Understanding and Managing Anaphylaxis: A Guide for Junior Doctors

Introduction

Anaphylaxis is a severe, potentially life-threatening allergic reaction that requires immediate recognition and treatment. As junior doctors, it’s crucial to know how to swiftly identify and manage this medical emergency. This guide will walk you through the essential steps in history taking, examination, investigations, and management of anaphylaxis, ensuring you are well-prepared to handle this condition in the emergency department.

History Taking: Key Questions

When suspecting anaphylaxis, obtaining a thorough history is essential. Here are the crucial questions to ask:

1. Trigger Identification

   • What were you doing when the symptoms began? (e.g., eating, taking medication, exercise)

   • Have you been exposed to any known allergens recently? (e.g., foods, insect stings, latex, drugs)

2. Symptom Onset and Progression

   • When did the symptoms start?

   • How quickly did the symptoms develop?

   • Are the symptoms getting worse, better, or staying the same?

3. Previous Episodes and Allergies

   • Have you ever had a similar reaction before?

   • Do you have any known allergies?

   • Do you carry an adrenaline auto-injector (e.g., EpiPen)? If so, have you used it?

4. Systemic Involvement

   • Do you have any difficulty breathing, wheezing, or chest tightness?

   • Are you experiencing any swelling of the lips, tongue, or throat?

   • Have you had any gastrointestinal symptoms like nausea, vomiting, or diarrhea?

   • Have you noticed a skin rash, hives, or itching?

5. Medical History and Medications

   • Do you have a history of asthma or other respiratory conditions?

   • Are you on any regular medications, including over-the-counter drugs and supplements?

   • Have you started any new medications recently?

Examination Findings

A focused but thorough examination is critical in identifying anaphylaxis. Look for signs affecting multiple systems:

1. Airway

   • Inspect for swelling of the tongue, uvula, or throat.

   • Listen for stridor or hoarseness, indicating upper airway obstruction.

2. Breathing

   • Check for tachypnea (increased respiratory rate), use of accessory muscles, and cyanosis.

   • Auscultate for wheezing or decreased breath sounds.

3. Circulation

   • Measure blood pressure (watch for hypotension).

   • Assess heart rate (tachycardia is common).

   • Check capillary refill time and look for signs of poor perfusion (e.g., cool, clammy skin).

4. Skin

   • Look for urticaria (hives), angioedema, or flushing.

   • Note any widespread erythema or rash.

5. Neurological

   • Assess the patient’s level of consciousness and look for signs of confusion or agitation.

   • Check for dizziness or syncope.

Investigations

While anaphylaxis is a clinical diagnosis, certain investigations can support your assessment and management:

1. Blood Tests

   • Serum tryptase: Elevated levels can confirm anaphylaxis but are often a retrospective diagnosis as levels peak 1-2 hours post-reaction.

   • Full blood count and electrolytes: To assess for complications or differential diagnoses.

2. Point-of-Care Testing

   • Blood glucose: Hypoglycemia can present similarly to anaphylactic shock.

   • Arterial blood gas (ABG): To assess oxygenation and acid-base status, particularly in severe cases.

3. Other Investigations

   • Electrocardiogram (ECG): To monitor cardiac status, especially if hypotension or arrhythmias are present.

Management Plan

Anaphylaxis requires immediate intervention. Follow these steps:

1. Immediate Actions

   • Call for help: Alert senior staff and prepare for advanced interventions.

   • Adrenaline (Epinephrine): Administer 0.5 mg (0.5 mL of 1:1000 solution) intramuscularly into the mid-outer thigh. Repeat every 5 minutes if there is no improvement.

   • Airway Management: Ensure the airway is open. Prepare for intubation if there is severe airway swelling.

   • High-flow Oxygen: Administer via a non-rebreather mask.

2. Supportive Measures

   • IV Fluids: Start a large-bore IV line and give rapid boluses of crystalloids (e.g., 0.9% saline) to maintain blood pressure.

   • Antihistamines: Administer chlorphenamine 10 mg IV for additional relief of urticaria and angioedema.

   • Corticosteroids: Give hydrocortisone 200 mg IV to reduce the risk of biphasic reactions.

3. Ongoing Monitoring and Care

   • Continuous Monitoring: Monitor vital signs, oxygen saturation, and ECG continuously.

   • Reassessment: Regularly reassess the patient’s response to treatment.

   • Observation: Patients should be observed for at least 4-6 hours post-reaction due to the risk of biphasic anaphylaxis.

4. Post-Episode Care

   • Education: Ensure the patient and their family understand the trigger and avoidance strategies.

   • Prescription: Provide an adrenaline auto-injector and instruct on its use.

   • Referral: Arrange follow-up with an allergist for further testing and long-term management.

Conclusion

Managing anaphylaxis efficiently requires prompt recognition and decisive action. By asking the right questions, conducting a thorough examination, performing appropriate investigations, and following a structured management plan, junior doctors can significantly improve patient outcomes in this critical condition. Always stay vigilant, keep calm, and act swiftly to ensure the best possible care for your patients.