Anaphylactic shock

Clinical diagnostic criteria

The diagnosis of anaphylaxis is considered highly probable if at least one of the three scenarios is present:

1. Acute onset with skin or mucosal involvement. The patient develops pruritus, flushing, urticaria, or swelling of the lips and tongue. This is invariably accompanied by either respiratory compromise (bronchospasm, stridor, drop in saturation) or hemodynamic compromise (hypotension, collapse, syncope).
2. Contact with a probable allergen. Two or more organ systems are involved: skin/mucosa, respiratory, cardiovascular, or gastrointestinal (vomiting, cramps).
3. Contact with a known allergen. If the patient encounters a trigger already confirmed for them, a drop in blood pressure alone is sufficient to establish the diagnosis.

Assessment of severity

The severity of anaphylaxis is determined by the most affected organ system. Symptoms develop progressively:

• Mild degree. Local and non-life-threatening manifestations. Pruritus, urticaria, angioedema, sneezing, mild dyspnea, nausea, compensatory tachycardia.
• Moderate degree. Pronounced functional disorders join in. Spastic abdominal pain, diarrhea, hoarseness, barking cough, dysphagia appear. The patient experiences a «sense of impending doom». At this stage, absolute indications for epinephrine administration arise (stridor, marked dyspnea, wheezing).
• Severe degree. A life-threatening condition. Characterized by involuntary defecation, respiratory decompensation (cyanosis, apnea, SpO2 < 92%), hemodynamic catastrophe (collapse, cardiac arrest), and altered mental status down to coma.

Emergency care algorithm

Actions in case of anaphylaxis must be lightning-fast:

1. Recognition and basic measures. ABC assessment, administration of oxygen if available.
2. Administration of epinephrine (Adrenaline). First-line drug. Administered intramuscularly at a dose of 0.01 mg/kg (0.1% solution), maximum 0.5 mg per single dose. In severe shock, slow intravenous administration is permissible.
3. Assessment after 5 minutes. If there is no improvement, the epinephrine injection is repeated. This can be done every 5–10 minutes until the condition stabilizes.
4. Additional therapy. If shock persists — fluid infusion (20 ml/kg). For bronchoconstriction — salbutamol and budesonide nebulization. Antihistamines and glucocorticosteroids (GCS) are second-line drugs; they are not life-saving in the acute phase and cannot be used as monotherapy.

Prevention and patient management

After stopping the attack, the patient is referred to an allergist-immunologist to identify the allergen.

Patients at risk for anaphylaxis must carry an epinephrine auto-injector. Absolute indications for its prescription:

• History of severe reactions (involvement of the respiratory or cardiovascular systems);
• Combination of food allergy and bronchial asthma;
• Exercise-induced anaphylaxis or idiopathic form.

Relative indications include reaction to trace amounts of the allergen, peanut or tree nut allergy, adolescence, and living far from hospitals.

Class and exam questions

What else to study on this topic

• Classification of anaphylaxis by duration of the course (monophasic, biphasic, protracted)
• Features of exercise-induced anaphylaxis
• Specifics of food allergy as a cofactor for anaphylactic reactions
• Criteria for arterial hypotension in children under 1 year and over 11 years of age

Other topics in "Chapter 13. Main syndromes requiring emergency care"

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.