Clinical Quick Reference Monthly Newsletter - Ed. 2 - May 2022 - Anaphylaxis
Clinical Quick Reference Guides - Clinical Concept Review/Anaphylaxis
This review will help clarify the etiology, potential symptoms, and clinical management of anaphylaxis.
What is Anaphylaxis?
Anaphylaxis is considered an acute, life-threatening hypersensitivity disorder. It is defined as a generalized, rapidly evolving, multi-systemic allergic reaction (NIH). Symptoms of the condition can range from mild skin flushing and itching to severe respiratory symptoms. Without prompt recognition and treatment, anaphylaxis may be fatal.
Potential Triggers
Worldwide, the lifetime incidence for these hypersensitivity reactions is noted to be about 1-3%. However, healthcare professionals should be aware that such events are becoming more prevalent.
Although anaphylaxis can occur at any age, it is most commonly noted in younger individuals. It appears to occur with greater frequency in developed countries.
Potential triggers often include:
exposure to some medications
contact with certain foods
insect stings
For example:
-Immunotherapy injections
These treatments directed at improving overall allergic response can sometimes induce a hyper-acute reaction.
-Latex products
Hypersensitivity to latex is occurring at an increased rate
Note: The offending agent (allergen) will not always be identifiable; these type of reactions are called idiopathic anaphylaxis.
A&P/Pathophysiology
Anaphylaxis is generally an IgE-mediated (type 1) hypersensitivity reaction, involving release of chemical mediators from the degranulation of basophils and mast cells after re-exposure to a specific antigen.
The chemical mediators involved play a key role in the symptoms noted in anaphylaxis.
Chemical Mediators in Anaphylaxis
Histamine:
Causes an increase in vascular permeability and vasodilation;
Leads to hypoperfusion of tissues
The patient’s body responds to such changes by increasing heart rate and cardiac contractility
Prostaglandin D:
Functions as a bronchoconstrictor;
Simultaneously causing cardiac and pulmonary vascular constriction
Additionally, it potentiates peripheral vasodilation which contributes to decreased perfusion of the patient’s vital organs
Leukotrienes:
Adds to the bronchoconstriction; vascular issues and induce continued airway problems
Platelet activation factor:
This also acts as a bronchoconstrictor, increases vascular permeability
TNF-alpha:
Activates neutrophils (a type of white blood cell)
What symptoms should the health care provider be aware of when they suspect anaphylaxis?
Healthcare professionals should keep in mind that the presentation of anaphylaxis can range from mild skin flushing and pruritis (itching) to severe respiratory symptoms.
The clinical presentation often begins with a “mild” reaction. Primary symptoms may be dependent on the mode of exposure (for example, eating a shrimp, when you are allergic to shellfish). Although flushing, itching and hives are common, they might not occur until after the onset of respiratory symptoms. This is common in oral exposures.
Fullness, feeling a "lump in the throat," persistent throat clearing, or difficulty breathing can all be concerning symptoms of anaphylaxis.
Other typically noted respiratory symptoms are:
hoarseness,
wheezing,
and stridor.
*When these symptoms are presenting or diagnosed, rapid intervention is indicated.
Although anaphylaxis tends to unfold rapidly (starting within one hour of exposure), with NIH sources citing half of all anaphylactic-related fatalities occuring within that first hour, the first hour is not the only time of concern. Anaphylactic reactions may also present in a biphasic manner (20% of cases). This is possible even after successful treatment of the initial symptoms. With the biphasic cases, there can be a recurrence of symptoms peaking 8 to 11 hours after the initial reaction.
While a majority of the clinician focus is generally placed on the symptoms related to breathing, skin and the blood pressure, it is important to evaluate the patient for any other signs of end-organ damage from hypo-perfusion. This can include: abdominal cramps, vomiting, poor muscle tone, fainting, or incontinence. Gastrointestinal (GI) symptoms may be noted in 25% to 30% of individuals suffering from these reactions (NIH).
General Symptoms
Can include (but are not limited to):
- hives
- rash
- difficuty breathing
- decreased BP
- increased pulse
- increased respirations
- dilated pupils
- diaphoresis (sweating)
- “panicked feeling”
Management
May include:
- triage
- airway management
- epinephrine
- decontamination (when possible)
- IV fluids
- adjunctive medications/therapies
> steroids
> antihistamines
> inhaled bronchodilators
> vasopressors
Remember:
✔ anaphylaxis generally involves a rapidly evolving presentation
✔ anaphylaxis usually occurs within one hour of exposure to offending allergen(s)
✔ the first hour after initial symptom onset is regarded as the most crucial in ensuring optimal management of the patient’s condition
✔ healthcare professionals should understand that prompt recognition of symptoms and thorough treatment greatly reduce the risk for adverse outcomes
Medical Terminology
Getting to know these terms will help reinforce the above material.
Allergen - a substance that can cause an allergic reaction
Hypersensitivity - altered reactivity where the body reacts with an exaggerated immune response to a foreign agent (usually considered to be an otherwise innocuous substance)
IgE - type of antibody found only in mammals; it is synthesized by plasma cells. In immune system overreaction to an allergen, production of antibodies called Immunoglobulin E (IgE) leads the antibodies traveling to cells that release chemicals resulting in an “allergic reaction”
Neutrophil - also known as polymorphonuclear “PMN” leukocytes (type of white blood cell); are the most abundant cell type in human blood. These cells are produced in large numbers in the bone marrow. They represent the “first line” of cells recruited to areas of infection – where they attack, ingest, and digest microorganisms
Anatomy & Physiology
Becoming familiar with body system components & functions will help increase understanding of body processes and medical conditions
stridor
type of “noisy” breathing
high-pitched wheezing sound related to something narrowing/obstructing the airway
airflow is usually disrupted by a blockage/narrowing in the larynx or trachea
not in and of itself a diagnosis, but rather a symptom/sign that points to a specific airway disorder
Helpful video (includes stridor audio clip):
Disclaimer: The above study guide represents study materials, always follow the advice and direction of your medical provider/emergency services provider for acute and/or chronic medical issues.