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