Allergic Reactions &
Anaphylaxis
MARCH 30, 2012 PCP
Adapted From EMS Professions
Temple College
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Anaphylaxis is an immediate,
systemic, life-threatening allergic
reaction. Prompt recognition and
appropriate drug therapy in the
prehospital phase are crucial to
patient survival.
Today’s Objectives
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Epidemiology
Review the patho of an Allergy & Anaphylaxis
Review the mechanism injury
Review the sign & symptoms
Review the Principles of Management
PCP Anaphylaxis Protocol
Recall the use of Epinephrine
Recall the procedure for administering SC injection
Other Protocols that may used in conjunction with the
Anaphylaxis protocol
Demonstrate the assessment & management of an Anaphylaxis
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Practice Simulations
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Incidence
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In North America- 400 to 800 deaths/year
Parenterally administered penicillin accounts
for 100 to 500 deaths per year
Insect stings (bees) account for 40 to 100 deaths
per year
Risk factors: beta-blockers, adrenal
insufficiency
Causes of Deaths
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Laryngeal edema and acute bronchospasm
with respiratory failure account for >70%
Circulatory collapse accounts for 25%
Other <5% - ?brain ?MI
Allergic Reaction
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 Physiologic response to antigens
– Oversensitive response = allergic
– Occurs after sensitization to antigen
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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
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Systemic reaction of multiple organ systems to
antigen-induced IgE-mediated immunulogic
mediator release in previously sensitized
individual
An event that can lead to death
Allergic Rx – Induces Antibody
Formation
Anaphylaxis
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Antigens enter body by:
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Injection
Ingestion
Inhalation
Absorption
Anaphylaxis Pathophysiology
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Antigen enters body & Antibodies produced
Attach to surface of mast or basophil cells
Mast cells become sensitized
Anaphylaxis Pathophysiology
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Mast cells
– In all subcutaneous/submucosal tissues,
– Including conjunctiva, upper/lower respiratory
tracts, and gut
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Basophils
– Circulate in blood
Mast Cells Blasting
Anaphylaxis Pathophysiology
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Antigen reenters body
Attaches to antibodies on mast or basophil cells
Mast cell degranulates, releases
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Histamine
Leukotrienes
Slow reacting substance of anaphylaxis (SRS-A)
Eosinophil chemotactic factor (ECF)
Where Do Things Go
Histamine
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Three histamine receptor types:
– H1
– H2
– H3
Histamine
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Acts on H1 receptors to cause
– Smooth muscle contraction
– Increased vascular permeability
– Prostaglandin generation
Histamine
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Acts on H2 receptors to cause
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Increased vascular permeability
Gastric acid secretion
Stimulation of suppressor lymphocytes
Decreased PMN enzyme release
Release of more histamine from mast cells
and basophils
Histamine
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Acts on H3 receptors to cause
– Inhibition of central, peripheral nervous
system neurotransmitter release
– Inhibition of further histamine formation,
release
Vasodilation
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Decreased peripheral vascular resistance
Hypotension
Tachycardia
Peripheral hypoperfusion
Increased Capillary Permeability
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Tissue edema, urticaria (hives), itching
Laryngeal edema
– Airway obstruction
– Respiratory distress
– Stridor
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Fluid leakage from vascular space
– Hypovolemic shock
Urticaria
Describe What You See
Describe What You See
Describe What You See
Describe What You See
Describe What You See
Smooth Muscle Spasm
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Bronchospasm
– Respiratory distress
– “Tight Chest”
– Wheezing
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GI Tract Spasm
– Nausea, vomiting
– Cramping, diarrhea
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Bladder Spasm
– Urinary urgency
– Urinary incontinence
Anaphylactic Reaction
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Leukotrienes
– Potent bronchoconstrictors,  vascular
permeability & possibly coronary
vasoconstriction
– Slower onset than histamine
– Effects last longer than histamine
Allergic Reactions
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Generally classified into 3 groups:
– Mild allergic reaction
– Moderate allergic reaction
– Severe allergic reaction (anaphylaxis)
Mild Allergic Reaction
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Characteristics
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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
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Characteristics
– Mild signs/symptoms with any of following:
» Dyspnea, possibly with wheezes
» Angioneurotic edema
» Systemic, not localized
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No hypotension/hypoperfusion
Severe Allergic Reaction
(Anaphylaxis)
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Characteristics
– Mild and/or moderate signs/symptoms plus
– Shock / hypoperfusion
Clinical Manifestation
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Dependent on:
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Degree of hypersensitivity
Quantity, route, rate of antigen exposure
Pattern of mediator release
Target organ sensitivity and responsiveness
Clinical Manifestation
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Severity varies from mild to fatal
Most reactions are respiratory, dermatologic
Less severe early findings may progress to lifethreatening 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
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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
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May progress to involvement of respiratory
system
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cough
chest tightness
dyspnea
wheezing
throat tightness
dysphagia
hoarseness
Clinical Manifestation
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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
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Physical Exam findings may include
– urticaria, angioedema, rhinitis, conjunctivitis
– tachypnea, tachycardia, hypotension
– laryngeal stridor, hypersalivation, hoarseness,
angioedema
Insect Sting Hypersensitivity
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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
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Treatment depends upon severity of
reaction and signs/symptoms of its
presentation
Epinephrine
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Treatment of Choice for Anaphylaxis – No
absolute contraindications in anaphylaxis
Route IM, SC, IV
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Sympathomimetic
Relaxes smooth muscle in the airways (Beta)
Peripheral vascular constricting (Alpha)
Counteracts histamine and other cytokines
Raises blood sugar level
Raises heart rate, blood pressure, and myocardial
oxygen demand
S/A – Tremors, anxiety, headache, palpitations
Peak 1 to 2 minutes to a duration of 5 to 10
min
Benadryl
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Second Treatment of Choice for Anaphylaxis –
Route PO, IM, IV
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Antihistine
H1 receptor antagonist
Counteracts histamine and other cytokines
Blocks histamine activity at receptor site
Raises heart rate, blood pressure, and myocardial
oxygen demand
S/A – Drowsiness, dizziness, dryness of mouth,
nervousness, nausea
Peak < 1 hour
½ life 2.4 to 9.3 hours
Management
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Optimal management requires
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High index of suspicion (suspect, treat within minutes)
Early diagnosis
Pharmaceutical intervention
Observation
Disposition
Patient Self-Management
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Benadryl (Diphenhydramine ) 50 mg PO
At any sign of anaphylaxis, self-administer
subcutaneous epinephrine (Epi-Pen®, AnaKit®)
Mild Allergic Reaction
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Often self-treated at home
High Flow Oxygen
Base line vitals
Diphenhydramine 25 - 50mg PO or IM
– IV is reasonable but should include transport
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If stinger present, flick it away with credit card
or fingernail
Anticipate crisis
Moderate to Severe Allergic or
Anaphylaxis Reaction
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High flow oxygen
Base line vitals
IV NS ( Patient > 12 yrs
– Maintenance Rate
– Bolus BP < 90 mm Hg
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ECG monitor
Diphenhydramine 25-50 mg PO*
Transport
Contact EP if unstable
*6-11 years 25 mg Diphenhydramine
*2-5 years 12.5 mg Diphenhydramine
Differential DX
Presentation
Differential diagnosis
Hypotension
Septic shock
Vasovagal reaction
Cardiogenic shock
Hypovolemic shock
Respiratory distress with wheezing or stridor
Airway foreign body
Asthma and chronic obstructive pulmonary disease
exacerbation
Vocal chord dysfunction syndrome
Differential Dx
Postprandial collapse
Airway foreign body
Monosodium glutamate ingestion
Sulfite ingestion
Scombroid fish poisoning
Flush syndrome
Carcinoid
Postmenopausal hot flushes
Red man syndrome (vancomycin [Vancocin])
Miscellaneous
Panic attacks
Systemic mastocytosis
Hereditary angioedema
Leukemia with excess histamine production
Case Presentation #1
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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 like
at this point?
Case Presentation #1
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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
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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?