Severe Allergic Reaction (Anaphylactic Shock) 过敏性休克 Fang Hong 方 红 1st Affiliated Hospital, Zhejiang University.

Severe Allergic Reaction (Anaphylactic Shock)

过敏性休克

Fang Hong 方 红1st Affiliated Hospital, Zhejiang University

Overview• Anaphylaxis is a severe allergic reaction that occurs

rapidly and causes a life-threatening response involving the whole body. This reaction can lead to difficulty breathing and shock ultimately leading to death.

• An anaphylactic reaction occurs when the body's immune system overreacts to an antigen, which it recognizes as an "invader" or foreign substance.

• The reaction usually occurs within seconds to minutes of exposure.

Causes

Triggers of allergic reactions may include:• Drugs, prescription and over-the-counter medication

and blood or blood products;• Venom of stinging insects;• Foods, especially high-protein foods , most

commonly, fish, nuts, fruit, wheat, milk, eggs, soy products;

• Food additives, such as sulfites;• Other substances ,such as latex (natural rubber);• Dyes and contrast materials, used during radiologic

procedures or tests;• Often, however, the trigger is unknown.

Pathogenesis

• The body's white blood cells produce antibodies as a reaction to that antigen. The antibodies circulate in the bloodstream and attach themselves to mast cells in the body.

• In an allergic reaction, the antibody is called immunoglobulin E, or IgE.

• When the antibodies come in contact with the antigen, they signal other cells to produce mediators. Histamine is an one of the mediators.

• The effects of these mediators on organs and tissues of the body cause the symptoms of the reaction.

Symptoms

• The symptoms of anaphylaxis can vary. In some people, the reaction begins very slowly, but in most the symptoms appear rapidly and abruptly.

• The most severe and life-threatening symptoms are difficulty breathing and loss of consciousness.

• Difficulty breathing is due to swelling and/or spasm in the airways. In very rare cases, breathing can stop altogether.

• Loss of consciousness is due to dangerously low blood pressure, which is called "shock."

• In the most serious cases, the heart can stop pumping altogether.

• These events can lead to death from anaphylaxis.

Symptoms

• Generally, a reaction must involve at least two different body systems, such as skin and heart.

• Skin: Most anaphylactic reactions involve the skin.

• Wheals (raised bumps): Hives can cause severe itching;

• Generalized erythema (redness);

• Swelling in the face, eyelids, lips, tongue, throat, hands, and feet.

Symptoms

• Breathing: Difficulty breathing, wheezing, chest tightness, coughing, hoarseness, nasal congestion, sneezing;

• Cardiovascular: Blood pressure may drop to dangerously low levels, rapid or irregular heart beat; dizziness, faintness; loss of consciousness, collapse;

• General: Tingling or sensation of warmth, difficulty swallowing; Nausea, vomiting; Diarrhea, abdominal cramping, bloating; Anxiety, fear, feeling that you are going to die.

Medical Care• Anaphylaxis is a medical emergency and requires

immediate treatment in an emergency department of a hospital.

• If swelling develops rapidly, particularly involving the mouth or throat, and the patient has trouble in breathing or feels dizzy, light-headed, or faint, go immediately to the nearest emergency department or call an ambulance.

Treatment

• The first priority in the emergency department is to protect the airway (breathing) and maintain adequate blood pressure.

• The emergency team will make sure that your airway is open and that you are getting adequate oxygen.

• Oxygen may be given through tubes into the nose or by face mask.

• In severe respiratory distress, mechanical ventilation may be required.

Treatment

• If blood pressure is dangerously low, medication to increase blood pressure will be given.

• An intravenous (IV) catheter may be inserted in order to give saline solution to help boost blood pressure.

• The IV line may also be used to give medication.

Treatment

Medications include:• Epinephrine (0.5ml) should be given by injection into the muscle, through an

IV line, or by injection under the skin;

• H1-receptor blockers/antihistamines: May be given by IV, by injection in the muscle, or by mouth;

• Inhaled beta-agonists: Used to treat bronchospasm (spasms in the lung) and dilate the airways;

• Corticosteroids: Help to decrease the severity and recurrence of symptoms; may be given orally, injected in muscle, or by IV line;

• If low blood pressure does not improve, additional medications, such as dopamine, may be given.

Keywords

• Severe allergic reaction (anaphylactic shock);

• Allergy;

• Antibodies, antibody, antigen;

• Immunoglobulin E, IgE;

• Epinephrine.

Question

• Please describe your experience with anaphylaxis.