6
7. Ice:
- avoid any method of cooling
- may drive certain venom components deeper into tissues and cause further ischemia
8.
Watch for Adverse Reactions:
- rare documented cases of anaphylaxis (IgE-mediated) caused by snake venom in patients
previously bitten or otherwise exposed to snake venom
- some evidence that venom can activate the alternate complement system directly and
cause a similar reaction
9.
Rapid Transportation to a Medical Facility:
- the most important measure in first aid
- no other measures should delay this since antivenom is the only proven efficacious
therapy
B.
Hospital Management of Pitviper Envenomation:
-
a medical emergency that requires immediate attention and the use of considerable clinical judgement
1.
General:
-
ABC's;
0
2
; monitor; 2 large-bore IV's (NS or RL)
- rapid H&P
- measure circumference of extremity at bite site and 2 sites more proximal (mark positions)
and follow q 15 min
2. Antivenom Currently two for use in North American pitviper bites:
a)
Antivenin [Crotalidae] Polyvalent (ACP) (Wyeth Labs) used since 1954
- a polyvalent, equine serum good for all N. American pitvipers, most C.&S.
American pitvipers, and some Asian species
- made by immunizing horses with eastern diamondback rattlesnake (Crotalus
adamanteus), western diamondback rattlesnake (C. atrox), tropical rattlesnake (C.
durissus terrificus) and fer-de-lance venom (Bothrops atrox)
- contains whole immunoglobulin molecules and other contaminants (such as
albumin) that can cause adverse reactions (see below)
b)
CroFab (Protherics) released by the FDA in 10/00
- a monclonal polyvalent bovine antivenom good for all U.S. pitvipers and
probably all New World pitvipers
- made by immunizing sheep with a single venom - eastern diamondback
rattlesnake (Crotalus adamanteus), western diamondback rattlesnake (C. atrox),
Mojave rattlesnake (C. scutulatus) or cottonmouth water moccasin (Agkistrodon
piscivorus) venom.
- antibodies are collected and papain digested to Fab & Fc fragments
- immunogenic Fc fragments are discarded and the Fab fragments are purified
- equal amounts of the four components are mixed to yield the polyspecific product
- In general, all antivenoms:
- contain specific antibodies against various venom fractions (confer passive
immunity to patient); but variable purity depending on the product
- should only be given IV
- are effective in reversing systemic effects (including coagulopathy) and possibly
some benefit in reducing local destruction if given very early
- are most effective if given within 2 hr (once venom is bound to tissue receptor
sites, antivenom is of little benefit), but probably efficacious up to 24 hr after the
bite (though not for limiting necrosis)
- after 24 hr, use only if significant coagulopathies or other severe systemic
manifestations are present
- if the victim applied a CB, should begin antivenom, if indicated, a few minutes before
releasing
