Allergic Reactions and Anaphylaxis - NREMT AEMT Level

Which immune mediator is most associated with vasodilation and bronchospasm in anaphylaxis?

Histamine. Released by mast cells and basophils, it triggers increased vascular permeability and smooth muscle contraction.
Which epinephrine auto-injector dose is commonly used for small children?

$0.15\text{ mg}$ auto-injector. Designed for children under 30 kg to deliver an appropriate reduced dose for safety and effectiveness.
What is anaphylaxis as defined for prehospital care?

Severe, systemic allergic reaction with airway or circulatory compromise. Involves rapid onset of life-threatening symptoms due to massive histamine release affecting multiple organ systems.
What is the most common life threat in fatal anaphylaxis: airway compromise or hypotension?

Airway compromise (laryngeal edema/bronchospasm). Fatal outcomes often result from asphyxiation due to upper or lower airway obstruction rather than cardiovascular collapse alone.
Which fluid type is preferred for hypotension from anaphylaxis in the prehospital setting?

Isotonic crystalloid (normal saline or lactated Ringer's). Replenishes intravascular volume lost to increased permeability, aiding in blood pressure restoration.
Which inhaled medication is appropriate for persistent wheezing after epinephrine in anaphylaxis?

Albuterol (beta-2 agonist) via nebulizer. Targets residual bronchospasm by promoting bronchodilation as a supportive measure following primary treatment.
What is the typical pediatric IM epinephrine dose for anaphylaxis using $1\!:\!1{,}000$ solution?

$0.01\text{ mg/kg}$ IM (max $0.3\text{ mg}$ ). Weight-based dosing ensures efficacy while minimizing overdose risk, with a cap aligned to adult standards.
Which medication class is used as an adjunct to reduce late-phase inflammation in anaphylaxis?

Corticosteroids (for example, methylprednisolone). Inhibit prolonged inflammatory responses, helping prevent biphasic reactions in the recovery phase.
Which epinephrine auto-injector dose is commonly used for most adults and larger children?

$0.3\text{ mg}$ auto-injector. Provides a pre-measured dose suitable for individuals over approximately 30 kg to ensure rapid administration.
Which medication is an adjunct for itching and hives but is not first-line for anaphylaxis?

Diphenhydramine (H $1$ antihistamine). Blocks histamine receptors to mitigate secondary symptoms, though it does not address acute life-threatening features.
Identify the key scene history question that most directly supports anaphylaxis recognition.

Recent exposure to a known or likely allergen before symptom onset. Establishes temporal association between trigger and symptoms, crucial for confirming the diagnosis in the field.
Which airway-related symptom is most concerning for impending obstruction in anaphylaxis?

Stridor. Results from turbulent airflow through a narrowed upper airway, signaling potential rapid deterioration to complete obstruction.
Which finding best distinguishes anaphylaxis from a mild allergic reaction?

Respiratory distress or hypotension after allergen exposure. Indicates systemic involvement beyond localized symptoms, requiring immediate intervention to prevent progression.
Which route and site are preferred for initial epinephrine in anaphylaxis when possible?

Intramuscular injection into the anterolateral thigh. Provides optimal absorption and onset due to the muscle's vascularity, recommended by guidelines for non-IV access.
What is the primary physiologic effect of epinephrine that improves anaphylactic shock?

Alpha-1 vasoconstriction raising SVR and blood pressure. Counteracts histamine-induced vasodilation by increasing peripheral resistance, thereby stabilizing hemodynamics.
What is angioedema?

Deeper swelling of skin/mucosa, often lips, tongue, or airway. Involves histamine-mediated fluid accumulation in subcutaneous or submucosal layers, potentially compromising airways.
What is the most appropriate initial oxygen strategy for anaphylaxis with respiratory distress?

High-flow oxygen; titrate to adequate oxygenation and ventilation. Supports oxygenation in hypoxemic patients while avoiding hyperoxia, aligned with EMS protocols for respiratory emergencies.
Which condition can mimic anaphylaxis with wheezing but typically lacks hives and angioedema?

Asthma exacerbation. Presents with similar respiratory symptoms but usually without cutaneous or gastrointestinal signs of allergy.
What is the definition of an allergic reaction in EMS terms?

Immune hypersensitivity response to an antigen (allergen). Represents an exaggerated immune system activation by a foreign substance, leading to symptoms like itching or swelling.
What is biphasic anaphylaxis?

Recurrence of anaphylaxis after initial resolution without re-exposure. Involves a secondary release of mediators hours later, necessitating monitoring even after initial symptom resolution.
What is the typical adult IM epinephrine dose for anaphylaxis using $1\!:\!1{,}000$ solution?

$0.3\text{ mg}$ IM (= $0.3\text{ mL}$ of $1\!:\!1{,}000$ ). Delivers a standardized dose to achieve therapeutic adrenergic effects without exceeding safe limits for adults.
What is the first-line medication for anaphylaxis in prehospital care?

Epinephrine. Acts rapidly to reverse bronchospasm and hypotension through adrenergic effects, making it essential for stabilizing the patient.
Which lung sound is most consistent with lower-airway involvement in anaphylaxis?

Wheezing. Arises from bronchoconstriction due to inflammatory mediators, indicating lower respiratory tract involvement.
What is urticaria?

Raised, itchy wheals (hives) from histamine-mediated skin edema. Occurs when histamine causes fluid leakage into dermal tissues, producing characteristic skin manifestations.
What is the primary physiologic effect of epinephrine that improves bronchospasm?

Beta-2 bronchodilation. Relaxes bronchial smooth muscle to alleviate constriction caused by inflammatory mediators in the airways.

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