2
B. Coral Snakes:
- 2 enlarged, hollow, anterior maxillary fangs that are fixed in erect position (smaller than
pitvipers')
- hang-on and chew (do not "strike"); can bite any location with relatively loose skin
- less than 40% of bites result in envenomation
- approximately 20 bites in U.S. per year
V. VENOM:
- old classification of "neurotoxic","hemotoxic","cytotoxic","myotoxic" is too simplified for crude venoms and
apt to result in inappropriate management; virtually every organ system can be effected by any one venom
- treat the envenomated patient as a multiple poisoning
- venom composition varies:
- species to species
- snake to snake within the same species
- time of year/environmental conditions
- age, size, health of snake
- most venoms contain 10-20 distinct, biologically active components:
-
5-15
enzymes
- 3-12 nonenzymatic, low molecular weight polypeptides
- probably account for most lethal fractions of venoms
- some are 5-20 X more lethal than crude venom
- > 6 other unidentified substances
- elapid venoms are less complex than viperid venoms
- the effects of all venom components are compounded by the release of vasoactive autopharmacologic
compounds such as histamine, bradykinin, and serotonin in the victim
VI. SIGNS AND SYMPTOMS OF SNAKE VENOM POISONING:
A. Pitvipers:
1. Local:
a.
Puncture
Wounds/Scratches:
- pattern can be misleading (venomous vs nonvenomous)
- must differentiate from other animal/insect bites or plant puncture wounds - usually
venomous snakebite wounds are larger, with more bleeding
- may be one or many fang marks present; range few mm to >4 cm apart
b.
Pain, Edema, Erythema:
- usually present within 30 minutes if envenomation occurs
- more severe envenomation generally yields more rapid progression and more severe pain
i)
Pain:
- usually burning & immediate in onset
- usually confined to bite site
ii)
Edema:
- usually limited to SQ tissues (with no increase in intracompartmental
pressures)
- usually starts within 5 minutes (if none in 10 minutes probably no
significant envenomation unless dealing with Mojave rattlesnake [Crotalus
scutulatus
)
- gradually spreads up extremity for > 36 hours (severe envenomation may
have total involvement of extremity in 1 hour)
- danger of airway obstruction in bites to face or neck
c.
Ecchymosis:
- starts within several hours
- may involve entire extremity (especially common in areas of skin-skin contact -
fingers, axilla)
