0071643192.pdf

ENVIRONMENTAL EMERGENCIES

Black widow spider

envenomation →severe

cramping of abdominal, back,

and leg muscles.

A 10-year-old boy is brought to the ED by his parents with c/o severe

abdominal back and leg muscle cramping after being “bit by a spider”

two hours earlier while playing outdoors. On examination, he appears

anxious, sweaty, and is mildly hypertensive. What is the most definitive treat-

ment for this patient?

This patient has likely been bitten by a black widow spider. Black widow

spider venom is a neurotoxin that causes release of acetylcholine and nor-

epinephrine at nerve terminals. All cases should be treated with opioid analgesia

and benzodiazepines to control symptoms. Definitive treatment in this case, given

the patient’s age < 16 years (which increases the likelihood of severe toxicity) is

the administration of black widow spider antivenom.

Spider Bites

BLACKWIDOWSPIDER(LATRODECTUSSP.)

The black widow spider can be found throughout the United States (except

Alaska) in woodpiles, sheds, barns, and outhouses. It is classically identified by

a yellow-red hourglass shape on its belly (see Figure 13.1). The venom is a

neurotoxin.

MECHANISM OFTOXICITY

■ Envenomation→release of acetylcholine and norepinephrine at nerve

terminals →muscle cramping and systemic effects.

SYMPTOMS/EXAM

■ Bite site: Target lesion with local redness and pain. Sometimes bite site

cannot be seen.

■ Prominent muscle cramping and pain most notably of abdominal, back,

and leg muscles, starting locally and then progressing diffusely

■ Tachycardia, hypertension

■ Diaphoresis

■ Nausea/vomiting

■ Symptoms may wax and wane, but generally disappear over 2–3 days.

TREATMENT

■ Local wound care

■ Tetanus prophylaxis

■ Symptomatic treatmentis the mainstay of therapy.

■ Opioid analgesia

■ Benzodiazepinesto reduce muscle spasm

■ Calcium gluconate intravenous (controversial—no proven benefit)

■ Antihypertensives as needed

■ Black widow antivenom

■ If severe symptoms or high-risk patient (see Table 13.3)

■ A horse serum antivenom, therefore administer a test dose first

FIGURE 13.1. Black

widow spider. (See also

color insert.)

(Courtesy of Fred Severyn,

MD.)

Symptomatic treatment with

opioids and benzodiazepines

is the mainstay of therapy.