Black widow spider bite

Background

• Identification: red hourglass on otherwise black spider

Mechanism

Envenomation causes release of acetylcholine and norepinephrine from the nerve terminals causing muscle cramps, tachycardia and hypertension

Clinical Features

1. Local
   1. Pinprick sensation; then increasing local pain that may spread to entire extremity
   2. Erythema appears 20-60 min after the bite
   3. Pain begins to abate after several hours and disappears by 2-3d
2. Systemic
   1. Muscle cramp-like spasms in large muscle groups (although exam rarely reveals rigidity)
   2. Pain becomes generalized
      1. Severe abdominal wall musculature pain and cramping
   3. HA, n/v, diaphoresis, photophobia, dyspnea
   4. A-fib, myocarditis, priapism, and death are rare

Management

1. Pain and muscle spasms
   1. Opiods and benzos
2. Systemic illness
   1. Antivenin
      1. Consider for:
         1. Children
         2. Pregnant women
         3. Elderly

Disposition

1. Consider admission for:
   1. Symptoms of moderate envenomation
   2. Pregnant women
   3. Children
   4. Pts w/ preexisting cardiovascular disease or HTN

See Also

• Bites and Stings