Chapter 120. Bites and Stings

Wasps, bees, and stinging ants are members of the order Hymenoptera. Local and generalized reactions may occur in response to an encounter. Africanized bees often attack in massive numbers with a venom load that may result in lethal toxicity. Fire ant venom may cross-react in individuals sensitized to other Hymenoptera stings.

Clinical Features

Local reactions consist of pain, erythema, edema, and pruritus at the sting site. Severe local reactions increase the likelihood of serious systemic reactions if the patient is reexposed. The local reaction to a fire ant sting consists of a sterile pustule that evolves over 6 to 24 hours, sometimes resulting in necrosis and scarring. Toxic reactions are the nonantigenic result of a direct venom effect. They have many of the same features of true systemic (allergic) reactions, but there is a greater frequency of gastrointestinal disturbance while bronchospasm and urticaria are infrequent. Symptoms typically subside within 48 hours, though severe cases last longer and lead to rhabdomyolysis and hepatorenal failure. Systemic or anaphylactic reactions are true allergic reactions that range from mild to fatal. In general, the shorter the interval between the sting and the onset of symptoms; the more severe the reaction. Nearly all episodes of anaphylaxis occur within 6 hours; the majority occur within 15 min. Initial symptoms usually consist of itchy eyes, urticaria, and cough. As the reaction progresses, patients may experience respiratory failure and cardiovascular collapse. Delayed reactions may occur 5 to 14 days after a sting, resemble serum sickness. Symptoms include fever, malaise, headache, urticaria, lymphadenopathy, and polyarthritis.

Emergency Department Care and Disposition

1. Remove the bee stinger and clean the wound with soap and water. Intermittent application of ice packs and elevation may reduce swelling.

2. For local reactions, oral antihistamines and analgesics provide symptomatic relief. Localized erythema and swelling may be difficult to distinguish from cellulitis but infection is uncommon.

3. Treat multisystem reactions (anaphylaxis) in the standard fashion. (See Chapter 6 “Anaphylaxis, Acute Allergic Reactions, and Angioedema”)

   1. First-line therapy for anaphylaxis is epinephrine. Administer 0.3 to 0.5 milligram (0.3 to 0.5 mL of 1:1000; pediatric dose, 0.01 milligram/kilogram to a maximum of 0.5 milligram) IM in the anterolateral thigh. Repeat every 5 min as needed. Patients refractory to IM dosing or in significant shock should receive intravenous epinephrine. A bolus of 100 micrograms of 1:100 000 dilution (0.1 mL of 1:1000 in 10 mL normal saline) can be given over 5 to 10 min followed by an infusion, with close observation for chest pain or arrhythmias.

   2. Hypotensive patients require aggressive fluid resuscitation with normal saline 1 to 2 L (pediatric dose, 10 to 20 mL/kg).

   3. After epinephrine, administer parenteral H1 and H2 receptor antagonists (eg, diphenhydramine 50 milligrams PO/IV/IM [pediatric dose, 1 milligram/kilogram] and ranitidine 50 milligrams IV [pediatric dose, 0.5 milligram/kilogram]).

   4. Administer steroids to control persistent or delayed reactions, methylprednisolone 125 milligrams IV (pediatric dose, 2 milligrams/kilogram) or prednisone 60 ...