8
- Complications of Antivenom Therapy:
i) Anaphylaxis/Anaphylactoid
Reactions:
- 3-54% of patients develop some early rxn to whole immunoglobulin equine antivenoms
- the incidence & severity of reactions to CroFab appears to be significantly reduced (7 of first 42
patients treated had an early reaction 5 urticaria, 1 cough, 1 urticaria/dyspnea and wheezing)
- due to a type I hypersensitivity reaction (IgE-mediated) or direct complement activation (more
likely)
- most reactions are mild (urticaria, N/V, diarrhea, headache, fever); 40% severe; very few deaths
reported
ii) Serum
Sickness:
-
occurrence
not predicted by results of skin testing
- a type III hypersensitivity reaction (IgG, IgM production in response to an injected antigen - i.e.
antivenom)
- occurs in 30-75% receiving ACP, depending on total dose given (occurs in approx. 100% if given >
7 vials)
- again, less common with CroFab (5 of first 42 patients 2 rash, 1 pruritus, 1 urticaria, 1 severe rash
& pruritus; early high incidence due to production problem since fixed; current rate approx 6%)
- usually occurs 1-2 weeks after ACP therapy
- serious rxns are rare
-
treatment:
- steroids: e.g. Prednisone 40-100mg qd until Ssx's resolve & taper over 7-10 days
- diphenhydramine for symptomatic relief
3.
Surgical
Modalities: Source of major controversy in some regions
i)
Excision of Bite Site:
- venom spreads too rapidly to be significantly removed by this method
-
many
complications
ii)
Exploration
and
Debridement
(E&D)/Fasciotomy:
- does nothing to mitigate systemic venom effects
- may worsen outcome by adding unnecessary surgical trauma & hemorrhage
-
prolongs
hospitalization
- fasciotomy will decrease any rise in intracompartmental pressure (ICP) if such a
rise occurs
- if concerned, follow ICP:
- if pressures < 30mm Hg, no surgery; antivenom alone
- if pressures > 30-40,and concern re: ischemic muscles, get informed
consent and proceed with fasciotomy in addition to antivenom
4. Crystalloids/Colloids:
- volume expansion is the treatment of choice for shock secondary to snake venom
poisoning (not reversed by antivenom alone)
- 5% albumin appears to be more efficacious than saline, Ringer's lactate, or dextran (stays
in vascular space longer; does not bind or inactivate venom); use if patient fails to respond
to crystalloids
- pressors can be tried in refractory cases
5. Blood
Products:
- PRBC's, cryoprecipitate, FFP, platelets, etc.: use as needed to treat coagulopathies (with
evidence of clinically significant bleeding) and anemia
- must begin antivenom therapy first - otherwise any blood components given will add
further fuel to the ongoing consumptive coagulopathy
6. Analgesics:
- frequently required (acetaminophen, hydrocodone, meperidine, MS, etc.)
7. Wound
Care:
