anaphylaxis /an′əfilak″sis/ [Gk, ana + phylaxis, protection] , an exaggerated, life-threatening hypersensitivity reaction to a previously encountered antigen. It is mediated by antibodies of the E or G class of immunoglobulins and results in the release of chemical mediators from mast cells. The reaction may consist of a localized wheal-and-flare reaction of generalized itching, hyperemia, angioedema, and in severe cases vascular collapse, bronchospasm, and shock. The severity of symptoms depends on the original sensitizing dose of the antigen, the number and distribution of antibodies, and the route of entry and dose of subsequently encountered antigen. Penicillin injection is the most common cause of anaphylactic shock. Insect stings, radiopaque contrast media containing iodide, aspirin, antitoxins prepared with animal sera, and allergens used in testing and desensitizing patients who are hypersensitive also produce anaphylaxis in some individuals. Kinds include aggregate anaphylaxis, antiserum anaphylaxis, cutaneous anaphylaxis, cytotoxic anaphylaxis, indirect anaphylaxis, inverse anaphylaxis. −anaphylactic, adj. ▪ OBSERVATIONS: Manifestations can range from mild to severe. Mild symptoms include queasiness, anxiety, urticaria, itching, flushing, sneezing, nasal congestion, runny nose, cough, conjunctivitis, abdominal cramps, and tachycardia. Moderate reactions include a range of symptoms, including malaise; urticaria; pulmonary congestion, dyspnea, wheezing, and bronchospasm; hoarseness; edema of the periorbital tissue and/or tongue, larynx, and pharynx; dysphagia; nausea; vomiting; diarrhea; hypotension; syncope; and confusion. Severe anaphylaxis presents with pallor and cyanosis, stridor, airway obstruction, and hypoxia. If not treated immediately, respiratory arrest, cardiac arrhythmia, circulatory collapse, seizures, coma, and death rapidly ensue. ▪ INTERVENTIONS: Treatment centers on immediate and aggressive management of emerging symptoms. Maintaining the airway and blood pressure is critical. Epinephrine and other drugs are used to counteract effects of mediator release and to block further mediator release. Vasoconstrictors are used to maintain blood pressure. Intubation or tracheostomy may be necessary to maintain an airway. ▪ PATIENT CARE CONSIDERATIONS: The patient suffering an allergic reaction needs careful monitoring for signs of respiratory distress, hypotension, and decreased circulatory volume. Nursing interventions for anaphylactic shock center on the promotion of adequate ventilation and tissue perfusion. Airway needs are maintained, vital signs are monitored for hypotension, blood gases are monitored for acidosis, ECG is monitored for dysrhythmias, and fluid volume is replaced with IV solutions. Education about prevention of future attacks should include instruction in prophylaxis, such as avoiding known allergens, wearing a Medic Alert bracelet or necklace that identifies allergies, and ensuring that all medical records have allergies highlighted in a prominent place. Those with severe allergic reactions should consider carrying an anaphylaxis kit with preloaded epinephrine syringes.
