IMMUNOLOGY (ALLERGIC REACTIONS AND ANAPHYLAXIS)
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Transcript of IMMUNOLOGY (ALLERGIC REACTIONS AND ANAPHYLAXIS)
Paramedic Care:Principles & Practice
Volume 4Medical Emergencies
Chapter 5 Allergies and Anaphylaxis
Topics
PathophysiologyAssessment Findings in AnaphylaxisManagement of AnaphylaxisManagement of Allergic ReactionsPatient Education
IntroductionAllergic Reaction– An exaggerated
response by the immune system to a foreign substance
IntroductionAnaphylaxis– An unusual or exaggerated allergic reaction– A life-threatening emergency
Injected penicillin and bee and wasp (Hymenoptera) stings are the two most common causes of fatal anaphylaxis
Pathophysiology
PathophysiologyThe Immune System– The goal is destruction or inactivation of:
PathogensAbnormal cellsForeign molecules
– Cellular Immunity(direct attack)– Humoral Immunity (chemical)
It’s Complicated
Antigen
Antigen
Substance capable of immune response
Antibody
Principal agent of a chemical attack.
Pathophysiology
Immune Response– Exposure to antigen produces primary
response. Immune system develops antigen-specific antibodies
– Future exposures generate a faster secondary response
Humoral Immunity
Primary ResponseB Lymphocyte
Primary Response
Initial response to an antigenA ‘memory’ of the cell is developed
B Lymphocytes secrete immunoglobins
IgMIgG
IgGHas the memory
85%
IgMThe Largest Immunoglobin
produced during primary response
IgDPresent in low concentrations
IgADominant in body secretions
IgEPrinciple for allergic reactions
Lymphocyte B Clones
Cellular Immunity
T LymphocytesTd delayed hypersensitivity
Tc cytotoxic cells
Ts suppressor cells
Other T Cells
Thhelper cells
Memory Cells
Immunity
ImmunityNatural Immunity (Innate)– Genetically predetermined– Everyone is born with it
Immunity
Acquired Immunity– Naturally acquired
(Chicken pox)– Induced active immunity
(vaccinations)
Immunity
Passive Immunity- Administration of antibodies– Natural
In the uterusVia breast milk
– Induced (tetanus booster)
Allergies
Sensitization– Initial exposure of an individual to an antigen
Hypersensitivity– Delayed
Results from cellular immunity and does not involve antibodiesCommonly results in skin rashResults from exposure to certain drugs or chemicals
– ImmediateExposure quickly results in secondary responseMore severe than delayed hypersensitivity
Allergies
Allergen– Exposure generates secondary response
Large quantities of IgE are releasedAllergen binds to IgE, causing chemical release
Release is “allergic reaction”Includes histamines, heparin, and other substances that are designed to minimize the body’s exposure to an antigenHistamine causes bronchoconstriction, vasodilation, increased gastric motility, and increased vascular permeability
Histamine
A defense mechanism to destroy antigensReleased from basophils and Mast cells– H1: bronchoconstriction, contractions of intestines– H2: peripheral vasodilation, secretion of gastric acids
Histamine
Bronchoconstriction – prevents antigen from entering lungs.
Vasodilation – helps remove antigen from circulation.
Secretion of gastric acid – kills ingested antigens.
Allergic Response
Anaphylaxis
Causes– Antigen that causes release of the IgE
antibodies is referred to as an allergen
AnaphylaxisCauses– Injections
Most anaphylaxis results from injected allergenAllergen rapidly distributed throughout the body, resulting in massive histamine release
Assessment Findings in Anaphylaxis
Assessment Findings in Anaphylaxis
Focused History and Physical Exam– Focused History
SAMPLE and OPQRST HistoryRapid onset, usually 30–60 seconds following exposureSpeed of reaction is indicative of severityPrevious allergies and reactions
– Physical ExamPresence of severe respiratory difficulty is key to differentiating anaphylaxis from allergic reaction
Physical Exam– Facial or laryngeal
edema– Abnormal breath
sounds– Hives and urticaria– Hyperactive bowel
sounds– Vital sign deterioration
as the reaction progresses
Assessment Findings in Anaphylaxis
Pathophysiology of Anaphylaxis
Management of Anaphylaxis
Management of Anaphylaxis
Scene Safety:– Consider the possibility of trauma
Protect the airway– Use airway adjuncts with care– Intubate early in severe cases to prevent total
occlusion of the airway– Be prepared to place a surgical airway
Management of Anaphylaxis
Support breathing– High-flow, high-concentration oxygen or assisted
ventilation if indicatedEstablish IV access– Patient may be volume-depleted due to “third
spacing” of fluidAdminister crystalloid solution at appropriate ratePlace a second IV line if indicated
Management of Anaphylaxis Administer medications:– Oxygen– Epinephrine– Antihistamines– Corticosteroids– Vasopressors– Beta-agonists– Other agents
Psychological support
Management of Allergic Reactions
Scene safetyProtect the airwaySupport breathingEstablish IV accessAdminister medications:– Antihistamines– Epinephrine
Management of Allergic Reactions
© Craig Jackson/In the Dark Photography
Management ofAnaphylaxis and Allergic Reactions
Click here to view the management of Anaphylaxis and Allergic Reactions.
Patient Education
Patient Education
Prevention of ReactionsRecognition of Signs/Symptoms– Patient-initiated treatment
Epinephrine auto-injectors
Desensitization
Sting RemediesOnionTobaccoHoneyVinegarBaking SodaMeat tenderizerToothpasteIceCalamine/Benadryl/Cortizone
Summary
PathophysiologyAssessment Findings in AnaphylaxisManagement of AnaphylaxisManagement of Allergic ReactionsPatient Education
Stevens-Johnson Syndrome
Not all rashes are urticaria
Impetigo
Ring Worm
Psoriasis