0071643192.pdf

ENVIRONMENTAL EMERGENCIES

■ Irrigate copiously.

■ Consider antibiotics.

■ Tetanus prophylaxis

A 50-year-old male presents to the ED after sustaining a snake bite while

hiking in southern North Carolina. A digital picture he took of the snake

shows red/yellow/black bands with red bands touching yellow bands.

The patient complains of some localized paresthesias around a small puncture

wound to his L leg, but review of systems and examination is otherwise normal.

Does this patient need antivenom?

Yes. The coral snake venom irreversibly binds acetylcholine receptors lead-

ing to diffuse neuromuscular symptoms, including respiratory paralysis. Early

treatment of eastern coral snake bites, even if asymptomatic, is the key to a

good outcome.

SNAKE ENVENOMATIONS

There are five families of venomous snakes worldwide. Two of these families,

Viperidae (subfamily Crotalinae) and Elapidae, cause the majority of enveno-

mations in the United States. Envenomations may be characterized by either

local toxicity ±coagulopathy or neurotoxicity.

Viperidae Family

Envenomation is characterized by local tissue toxicity and, less commonly,

systemic effects. Approximately 25% of bites with fang marks are “dry”

bites.

The viperidae are characterized by:

■ Pit or depression midway between the eyes(heat-sensitive thermoreceptor)

■ Vertical or elliptical eyes

■ Triangular shaped head

■ Retractable fangs

Viperidae family includes:

■ Rattlesnakes (eg, majave, diamondback)

■ Copperheads

■ Water moccasin (cottonmouth)

MECHANISM OFTOXICITY

■ The venom has digestive enzymes and proteins →local tissue edema and

toxicity and (less commonly) systemic toxicity and coagulopathy.

SYMPTOMS/EXAM

■ Local tissue toxicity (see Figure 13.3)

■ Pain(within 15–30 minutes)

■ Swelling (may be marked, but compartment is syndrome rare)