🚨 Anaphylaxis
Overview
Anaphylaxis is a severe, life-threatening, generalised or systemic hypersensitivity reaction. It is characterised by rapidly developing airway and/or breathing and/or circulatory problems, usually associated with skin and mucosal changes. Immediate recognition and treatment are vital.
Recognition
Rapid onset of symptoms, typically within minutes of exposure to an allergen. Look for sudden onset of difficulty breathing (wheeze, stridor, hoarseness), circulatory collapse (hypotension, faintness, tachycardia), and skin changes (urticaria, angioedema, flushing). Gastrointestinal symptoms (abdominal pain, vomiting) can also occur.
Initial Assessment (ABCDE)
A: Assess for airway obstruction (stridor, hoarseness, swelling). B: Assess for respiratory distress (wheeze, tachypnoea, SpO2). Administer high-flow oxygen. C: Assess for circulatory collapse (hypotension, tachycardia, prolonged CRT). Lie patient flat with legs raised. D: Assess conscious level (AVPU/GCS). E: Look for skin rash, angioedema, and identify potential trigger.
Red Flags
Any signs of airway compromise (e.g., worsening stridor, hoarseness), persistent hypotension despite initial treatment, increasing respiratory distress, or deteriorating conscious level. These indicate a severe, ongoing reaction requiring further aggressive management and potentially advanced airway interventions.
Investigations
Bedside: SpO2, ECG, blood pressure, capillary blood glucose. Bloods: Serum tryptase (taken during reaction and 1-2 hours post-reaction, then baseline 24 hours later) can confirm diagnosis retrospectively. No immediate diagnostic tests are required before treatment.
Immediate Management
Call for help immediately. Administer oxygen at high flow. Give intramuscular adrenaline into the anterolateral thigh; repeat every 5-15 minutes if no improvement. Administer intravenous fluids (crystalloids) for hypotension. Give antihistamines (e.g., chlorphenamine) and corticosteroids (e.g., hydrocortisone) intravenously after adrenaline.
Escalation Triggers
Any suspected anaphylaxis requires immediate senior medical review. Failure to respond to initial adrenaline doses, persistent airway compromise, profound or refractory hypotension, or the need for advanced airway management (e.g., intubation) mandates urgent critical care involvement.
MLA High-Yield Notes
Adrenaline is the first-line and most crucial treatment for anaphylaxis. Always give intramuscularly into the anterolateral thigh. Antihistamines and corticosteroids are second-line and do not treat the life-threatening airway/breathing/circulation issues. Patients should be observed for several hours due to biphasic reactions.
References
- Resuscitation Council UK: Emergency treatment of anaphylactic reactions - Guidelines for healthcare professionals
- NICE Guideline CG134: Anaphylaxis: assessment and management
- Joint Royal Colleges Ambulance Liaison Committee (JRCALC) Guidelines