WEAK AND FEELING nauseated, David Dixon, 16, arrives in the ED accompanied by his parents. He says he was bitten by a spider and now has moderate cramping, especially in his back, shoulders, abdomen, and thighs. You immediately escort him to a room and obtain his vital signs: BP, 160/94; pulse, 110 and regular; respirations, 20; temperature, 98.8° F (37.1° C); and SpO2, 98% on room air.
What's the situation?
David had been helping his parents clean out the attic 2 hours earlier when he noticed a black spider on his right knee. As he brushed it off, he felt a painful bite. He says he noticed a red hourglass marking on the spider's underside. When you assess his right knee, you notice that the bite looks like a target lesion, with a pale center and an erythematous outer ring.
Only two spiders in the United States are considered venomous to humans—the brown recluse and the black widow. Both prefer hidden places such as attics, garages, or woodpiles. The Southern Black Widow has a distinctive red hourglass marking on its underside; the Northern Black Widow has a row of red, white, or yellow spots down the middle of the abdomen and two crosswise bars.
Because black widow venom affects the nervous system, reactions can range from mild localized pain and a pruritic rash to severe muscle cramps followed by headache, weakness, tremor, and dizziness. In severe cases, patients can experience nausea and vomiting, chest pain, respiratory symptoms, and paralysis. Hypertension and tachycardia may occur in children.
What's your assessment?
David's history, description of the spider, and signs and symptoms lead you to suspect he was bitten by a black widow. Although black widow spider bites are rarely fatal, anyone experiencing systemic signs and symptoms needs immediate treatment.
What must you do immediately?
Reassure David and his family. Notify the ED physician of the situation and your assessment findings. Establish I.V. access and prepare to administer I.V. fluids, antiemetics, and analgesics as ordered. Intravenous, intramuscular, or oral muscle relaxants, antihistamines, and benzodiazepines also may be ordered.
Antivenin is usually reserved for very young or very old patients who have breathing difficulties, or for patients with severe pain or muscle spasms that can't be adequately controlled with other medications. Before administering antivenin, perform a skin test for possible allergic reaction to the horse serum used in antivenin. Even if the skin test is negative, have resuscitation equipment and medications available in case he has an anaphylactic reaction to the antivenin.
The ED physician decides against administering antivenin to David. Because of his pain and symptoms, David is admitted to the hospital for observation.
What should be done later?
Clean the bite site, and monitor it for signs of infection. Teach David and his parents to watch for and report signs of infection when he goes home.
Obtain a wound culture and sensitivity if David develops signs and symptoms of infection. Some spider bite infections involve methicillin-resistant strains of Staphylococcus aureus, which is sensitive to trimethoprim-sulfamethoxazole (Bactrim).
Tell patients who receive antivenin to see their primary care provider for follow-up if serum sickness occurs. Although rare, serum sickness can occur 7 to 12 days after the antivenin was received. Signs and symptoms include fever, arthralgia, swollen lymph glands, and skin lesions; antihistamines and corticosteroids may be prescribed for symptom control. Serum sickness is self-limiting and resolves in 2 to 3 weeks.
David is discharged home the next day with prescriptions for an as-needed antiemetic, analgesic, and antihistamine.