Allergic Reactions & Anaphylaxis

Incidence In USA - 400 to 800 deaths/year Parenterally administered penicillin accounts

for 100 to 500 deaths per year Hymenoptera stings account for 40 to 100

deaths per year Risk factors: beta-blockers, adrenal

insufficiency

Causes of Deaths Laryngeal edema and acute bronchospasm

with respiratory failure account for >70% Circulatory collapse accounts for 25% Other <5% - ?brain ?MI

Allergic Reaction

Physiologic response to antigens– Oversensitive response = allergic

– Occurs after sensitization to antigen Antigen binds with Antibody

– Less severe result in inflammatory response

– Type I reaction involves antibodies attached to mast cells or basophils = most severe form

Anaphylaxis Systemic reaction of multiple organ systems to

antigen-induced IgE-mediated immunulogic mediator release in previously sensitized individual

Allergic Reaction

Antigen– Induces antibody formation– Examples

» Drugs (antibiotics)

» Foods (nuts, shellfish)

» Insect venoms

» Animal serum

» Incompatible blood types

Anaphylaxis

Antigens enter body by:– Injection– Ingestion– Inhalation– Absorption

Anaphylaxis Pathophysiology

Antigen enters body Antibodies produced Attach to surface of mast or basophil cells Mast cells become sensitized

Anaphylaxis Pathophysiology Mast cells

– In all subcutaneous/submucosal tissues,

– Including conjunctiva, upper/lower respiratory tracts, and gut

Basophils– Circulate in blood

Anaphylaxis Pathophysiology

Antigen reenters body Attaches to antibodies on mast or basophil cells Mast cell degranulates, releases

– Histamine

– Leukotrienes

– Slow reacting substance of anaphylaxis (SRS-A)

– Eosinophil chemotactic factor (ECF)

Histamine Three histamine receptor types:

– H1– H2– H3

Histamine Acts on H1 receptors to cause

– Smooth muscle contraction– Increased vascular permeability– Prostaglandin generation

Histamine Acts on H2 receptors to cause

– Increased vascular permeability– Gastric acid secretion– Stimulation of suppressor lymphocytes– Decreased PMN enzyme release– Release of more histamine from mast cells

and basophils

Histamine Acts on H3 receptors to cause

– Inhibition of central, peripheral nervous system neurotransmitter release

– Inhibition of further histamine formation, release

Vasodilation

Decreased peripheral vascular resistance Hypotension Tachycardia Peripheral hypoperfusion

Increased Capillary Permeability

Tissue edema, urticaria (hives), itching Laryngeal edema

– Airway obstruction

– Respiratory distress

– Stridor Fluid leakage from vascular space

– Hypovolemic shock

Urticaria

Smooth Muscle Spasm

Bronchospasm– Respiratory distress

– “Tight Chest”

– Wheezing GI Tract Spasm

– Nausea, vomiting

– Cramping, diarrhea

Bladder Spasm– Urinary urgency

– Urinary incontinence

Anaphylactic Reaction

Leukotrienes– Potent bronchoconstrictors, vascular

permeability & possibly coronary vasoconstriction

– Slower onset than histamine– Effects last longer than histamine

Allergic Reactions

Generally classified into 3 groups:– Mild allergic reaction

– Moderate allergic reaction

– Severe allergic reaction (anaphylaxis)

Mild Allergic Reaction Characteristics

– Urticaria (hives), itchy

– Erythema (redness)

– Rhinitis

– Conjunctivitis

– Mild bronchoconstriction

– Usually localized (look on abdomen, chest, back) No SOB or hypotension/hypoperfusion Often self-treated at home

Moderate Allergic Reaction

Characteristics– Mild signs/symptoms with any of following:

» Dyspnea, possibly with wheezes

» Angioneurotic edema

» Systemic, not localized

No hypotension/hypoperfusion

Severe Allergic Reaction (Anaphylaxis)

Characteristics– Mild and/or moderate signs/symptoms plus

– Shock / hypoperfusion

Clinical Manifestation

Dependent on:– Degree of hypersensitivity– Quantity, route, rate of antigen exposure– Pattern of mediator release– Target organ sensitivity and responsiveness

Clinical Manifestation

Severity varies from mild to fatal Most reactions are respiratory, dermatologic Less severe early findings may progress to life-

threatening over a short time Initial signs/symptoms do NOT necessarily

correlate with severity, progression, duration of response

Generally, quicker symptoms = more severe reactions

Clinical Manifestation

First manifestations involve skin– Warmth and tingling of the face, mouth,

upper chest, palms and/or soles, or site of exposure

– Erythema– Pruritus is universal feature, erythema– May be accompanied by generalized

flushing, urticaria, nonpruritic angioedema

Clinical Manifestation May progress to involvement of respiratory

system– cough

– chest tightness

– dyspnea

– wheezing

– throat tightness

– dysphagia

– hoarseness

Clinical Manifestation Other Signs and Symptoms

– lightheadedness or syncope caused by hypotension or dysrhythmia

– nasal congestion and sneezing

– ocular itching and tearing

– cramping abdominal pain with nausea,vomiting, or diarrhea

– bowel or bladder incontinence

– decreased level of consciousness

Clinical Manifestation Physical Exam findings may include

– urticaria, angioedema, rhinitis, conjunctivitis

– tachypnea, tachycardia, hypotension

– laryngeal stridor, hypersalivation, hoarseness, angioedema

Insect Sting Hypersensitivity Hymenoptera - yellow jackets, honeybees,

hornets, wasps, bumble bees 90%: Local hives, pruritus 10%: Massive local reaction, including

swelling beyond two joints of extremity 1%: Systemic reaction 10%: have worse reaction on second sting 28%: have recurrent systemic reaction

Management

Treatment depends upon severity of reaction and signs/symptoms of its presentation

Management

Optimal management requires– High index of suspicion (suspect, treat within minutes)

– Early diagnosis

– Pharmaceutical intervention

– Observation

– Disposition

Patient Self-Management Benadryl 50 mg p.o. At any sign of anaphylaxis, self-administer

subcutaneous epinephrine (Epi-Pen®, Ana-Kit®)

If short of breath or wheezing, use aerosolized epinephrine (Primatene Mist, Medihaler-Epi)

Mild Allergic Reaction Often self-treated at home Diphenhydramine 25 - 50mg PO or IM

– IV is acceptable but should include transport If stinger present, flick it away with credit card

or fingernail May consider (if available and indicated):

– cimetidine or ranitidine

– prednisone

– inhaled beta-agonists

Moderate Allergic Reaction High flow oxygen IV NS

– Titrated to systolic BP 90 mm Hg ECG monitor Beta agonists

– Nebulized albuterol, isoetharine, terbutaline

– SQ terbutaline or epinephrine 1:1000 or IV aminophylline if severe bronchoconstriction

Diphenhydramine 25-50 mg IM or IV Methylprednisolone 125 mg IV Transport

Anaphylaxis

Airway and Breathing– High concentration oxygen

– Ventilations, ETT, alternative airway prn

– Consider inhaled beta agonists Circulation

– Large bore IV NS X 2

– Quickly titrate fluids to perfusion with bolus therapy

– ECG monitor Treat as pre-arrest patient

Anaphylaxis

Epinephrine 0.5 - 1.0 mg 1:10,000 IV prn– Hypotension unresponsive to fluids and epinephrine

consider dopamine ~10 mcg/kg/min– Bronconstriction unresponsive to Epi consider

aminophylline Diphenhydramine 50 mg IV Methylprednisolone 125 mg IV Consider MAST if unresponsive to fluids Rapid transport

Disposition Regardless of response to therapy, all

patients with systemic features must be observed for 6 to 8 hours

Latex Allergies

Due to a growing number of persons experiencing latex allergies, EMS providers should be prepared to treat patients with such allergies– Have latex free equipment

– Use the patient’s latex free supplies

Case Presentation #1

You are dispatched to an electronics manufacturing plant to see a 28-year-old woman. The woman believes she is having an allergic reaction. Security officers will meet you at the front gate and escort you to the patient.

What specific information would you likeat this point?

Case Presentation #1

You find this patient in an office area sitting at her desk. From a distance, you notice she is awake and speaking clearly. She does not appear to have any breathing difficulty. She states she had just returned from lunch and began to feel hot and light headed. Her friend pointed out that the patient’s arms and neck are very red, and that her face appears “puffy”.

Case Presentation #1 The patient states she is allergic to peanuts but has not

eaten any. She went to a health food café where she had grilled chicken and steamed vegetables. She has no other past history and takes no medications. Her last allergic rx was similar to this. Vitals are: BP-116/70; Pulse-100; RR-20; Lung sounds-clear and equal. No difficulty swallowing, redness to her arms, chest, neck and face.

Would you like to perform any other procedures/exams/testing or obtain other history before treating?

Case Presentation #1

So, what is your complete treatment plan for this patient?

Case Presentation #2

39 year-old male found at home in respiratory arrest with a bradycardic carotid pulse. His wife states he was helping a friend paint when he was apparently stung by a bee. He walked into the house, saying “I don’t feel good,” and collapsed.

Case Presentation #2

PMH: depression, gastritis, seasonal allergies Medications: Ritalin, Zantac, Prozac, Claritin No known drug allergies No prior reactions to hymenoptera

What therapies would you like to begin for this man?

Case Presentation #2

You have done the following:

– intubated orotracheally

– administered intravenous epinephrine, 0.5 mg & diphenhydramine 50 mg

– started 2 large-bore IVs of NS and given 500 cc fluid At this point, the patient no longer has a pulse

Case Presentation #2

You begin CPR and give the following:

– Dopamine drip at 10 mcg/kg/min

– Epinephrine, 1:10,000, 1 mg IV q 3-5 min You now note the following:

– ECG: Idioventricular rhythm

– Lung Sounds: difficult to hear

– Obvious facial edema

Can you think of any ideas for further treatment?