...,._ Spiders

North American black widow spiders tend to be nonag ­

gressive and only attack when their web is encroached on.

These areas tend to be in dark places, such as garden equipment, shoes, socks, and other clothing. Recluse spiders in

North America tend to cause envenomation in domestic

environments, where they hide in furniture, clothing, and

sheets, particularly if they have not been used or disturbed

for a while. Most recluse bites therefore happen at night or

in the early morning and occur on the thigh, trunk, or

proximal arm.

PHYSICAL EXAMINATION

Focused physical examination includes inspection of the

possible bite area as well as screening for any associated

traumatic injury. Palpation of the bite area and marking of

CHAPTER 65

History & physical exam

Identify snake/spider

Determine clinical effects

Ca ll poison contro l center

Figure 65-5. Envenomation diagnostic algorithm.

any wound margins will assist in deciding whether there is

progression of local tissue injury from envenomation.

However, as was discussed previously, local inspection of

elapid snakebites can be deceptively reassuring. Instead, in

these patients, physical examination may focus on a more

detailed neurologic examination.

DIAGNOSTIC STUDIES

For crotaline envenomations, obtain a complete blood

count (CBC; specifically for hemoglobin and platelet

counts), coagulation studies, and fibrinogen level. If concern

for retained foreign body at a bite site exists, an x-ray may be

obtained.

If there is concern for systemic loxoscelism, a CBC and

coagulation studies are recommended as well as chemistry

panel to assess for renal dysfunction.

MEDICAL DECISION MAKING

If available, a picture of the snake/spider will aid in

identification and further management. A thorough

history and physical examination to determine any clinical

effects, which can be local, hematologic, or systemic, is

performed. Examination of the skin for bite marks to

determine whether significant envenomation has occurred

is unreliable, especially in cases of a coral snake bite.

Contact the poison control center for assistance in

identification and management (Figure 65-5).

TREATMENT

� Snakes

Many field treatments exist particularly for crotaline

snakebites. However, few of them have been found to be

particularly helpful, and many may be quite harmful to the

patient. Such dangerous techniques include but are not

limited to cutting the bite site, attempting to extract venom

from the site (either orally or via commercially available

devices), applying tourniquets to the bitten extremity, or

applying electrical shocks to the victim. Instead, field

management should consist solely of immobilization of

the bitten extremity, limiting the victim's exertion, and

rapidly obtaining medical evacuation and attention.

In the ED, further stabilization measures for crotaline

snakebites include extremity immobilization and elevation,

pain treatment, management of systemic symptoms, and

assessment of tetanus vaccination status. Treatment and

disposition management decisions should always involve

the assistance of a poison control center ( 1-800-222-1222)

or a local toxicologist.

ENVENOMATION

Moderate to severe North American crotaline

envenomations should be treated with Crotalidae polyvalent immune fab ( ovine) snake antivenom ( CroFab). These

envenomations will be characterized by the presence of a

bite site with more than minimal swelling, redness, or

ecchymosis, or one with progression of any of these

findings. Additionally, systemic findings and any

hematologic abnormalities should prompt initiation of

antivenom. Antivenom is given by intravenous infusion of

4-6 vials of antivenom in 250 mL of normal saline given

over 1 hour. lf initial control has been achieved with this

initial dose, the patient should be admitted to an intensive

care unit (ICU) for observation and consideration of

maintenance dosing. lf control was not achieved by the

initial dose, that dose can be repeated.

Prophylactic antibiotics are not recommended for

routine use in crotaline envenomations. Additionally,

unless the patient develops an allergic reaction of some

sort, routine use of steroids is not recommended. Because

of theoretical hematologic effects of nonsteroidal antiinflammatory drugs (NSAIDs), some experts prefer pain

control with opioids.

Because of the deceptively benign appearance of

potentially significant elapid snakebites, the treatment

course is more reflexively conservative than that described

for crotaline envenomations. It was previously recommended

that any patient with bite marks or evidence of skin penetration receive elapid (equine) antivenin. However, the makers

of the product have discontinued manufacture, so there is

currently only very limited supply in endemic areas. In the

event of a suspected elapid snakebite, the poison control

center should be contacted immediately to determine need

for and possible location of any available antivenin.

..... Spiders

Although multiple therapeutic options have been investigated

for black widow spider bites, aggressive supportive symp ­

tomatic care is currently recommended. Studies on the use

of intravenous calcium and Latrodectus antivenoms have

been contradictory and largely unimpressive for appreciable

difference from placebo. It is therefore recommended that

pain associated with black widow spider bites be managed as

other painful conditions would be, with attempts at treating

with NSAIDs, opioids, and/or benzodiazepines as deemed

appropriate.

Multiple specific therapies have also been studied for

loxoscelism. The most dangerous and ill-advised of these

therapies have included shock therapy, liberal use of

prophylactic surgical excision, and dapsone. These thera ­

pies, while ineffective in treating recluse envenomation,

also are thought to cause worsening wound healing

(for shock and surgical excision) or undesirable medication effects (such as methemoglobinemia with dapsone).

Antivenoms are currently investigational and are not

available in the United States. What is instead recommended

is excellent wound care, symptomatic management, and

appropriate focused treatment of potential adverse effects

of systemic loxoscelism.