0071643192.pdf

ENVIRONMENTAL EMERGENCIES

BROWNRECLUSESPIDER(LOXOSCELES RECLUSA)

The brown recluse spider is identified by the brown violin shape on its
cephalothorax (“fiddleback”)(see Figure 13.2). It is found primarily in the
southern midwestern United States under rocks, woodpiles, and in attics.

MECHANISM OFTOXICITY

■ Venom contains a variety of cytotoxic enzymes →localnecrotic wound
and (rarely) systemic toxicity.

SYMPTOMS/EXAM

■ The initial bite is painlessand causes a localized red lesion that usually
heals.
■ If severe:
■ A target lesion or pustule forms.
■ Bulla and necrotic tissue develop over 3–4 days →eschar formation.
■ Systemic effects (in 24–72 hours) with fevers, chills, nausea/vomiting
■ Hemolysis, seizures, renal failure, DIC are possible.

TREATMENT

■ Supportive therapy as needed
■ Local wound care and tetanus prophylaxis
■ An antivenom is notavailable in the United States.
■ Nitroglycerin, phentolamine, heparin, hyperbaric O 2 , cyproheptadine,
and steroids have all been used but show no clear evidence for efficacy.
■ Dapsoneis still recommended in some texts, but has limited benefit and
is associated with hemolysis (in G6PD) and methemoglobinemia.
■ Delayed(not early) excision, debridement, and possible skin grafting

Hymenoptera Stings

The class hymenoptera include the following stinging insects:

■ Bees
■ Wasps
■ Fire ants

TABLE 13.3. Indications for Antivenom in Black Widow Spider Bite

Age: <16 yr or >65 yr

Severe pain despite symptomatic treatment

Severe envenomation (seizures, uncontrolled HTN, respiratory failure)

Severe comorbidities (HTN, atherosclerotic disease)

Pregnancy

FIGURE 13.2. Brown

recluse spider.

(Reproduced, with permis-

sion, from Dillaha CJ,

Jansen GT, et al: North

American loxocelism.

JAMA188:33, 1964.

Copyright © 1964

American Medical Associa-

tion. All rights reserved.)

Brown recluse spider bite

wounds should undergo

delayed excision and

debridement.