chapter 21

Chapter 21: Allergy and Anaphylaxis

AAQS (American Academy of Quality Standards)

  • Acknowledgment of the 12th anniversary edition of Emergency Care and Transportation of the Sick and Injured, covering essential emergency medical services (EMS) topics including allergy treatment and management.

National EMS Education Standard Competencies

Medicine

  • Fundamental knowledge applied to provide emergency care and transport.

    • Key Competency: Rapid assessment and intervention for acutely ill patients based on findings.

Immunology

  • Understanding of:

    • Recognition and management of shock and difficulty breathing related to anaphylactic reactions.

    • Anatomy, physiology, pathophysiology pertinent to hypersensitivity disorders and emergencies.

Introduction to Allergic Emergencies

  • EMT role: Responding to calls regarding allergic reactions, which may involve:

    • Acute Airway Obstruction: Blockage leading to respiratory distress.

    • Cardiovascular Collapse: Potential severe drop in blood pressure leading to shock.

  • Required skills:

    • Treat life-threatening complications promptly.

    • Distinguish normal immune response from allergic reactions.

    • Immunology defined: Study of the body's immune system.

    • Five categories of stimuli:

    1. Food

    2. Insect stings and bites

    3. Medications

    4. Chemicals

    5. Plants

Anatomy and Physiology of the Immune System

  • Function of the immune system:

    • Protects body from foreign substances.

    • Initiates a series of responses upon invasion:

    • Recognition of invader

    • Response assignment

Pathophysiology of Allergic Reactions

  • Definition of allergic reaction: Exaggerated immune response to substances not directly harmful, not triggered by the foreign agent but by the body's misidentification.

  • Chemical release during reactions includes:

    • Histamines: Chemicals that cause allergy symptoms.

    • Leukotrienes: Inflammatory mediators that contribute to bronchoconstriction, nasal congestion, and other symptoms.

  • Signs and symptoms:

    • Can range from mild to severe (mild local reactions vs. severe systemic reactions).

Anaphylaxis

  • Extreme, life-threatening allergic reaction affecting multiple organ systems.

  • Fast progression to shock and potentially death. The process of anaphylaxis typically follows:

    • Introduction of antigen

    • Reaction of the antigen with antibodies on mast cell surfaces

    • Release of mast cell mediators

    • Effects on end organs.

  • Common signs include:

    • Urticaria (hives)

    • Multiple, raised areas of skin with associated itching or burning, often a precursor to anaphylaxis.

    • Angioedema: Localized swelling which can severely obstruct airways when involving facial structures.

    • Wheezing: High-pitched breath sounds caused by bronchospasm.

  • Additional symptoms may include:

    • Stridor: Indicates upper airway narrowing.

    • Hypotension: Caused by vasodilation and increased capillary permeability.

    • Gastrointestinal symptoms: Nausea, vomiting, abdominal cramps.

Common Allergens

  • Food Allergens:

    • Shellfish and nuts, reactions possible after 30 minutes or more.

  • Medication Allergens:

    • Examples include antibiotics (like penicillin) and NSAIDs; injection may cause immediate reactions while oral medications may be delayed.

  • Plant Allergens:

    • Include pollens from ragweed, ryegrass, and various oaks.

  • Chemical Allergens:

    • Present in cosmetics, soaps, and particularly latex materials.

  • Insect Stings:

    • Envenomation occurs when insects, such as bees, wasps, and hornets inject venom; possible severe systemic reactions.

    • Roughly 2 million Americans allergic to insect venom; with around 62 deaths annually due to severe reactions, half of which occur in individuals with no prior history of reactions.

  • Stinging Mechanism: Most insects have a stinger that injects venom, with honeybees having barbed stingers that remain after stinging.

Symptoms of Insect Stings

  • General Symptoms:

    • Sudden pain, swelling, localized heat, redness, and urticaria.

    • Severe symptoms include stridor, bronchospasm, wheezing, dyspnea, chest tightness, gastrointestinal complaints, and hypotension.

  • Untreated anaphylaxis can lead to rapid death, with significant likelihood of death occurring within the first 30 minutes of onset.

Patient Assessment in Immunologic Emergency

  • Initial steps include assessing scene safety and understanding the patient’s recent activity to identify allergen sources (food allergies, insect stings, etc.).

  • Primary Assessment involves:

    • Identifying life threats and forming a general impression, looking for signs of shock or respiratory distress.

    • Investigate airway and breathing status closely due to rapid airway swelling from anaphylaxis.

    • Circulation checks: Look for hypotension, quality of pulse, skin condition (cool, cyanotic, or warm and flushed).

  • Transport Decision: Prompt transport is vital for any allergy-related symptoms, especially if severe; err on the side of caution and transport if symptoms could indicate anaphylaxis.

History Taking in Allergic Reactions

  • Investigate chief complaint and present illness:

    • Use the SAMPLE history format: Signs and symptoms, Allergies, Medications, Past medical history, Last oral intake, Events leading up to the incident.

    • Recognize food ingestion, any prior severe allergic reactions, and gastrointestinal complaints.

Secondary Assessment

  • Involves thorough physical examination,

    • Check for abnormal breath sounds, skin conditions, and vital signs.

  • Monitoring devices like pulse oximetry may assist in assessing patient status.

Reassessment Protocol

  • Repeat assessments, monitor vital signs, and look for shock indicators. If unstable, reassess every 5 minutes; if stable, every 15 minutes.