TRANSITION SERIES
Topics for the Advanced EMT
CHAPTER
19
Immunology:
Anaphylactic and
Anaphylactoid Reactions
Objectives
• Review the frequency with which
immunologic emergencies occur.
• Understand the pathology of
immunologic emergencies.
• Illustrate the relationship between
pathology and symptomatology.
• Discuss treatment strategies.
Introduction
• Allergic reactions may present from
mild to severe.
• Manifestations can be related to the
body system failing due to the reaction.
• Although an allergic reaction is
designed to be beneficial to the body,
when the response is severe it can be
fatal.
Epidemiology
• Anaphylaxis is not a reportable disease.
• An estimated 20,000 to 50,000 persons
suffer an anaphylactic reaction each
year.
Epidemiology (cont’d)
• Certain drugs, medical dye, and food
are the most common triggers.
– Food is the most common trigger in
children through young adults.
– Insect venom and idiopathic causes are
most common in middle age.
Pathophysiology
• Anaphylactic reaction
– Patient must be sensitized
– Chemical mediators released with
subsequent exposure
– Effects of mediators causes organ and
system failure
– Characteristic presentation
Common Causes of Anaphylactic Reactions.
Pathophysiology (cont’d)
• Anaphylactoid reaction
– Not the typical immunologic antigenantibody reaction
– Anaphylactoid trigger “directly” causes
the breakdown of mast cells and
basophils
– Chemical mediators released
– Characteristic presentation similar to
anaphylactic reaction
Common Causes of Anaphylactoid Reactions
Pathophysiology (cont’d)
• Effects of chemical mediator release
– Increased capillary permeability
– Decreased vascular smooth muscle tone
– Increased bronchial smooth muscle tone
– Increased mucus secretions in the
tracheobronchial tract
Life-threatening responses in anaphylactic reaction: bronchoconstriction,
capillary permeability, vasodilation, and an increase in mucus production.
Pathophysiology (cont’d)
• General considerations
– Fatal episodes related to airway
occlusion, respiratory failure, severe
hypoxia, and circulatory collapse
Localized angioedema to the tongue from an anaphylactic reaction. (© Edward T.
Dickinson, MD)
Urticaria (hives) from an allergic reaction to a penicillin-derivative drug. (©
Charles Stewart, MD & Associates)
Common Signs and Symptoms of Anaphylactic Reactions
Common Signs and Symptoms of Anaphylactic Reactions
Common Signs and Symptoms of Anaphylactic Reactions
Common Signs and Symptoms of Anaphylactic Reactions
Assessment Findings
• Other notable assessment
characteristics
– Parenteral injections produce the
severest reactions.
– The faster the onset, the worse the
reaction.
– Signs and symptoms peak in 15-30
minutes.
Assessment Findings (cont’d)
• Other notable assessment
characteristics
– Skin and respiratory reactions are the
earliest to present.
– Mild reactions could suddenly turn
severe.
– Most fatalities occur within 30 minutes.
– The patient may have a biphasic or
multiphasic reaction following treatment.
Differentiating Between a Mild and a Moderate to Severe Reaction.
Assessment Findings (cont’d)
• Epinephrine as drug of choice
– Stimulation of alpha receptor sites
– Stimulation of beta receptor sites
– Ability to be given IM (by EMTs) or
intravenously (by paramedics)
– Preferred site: IM anterior thigh
Emergency Medical Care
• Keep airway patent.
• Suction secretions.
• Administer high-flow oxygen.
– Ventilate the patient if needed.
• Administer epinephrine by auto-injector
if indicated.
• Initiate rapid transport.
Emergency Medical Care (cont’d)
• If an extremity is involved consider
application of a loose tourniquet.
• Some systems allow Advanced EMTs to
administer diphenhydramine (Benadryl).
• Treat wheezing with beta-2 agonist.
• Treat hypotension with IV fluid bolus.
• Treat hypotension secondary to beta
blockers with glucagon.
Case Study
• You are alerted for an emergency
involving a possible allergic reaction.
When you arrive at the residence address,
you see an adult male on the porch being
propped up in a sitting position by family
members on each side. His head is limply
flexed forward on his chest. As you
approach, you see his head bobbing with
each breath, and hives covering his body.
Case Study (cont’d)
• Scene Size-Up
– Standard precautions taken.
– Scene is safe, no entry or egress
problems.
– One patient, adult male, appears
unresponsive, mid-30s.
Case Study (cont’d)
• Scene Size-Up
– NOI is suspected allergic
reaction/dyspnea.
– Given the grave scene size-up, your
partner radios for the ALS supervisor to
also respond.
Case Study (cont’d)
• What are some concerns you have,
based on the scene size-up?
• What are possible conditions you
suspect at this time?
Case Study (cont’d)
• Primary Assessment Findings
– Patient responds to noxious stimuli with
nonpurposeful motion.
– With each inhalation, you hear sonorous
sounds and slight stridor.
– Breathing depth is minimal due to
airway blockage, peripheral pulses are
absent.
Case Study (cont’d)
• Primary Assessment Findings
(continued)
– Skin is cool, pale, and diaphoretic; hives
cover face, neck, chest, and arms.
– No indication of significant trauma.
Case Study (cont’d)
• Is this patient a high or low priority?
Why?
• What are the life threats to this
patient?
• Based on the primary survey, what
emergency care would be warranted at
this time?
Case Study (cont’d)
• Medical History
– Per family, he is allergic to bee stings,
but never this bad.
• Medications
– Patient has an auto-eject epi pen; no
other medications.
• Allergies
– None per the patient's family.
Case Study (cont’d)
• Pertinent Secondary Assessment
Findings
– Patient reportedly was outside when he
walked onto the porch and said he was
“stung” and then passed out.
– Sonorous airway sounds now absent
with positioning, faint inspiratory stridor
still present.
– Bilateral wheezing with auscultation,
also poor alveolar sounds.
Case Study (cont’d)
• Pertinent Secondary Assessment
Findings (continued)
– Peripheral pulses absent, carotid rapid
and weak.
– Hives noted to body, skin cool and
diaphoretic.
– Poor muscle tone bilaterally.
Case Study (cont’d)
• Pertinent Secondary Assessment
Findings (continued)
– B/P 72/palp, heart rate 126, resps 34
and shallow.
– No other findings contributory to
presentation.
Case Study (cont’d)
• With this information, has your field
impression changed at all?
• What would be the next steps in
management you would provide to the
patient?
• Should the Advanced EMT still use the
epi pen?
Case Study (cont’d)
• Care provided:
– Supine positioning, legs elevated.
– PPV with high-flow oxygen, NPA inserted.
– All tight or constrictive clothing and
jewelry removed.
– Epi auto-eject pen administered x1 (0.3
mg).
– Intravenous access and administration of
IV fluid.
Case Study (cont’d)
• In a patient with this field impression,
discuss the benefits of the following
interventions:
– Providing high-flow oxygen
– Positioning the patient supine
– Loosening tight clothing
– Administering epinephrine
– Intravenous therapy
Summary
• An allergic reaction may range from
mild to severe.
• Anaphylactic and anaphylactoid
reactions can rapidly cause death to the
patient.
• The Advanced EMT's goal is to
recognize the acute allergic reaction
and provide appropriate care based on
findings.