Questions and Answers
What is anaphylaxis?
Anaphylaxis is a life-threatening clinical manifestation of the immunoglobulin E (IgE) mediated immediate hypersensitivity reaction.
There is an absolute contraindication to using epinephrine in anaphylaxis.
False
Which of these is a principal effect of mediators released during anaphylaxis?
What is the recommended dose of epinephrine for patients of any age in the event of anaphylaxis?
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What should be done if a patient with anaphylaxis shows no response to the initial epinephrine injection?
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Patients should carry pre-loaded ______ syringes for anaphylaxis.
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What is the purpose of corticosteroids in the treatment of anaphylaxis?
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Which of the following is a method of prophylactic treatment for anaphylaxis?
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What role do IgG antibodies play in the mechanism of action of desensitization?
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Study Notes
Definition of Anaphylaxis
- Anaphylaxis is a life-threatening reaction caused by immunoglobulin E (IgE) mediated immediate hypersensitivity.
- It is characterized by rapid onset and severe symptoms after exposure to an allergen.
Pathophysiology
- Exposure to allergens stimulates B lymphocytes, leading to the production of IgE antibodies.
- IgE antibodies bind to mast cells and basophils, sensitizing them for future exposure.
- Subsequent exposure to the allergen causes cross-linking of IgE, triggering degranulation of mast cells and basophils.
- Degranulation releases histamine, tryptase, prostaglandins, and leukotrienes, causing vasodilation, capillary leak, and smooth muscle contraction.
Symptoms and Diagnosis
- Symptoms can vary in severity and may include significant cardiac, respiratory, or gastrointestinal distress.
- A decrease in systolic blood pressure (SBP) by 30% from baseline is a key diagnostic criterion.
Emergency Treatment
- Immediate administration of epinephrine is critical; it should be given as soon as anaphylaxis is suspected.
- Utilize an Epinephrine Autoinjector (EpiPen), dosing at 0.01 mg/kg (max 0.5 mg), injected intramuscularly into the mid-outer thigh.
- Patients can self-administer up to 2 doses if symptoms persist.
Supportive Measures
- Prioritize airway, breathing, circulation, and mental status assessment.
- Position the patient supine with elevated legs, unless respiratory distress necessitates upright positioning.
- Administer supplemental oxygen at high flow rates (70% to 100%).
Fluid Resuscitation
- Large-bore IV catheters for intravenous access; normotensive adults receive isotonic saline at 125 mL/hour.
- Hypotensive patients may need 1-2 liters rapidly; up to 7 liters may be required for severe cases.
Monitoring and Advanced Care
- Continuous monitoring of cardiovascular status, blood pressure, heart rate, respiratory rate, and oxygen saturation.
- Intubation may be necessary for patients with stridor or severe respiratory compromise.
Epinephrine Administration
- No absolute contraindication for epinephrine; it is the first-line treatment.
- IM administration can be repeated every 5-15 minutes as needed.
- Avoid IV bolus due to risks of cardiovascular complications; IV infusion is an option if IM is ineffective.
Mechanism of Action of Epinephrine
- Alpha-1 effect: causes vasoconstriction and decreases mucosal edema.
- Beta-1 effect: increases heart rate and contractility.
- Beta-2 effect: induces bronchodilation and reduces inflammatory mediator release.
Side Effects of Epinephrine
- Common side effects include anxiety, restlessness, headache, dizziness, palpitations, and tremors.
- Rare but severe side effects: myocardial infarction, arrhythmias, and intracranial hemorrhage.
Additional Treatments
- Antihistamines (H1 & H2 blockers) for symptomatic relief.
- Inhaled bronchodilators like albuterol to alleviate bronchospasm.
- Glucagon for patients on beta-blockers (1-2 mg IV/IM).
- Corticosteroids (e.g., Methylprednisolone) to prevent secondary phase reactions.
Prophylactic Treatment
- Education on allergen avoidance and the importance of carrying EpiPens.
- Desensitization therapy can be considered for unavoidable allergens, especially in IgE-mediated hypersensitivity.
- Immunologic mechanisms of desensitization include development of non-IgE antibodies, regulatory T cell induction, and immune deviation from Th2 to Th1 response.
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Description
Test your understanding of anaphylaxis, a critical and potentially life-threatening allergic reaction. This quiz covers definitions, pathophysiology, and clinical manifestations of this immediate hypersensitivity reaction. Enhance your knowledge on how it presents and how to respond to it effectively.
