ENVENOMATIONS - Medicine for Mountaineering and Other Wilderness Activities - page 495

crotalids or pit vipers, these snakes appear harmless, but their venoms are vicious. Travel-
ers who are not knowledgeable should avoid all snakes in areas inhabited by these reptiles.
Snake Venoms
Thevenomsofallvenomoussnakescontainsimilartoxins.Toclassifysnakesaccording
to a single target for their toxin is misleading and can result in inadequate medical therapy.
Vascular toxins damage the walls of blood vessels and inhibit blood clotting. The com-
bination of the two results in bleeding into the tissues at the site of the bite as well as spon-
taneousbleedingfromthegums,nose,orgastrointestinal tract.Thedamagedbloodvessels
allowproteinsandfluidtoleakintothetissues,whichproducesswellingatthepointwhere
the bite occurs. Such fluid loss in combination with the destruction of red blood cells and
bloodproteinsreducesthecirculatingbloodvolumeandleadstoshock,aconsistentfeature
of severe envenomation by snakes of all species.
The ultimate effect of the neurotoxins is paralysis, most importantly respiratory para-
lysis. However, abnormal sensations such as tingling or prickly feelings and partial para-
lysis of the eyelids are more common. Although pit vipers have been described as having
predominantlyhemolytictoxins,characteristic earlysymptomsfollowingthebitesofsome
rattlesnakes are numbness and tingling of the lips and a metallic taste, both of which result
from the effects of the toxin on neural tissues.
Crotalid venoms do tend to have higher concentrations of hemolytic toxins; elapid and
viper toxins tend to have higher concentrations of neurotoxins. However, more than a
dozen different venom components have been identified. Different species within the same
family have venoms of different composition.
Venom concentrations also vary. Some, like that of the copperhead, are rather weak,
whereas others, like that of the Mojave rattlesnake, are concentrated and quite potent. In
addition, larger snakes are able to inject a larger volume of venom than smaller snakes.
The concentration of the venom, the concentrations of its individual components, and the
venom's total volume are different in the same snake at different times of the year. Snakes
tendtohavemoreconcentratedvenomwhentheyhavejustcomeoutofwinterhibernation.
Because the venom of a copperhead is so mild, persons bitten by these snakes often re-
quire little more than supportive therapy. Antivenom may not be needed for adults bitten
bya single snake. Ina compilation ofover 400copperhead bites in eastern North Carolina,
onlytwodeathscouldbefound.Inbothinstances,theunfortunateindividualshadbeenbit-
ten simultaneously by three or more snakes.
In contrast, the eastern diamondback rattlesnake, a large species that is more aggressive
than most snakes, produces venom that isonlymoderately toxic, butthe volume issogreat
that bites by this snake require vigorous treatment. In the United States this species is re-
sponsible for more venomous snakebite deaths than any other. Most of the bites occur in
Florida.