Anaphylaxis is a severe, life-threatening, multi-system allergic reaction that requires immediate recognition and emergency management. The UK’s guidelines, particularly from the Resuscitation Council (UK) and NICE, have refined the approach to focus on rapid administration of adrenaline and a structured ABCDE assessment.
Diagnosis and Triggers
Anaphylaxis is a clinical diagnosis. It should be considered when there is an acute onset of an illness with involvement of skin or mucosal membranes (e.g., hives, flushing, angioedema) AND at least one of the following:
Respiratory Compromise: Stridor, hoarseness, wheezing, or difficulty breathing.
Cardiovascular Compromise: Hypotension, pallor, or signs of shock (e.g., prolonged capillary refill time, altered consciousness).
Less commonly, it can be diagnosed with hypotension alone after exposure to a known allergen, or with persistent gastrointestinal symptoms. Common triggers include foods (nuts, milk), insect stings, drugs (e.g., antibiotics), and latex.
Red Flags and Risk Factors
Biphasic Reactions: Be aware that a second wave of symptoms can occur hours after the initial reaction, even if the child appears to have recovered.
Co-factors: Exercise, alcohol, or taking non-steroidal anti-inflammatory drugs (NSAIDs) can lower the threshold for a reaction.
Risk Factors for Severe Outcome:
Poorly controlled asthma: A child with underlying asthma is at much higher risk of a life-threatening respiratory component.
Adolescence: This age group is at a higher risk of fatal anaphylaxis, possibly due to risk-taking behaviours or delayed adrenaline use.
Underlying cardiac or respiratory conditions.
Emergency Management (APLS Approach)
The management of anaphylaxis is a time-critical emergency following the ABCDE approach.
1. Immediate Assessment and Adrenaline (First Few Minutes)
Assess: Check for airway compromise (stridor, hoarseness), breathing difficulties (wheeze, cyanosis), and signs of shock (tachycardia, hypotension).
Call for Help: Alert senior medical staff, as they may be needed to manage airway or circulation issues.
Administer Adrenaline: The single most important step. Administer intramuscular (IM) adrenaline into the anterolateral thigh without delay. The dose is weight-based.
<6 months: 150 micrograms
6 months – 6 years: 150 micrograms
>6 – 12 years: 300 micrograms
>12 years: 500 micrograms
Repeat the dose every 5 minutes if there is no clinical improvement.
2. Supportive Care
Airway and Breathing: Administer high-flow oxygen via a face mask.
Circulation: Place the child flat with legs elevated. Gain IV access and give a fluid bolus (20 mL/kg of 0.9% sodium chloride) to counteract vasodilation and shock.
Other Medications (Second-line):
Antihistamines: Intravenous (IV) or oral chlorphenamine (an H1 blocker) can help with skin symptoms but does not treat the life-threatening features.
Corticosteroids: IV hydrocortisone can help prevent protracted or biphasic reactions but has a slow onset of action and is not a first-line treatment for the acute episode.
Nuances and Pitfalls
Adrenaline is First-Line: The biggest pitfall is a delay in administering IM adrenaline. Many clinicians mistakenly give antihistamines or steroids first, which do not address the life-threatening respiratory or circulatory collapse.
Route of Administration: IM adrenaline is the standard of care. Subcutaneous administration is ineffective, and IV adrenaline is only for experienced clinicians in specific scenarios (e.g., cardiac arrest).
Monitoring: Continuous monitoring of vital signs (HR, BP, SaO2) is crucial. A bolus of IV fluids may be needed, as anaphylaxis can lead to massive fluid shifts and distributive shock.
Follow-up: After a significant anaphylactic reaction, the child must be observed for at least 6-8 hours due to the risk of a biphasic reaction. A follow-up plan, including a referral to an allergy specialist, is essential. The family should be trained in using an adrenaline auto-injector (e.g., EpiPen).
Biphasic Reaction: A biphasic reaction is when symptoms return after initial resolution, without re-exposure to the trigger. This is why a period of observation is essential.
Recent UK guidelines from the Resuscitation Council (UK) and NICE have refined the management of anaphylaxis, shifting the focus to immediate adrenaline administration and a structured, time-critical approach. The key change is a stronger emphasis on using intramuscular (IM) adrenaline as the first-line treatment, with other medications like steroids and antihistamines being considered second-line.
Key Updates to Management
Adrenaline is King: IM adrenaline is the most important treatment and should be given immediately without waiting for other assessments or medications. The dose is weight-based and should be given into the anterolateral thigh.
Dosage for Children: The recommended dose for children has been simplified: 150 micrograms for children under 6 years, 300 micrograms for those aged 6-12, and 500 micrograms for adolescents and adults. The dose can be repeated every 5 minutes if there is no clinical improvement.
Fluid Resuscitation: A fluid bolus of 20 mL/kg of 0.9% sodium chloride should be given to treat hypotension and shock. This addresses the massive fluid shift that occurs during anaphylaxis.
Second-Line Medications: Antihistamines (like chlorphenamine) and corticosteroids (like hydrocortisone) are considered second-line. They are useful for managing skin symptoms or preventing a biphasic reaction but do not treat the life-threatening respiratory or circulatory compromise. The crucial point is that they should not delay the administration of adrenaline.
Biphasic Reactions: There is a greater awareness of the risk of a biphasic reaction, where symptoms return hours after the initial reaction has resolved. Patients who have had a significant anaphylactic episode should be observed for at least 6-8 hours.
Post-Anaphylaxis Care: All patients who have experienced anaphylaxis should be referred to an allergy specialist for investigation and provided with an adrenaline auto-injector and a clear emergency plan.