Recognize the signs of anaphylaxis (type I hypersensitivity) and know how to treat it aggressively
Recognize the signs of anaphylaxis (type I hypersensitivity) and know how to treat it aggressively: Excerpt from Avoiding Common Pediatric Errors
Author:
Yolanda Lewis-Ragland, MD
What to Do - Interpret the Data, Make a
Decision, Take Action
Anaphylaxis is an acute, multisystem, and severe allergic reaction, known
also as type I hypersensitivity reaction. The term comes from the Greek
words ana (again) and phylaxis (protection). Anaphylaxis occurs when a
person is exposed to a trigger substance, called an allergen, to which they are
sensitized. Re-exposure to the trigger substance intensifies what is normally
a protective immune response and it become detrimental.
Classification
Gell and Coombs classified hypersensitivity reactions into four types:
• Type I reactions (i.e., immediate hypersensitivity reactions) involve immunoglobulin (Ig) E-mediated release of histamine and other mediators
from mast cells and basophils.
• Type II reactions (i.e., cytotoxic hypersensitivity reactions) involve IgG
or IgM antibodies bound to cell surface antigens, with subsequent complement fixation.
• Type III reactions (i.e., immune-complex reactions) involve circulating
antigen-antibody immunecomplexesthatdeposit in postcapillaryvenules,
with subsequent complement fixation.
• TypeIVreactions (i.e.,delayedhypersensitivityreactions,cell-mediated
immunity) are mediated by T cells rather than by antibodies.
Type I Hypersensitivity
Type I hypersensitivity reactions are extremely important to recognize and
treat because their reactions are immediate; abrupt in onset, usually occurring within 15 to 30 minutes from the time of exposure; and potentially life
threatening. This "immediate" reaction assists with the identification of the
triggering antigen. Anaphylaxis is related to the action of IgE and other anaphylatoxins, which act to release histamine and other mediators from mast
cells during degranulation. Histamine has a number of effects, including the
vasodilation of arterioles and constriction of bronchioles in the lungs.
Signs and Symptoms. Patients with anaphylaxis may report or experience
the following signs and symptoms:
• Respiratory distress
• Hypotension
• Fainting
• Unconsciousness
• Urticaria
• Flushed appearance
• Angioedema (swelling of face, neck and throat)
• Tears (due to angioedema and stress)
• Vomiting
• Pruritus (itching)
• Diarrhea
• Abdominal pain
• Anxiety
Treatment
The firstthingtoconsiderinapatientexperiencinganaphylaxis
is the cause of the reaction, if it can be identified, and the withdrawal of the
offending agent (i.e., stop drug infusion, remove bee stinger). This point
is often overlooked but is an essential part of practice. Next, the patient
needs to be assessed for airway involvement because a rapid constriction
of the airway can lead to respiratory failure and respiratory arrest. Patients
withrespiratorycompromisemayrequireintubation. Occasionally,laryngeal
edema will be so severe that oral intubation is difficult and a tracheostomy
needs to be performed. The level of consciousness and vital signs can assist
in directing interventions.
Interventions
• Epinephrine should be administered immediately. Epinephrine prevents
worsening of airway constriction, stimulates the heart to continue beating,
and may be lifesaving. It acts on β2-adrenergic receptors in the lung as
a powerful bronchodilator. Tachycardia results from stimulation of β1-adrenergic receptors of the heart. Repetitive administration of epinephrine
can cause tachycardia and arrhythmias. The administration of 0.3 to 0.5
mL of a 1:1,000 dilution is often prescribed.
• The rapid administration of isotonic intravenous fluids should be administered to restore blood pressure.
• Vasoactive agents (i.e., dopamine) may be prescribed if hypotension persists and is unresponsive to fluids.
• H1-and H2-receptor blockers can alleviate pruritus and urticaria. Cimetidine, when combined with any of several H1 antihistamines, blocks
histamine-induced hypotension.
• Albuterol nebulizers can be used to treat bronchospasm.
• Corticosteroids help to prevent or control the latent phase of the reaction.
Patients are often observed in the hospital because of biphasic reactions
with recurrent symptoms even after the patients condition has stabilized.
Usually, patients do well with acute management after the offending agent
is removed and the patient's condition stabilized.
Suggested Readings
Anand MK, Routes JM. eMedicine—Hypersensitivity Reactions, Immediate. Available at:
www.emedicine.com/med/topic1101.htm. Accessed December 20, 2007.
Hypersensitivity—Global Advanced Trait Descriptions. Available at: www.similarminds.com/
types/hypersensitivity.html. Accessed December 20, 2007.
Hypersensitivity Reactions. Available at: www.pathmicro.med.sc.edu/ghaffar/hyper00.htm.
Accessed December 20, 2007.
Book Source Details
- Book Title: Avoiding Common Pediatric Errors
- Author(s): Anthony D Slonim MD, DrPH; Lisa Marcucci MD
- Year of Publication: 2008
- Copyright Details: Avoiding Common Pediatric Errors, Copyright © 2008 Lippincott Williams & Wilkins.
More About Anaphylaxis
More Medical Textbooks Online about Anaphylaxis
Review other book chapters online related to Anaphylaxis:
Medical Books Excerpts
- Anaphylaxis
- "Professional Guide to Diseases (Eighth Edition)" (2005)
- [ read ]
- Shock
- "Field Guide to Bedside Diagnosis" (2007)
- [ read ]
Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.
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More About This Book:
Title: Avoiding Common Pediatric Errors
Authors: Anthony D Slonim MD, DrPH; Lisa Marcucci MD
Publisher: Lippincott Williams & Wilkins
Copyright: 2008
ISBN: 0-7817-7489-6
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