Anaphylaxis and Allergic Reactions

Immunology and Allergic Reactions

Anaphylaxis and Its Complications

• Leaky Vessels & Hypotension: Anaphylaxis leads to blood leakage, causing hypotension and potential cardiovascular collapse.
• Angioedema: Swelling in the airway, a life-threatening complication.

Introduction to Immunology

• Definition: Immunology is the study of the body's immune system.
• Immune System Function: Protects the body from foreign substances and organisms.
• Allergic Reaction: An exaggerated immune response to a substance.

The Body's Reaction

• Leukocytes and immune cells overreact to a stimulus, causing a negative chain reaction.
• Allergic reactions are caused by the body's immune system, which releases chemicals like histamines and leukotrienes to combat the stimulus.

Recognizing Allergic Reactions

• Patients may not know the cause of their reaction, especially if it's a new allergy.
• Those with known allergies are often prescribed EpiPens.
• Reactions range from mild and local (itching, redness, tenderness) to severe and systemic (anaphylaxis).

Cellular Events During an Allergic Reaction

• Exposure to an antigen causes immune cells to react, leading to bronchospasm, bronchoconstriction, decreased cardiac output and perfusion, and vasodilation.

Signs and Symptoms

• Urticaria: Multiple small areas of generalized itching and burning, appearing as small, raised areas on the skin.
• Wheal: A single bump from an insect bite or sting.
• Angioedema: Airway swelling affecting the lips, tongue, larynx, pharynx, nose, and trachea.
• Wheezing: Caused by constricted airways.
• Stridor: A high-pitched whistling sound.
• Hypotension: Due to vasodilation and increased permeability.
• Gastrointestinal Symptoms: Nausea, vomiting, and cramping.

Categories of Allergens

1. Food

• Common examples: Shellfish and peanuts.
• Onset: May take more than 30 minutes after ingestion.
• May not always include skin signs.
• Can still severely impact the respiratory and cardiovascular systems.

2. Medications

• Common examples: Penicillin and NSAIDs.
• Onset:
  • Ingested medications: Slow onset, more than 30 minutes.
  • Injected medications: Rapid onset, within 30 minutes.

3. Plants

• Includes dust, pollens, and other plant material.
• Common examples: Ragweed, ryegrass, maple, and oak.
• Onset: Rapid, within 30 minutes.

4. Chemicals

• Examples: Makeups, soaps, hair dyes, and latex.
• Latex is a concern for healthcare providers; nitrile gloves are now common.

5. Insect Bites and Stings

• Envenomation: The process of venom injection.
• Reactions can be localized or severe and systemic, leading to anaphylaxis.
• Approximately two million Americans are allergic to bee, wasp, and hornet venom, causing about 62 deaths per year in the US.
• Many patients experiencing new reactions were not previously aware of their allergy.
• Stingers:
  • Barbed stingers (e.g., honeybees) cause a single sting because the stinger remains in the skin.
  • Unbarbed stingers (e.g., wasps) allow multiple stings.
• Retained stingers continue to inject venom, prolonging reaction.
• Ants (e.g., fire ants) inject toxins at multiple sites, typically on the feet and legs, resulting in small raised pustules.

Insect Sting Symptoms

• Sudden pain
• Swelling
• Localized heat
• Widespread urticaria
• Redness
• Itching
• Wheal formation

Progression to Severe Reaction

• Bronchospasms, bronchoconstriction.
• Stridor and wheezing.
• Chest tightness.
• Coughing.
• Shortness of breath.
• Anxiety and altered mental status.
• Gastrointestinal complaints.
• Hypotension.
• Respiratory failure if untreated.
• Death if untreated.

Importance of Rapid Intervention

• Two-thirds of anaphylaxis deaths occur within the first 30 minutes.
• Rapid intervention is necessary due to the quick progression of severe cases.

Scene Size-Up and Safety

• Prioritize safety for yourself and your partner.
• Consider potential overlap between trauma and medical issues.
• Call for ALS early, as they can administer multiple doses of epinephrine.

Patient Assessment

• Look for medical alert bracelets.
• Assess for increased work of breathing.
• Treat for shock (oxygen, blanket).
• Reassess the need for more epinephrine.
• Administer oxygen, especially with breathing difficulties.

Prioritization and Transport

• Local allergic reactions are lower priority.
• Signs of airway compromise or anaphylaxis are high priority.

History Taking

• Investigate the chief complaint and obtain a sample history from the patient or family members.
• Inquire about prior interventions and previous severe reactions.
• Ask about recent food or drink intake.

Physical Examination

• Perform a systematic head-to-toe or focused assessment.
• Assess for insect stings and remove stingers when present.
• Remove clothing and jewelry as necessary.
• Auscultate breath sounds for wheezing and stridor.
• Assess skin for redness and urticaria.
• Assess oxygen saturation and respiratory effort.

Ongoing Care During Transport

• Repeat primary assessment and vital signs every 5 minutes for high-priority patients, and every 15 minutes for low-priority.
• Compare vital signs to baseline.
• Monitor for signs of shock.
• Reassess the need for epinephrine based on patient condition.

Stinger Removal

• Scrape stingers with a card to avoid squeezing more venom into the skin.
• Wash the area gently with soap
• Apply ice or cold packs for no more than 10 minutes at a time.
• Keep the injection site slightly below the level of the heart.
• Position patients for comfort, especially those with respiratory difficulty instead of a supine position.

Epinephrine

• Medication of choice for anaphylactic reactions.
• It is a sympathomimetic, it mimics the sympathetic nervous system (fight or flight response).
• Causes blood vessels to constrict and reverse vasodilation and hypotension (distributive shock).
• Increases cardiac contractility helping the heart beat more easily.
• Relieves bronchospasms by dilating bronchioles.
• Has a rapid onset but short duration.
• Additional doses may be needed during transport and ALS should be called quickly.

Epinephrine is pre-dosed:

• Under 5, 0.15mg.
• Over 5, 0.3mg.

Side effects are the same as adrenaline:

• Hypertension.
• Anxiety.
• Headaches.
• Dizziness.
• Chest oain.
• Nausea and vomiting.

Contraindications when the patient does not have:

• Hypotension.
• Respiratory Compromise.

Consult with medical direction when:

• Asthma is present.
• Pregnancy.

Key Anaphylaxis Signs: Urticaria, Angioedema, Wheezing.

EpiPen Doses:

• Adult: 0.3 mg
• Child: 0.15 mg