Clinical picture and stages of development
Recognition of anaphylaxis requires rapid assessment of symptoms that develop precipitously. Cutaneous manifestations (urticaria) are common but are not a mandatory criterion for diagnosis.
- Prodromal period (develops 1–15 minutes after contact with the trigger). The patient experiences general malaise, headache, nausea. Local reactions appear: nasopharyngeal itching, sneezing, polymorphic rash. Visceral and psychoemotional disturbances occur — feeling of chest tightness, abdominal pain, chills, confusion, and severe anxiety.
- Fully developed stage (occurs 1–2 minutes after the prodrome). Characterized by acute circulatory failure (drop in blood pressure, tachycardia, thready pulse). Accompanied by respiratory disorders (bronchobstructive syndrome, stridor due to laryngeal edema), neurological disorders up to coma and seizures, as well as urinary and fecal incontinence.
Basic Emergency Care Algorithm
The logic of action is based on the immediate cessation of contact with the allergen and rapid assessment of vital functions using the ABC system (airway patency, adequacy of breathing, and hemodynamics).
- Step 1. Immediately discontinue drug administration or contact with the allergen. Initiate oxygen therapy.
- Step 2. Administer epinephrine intramuscularly (0.1% solution). In severe shock, slow intravenous administration is permitted.
- Step 3. Assess the effect after 5 minutes. If no improvement occurs, adrenaline injections are repeated every 5–10 minutes until the condition stabilizes.
- Step 4. If shock persists, initiate volume replacement — intravenous fluid infusion at 20 ml/kg.
Pharmacotherapy: first-line and adjunctive agents
The use of diuretics, bronchodilators, or antibiotics is not a primary measure. Adjunctive therapy is prescribed only after epinephrine administration.
| Drug group | Representatives | Purpose of use and dosages |
|---|---|---|
| Sympathomimetics | Epinephrine, Ephedrine | Relief of blood pressure drop and bronchospasm (0.5 ml of 0.1% solution s/c or i/m) |
| Glucocorticoids | Prednisolone, Dexamethasone | Systemic anti-inflammatory effect (i/m or i/v, e.g., prednisolone 30 mg) |
| Antihistamines | Diphenhydramine, Chloropyramine | Relief of cutaneous manifestations and pruritus (1–2 ml of 1% solution i/m) |
| Diuretics | Furosemide | Used only for pronounced edema |
The mechanism of action of epinephrine in anaphylaxis involves universal stimulation of α1-, α2-, β1-, and β2-adrenergic receptors, leading to relaxation of bronchial smooth muscle and restoration of vascular tone.
General principles of anti-shock therapy
In severe and refractory reactions, the assistance of an anesthesiologist-resuscitator is required. Treatment is carried out according to general principles of hemodynamic and microcirculatory restoration:
- Vasopressors: norepinephrine, ephedrine.
- Normalization of BCC (blood volume): use of colloidal solutions, gelatin, dextran (average molecular weight 30,000–40,000).
- Antigen inactivation: use of specific enzymes, e.g., penicillinase (beta-lactamase) in shock due to penicillin-class antibiotics.
Specific aspects of care for children with drug-induced anaphylaxis
If shock is caused by injection of a drug into a limb, the tactics have several specific features:
- Lay the child flat, elevate the lower extremities, turn the head to the side.
- Apply a tourniquet proximal to the injection site (maximum for 25 minutes).
- Infiltrate the injection site with a mixture of 0.5% novocaine solution and 0.1% adrenaline solution (0.3–0.5 ml), apply ice for 10–15 minutes.
- Administer systemic adrenaline (0.1% solution at 0.01 ml/kg) subcutaneously in the opposite arm.
- In persistent hypotension, intravenous administration of dopamine, phenylephrine, or norepinephrine in 5% glucose solution is indicated.
The rule of three "A"s in anaphylaxis: Allergen (remove immediately) — ABC assessment (check vital functions) — Adrenaline (administer first).
Class and exam questions
Can treatment begin with the administration of antihistamines or glucocorticoids?
No. Epinephrine is the only first-line drug. Glucocorticoids and antihistamines are strictly adjunctive and are not life-saving in the acute phase.
Is hospitalization of the patient mandatory after the relief of anaphylactic shock?
Yes, hospitalization is strictly mandatory for all patients, regardless of the severity of the initial reaction, for monitoring and recurrence prevention.
What should be done if the patient's condition does not improve after the first adrenaline injection?
It is necessary to repeat intramuscular administration of epinephrine after 5 minutes. Injections can be repeated every 5–10 minutes until hemodynamics and respiration are fully stabilized.
What else to study on this topic
- Mechanism of action of mast cell membrane stabilizers and leukotriene inhibitors.
- Differential diagnosis of allergic laryngeal edema and other types of upper airway obstruction.
- Indications for immunosuppressants (sirolimus, tacrolimus) in severe allergic conditions.
- Pharmacodynamics of first-generation H1-antihistamines and their effect on the central nervous system.
Master the complete topic in the «Infectious Diseases» course
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- Complete guideline on "Anaphylactic shock: emergency care" and 3,312 more pages of the subject
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