Med-Surg: Chapter 19: Type I Hypersensitivity Reaction: Immediate Flashcards
Type I Hypersensitivity Reaction
a rapid or immediate allergic reaction
-can be local (atopic) reaction or a systemic reaction
Atopic
having an inherited tendency to become sensitive to environmental allergens (substances that cause an allergic response)
The Most Common Reaction
-allergic rhinitis
or
-hay fever, a local reaction
The Most Severe form
anaphylaxis, a systemic reaction
Potential Allergens
- food
- medications
- insect bites (e.g. bees, fire ants, hornets, yellow jackets, and wasps)
- biting insects (E.g. mosquitoes)
- diagnostic testing substances (e.g. radiocontrast media)
- blood
Pathophysiology
-the primary mediator is immunoglobulin E (IgE)
-the first time a patient is exposed to an allergen, IgE is produced
>the IgE antibodies attach to mast cells; causes mast cell to degranulate, releasing histamine and other chemicals such as leukotrienes and prostaglandins that cause smooth muscle contraction, vasodilation, increased vascular permeability, bronchoconstriction, and edema; this results in the symptoms associated with the allergy
Anaphylaxis
most severe form of Type I Hypersensitivity Reaction
- exhibits extremes of the symptoms
- can occur when the mediators are released systemically
Clinical Manifestations
-may be local or systemic
> allergic rhinitis: nasal discharge, sneezing, and pruritis (itching) of the upper airways
- may complain of headache or sinus pressure
- itchy, watery eyes
> anaphylaxis: there is immediate response to an allergen
- dyspnea and SOB
- audible wheezes and/or crackles
- skin reaction or rash
- may experience nausea, vomiting, or diarrhea
- complain of anxiety and often state they feel a flush of heat
- angioedema (swelling just below the surface of the skin, typically around the mouth and eyes)
> Severe Anaphylaxis: a severe and rapid onset of symptoms
- bronchospasm with extreme dyspnea and SOB and wheezing
- hoarseness and stridor (a high-pitched crowing sound, which indicates narrowing of the airways)
> Severe or untreated reactions result in anaphylactic shock with hypotension and tachycardia due to the vasodilation and capillary leak
Severe or untreated reactions may result in what?
anaphylactic shock
-with hypotension and tachycardia due to the vasodilation and capillary leak
Diagnosis
> WBC count and differential
-reveals increase in eosinophils, which indicates an allergic response
-eosinophils are the key inflammatory cells seen in allergic rhinitis
-as eosinophils increase, the symptoms severity increases
Skin Testing to determine the specific allergen
WBC count and Differential
reveals increase in eosinophils, which indicates an allergic response
Eosinophils
indicates presence of allergic response
- increases
- as it increases, severity of symptoms increase
- normal count= 1 to 2%
- key inflammatory cells seen in allergic rhinitis
Skin Testing
performed to determine the specific allergen
-various allergens are introduced via a scratch test to determine which produce a positive reaction that indicates an allergy
-the results are used to determine the causes of allergic rhinitis, urticaria or hives, and asthma
-a localized reaction or wheal indicates a positive result within 15 to 20 minutes
>Glucocorticoids and antihistamines are discontinued before allergy testing
>NSAIDs may also be discontinued before allergy testing
>forearm and the back are used as sites for scratch testing
Treatment: allergy management
-allergy management includes the identification, treatment, and prevention of allergic responses
-avoidance therapy can be successful when the allergies have been identified
-if a reaction does occur but is mild, removing the offending agent may be the only necessary action
-if symptoms persist, antihistamines and decongestants utilized
>Decongestants can be used to decrease edema and secretions, especially in allergic rhinitis
>Diphenhydramine hydrochloride (Benadryl), an antihistamine, decreases edema and constriction of smooth muscle in the respiratory tract and blood vessels
>Steroids may be indicated to decrease the inflammatory response and decrease mast-cell degradation
>Beta-agonist bronchodilators may aid in easing respiratory distress by causing respiratory smooth muscle relaxation
Diphenhydramine hydrochloride (Benadryl)
antihistamine
- decreases edema and constriction of smooth muscles in the respiratory tract and blood vessels
- is a histamine receptor blocker
Treatment: Severe cases of anaphylaxis
prompt recognition and treatment
- emergency intervention and cardiopulmonary resuscitation may be necessary
- first-line treatment= IM epinephrine
- epinephrine is effective as a respiratory smooth muscle relaxant and vasoactive medication to open airways to ease respiratory distress and constrict blood vessels to maintain the patients blood pressure; may be repeated every 5 to 15 minutes
- IV epinephrine is indicated in patients unresponsive to IM doses
- Glucagon is indicated in patients on beta-blockers who are unresponsive to epinephrine
- Second-line treatment: antihistamines and corticosteroids, but should not be given before first-line therapy
What is the First-line treatment for severe anaphylaxis?
IM epinephrine
- IV is indicated if patients unresponsive to IM injection
- Glucagon is indicated in patients on beta-blockers who are unresponsive to epinephrine
Epinephrine
effective as a smooth muscle relaxant and vasoactive medication to open airways to ease respiratory distress and constrict blood vessels to maintain the patients blood pressure
- medication of choice to counteract anaphylactic shock by causing blood vessel constriction, raising blood pressure, and improving cardiac output through inotropic and chronotropic activity
- also acts as a beta-2 agonist to promote bronchial smooth muscle relaxation
Mediator: Histamine
main mediator
- increases vascular permeability, constricts smooth muscle, increases gastric acid secretion
- Symptoms produced: edema of the airways and larynx, bronchial constriction, urticaria (hives), angioedema, pruritis, nausea, vomiting, diarrhea, shock
Mediator: Leukotrienes
enhance the effect of histamine on the smooth muscle, constrict smooth muscle of the bronchi, increase vascular permeability
-Symptoms Produced: bronchial constriction: wheezing
Mediator: Prostaglandin
stimulates smooth muscle contraction, increases cellular permeability, stimulates the inflammatory response, increases platelet aggregation, increase gastric acid creations
-Symptoms produced: bronchial constriction: wheezing, edema, nausea, and vomiting
The Clinical Manifestations associated with Type I Hypersensitivity Reaction are caused by what?
the release of histamine and other chemical mediators from mast cells upon exposure to the antigen
What are the typical results of histamine release?
- bronchoconstriction and increased capillary permeability
- a runny nose, itching, red eyes, and rash are common
- in extreme cases, SOB and dyspnea; wheezes evident on auscultation
Nursing Interventions: Assessment
> monitor respiratory rate, depth, and lung sounds; pulse oximetry; and arterial blood gases (ABGs):
-b/c of bronchoconstriction produced by the histamine release, the respiratory rate may be increased, and wheezing, dyspnea and chest tightness, and throat or palate tightness may be present; B/c of decreased oxygenation, the SpO2 is decreased and the ABGs demonstrate hypoxemia
> blood pressure/ pulse
- if anaphylaxis occurs, hypotension may be present b/c of vasodilation and capillary leak
- tachycardia is present as a compensatory response to the hypotension
- irregular and increased pulse and decreased BP are also due to leukotriene release, which constricts airways and coronary vessels
> general systems assessment:
- initial symptoms caused by the histamine release may be a rash and itching followed by watery red eyes, runny nose, and sneezing
- angioedema may be present
- may complain of feeling faint and diaphoretic
- diarrhea, stomach cramps, and abdominal pain b/c of increased acid production due to histamine release
Nursing Actions
> discontinue offending agent ASAP; if the offending agent is in an IV infusion, stop the IV medication, change the IV tubing, and hang normal saline
> Administer oxygen as ordered via 100% nonrebreather
-the vasodilation, capillary leak, and other shock responses are interfering with oxygenation and tissue perfusion; starting oxygen enhances oxygen delivery to the tissues, especially the brain cells and cardiac muscle cells
> Elevate the head of the bed as able; care is taken if hypotension is present
-to improve ventilation, elevate the head of the bed, but do not compromise BP if low
> Medication as ordered
- diphenhydramine hydrochloride (Benadryl)
- corticosteroids
- bronchodilators
- IM epinephrine
- vasopressors
> have emergency resuscitation equipment available (endotracheal intubation or tracheostomy) for possible progression to anaphylactic shock
-there may be complete circulatory and ventilatory collapse requiring resuscitation
> stay with patient and provide reassurance
Corticosteroids
to inhibit the inflammatory response exacerbating the allergic response
Bronchodilators
beta agonists or bronchodilators facilitating bronchial smooth muscle relaxation may be indicated to ease bronchoconstriction
Vasopressors
if anaphylaxis occurs, vasoactive medications may be indicated to constrict blood vessels and increase BP
Teachings
> educate patient regarding potential causes in the environment and ways to avoid exposure to the allergen
educate regarding signs and symptoms of an initial reaction: rash and itching
educate on the use of a EpiPen
-can inject a small dose of epinephrine when the patient has been exposed to an allergen and is at risk for anaphylaxis
advise patient to obtain a Medic Alert bracelet or pendant and ensure the healthcare professionals are aware of any potential allergies
Evaluating Care Outcomes
- well-managed patient is free of symptoms of the allergic reaction and has a normal oxygen level
- with the removal of the offending agent and appropriate treatment of the allergic reaction with diphenhydramine hydrochloride (Benadryl), steroids, bronchodilators, and epinephrine if necessary, there is no further evidence of a rash, itching, or difficulty breathing
- discharged when respiratory and cardiovascular assessment criteria have returned to baseline
- after severe allergic reaction for which the cause is unknown, a trigger should be identified; an allergist/immunologist should perform an evaluation
