Download Allergic Reaction

Emergency Medical Training Services
Emergency Medical Technician – Paramedic Program Outlines
Outline Topic: Allergic Reaction
Revised: 11/2013
Allergic reaction is an exaggerated response by the immune system.
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Range from mild, moderate to severe (anaphylaxis)
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“phylaxis” means protection.
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Injected penicillin and bee/wasp stings are the two most common causes of anaphylaxis.
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100-500 deaths per year with penicillin. 25-40 deaths due to bee stings.
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The immune system is the primary cause of allergic reactions that also affect the cardiovascular system,
respiratory system, nervous system, and GI system.
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Immune system is found in the blood, bone marrow, lymphatic system.
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Pathogen is an invading substance which triggers an immune response.
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Immunity
Cellular immunity – Direct attack of the foreign (pathogen) substance by specialized cells of the immune
system.
Humoral immunity – Chemical attack of the invading substance. Antibodies also called immunoglobulin (Igs).
Antibodies are made by special immune cells “B cells”.
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IgA
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IgE
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IgE
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IgG
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IgM
1.
Antigen is defines as a substance capable of starting an immune response.
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So a pathogen/antigen may get into the body but only some are antigens that trigger immune
response. Most antigens are proteins.
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Allergen is a substance capable of inducing allergy of specific hypersensitivity once reacting to an
antigen.
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Primary response
Exposure to a new antigen it will take several days before an immune response takes place. IgG & IgM
released first.
Other immune cells are released to develop antibodies. Memory cells learn the particular antigen. Like
chicken pox so the next time you are exposed the immune system has a head start for a fast response.
Note: Most severe: Type 1 reactions release IgE and are the fast acting anaphylaxis reactions.
Note: Length of exposure is important but not to the same degree an frequency of exposure.
Note: Mast cells release Histamines which cause vasodilation etc… Mast cells also release Leukotrienes cause
major bronchoconstriction.
Note: If epi does not work due to the patient taking a beta blocker give glucagon. Glucagon -- Has inotropic,
chronotropic, and vasoactive effects that are independent of beta-receptors.
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1.
Secondary response
Antibodies specific for the antigen are released to eliminate the antigen.
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Acquired immunity begins with birth and builds antibodies through life exposures.
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Artificially Acquired Immunity is vaccinations.
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Active Immunity occurs following exposure to an antigen.
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Passive Immunity are released until active immunity kicks in. For example they are the night security
guard and if something goes wrong they call the police.
Allergies
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Must be sensitized to an allergen becoming an antigen.
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As a result some individuals develop hypersensitivity to a particular substance.
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Two types of hypersensitivity
1. Delayed – cellular immunity. Poison ivy, certain drugs.
2. Immediate – hay fever, drug allergies, food allergies, asthma etc….
Routs of Entry
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Oral
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Inhalation
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Topically
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Injection/envenomation – penicillin injections most common fatalities.
Bee sting events:
IgE released.
Attach to mast cells (these cells release histamines).
Histamine are chemical mediators. Dilates vessels, spasms lungs, GI irritability.
Swelling of the head/neck/airway is agnioedema.
H1 & H2
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H1 receptors cause bronchoconstriction and contraction of the intestine. To a higher degree mast cells
also release Leukotrienes which is the major cause of bronchoconstriction not histamines.
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H2 receptors cause vasodilatation, secretion of gastric acids.
Signs:
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Urticaria (hives)
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N/V
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Diarrhea
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GI irritability
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IV, Airway, 100% O2 intubation if needed
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Drugs
Care:
1. Oxygen high flow
2. Epi 0.3-0.5mg SQ, IV, Sublingual Injection depending on moderate or severe reactions.
3. Benadryl 25-50mg IV or IM (phenergan might be helpful)
4. H2 medication like Tagament (cimetadine) to reverse the dilation of vessels.
5. Corticosteroids – Solu-medrol or Decadron
6. Vassopressors – to support blood pressure.
7. Beta agonist – albuterol to stimulate bronchdilation
8. Glucagon if pt on beta blocker and epi does not work.