Latrodectus moctons/ with the characteristic

ventral red hourglass. Reproduced with

permission from Knoop KJ, Stack LB, Storrow

AB, et al. The Atlas of Emergency Medicine.

3 rd ed. New York: McGraw-Hill Medical,

2009:505. Photo contributor: Lawrence B.

Stack, MD.

characteristics of the envenomed patient. In 20-25% of

crotaline bites, no significant amount of venom is delivered, resulting in a "dry bite." Multiple grading systems

for crotaline envenomation severity have been developed,

although most of these systems have limited utility in

clinical practice. Instead, the clinical effects of these

envenomations can be divided into 3 major categories:

local/tissue, hematologic, and systemic effects. Local t issue damage from crotaline envenomation can range from

minimal swelling and pain to severe edema, blistering,

ecchymosis, and necrosis. Hematologic effects can be

extreme after moderate to severe envenomations and

include thrombocytopenia, elevated coagulation studies

(prothrombin time and partial thromboplastin t ime), as

well as degradation of fibrinogen. Even with laboratory

evidence of severe coagulopathies, however, most patients

do not develop clinically significant hemorrhage.

Systemic effects are nonspecific; include abdominal pain,

vomiting, diaphoresis, tachycardia, and hypotension; and

may also be related to concomitant fear, anxiety, pain, or

intoxication.

In contrast with crotaline envenomations, patients

with significant elapid envenomations may initially

present with minimal symptoms. The neurologic

systemic symptoms that characterize North American

elapid envenomations are classically delayed for hours,

with reports of patients being asymptomatic up to 13

hours before developing ventilator-requiring r espiratory

failure. It is difficult to determine who with an elapid

exposure will develop symptoms of envenomation, as it

has been estimated that approximately 60% of those

bitten by a coral snake did not have an envenomation.

Alternatively, 15% of those with coral snake envenom ­

ations have no fang marks, and only 40% have any local

swelling.

ENVENOMATION

Figure 65-4. Brown recluse spider, Loxosceles recluso, with the characteristic dorsal violinshaped marking. Photos contributed by R. jason Thu rman, MD. Repri nted from Zafren K,

Thurman Rj, jones 10. Chapter 1 6. Environmental conditions. In: Knoop Kj, Stack LB, Storrow AB,

Thurman Rj, eds. The Atlas of Emergency Medicine. 3rd ed. New York: McGraw-Hill, 201 0 .

...,._ Spiders

The clinical presentation of black widow spider bites is

also referred to as latrodectism. The key feature of this

syndrome is pain, which can be localized, radiating, or

referred. This pain is gradual, beginning upward of an

hour after the time of the bite, and is typically described

as being severe muscle cramping pain in the bitten

extremity, but especially with the North American black

widow spider can involve the abdominal muscles,

mimicking a surgical abdomen. Additional findings in

latrodectism include localized areas of diaphoresis, nau ­

sea, vomiting, restlessness, fasciculations, fear of death

(pavor mortis), and rarely priapism. The constellation of

symptoms called "facies latrodectismica" is also specific to

black widow spider envenomation and is a painful facial

grimace with associated conjunctivitis, blepharitis,

diaphoresis, and trismus.

"Loxoscelism" is the term used to describe envenomation from recluse spiders and can be divided into

cutaneous and viscerocutaneous or systemic forms. Of

significant recluse spider envenomations, the cutaneous

form is the most commonly seen in North America. These

patients will initially have little to no pain at the bite site,

only to develop a more remarkable hemorrhagic or ulcerative painful lesion 2-8 hours after the bite. This progresses

to ulceration and necrosis with surrounding erythema and

induration up to 7 days after the initial bite when an eschar

generally forms. This wound then slowly heals over weeks

to months. Systemic loxoscelism occurs 1-3 days after the

recluse spider bite and is primarily characterized by hemolytic anemia. Clinically, the patient may develop nonspe ­

cific systemic symptoms such as fever, rash, weakness,

arthralgia, nausea, and vomiting. This autoimmune

hemolytic anemia can be accompanied by tluombocytope ­

nia and rhabdomyolysis and rarely progresses to renal

failure and death.

HISTORY

...,._ Snakes

North American snakes rarely attack unprovoked, although

this provocation may be unintentional by the envenomed

patient. Most bites occur during warm months, as snakes

hibernate in the winter. They also more commonly occur

on extremities-the areas of the body most likely to disturb a venomous snake. Young men are at particularly high

risk of being bitten by a venomous snake, and it has been

recognized that snakebites are frequently associated with

alcohol intoxication.