Allergic Reactions
Anaphylaxis
Signs and Symptoms
1. Urticaria (hives), diffuse erythematous rash, and soft tissue edema present in up to 90% of patients
2. Wheezing, stridor, cough, chest tightness, hoarseness, dyspnea
3. Dysphagia, nausea and vomiting, diarrhea, abdominal pain
4. Hypotension and tachycardia (shock)
6. Edema involving the face, lips, tongue, pharynx, and larynx, producing an obstructed airway and respiratory arrest
7. Cardiovascular collapse with shock can occur rapidly, without any other antecedent symptoms.
8. In general, the more immediate the reaction after exposure to the inciting antigen, the more severe the degree of anaphylaxis.
9. Most anaphylactic reactions occur within 5 minutes to 2 hours after exposure to an inciting agent. The median time interval between onset of symptoms and respiratory or cardiac arrest is 5 minutes in medication-induced anaphylaxis, 15 minutes in stinging insect venom–induced anaphylaxis, and 30 minutes in food-induced anaphylaxis.
Treatment
1. In the event of anaphylactic shock, immediately administer epinephrine in the field.
a. Epinephrine 1 : 1000 (1 mg/mL solution) should be injected intramuscularly into the mid–anterolateral thigh (vastus lateralis muscle). Subcutaneous administration results in slower absorption and is less reliable.
b. The dose for an adult is 0.3 to 0.5 mL (0.3 to 0.5 mg), and for a child it is 0.01 mL/kg (0.1 mg/kg), not to exceed a total dose of 0.3 mL (0.3mg). Repeat in 5 to 15 minutes if relief is not complete.
c. Epinephrine is available in a spring-loaded injectable cartridge that facilitates self-administration (EpiPen 0.3 mg [Figs. 26-1 and 26-2
