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Medical Emergencies > Allergies and Anaphylaxis > Flashcards

Allergies and Anaphylaxis Flashcards

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USMLE® Step 1 flashcards
1
Q

introduction

A
  • at least 1,000 americans per year die of allergic/anaphylactic reactions
  • allergy related emergencies may involve:
  • acute airway obstruction
  • cardiovascular collapse
  • you must be able to treat these life threatening complications
  • immunology is the study of the bodys immune system
  • reactions may be mild and local, involve itching, redness, and tenderness, or they may be severe and systemic*, including shock and respiratory failure
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2
Q

allergic reaction

A

-a response to chemicals the body releases to combat certain stimuli called allergens

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3
Q

5 categories of stimuli

A
    1. insect bites and stings
    1. medications
    1. food
    1. plants
    1. chemicals
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4
Q

antigen

A
  • any molecule that can cause an immune response (antibody production against it)
  • may be from the environment (non self) or form inside the body (self antigen)
  • vaccines are examples of antigens
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5
Q

haptens

A

-too small to be antigenic but can attach to a larger molecule (protein) and cause immune response

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6
Q

anaphylaxis

A
  • life threatening allergic reaction mounted by multiple organ systems, which must be treated with epinephrine
  • wheezing and urticaria wheals can be signs of anaphylaxis
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7
Q

epipen

A
  • people allergic to bee, hornet, yellow jacket, or wasp venom often carry a kit that contains epinephrine in an autoinjector
  • all patients with suspected anaphylaxis require oxygen
  • check patients who may be having an allergic reaction for flushing, itching, and swelling of skin, hives, wheezing and stridor, persistent cough, decrease in blood pressure, weak pulse, dizziness, abdominal cramps, and headache
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8
Q

pathophysiology: allergic reactions

A
  • immune system protects the body from foreign substances and organisms
  • when foreign substance invades the body:
  • body goes on alert
  • body initiates a series of responses to inactivate the invader
  • an allergic reaction is an exaggerated immune response to any substance
  • may be mild and local, or severe and systemic
  • not caused directly by an outside stimulus
  • caused by the bodys immune system
  • releases chemicals to combat stimulus
  • include histamines and leukotrienes
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9
Q

leukotrienes

A

a family of eicosanoid inflammatory mediators produced in leukocytes. One of their roles (specifically, leukotriene D4) is to trigger contractions in the smooth muscles lining the bronchioles; their overproduction is a major cause of inflammation in asthma and allergic rhinitis.[

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10
Q

allergy

A
  • Type of hypersensitivity reaction of the immune system: may involve more then one type of reaction
  • An allergy is an immune reaction to something that does not affect most other people
  • Substances that often cause reactions are: pollen, dust mites, mold spores, animal dander, food, insect stings, medicines
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11
Q

hypersensitivity

A
  • Hypersensitivity(hypersensitivity reaction): excessive, harmful immune reaction to antigens
  • Hypersensitivity reactions require a pre-sensitized (immune) state of the host
  • Hypersensitivity reactions: four types; based on the mechanisms involved and time taken for the reaction
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12
Q

5 classes of antibodies

A
    1. IgG: 80% of all antibodies -> resistance against viruses & bacteria
    1. IgE: attaches to basophil & mast cell surface -> triggers release of histamine, increases inflammation
    1. IgD: on the surface of B cells
    1. IgM: 1st antibody secreted by plasma cells after antigen is encountered -> anti-A & anti-B antibodies of blood typing
    1. IgA: in glandular secretions (saliva, sweat)
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13
Q

4 types of hypersensitivity reactions

A
    1. Type I (acute/immediate) hypersensitivity (IgE)
      1. Type II (antibody-dependant cytotoxic) hypersensitivity (IgG, IgM)
    1. Type III (Ag-Ab immune complex) hypersensitivity
      1. Type IV (delayed) hypersensitivity (T cells, cell-mediated) -> poison ivy
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14
Q

type 1 hypersensitivity: IgE mediated

A
  • allergic
  • overreaction to an allergen contracted through skin, inhaled through lung, swallowed or injected
  • triggered by harmless substances such as; pollen, dust, animal dander, food
  • can also occur as a result of drug or bee stings or stings from other insects (an allergen)
  • ex. bee stings, latex, certain medications (penicillin)
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15
Q

allergen

A

an antigen that causes allergy, either inhaled, ingested

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16
Q

immunopathogenesis

A
  • both mast cells and basophils are involved in immunopathogenesis of IgE mediated diseases
  • Mast cell and basophil cell membranes express a high-affinity receptor for IgE
  • Immediate hypersensitivity reactions are mediated by IgE, but T and B cells play important roles in the development of these antibodies
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17
Q

histamine

A
  • dilates blood cells
  • chemical mediators
  • causes reactions
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18
Q

mast cells

A
  • Mast cells are abundant in the mucosa of the respiratory, gastrointestinal tracts and in the skin, where atopic reaction localize
  • Mast cells release mediators which cause the pathophysiology of the immediate and late phases of atopic diseases
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19
Q

type 2 cytotoxic/antibody mediated

A
  • cytotoxic
  • ex. hemolytic reactions
  • goodpasture syndrome
  • hyperacute graft reactions
  • Goodpasture syndrome is a rare disease that can involve quickly worsening kidney failure and lung disease. Goodpasture syndrome is an autoimmune disorder. It occurs when the immune system mistakenly attacks and destroys healthy body tissue. Persons with this syndrome develop substances that attack a protein called collagen in the tiny air sacs in the lungs and the filtering units (glomeruli) of the kidneys. A purified protein derivative (PPD) skin test is a test that determines if you suffer from tuberculosis (TB).
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20
Q

type 3 immune complex/IgG/IgM mediated

A
  • immune complex deposition
  • ex. hypersensitivity pneumonitis
  • systemic lupus erythematosus
  • polyarteritis nodosa
  • serum sickness
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21
Q

type 4 delayed or cell mediated

A
  • delayed
  • ex. chronic graft rejections
  • PPD test
  • latex
  • nickel
  • poison ivy
22
Q

mechanism

A
  • First-time exposure may only produce a mild reaction, repeated exposures may lead to more serious reactions
  • Once a person is sensitized (has had a previous sensitivity reaction), even a very limited exposure to a very small amount of allergen can trigger a severe reaction
  • Most occur within seconds or minutes after exposure to the allergen, but some can occur after several hours
23
Q

prevention

A
  • Avoid triggers such as foods and medications,…… that have caused an allergic reaction, even a mild one. This includes detailed questioning about ingredients when eating away from home. Ingredient labels should also be carefully examined.
  • A medical ID tag should be worn by people who know that they have serious allergic reaction.
  • If any history of a serious allergic reactions, carry emergency medications (such as diphenhydramine and injectable epinephrine.)
  • Do not use your injectable epinephrine on anyone else. They may have a condition (such as a heart problem) that could be affected by this drug.
24
Q

anaphylaxis

A
  • extreme systemic* form of an allergic reaction
  • urticaria- blotchy redness
  • involves 2 or more body systems
  • overreaction of immune system
  • immune system becomes hypersensitive to 1 or more substances
  • mast cell activation in response to invading substances
  • histamine released- vasodilation and capillary leakage -> hypotension*
  • leukotrienes released- more powerful than histamine
  • in anaphylaxis, this effect is more widespread and powerful than allergic reaction
25
Q

allergic reaction vs anaphylaxis

A
  • more localized
  • one body system
  • itchy skin

-anaphylaxis- multiple body systems, difficulty breathing, urticaria systemically, hypotensive

26
Q

pathophysiology anaphylaxis

A
  • urticaria (hives)
  • small areas of generalized itching or burning that appear as multiple, small, raised areas on the skin
  • histamine also causes hypotension
  • later effect of more powerful leukotrienes compounds effects of histamine
  • hypotension as a result of hypovolemic shock
  • highly potent bronchoconstrictors also released: respiratory status deteriorates quickly
27
Q

common allergens

A
  • medications
  • penicillin- injection may cause immediate severe reaction
  • oral may take longer
  • person will typically experience an allergic reaction after becoming sensitized
28
Q

medications

A
  • penicillin- injection may cause immediate severe reaction
  • oral may take longer
  • person will typically experience an allergic reaction after becoming sensitized
29
Q

insect bites and stings

A
  • when an insect bites and injects the bite with its venom
  • envenomation
  • the reaction may be local (swelling/itchiness) or systemic (involving the entire body)
  • death from stinging insects far outnumber deaths from snakebites
  • stinging organ of most insects is a small hollow spine projecting from the abdomen
  • venom can be injected directly into skin
  • honeybees cannot withdraw their stinger -> fly away and die
  • wasps, hornets, and fire ants can sting multiple times
  • stinger of the honeybee can continue to inject venom for up to 20 mins
  • attempt to remove the stinger by scraping the skin with the edge of a sharp, stiff object such as a credit card -> tweezers or squeezing will inject more venom into the skin
30
Q

plants

A

-dusts, pollens, other plants materials

31
Q

food

A
  • reaction can be relatively slow

- shellfish, nuts

32
Q

chemicals

A

makeup, soap, latex

33
Q

signs and symptoms of insect stings

A
  • sudden pain
  • swelling
  • localized heat
  • redness in light- skinned individuals
  • itching, possibly a wheal
  • wheal- area of skin that is temporarily raised, typically reddened, and usually accompanied by itching
  • generalized itching and burning
  • widespread urticaria
  • wheals
  • swelling of the lips and tongue
  • bronchospasms and wheezing
  • chest tightness, coughing, dyspnea
  • anxiety
  • abdominal cramps
  • hypotension
  • occasionally, respiratory failure
34
Q

hypotension

A
  • vessel dilate -> hypotension
  • histamine is causing the vasodilation
  • heart is working harder - higher heart rate
  • hypovolemic shock -> organs shock down due to lack of blood/oxygen
35
Q

treatment for insect stings

A
  • no specific treatment
  • applying ice sometimes helps
  • swelling may be dramatic and frightening
  • local manifestation are not serious
  • do not use tweezers or forceps
  • wash the area with soap and water
  • remove any jewelry from the area
  • be alert for vomiting or signs of shock
  • give oxygen if needed
  • monitor the patients vital signs
  • if untreated, anaphylactic reaction can proceed rapidly to death
36
Q

wheels vs urticaria

A
  • urticaria is systemic

- wheels is localized

37
Q

patient assessment

A
  • mechanisms of injury/nature of illness
  • may not be an allergic reaction
  • trauma may have occurred
  • determine the MOI/NOI
  • look for bee stings or chemicals and other indications of a reaction
38
Q

primary assessment

A
  • perform a rapid scan of the patient
  • form a general impression
  • may present as respiratory or cardiovascular distress in the form of shock
  • patients will be very anxious
  • try to get information on the chief complaint
39
Q

primary assessment: airway and breathing

A
  • anaphylaxis can cause rapid swelling of upper airway
  • only a few minutes to assess the airway and provide lifesaving measures
  • work quickly to determine the severity of the symptoms
40
Q

steps of primary assessment

A
  • airway and breathing
  • position conscious patients in tripod position and listen to lungs
  • do not hesitate to initiate high flow oxygen
  • in severe situation, the definitive care is an injection of epinephrine intramuscularly
  • circulation
  • palpate for radial pulse
  • may present with hypotension
  • if pt is unresponsive and without a pulse, start CPR and use an AED
  • if pulse if present, assess for a rapid pulse, and check skin condition and capillary refill
    1. oxygen
    1. positioning
    1. maintain normal body temperature
    1. always provide prompt transport for any patient who may be having an allergic reaction
  • take a long all pts medications and auto injectors
41
Q

history taking

A
  • SAMPLE history
  • if the pt is conscious ask:
  • have any interventions already been completed
  • do you have any prescribed, preloaded medications for allergic reactions
  • do you have any respiratory symptoms
  • do you have other symptoms
  • have you had previous allergic reactions, asthma, or hospitalizations
  • what were you doing or what were you exposed to before the onset of symptoms
42
Q

secondary assessment: physical assessment

A
  • includes a systemic head to toe or focused assessment
  • thoroughly assess breathing, including:
  • increased work of breathing
  • use of accessory muscles
  • head bobbing, nostril flaring, grunting
  • tripod positioning
  • auscultate both the trachea and the chest
  • wheezing may occur because of narrowing of the air passages
  • assess the circulatory system
  • assess the skin for swelling, rash, hives, or signs of the source of the reaction
43
Q

secondary assessment: vital signs

A
  • assess baseline vitals
  • pulse
  • respirations
  • blood pressure
  • skin
  • pupils
  • oxygen saturation
44
Q

reassessment

A
  • repeat the primary assessment and reassess the patients vital signs
  • deterioration of the patients condition could be rapid and fatal
  • give special attention to any signs of airway compromise
  • monitor the patients anxiety level
  • watch for signs of shock
  • communication and documentation -> signs and symptoms, reasons for choosing the care, pts response to your treatment
  • when to ask for help depends on your assessment findings
    1. intervention
    1. identify how much distress the patient is in
    1. severe reactions may require epinehprine and ventilatory support
  • milder reactions require supportive care such as oxygen
  • transport to a medical facility
  • recheck your interventions
45
Q

emergency medical care

A
  • if patient appears to be having a severe allergic (or anaphylactic) reaction:
  • administer basic life support, including oxygen
  • provide prompt transport to the hospital if reaction happens at home or facility
  • reassess vital signs every 5 minutes (unstable patient) or 15 minutes (stable patient)
  • place hypotensive or shock patients in the appropriate position
  • be prepared to maintain the airway or administer cardiopulmonary resuscitation
  • obtain an accurate account of the events preceding that led to the signs and symptoms associated with the anaphylactic reaction
  • if a stinger is present scrape away with a card
  • applying ice may help
  • epinephrine administration
46
Q

benadryl

A
  • antihistamine
  • diphenhydramine
  • blocks the effects of the naturally occurring chemical histamine in the body
  • helps with urticaria and itching associated with an allergic/anaphylactic reaction
  • emergency dosage- 50mg IV
  • be careful not to overdose patient if they previously took Benadryl prior to your arrival
47
Q

corticosteroids

A
  • anti-inflammatory
  • solu-medrol
  • helps to reduce inflammation over the long term as opposed to other medications such as epinephrine that work immediately
  • modifies the bodys immune response to various conditions and decreasing inflammation
  • long term acting
  • emergency dosage- 125 mg IV
48
Q

epinephrine

A
  • PRIMARY TOOL TO TREAT REACTION*
  • only thing that will stop the reaction
  • mimics the sympathetic (fight or flight) response
  • causes the blood vessels to constrict
  • reverses vasodilation and hypotension
  • increases cardiac contractility and relieves bronchospasms
  • rapidly reverses the effects of anaphylaxis
49
Q

indications

A
  • a severe allergic reaction
  • hypersensitivity to an exposed substance
  • remember that your EMS service of facility may or may not allow you to assist the patients in the administration of epinephrine
  • know the policies/procedures of your work environment
50
Q

kits

A
  • should contain a prepared, auto-injectable syringe of epinephrine
  • adult epipen delivers .3 mg of epinephrine
  • the infant-child system delivers .15mg
  • twinject auto injector contains two doses of epinephrine
51
Q

side effects of epipen

A
  • high blood pressure
  • increased pulse rate
  • anxiety
  • cardiac arrhythmias
  • pallor
  • dizziness
  • chest pain
  • headache
  • nausea or vomiting
52
Q

severe reactions can progress quickly

A
  • Be aggressive in managing your patient from a pharmacological and airway management standpoint
  • Be prepared that your patient could decompensate at any moment
  • Supplemental oxygen by NRB or BVM will help with respiratory compromise
  • Constant reassessment is necessary for these patients
  • (Recheck vital signs and continually listen to lung sounds)
  • Intubation may be necessary to secure the patient’s airway
  • A good assessment will help with patient management

Medical Emergencies (16 decks)

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