Ch 21 - Allergy & Anaphylaxis

• immunology


  study of the body's immune system
• When managing allergy-related emergencies, you must be aware of the possibility of acute airway obstruction and cardiovascular collapse.
• immune system


  body system that includes all of the structures and processes designed to mount a defense against foreign substances and disease-causing agents
• An allergic reaction is the only immunologic emergency you will treat as an EMT.
• allergic reaction


  body's exaggerated immune response to an internal or surface agent

  • not directly caused by outside stimulus
  • body's reaction is to release chemicals to combat the stimulus
  • may be mild and local (itching/redness/tenderness) or severe and systemic
• immune response


  body's response to a substance perceived by the body as foreign
• 2 chemicals released by the body's immune system that contribute to an allergic reaction/anaphylaxis:

  histamines and leukotrienes
• allergen


  substance that causes an allergic rxn
• sensitization


  exposure to an allergen to the first time that allows the immune system to recognize it
• Allergic reactions occur due to subsequent exposure to an allergen.
• anaphylaxis


  an extreme, life-threatening, systemic allergic rxn that may include shock and respiratory failure

  • involves multiple organ systems
  • may be fatal
• chemical mediators exert their effects on end organs:

  A) bronchospasm

  B) vasoconstriction

  C) coronary flow

  D) output

  E) vasodilation

  F) leakiness

  G) pruritus

  H) urticaria

  I) edema

  
• sequence of events in anaphylaxis:

  (A) the antigen is introduced into the body

  (B) the antigen-antibody reaction at the surface of a mast cell

  (C) the release of mast cell chemical mediators

  (D) specific antibody reacts with its corresponding antigen

  (D) chemical mediators exert their effects on end organs

  
• What are the 2 most common signs of anaphylaxis?

  widespread urticaria and angioedema
• urticaria/hives


  small areas of generalized itching and/or burning that appear as multiple raised areas on the skin

  • common sign of anaphylaxis

  
• angioedema


  localized areas of swelling beneath the skin, often around the eyes and lips, but can also involve other body areas as well

  • common sign of anaphylaxis
  • may result in airway obstruction

  
• wheezing


  high-pitched, whistling breath sound that is most prominent on expiration

  • suggests an obstruction or narrowing of the lower airways
  • occurs in asthma and bronchiolitis and sign of anaphylaxis
  • results from bronchospasm/bronchoconstriction and increased mucus production
• stridor


  harsh, high-pitched respiratory sound, generally heard during inspiration

  • caused by partial blockage or narrowing of upper airway
  • may be audible without a stethoscope
• You may also note hypotension in a Pt with anaphylaxis due to vasodilation, as well as increased capillary permeability (causing fluid form the bloodstream to seep into the tissues). One symptom that is often overlooked is persistent gastrointestinal dysfunction (ex: nausea, vomiting, abdominal cramps). Pts can also become confused.
• 5 categories of common allergens:

  food, medication, plants, chemicals, insect bites and stings
• food


  type of allergen that accounts for 30% of deaths, most commonly in adolescents and young adults

  • ex: shellfish and peanuts
  • S/S: abdominal cramping, vomiting, diarrhea -> involve respiratory and cardiovascular systems
  • symptoms may take more than 30 minutes to appear and may not include the presence of skin signs
  • Pt may be unaware of exposure
• medication


  second most common source of anaphylactic rxns

  • particularly antibiotics (ex: penicillin) and nonsteroidal anti-inflammatory drugs (NSAIDs)
  • injection: immediate and severe reaction (<30 min)
  • oral: gradual and severe reaction (>30 min)
• plants


  people who inhale dust, pollen, mold, mildew, or other organic materials to which they are sensitive may experience an allergic rxn

  • ex: ragweed, ryegrass, maple, oak
• chemicals

  certain chemicals, makeup, soap, hair dye, latex, and various other substances can cause severe allergic rxns
• insect bites and stings


  envenomation by a honeybee, wasp, ant, yellow jacket, or hornet causes a localized reaction, causing swelling and itching at the site, or anaphylaxis
• envenomation


  act of injecting venom
• If a bee stinger is not removed from the skin, it can continue to inject venom for up to 20 minutes. Wasps and hornets on the other hand, can sting repeatedly.
• toxin


  a poison or harmful substance that may be injected
• Some ants, especially the fire ant, also strike repeatedly, injecting a particularly irritating toxin at the bite sites. It is not uncommon for a Pt to rapidly sustain multiple ant bites, usually on the feet and legs.
• S/S of insect stings and bites: [7]

  • sudden pain
  • swelling
  • localized heat
  • widespread urticaria
  • redness in light-skinned people at the site of injury
  • itching
  • wheal
• wheal


  a raised, swollen, well-defined area on the skin resulting from an insect bite or allergic reaction

  
• The swelling associated with an insect bite may be dramatic and sometimes frightening to a Pt or to you. However, as long as these manifestations remain localized, they are not usually serious.
• If the Pt appears to be having a sever allergic/anaphylactic reaction, you should administer BLS and provide prompt transport to the hospital.
• If the allergic reaction was caused by an insect sting and the stinger is still in place, attempt to remove the stinger by scraping the skin with the edge of sharp, stiff object such as a credit card. Do not use tweezers or forceps to remove the stinger b/c this may squeeze more venom into the wound. Gently wash the area with soap and water or a mild antiseptic. Try to remove any jewelry from the area before swelling begins. Position the Pt with the injection site slightly below the level of the heart, and apply ice or cold packs to the area.

  
• Be alert for signs of airway swelling and other signs of anaphylaxis such as nausea, vomiting, and abdominal cramps, and do not give the Pt anything by mouth. Place the Pt in the supine position as indicated, and give oxygen if needed. Monitor the Pt's vital signs, and be prepared to provide further support as needed.
• epinephrine (adrenaline)


  a medication that increases HR and BP but also eases breathing problems by decreasing muscle tone of the bronchiole tree

  • drug of choice for an anaphylactic reaction b/c of its immediate action
• Epinephrine is a sympathomimetic hormone -> mimics the fight/flight response
• indications for epinephrine

  severe allergic reaction causing ABC compromise or an anaphylactic reaction
• contraindications for epinephrine

  none in a life-threatening emergency

  • consult medical control when the Pt has a Hx of heart disease or ACS
• actions for epinephrine

  vasoconstriction and increased cardiac contractility, bronchodilation