Allergic Reaction, Anaphylaxis, and Poisoning

Most common triggers of Allergic Reactions

Medication, food, insect, venom

Allergic Reaction

- Immune response to antigen entering the body

- Ingestion (food), injection (bite), inhalation (breathing), absorption (poison ivy)

Antigen

Foreign substance which triggers the immune system

Anaphlyaxis

- Systemic, potentially life-threatening overreaction of normal immune responses

- Two or more systems involved

- Airway/circulatory compromise

Antibodies/Immunoglobulins (Igs)

Chemicals secreted by the body to attack antigens

Histamines

Major chemical mediator in immune response to antigens

Humoral Immunity

- Bone marrow is site of production of B lymphocytes which mediate Ig molecule production

- Immediate hypersensitivity

- Antigen binds B cell, produces IgE specific to the antigen, IgE binds to mast cells

Cell-Mediated Immunity

- Produced in spleen and finalized in thymus

- Cytoxic T lymphocytes, cytokines, macrophages, NK cells

- Delayed hypersensitivity

Anaphylactoid Reaction

- The first time having a reaction to an exposure

- Signs and symptoms and treated the same way as anaphylaxis

- Antigen itself causes released of chemical mediators, rather than stimulating production of antibodies

Primary Response

- First exposure to an antigen sensitizes the immune system to that specific antigen

- Slower, smaller antibody response

Secondary Response

Subsequent exposure to the specific antigen has a quicker and greater release of antibodies

Release of Inflammatory Mediators

Mast cell membrane-bound IgEs degranulate inflammatory mediators, releasing histamine

Early Phase

Immediate cellular response to target cells

Late Phase

Cell-bound Ige on basophils bind histamine releasing factor, and release histamine

Inflammatory Response

- Primary chemical mediator released

- Cause: brachoconstriction, increase vascular permeability, increase vasodilation, stimulated nerve endings, increase mucous production

Normal Immune Response

- Bronchoconstriction: limited period of constriction preventing entry into lungs

- Vasodilation: slows distribution

- Vascular permeability: shift antigens out of circulation causing swelling

- Gastrointestinal: Increase activity to produce mroe stomach acid destroying antigens and excrete them more quickly

- Localized response

Hyper-Response of Immune System

- Not limited to point of introduction, can spread else where

- Increase bronchoconstriction: difficulty breathing

- Increase vascular permeability: edema, decrease BP, erythema

- Increase GI motility: nausea, vomitting

- Stimulation of nerve ending: Itchiness and pain

Biphasic Anaphylaxis

- Symptoms re-occur within 72 hours

- Occurs in up to 20% of patients

- May rebound even if not exposed

Refractory Anaphylaxis

Patient isn't responding to epi

Assessment of Anaphylaxis

- Prior allergic reactions to what antigen and its severity

- How does this reaction compare to the past, Epi-Pen used?

Epi Pen Action

- Vasoconstriction

- Bronchodilation

- Tachycardia

- Peaks in 5-10 minutes

- Does not counter all effects (antihistamines, steroids)

Epi Pen Rules

- See date, name, dose, expiration date, built in safety margin of 15 months

- Now, patient really needs to be transported!

Physical Exam of Anaphylaxis

- Airway - swelling or tightness in mouth, tongue, or throat

- Breathing - tachy, wheezing, diminished or absent sounds

- Circulation - Tachy, decrease BP, Hives + itchiness (localized or systemic)

Prehospital Management of Anaphylaxis

- Adequate ventilation = NRB @ 15 lpm

- Inadequate ventilation = BVM @ 15 lpm

- Pulse oximetry, assist with Epi Pen, monitor

Poisoning Routes

- Ingestion (swallowed)

- Inhaled (breathed in)

- Absorbed (through unbroken skin)

- Injected (inserted through skin)

Ingested Poison

Medications, plants (leaves/berries), household cleaners, and chemicals

Inhaled Poison

Carbon monoxide, ammonium chloride (bleach and ammonia), fumes

Injected Poison

Insects, snakes, drugs

Absorbed

Pesticides, herbicides, household chemicals

Syrup of Ipecac

- Induces vomiting in 20-40 minutes

- Not used by EMS personnel

- Increases risk of aspiration

- Gastric lavage more efficient at clearing stomach contents

Poison Control

Gives information on severity of poisoning, signs and symptoms, and antidotes

Poisoning History

- Scene safety

- Intentional or accidental

- What was it, what route, how much, when

- Any containers left

Physical Exam for Poisoning

- Airway - swelling, mucous, constriction

- Breathing - increase or decrease rate and volumes, hypoxia

- Circulation - increase or decrease pulse and BP, swelling/hives, wounds/burns

Ingestion Treatment

- Monitor for vomiting and aspiration

- Give activated charcoal, dilute with water

- Evaluate vomitus, when in relation to time of ingestion? Substances in it?

Inhaled Treatment

- Remove patient from source

- High flow oxygen to flush out system

- If CO poisoning, end tidal wont help, disrupts cellular respiration but not directly stop the body from producing and exhaling carbon dioxide

Absorbed Treatment

Remove source, brush off dry substances, flush with water

Injected Treatment

- Identify substance or creature

- DO NOT attempt to draw up poisons or use tourniquets

Acetaminophen Poisoning

- Often used as a cry for help, will cook your liver

- LD50 for 70 kg patient is 10g

- Extra-strength Tylenol has 500mg per capsule, so 20 pills needed