Anaphylaxis is an acute, potentially fatal, reaction of the multi-organ system caused by the release of chemical mediators from Mastocytes and Basophils.
The classic form implies a prior sensitization to an Allergen with subsequent re-exposure, producing symptoms through an immunological mechanism.
Signs and symptoms
Anaphylaxis most commonly affects the cutaneous, respiratory, cardiovascular and gastrointestinal systems. The skin or mucous membranes are involved in 80-90% of cases.
Most adult patients have some combination of urticaria, erythema, pruritus or angioedema.
However, for poorly understood reasons, children may more commonly present with respiratory symptoms followed by skin symptoms.
It is also important to note that some of the most severe cases of Anaphylaxis occur in the absence of skin findings.
Initially, patients often experience itching and redness. Other symptoms can evolve rapidly, such as the following:
- Dermatological / ocular: Redness, urticaria, angioedema, cutaneous and / or conjunctival injection or pruritus, heat and swelling.
- Respiratory: nasal congestion, coryza, rhinorrhea, sneezing, tightness in the throat, wheezing, difficulty breathing, cough, hoarseness, dyspnea.
- Cardiovascular: dizziness, weakness, syncope, chest pain, palpitations.
- Gastrointestinal: dysphagia, nausea, vomiting, diarrhea, swelling, cramps.
- Neurological: headache, dizziness, blurred vision and seizures (very rare and often associated with hypotension).
- Other: metallic taste, sense of imminent death.
Diagnosis of Anaphylaxis
Anaphylaxis is mainly a clinical diagnosis.
The first priority in the physical examination should be to assess the respiratory tract, respiration, circulation and the adequacy of the patient’s activity (eg, alertness, orientation, coherence of thought).
The test may reveal the following findings:
- General appearance and vital signs: they vary according to the severity of the anaphylactic episode and the system (s) of affected organs; Patients are generally restless and anxious.
- Respiratory findings: Severe angioedema of the tongue and lips; tachypnea; stridor or severe hunger for air; loss of voice, hoarseness and / or dysphonia; wheezing
- Cardiovascular: tachycardia, hypotension; Cardiovascular collapse and shock can occur immediately, without any other finding.
- Neurological: depressed level of consciousness or can be agitated and / or combative.
- Dermatological: the classic cutaneous manifestation is urticaria (that is to say, urticaria) in any part of the body; Angioedema (soft tissue swelling); generalized erythema (full body) (or flushing) without urticaria or angioedema.
- Gastrointestinal: vomiting, diarrhea and abdominal distension.
Laboratory studies are usually not necessary and are rarely useful.
However, if the diagnosis is not clear, especially with a recurrent syndrome, or if other diseases should be excluded, the following laboratory studies can be ordered in specific situations:
- Serum tryptase may help confirm the diagnosis of Anaphylaxis.
- 24-hr urine histamine can help in the diagnosis of recurrent anaphylaxis.
- Urinary levels of 5-hydroxyindoleacetic acid in 24 hours: if the carcinoid syndrome is considered.
Skin tests, immunoglobulin E (IgE) tests, in vitro or both may be used to determine the stimulus that causes the anaphylactic reaction. Such studies may include the following:
- Allergy test (s) to food.
- Allergy test (s) to the medication.
- Tests of causes of independent reactions of immunoglobulin E (IgE).
Supportive care for patients with suspected anaphylaxis includes the following:
- Airway management (eg, ventilator support with bag / valve / mask, endotracheal intubation)
- High flow oxygen
- Cardiac monitoring and / or pulse oximetry
- Intravenous access (large hole)
- Resuscitation with fluid with isotonic crystalloid solution
- Supine position (or comfort position if you have dyspnea or vomiting) with your legs elevated
The main pharmacological treatments for acute anaphylactic reactions are epinephrine and antihistamines H1. The medications used in patients with Anaphylaxis include the following:
- Adrenergic agonists (eg, Epinephrine)
- Antihistamines (eg, diphenhydramine, hydroxyzine)
- H2 receptor antagonists (eg, Cimetidine, ranitidine, famotidine)
- Broncodilatadores (p. Ej., Albuterol)
- Corticosteroids (eg, methylprednisolone, prednisone)
- Positive inotropic agents (eg, Glucagon)
- Vasopresores (p. Ej., Dopamina)
Education for counseling is crucial, especially in younger patients with food anaphylaxis.
Important problems include:
- Cross contamination and inadequate labeling of food.
- A study of children with food allergies who visited a subspecialty allergy clinic found that 59% had an epinephrine auto-injector with them, although 71% of parents reported that they kept the auto-injector available at all times.
- The only variable positively associated with having an autoinjector available was the epinephrine autoinjection instruction.
- Patients with sensitivity to multiple antibiotics should receive a list of alternative antibiotics. They can present this list to their primary care physicians when antibiotic therapy is required.
- Education about promotion is also important for people who are hypersensitive to insect bites.
- Warn patients to avoid the use of perfumes or hygiene products that include perfumes, in particular floral fragrances, as they attract flying hymenopterans.
- Brightly colored clothing attracts bees and other pollinating insects.
- Avoid locations of known hives or nests and avoid the use of equipment that alter the hive.
- People who are sensitive to Hymenoptera and who must be outdoors should carry an epinephrine auto-injector (see below).
- Inform patients who react to Hymenoptera venom of the availability of desensitization therapy.
- At discharge, warn patients of the possibility of recurrent symptoms and direct them to seek additional care if this occurs.
The practice parameter states that patients with a possible systemic reaction should be referred to an allergist or immunologist, where they should be informed about the risk of another reaction, their preventive treatment options and the benefits of wearing an identification bracelet or necklace. medical
Avoid insect bites and deal with an emergency.
Good evidence suggests that doctors prescribe less Epinephrine and that patients (or their parents) do not use Epinephrine as quickly as possible.
Consequently, at the time of discharge, all patients should receive an epinephrine auto-injector and should receive adequate instructions on how to self-administer in the event of a subsequent episode.
Patients should be instructed to maintain an epinephrine auto-injector with them at all times; They should also take Diphenhydramine and take this along with the use of the Epinephrine auto-injector. They should be instructed to keep the device away from extreme temperatures.
Epinephrine is sensitive to both light and temperature and, therefore, should not be stored, for example, in a refrigerator or in the glove compartment of a motor vehicle.
They should also receive instructions to replace any Epinephrine auto-injector before its expiration date.
Patients should be Patients should be id to have quick and immediate access to emergency medical services for transportation to the nearest emergency service for treatment.
They should also receive instructions for emergency medical attention immediately after epinephrine is injected because the effect is short-lived (<15 min) and biphasic reactions may occur.
An epinephrine autoinjector (eg, EpiPen) for adults is available with a single 0.3 mg (1: 1,000 v / v) dose.
Similarly, an EpiPen Jr., with a dose of 0.15 mg (1: 2,000 v / v), is available for children weighing less than 30 kg. Auvi-Q comes in similar dosage, and has the advantage of being a more compact device that provides visual and audio signals to help with proper administration.
Adrenaclick is also available as a single-dose autoinjector of 0.15 mg or 0.3 mg.
The Twinject is a device the size of a pen that contains 2 doses of epinephrine available as a 0.15 or 0.3 mg formulation.
In both cases, the first of the 2 doses is administered by autoinjection and the second is injected manually.
The placebo syringes are recommended as educational tools. Live demonstrations of injections can be considered on a case-by-case basis when the patient or parent expresses a fear of injection.