Anaphylactic shock Flashcards
Definition of Anaphylactic Shock
Severe and potentially life-threatening allergic reaction.
It occurs when the immune system overreacts to an allergen, triggering a rapid and systemic release of chemicals, such as histamine, into the bloodstream. This widespread release of chemicals leads to a cascade of allergic symptoms and can cause a sudden drop in blood pressure and impaired organ function.
Pathomechanism of Anaphylactic Shock
During anaphylactic shock, the immune system recognizes an allergen, which can be a food, medication, insect sting, latex, or other triggers, as a threat. This recognition leads to the release of a large amount of immune chemicals, such as histamine, from mast cells and basophils. Histamine causes blood vessels to dilate, smooth muscle to contract, and fluid leakage from blood vessels, resulting in a drop in blood pressure, constriction of airways, swelling, and other symptoms.
Symptoms of Anaphylactic Shock
Skin reactions: Itching, hives (urticaria), flushed or pale skin, and swelling, particularly of the face, lips, and throat.
Respiratory symptoms: Difficulty breathing, wheezing, chest tightness, coughing, and nasal congestion.
Cardiovascular symptoms: Rapid or weak pulse, low blood pressure, dizziness, lightheadedness, and fainting.
Gastrointestinal symptoms: Nausea, vomiting, abdominal pain, and diarrhea.
Other symptoms: Anxiety, confusion, a sense of impending doom, headache, and metallic taste in the mouth.
In severe cases, anaphylactic shock can lead to loss of consciousness, respiratory distress, and cardiac arrest.
Diagnosis of Anaphylactic Shock
Anaphylactic shock is primarily diagnosed based on clinical symptoms and the history of exposure to a potential allergen. If the person has a known allergy, the onset of symptoms shortly after exposure strengthens the diagnosis. Additional diagnostic tests may be performed to identify potential triggers and assess the severity of the reaction. These tests may include blood tests to measure specific IgE antibodies, skin prick tests, or allergy patch tests.
Treatment of Anaphylactic Shock
Immediate treatment of anaphylactic shock is critical and typically involves the following steps:
Epinephrine (adrenaline) injection: Epinephrine is the first-line treatment for anaphylaxis. It helps to reverse the allergic reaction by constricting blood vessels, relaxing airway muscles, and improving blood pressure. It should be administered as soon as possible using an auto-injector device (e.g., EpiPen). Emergency medical services should be contacted for additional assistance.
Supportive measures: Other supportive measures may be necessary to stabilize the person, including maintaining an open airway, providing oxygen, and intravenous fluids to support blood pressure.
Medications: Additional medications such as antihistamines (e.g., diphenhydramine) and corticosteroids (e.g., prednisone) may be given to help alleviate symptoms and prevent a potential biphasic or delayed reaction.
Observation and monitoring: Following the initial treatment, the person should be closely monitored in a medical facility for several hours to ensure stability and prevent recurrence.
Long-term management after an anaphylactic episode includes identifying and avoiding triggers, carrying an epinephrine auto-injector, and creating an emergency action plan with guidance from an allergist or immunologist.
