
- Antivenin indexes
- Phone: 301-562-0777
X. References
- Corbett (2016) Crit Dec Emerg Med 30(10): 28
- Cowling and Ferreri (2019) Crit Dec Emerg Med 33(2): 17-25
- Mason and Brandehoff (2020) EM:Rap 20(9): 13-4
- Dart (2001) Ann Emerg Med 37:181-8 [PubMed]
- Juckett (2002) Am Fam Physician 65(7):1367-74 [PubMed]
- McKinney (2001) Ann Emerg Med 37(2):168-74 [PubMed]