Allergic Reactions Flashcards
anaphylaxis mechanisms
Immunologic
In the immunologic mechanism, immunoglobulin E (IgE) binds to the antigen (the foreign material that provokes the allergic reaction). Antigen-bound IgE then activates FcεRI receptors on mast cells and basophils. This leads to the release of inflammatory mediators such as histamine. These mediators subsequently increase the contraction of bronchial smooth muscles, trigger vasodilation, increase the leakage of fluid from blood vessels, and cause heart muscle depression. There is also an immunologic mechanism that does not rely on IgE, but it is not known if this occurs in humans.
Non-immunologic
Non-immunologic mechanisms involved substances that directly cause the degranulation of mast cells and basophils. These include agents such as contrast medium, opioids, temperature (hot or cold), and vibration.
humoral immunity
(also called the antibody-mediated system) is the aspect of immunity that is mediated by macromolecules (as opposed to cell-mediated immunity) found in extracellular fluids such as secreted antibodies, complement proteins and certain antimicrobial peptides. Humoral immunity is so named because it involves substances found in the humours, or body fluids.
cell mediated immunity
Cell-mediated immunity is directed primarily at microbes that survive in phagocytes and microbes that infect non-phagocytic cells. It is most effective in removing virus-infected cells, but also participates in defending against fungi, protozoans, cancers, and intracellular bacteria. It also plays a major role in transplant rejection.
immune response that does not involve antibodies but rather involves the activation of phagocytes, antigen-specific cytotoxic T-lymphocytes, and the release of various cytokines in response to an antigen. Historically, the immune system was separated into two branches: humoral immunity, for which the protective function of immunization could be found in the humor (cell-free bodily fluid or serum) and cellular immunity, for which the protective function of immunization was associated with cells. CD4 cells or helper T cells provide protection against different pathogens. Cytotoxic T cells cause death by apoptosis without using cytokines, therefore in cell mediated immunity cytokines are not always present.
ALLERGEN
substance causing an exaggerated immune response
ANAPHYLAXIS
Exaggerated immune response
allergen binds to IgE
IgE binds to mast cell
mast cell degranulation
release histamine
effects of histamine (H1 and H2 receptors)
inflammation - swelling
bronchconstriction
vasodilatation
histamine
released by body in anaphylaxis
- contraction of bronchial smooth muscles,
- stimulation of vascular permeability, and
leukotiene
other chemical released by the body in anaphylaxis
They exhibit a number of biological effects such as - contraction of bronchial smooth muscles,
- stimulation of vascular permeability, and
- attraction and activation of leukocytes.
Compared to histamine, which causes constriction of airways and edema formation, the leukotrienes are three to four orders of magnitude more potent and the effects have longer duration
H1 RECEPTORs on our lungs cause
When stimulated it causes bronchoconstriction
What effect H2 RECEPTORs have on our GI tract & Blood Vessels
Throwing up or Diarrehea - on the blood vessels they dilate
What position should a patient having an allergic Rx be in?
lay them flat
What drug is a histamine blocker
benedryl
Dosage of epinephrine
epinephriene
adult 0.3mg pedi 0.15mg
bronchodialator
vasoconstrictor
name 2 of the allergens
ant, bee, shellfish, peanuts….. Common allergens
sound a patient having anaphylaxis might make
wheezing
adult dose epi
.3mg
pedi dose
.15 mg
list symptoms
swelling, flushing, warm, tingling feeling in face, mouth, chest, feet or hands
for a pt epi is only given when they have trouble breathing or blood pressure bad
epi
you respond to a child with hives and good blood pressure
take to hospital and monitor in route
anaphylaxis
respiratory arrest or signs and symptoms of shock
side effects of epi
Epinephrine is a chemical that narrows blood vessels and opens airways in the lungs. These effects can reverse severe low blood pressure, wheezing, severe skin itching, hives, and other symptoms of an allergic reaction.
- Increased heart rate
- Increased cardiac workload
Allergic Reactions
• Immune system naturally responds to foreign substances in body
Allergic reaction
exaggerated response to foreign substance
Allergen
substance causing exaggerated effect
Body’s Reaction to Allergen
• First exposure
– Immune system forms antibodies
– Antibodies identify and attack particular foreign substance
– Antibodies combine only with allergen they were formed in response to
Body’s Reaction to Allergen
• Second (and subsequent) exposures
– Antibodies exist
– Antibody combines with allergen, leading to
release of histamine and other chemicals into
bloodstream
– Chemicals cause harmful effects
• Effects of histamine and other chemicals
– Inflammation (swelling)
– Bronchoconstriction
– Vasodilation
Anaphylaxis
• Severe, life-threatening allergic reaction
• Can cause:
– Dilation of blood vessels (hypotension)
– Airway swelling (airway obstruction)
– Bronchoconstriction (respiratory failure)
Common Allergens
• Insects • Foods • Plants • Medications • Others – Dust, makeup, soap, etc.
Latex Allergy
• Common concern in EMS
– Many patients have latex sensitivity
– Providers can develop latex allergy from prolonged exposure
Course of Reaction
• No way to predict exact course of an allergic reaction • Severe reaction often takes place immediately, but can be delayed 30 minutes or more • Mild allergic reaction can rapidly progress to anaphylaxis
Signs and
Symptoms: Skin - Allergic Reactions
- Swelling
- Flushing (red skin)
- Warm, tingling feeling in face, mouth, chest, feet, or hands
- Hives
Signs and
Symptoms: Respiratory - Allergic Reaction
- Tightness in throat or chest
- Cough
- Rapid, labored, and/or noisy breathing
- Hoarseness, muffled voice, loss of voice
- Stridor
- Wheezing
Signs and
Symptoms: Cardiac - Allergic Reaction
- Increased heart rate
* Decreased blood pressure
Signs and
Symptoms: Generalized - Allergic Reaction
- Itchy, watery eyes and/or runny nose
- Headache
- Feeling of impending doom
Signs and Symptoms: Anaphylactic Shock
• Altered mental status • Flushed, dry skin or pale, cool, clammy skin • Nausea or vomiting • Changes in vital signs – Increased pulse, respirations – Decreased blood pressure
Distinguishing Anaphylaxis from Mild Allergic Reaction
- Any of previous signs and symptoms can be associated with an allergic reaction
- Anaphylaxis: patient has either respiratory distress or signs and symptoms of shock
Assessment Allergic Reaction
• Primary assessment • Identify and treat life-threatening problems – Airway – Breathing – Circulation
• History and physical exam – History of allergies – Exposure • What was the patient exposed to? • How (what method/route) was the patient exposed? – Signs and symptoms – Progression – Interventions
Treatment: Allergic Reaction
• Manage patient’s airway and breathing
• Apply high-concentration oxygen
• Provide artificial ventilations if patient is not breathing adequately
• Consider assisting patient with epinephrine auto-injector
• If patient is not wheezing or showing signs of respiratory distress or shock
– Continue with assessment
– Consult medical direction regarding use of auto-injector
Use of Auto-Injector
• When use of auto-injector may be appropriate
– If patient has come in contact with substance that caused allergic reaction in the past
– If patient also has respiratory distress or exhibits signs and symptoms of shock
After Administering Auto-Injector
- Record administration of auto-injector
- Transport patient
- Reassess
Additional Doses of Epinephrine
• Reassessment may show patient condition
deteriorating
• Additional doses of epinephrine may be
necessary
• Requires on-line medical control
• Requires bringing patient’s additional auto-injectors in ambulance
Additional Doses of Epinephrine
• If no auto-injector available
– Request ALS intercept
– Treat for shock
Think About It
- Should you administer an auto-injector for a simple allergic reaction?
- What assessment findings would indicate the need for epinephrine?
Epinephrine
- Commonly prescribed to patients with a history of allergy
- Auto-injectors are common for people to carry or have at home
- Hormone produced by body
- Constricts blood vessels
- Dilates bronchioles
Side Effects of Epinephrine
- Increased heart rate
* Increased cardiac workload
Auto-Injector
- Spring-loaded needle and syringe with a single dose of epinephrine
- Upon administration, medication automatically releases and injects
Administering Auto-Injector
• Injection site typically anterior-medial thigh (midway between waist and knee) • Remove clothing from site if possible • Use standard precautions • Remove cap • Press tip of auto-injector firmly against patient’s thigh • Once needle is deployed, allow full injection of medication before removing from injection site • Carefully discard auto-injector into sharps container
Pediatric Note
• Two sizes of auto-injectors
– Adult dose: 0.3 mg
– Children’s dose (for child less than 66 pounds): 0.15 mg
Chapter Review - Allergic
• Patients with anaphylaxis will be extremely
anxious. Their bodies are in trouble and
are letting them know it.
• The signs and symptoms of anaphylaxis
result from physiological changes: vasodilation, bronchoconstriction, leaky
capillaries, and thick mucus
• By quickly recognizing the condition, consulting medical direction, and administering the appropriate treatment, you can literally make the difference between life and death for these patients.
Remember - Allergic
• In an allergic reaction, the body’s immune
system overreacts to an allergen and
causes potentially harmful side effects.
• Anaphylaxis is a severe, systemic form of
allergic reaction; it is a life-threatening
emergency.
Remember - Allergic
• EMTs must use assessment to
differentiate a localized allergic reaction
from a systemic anaphylactic reaction.
• Epinephrine is useful in anaphylaxis
because it constricts dilated blood vessels
and opens bronchial passages.
• Epinephrine has potentially dangerous
side effects and should be used only in the
event of anaphylaxis.
Questions to Consider - Allergic
• What are the indications for administration
of an epinephrine auto-injector?
• List some of the more common causes of
allergic reactions.
Questions to Consider - Allergic
• List signs or symptoms of an anaphylactic reaction associated with each of the following:
– Skin
– Respiratory system
– Cardiovascular system
Critical Thinking - Allergic
• A 24-year-old male ate a meal that he
believes contained shellfish. He is allergic
to shrimp. He is sweating and nervous. He
appears to be breathing adequately. You
do not note any wheezing or stridor
Critical Thinking - Allergic
• His face is slightly red. His pulse is 88 strong and regular, respirations 24, blood pressure 108/74, and skin warm and moist. Should you administer epinephrine?
degranulation
Degranulation is a cellular process that releases antimicrobial cytotoxic molecules from secretory vesicles called granules found inside some cells. It is used by several different cells involved in the immune system, including granulocytes (neutrophils, basophils and eosinophils) and mast cells. It is also used by certain lymphocytes such as natural killer (NK) cells and cytotoxic T cells, whose main purpose is to destroy invading microorganisms.
mast cells
A mast cell (also known as a mastocyte or a labrocyte) is a resident granulocyte of several types of tissues that contains many granules rich in histamine and heparin. Although best known for their role in allergy and anaphylaxis, mast cells play an important protective role as well, being intimately involved in wound healing and defense against pathogens.
hypersensitivity
an exaggerated response by the immune system to a particular substance
histamine
Histamine is an important protein involved in many allergic reactions.
Allergies are caused by an immune response to a normally innocuous substance (i.e. pollen, dust) that comes in contact with lymphocytes specific for that substance, or antigen.
In many cases, the lymphocyte triggered to respond is a mast cell. For this response to occur, a free-floating IgE (an immunoglobulin associated with allergic response) molecule specific to the antigen must first be attached to cell surface receptors on mast cells.
Antigen binding to the mast cell-attached IgE then triggers the mast cell to respond. This response often includes the release of histamine (Janeway et al 1999).
