Anaphylaxis Diagnosis Criteria: A Comprehensive Guide for Healthcare Professionals

Anaphylaxis is a severe, life-threatening allergic reaction that requires immediate recognition and treatment. For healthcare professionals, prompt and accurate diagnosis is paramount to ensure timely intervention and improve patient outcomes. This guide, based on the latest ASCIA (Australasian Society of Clinical Immunology and Allergy) guidelines, provides a comprehensive overview of the Anaphylaxis Diagnosis Criteria, signs, symptoms, and immediate management strategies for anaphylaxis. It is crucial for medical practitioners, nurses, and emergency responders to be well-versed in these criteria to effectively manage anaphylactic emergencies.

Understanding Anaphylaxis: Definition and Diagnostic Benchmarks

Anaphylaxis is defined by ASCIA as a severe allergic reaction characterized by its rapid onset and potential to be life-threatening. Accurate diagnosis hinges on recognizing specific clinical criteria, which have been refined and standardized by international bodies like the World Allergy Organisation (WAO). According to both ASCIA and WAO guidelines, anaphylaxis diagnosis is highly probable when any one of the following two criteria are met:

Criterion 1: Acute Onset with Skin/Mucosal Changes AND Systemic Involvement

This criterion emphasizes the rapid development of symptoms, typically within minutes to a few hours of exposure to a trigger. It requires the presence of skin or mucosal tissue changes along with involvement of at least one other major body system.

Key Components of Criterion 1:

• Acute Onset of Illness: Symptoms appear suddenly and progress rapidly, usually within minutes to several hours.
• Skin and/or Mucosal Tissue Involvement: This includes typical skin features such as:
  • Generalized hives (urticaria): Raised, itchy welts that appear and disappear in different locations on the body.
  • Pruritus (itching) or flushing: Widespread itching or redness of the skin.
  • Angioedema: Swelling, particularly of the lips, tongue, uvula, face, or eyelids.
• AND at least ONE of the following systemic manifestations:
  • Respiratory Compromise: Signs of breathing difficulty such as:
    • Dyspnea (shortness of breath)
    • Wheezing (bronchospasm)
    • Stridor (high-pitched breathing sound indicating upper airway obstruction)
    • Reduced peak expiratory flow (PEF) rate
    • Hypoxemia (low blood oxygen levels)
  • Reduced Blood Pressure or End-Organ Dysfunction Symptoms: Indicators of cardiovascular involvement, including:
    • Hypotonia (collapse, particularly in infants and children)
    • Syncope (fainting or loss of consciousness)
    • Incontinence (loss of bladder or bowel control)
  • Severe Gastrointestinal Symptoms: Especially relevant after exposure to non-food allergens (though can occur with food allergens):
    • Severe crampy abdominal pain
    • Repetitive vomiting

Criterion 2: Acute Onset with Rapid Systemic Reactions After Known Allergen Exposure

This criterion is crucial when anaphylaxis is suspected following exposure to a known or highly probable allergen for a particular patient, even if typical skin signs are absent.

Key Components of Criterion 2:

• Acute Onset of Symptoms: Rapid development of symptoms within minutes to several hours after allergen exposure.
• Exposure to Known or Highly Probable Allergen: There should be a plausible history of exposure to an allergen known to cause anaphylaxis in the patient.
• AND ONE of the following rapid systemic reactions:
  • Hypotension: Sudden drop in blood pressure.
  • Bronchospasm: Tightening of the airways leading to wheezing and breathing difficulty.
  • Laryngeal Involvement (Upper Airway Obstruction): Swelling of the larynx causing stridor, hoarse voice, or difficulty breathing.
• Even in the Absence of Typical Skin Involvement: It’s vital to note that anaphylaxis can occur without skin signs in up to 20% of cases. Relying solely on skin symptoms can lead to underdiagnosis and delayed treatment.

Recognizing the Signs and Symptoms of Allergic Reactions: From Mild to Anaphylaxis

Understanding the spectrum of allergic reactions is critical for early recognition and intervention. Allergic reactions can range from mild to severe anaphylaxis. While mild to moderate reactions may precede anaphylaxis, it’s important to recognize that anaphylaxis can also occur suddenly without preceding milder symptoms.

Mild to Moderate Allergic Reaction Signs (May or May Not Precede Anaphylaxis):

• Swelling: Lips, face, eyes
• Skin: Hives (urticaria) or welts, itching
• Oral: Tingling mouth
• Gastrointestinal (Specific Context): Abdominal pain, vomiting – particularly significant as early signs of anaphylaxis in insect sting or injected drug (medication) allergies.

Anaphylaxis Signs – Indicating a Severe Allergic Reaction (Any One Sign is Sufficient):

• Respiratory Distress:
  • Difficult or noisy breathing
  • Swelling of the tongue
  • Swelling or tightness in the throat
  • Difficulty talking or hoarse voice
  • Wheezing or persistent cough – characteristically sudden onset, unlike asthma cough.
• Cardiovascular Compromise:
  • Persistent dizziness or collapse
  • Pale and floppy (in young children)
• Gastrointestinal (Specific Context): Abdominal pain, vomiting – especially in insect stings or injected drug (medication) allergies, indicating systemic reaction severity.

It’s crucial to remember that anaphylaxis is a clinical diagnosis. While these criteria and signs are highly indicative, clinical judgment is essential in making a rapid diagnosis and initiating treatment.

Immediate Actions for Anaphylaxis: A Step-by-Step Guide

Once anaphylaxis is diagnosed or strongly suspected, immediate action is critical. The primary goals are to reverse the life-threatening physiological changes and support the patient until emergency medical services arrive.

1. Identify and Remove Allergen (If Possible): If the trigger is known and still present (e.g., insect stinger, medication administration), remove it immediately.
2. Call for Help and Locate Adrenaline (Epinephrine): Immediately call for assistance and locate an adrenaline autoinjector or adrenaline ampoule/syringe if available.
3. Position the Patient Correctly: Lay the person flat immediately. Do NOT allow them to stand or walk.
   • Unconscious or Pregnant: Place in the recovery position. For pregnant women, position on their left side to avoid vena cava compression.

Alt text: Infographic illustrating correct anaphylaxis patient positioning: Lay flat, recovery position, left lateral position for pregnancy, sitting with legs outstretched for breathing difficulty, and holding infants flat.

*   **Breathing Difficulty:** If breathing is labored, allow them to sit with legs outstretched. Avoid sitting upright on a chair as this can worsen hypotension.
*   **Infants and Young Children:** Hold them flat, not upright.

4. Administer Adrenaline (Epinephrine) Without Delay: Adrenaline is the first-line treatment for anaphylaxis.
   • Intramuscular Injection (IMI): Inject adrenaline (1:1000) into the outer mid-thigh. Use an autoinjector if available, or draw up the correct dose from an ampoule and syringe if trained.
   • Dosage: Refer to the adrenaline dose chart based on age and weight (provided in the original document and crucial for accurate administration).
   • Repeat Dose: If there is no improvement after 5 minutes, a second dose of adrenaline may be given. When in doubt, administer adrenaline.
5. Administer Oxygen (If Available): Provide high-flow oxygen if available to support breathing and oxygenation.
6. Call Emergency Medical Services: Phone for an ambulance (911 in many English-speaking countries, 000 in Australia, 111 in New Zealand) to transport the patient to a hospital.
7. Contact Family/Emergency Contact: Inform the patient’s family or emergency contacts.
8. Monitor and Prepare for Further Adrenaline Doses: Reassess the patient’s condition every 5 minutes. Be prepared to administer further adrenaline doses if needed.
9. Hospital Transfer and Observation: Transport the patient to the hospital for at least 4 hours of observation due to the risk of biphasic reactions (recurrence of symptoms).
10. Commence CPR if Necessary: If the person becomes unresponsive and is not breathing normally, start cardiopulmonary resuscitation (CPR) immediately.

Important Note: Always administer adrenaline first in cases of anaphylaxis, especially if breathing difficulty is present, even before asthma relievers in patients with known asthma and allergies.

Anaphylaxis Triggers and Reaction Times: Key Considerations

Identifying potential triggers and understanding reaction times can aid in diagnosis and future prevention.

Common Anaphylaxis Triggers:

• Foods: Peanuts, tree nuts, milk, eggs, soy, wheat, fish, shellfish are among the most common.
• Insect Stings: Bees, wasps, hornets, and fire ants.
• Medications: Antibiotics (penicillin), NSAIDs, and neuromuscular blocking agents, radiocontrast agents.
• Latex: Natural rubber latex.

Less Common Triggers:

• Tick bites (mammalian meat allergy)
• Exercise (exercise-induced anaphylaxis, food-dependent exercise-induced anaphylaxis)
• Cold temperatures (cold urticaria, cold anaphylaxis)
• Immunotherapy (rare)
• Idiopathic anaphylaxis (unknown cause)

Reaction Times:

• Food Allergy: Typically within 1-2 hours of ingestion, but can be faster (within minutes) or delayed (several hours, e.g., mammalian meat allergy).
• Insect Stings and Injected Medications: Usually within 5-30 minutes, but can be delayed.
• Oral Medications: Reactions can occur but are less common than with injected medications.

Adrenaline (Epinephrine) Administration and Dosage: The Cornerstone of Anaphylaxis Treatment

Adrenaline is the crucial first-line treatment for anaphylaxis because it counteracts the major pathophysiological processes involved in anaphylaxis:

• Reduces airway mucosal edema: Opens up the airways by reducing swelling.
• Induces bronchodilation: Relaxes the muscles around the airways, making breathing easier.
• Induces vasoconstriction: Narrows blood vessels, raising blood pressure.
• Increases strength of cardiac contraction: Improves heart function and blood circulation.

Administration Guidelines:

• Route: Intramuscular injection (IMI) is the preferred route for initial treatment in non-hospital settings. Intravenous (IV) administration is typically reserved for advanced management in hospitals.
• Site: Outer mid-thigh. Intramuscular injection into the thigh is rapidly absorbed and easily accessible.
• Concentration: Use adrenaline 1:1000 (1mg/mL) for intramuscular injection. Adrenaline 1:10,000 is for IV use and should not be used for IM injection.
• Dosage: 0.01mg per kg of body weight, up to a maximum single dose of 0.5mg. Refer to the detailed dose chart provided in the original document for age and weight-specific dosages and corresponding volumes from adrenaline ampoules or autoinjector devices.

Adrenaline (epinephrine) dose chart
Age (years)
~
~1-2
~2-3
~4-6
~7-10
~10-12
~>12 and adults

*Adrenaline 1:1,000 ampoules contain 1mg adrenaline per 1mL

**EpiPen® Jr is a 150 microgram (0.15 mg) device.

***EpiPen® is a 300 microgram (0.3 mg) device.

****Anapen® 500 is a 500 microgram (0.5 mg) device.

Important Notes on Adrenaline Administration:

• Repeat Doses: If symptoms do not improve or worsen within 5 minutes, repeat the adrenaline dose. Multiple doses may be necessary in severe anaphylaxis.
• IV Infusion: In cases requiring multiple doses or in hospital settings, consider IV adrenaline infusion under specialist supervision.
• Avoid IV Boluses: IV bolus doses of adrenaline are generally not recommended outside of cardiac arrest situations and require specialized training due to the risk of cardiac arrhythmias.

Special Considerations: Anaphylaxis in Pregnancy and Infants

Management of Anaphylaxis in Pregnancy

Managing anaphylaxis in pregnant women follows the same principles as for non-pregnant adults. Adrenaline is the first-line treatment and should not be withheld due to concerns about placental perfusion. The benefits of adrenaline in treating anaphylaxis outweigh the potential risks to the fetus.

• Positioning: The left lateral recovery position is recommended for pregnant patients to optimize venous return and minimize vena cava compression by the uterus.

Management of Anaphylaxis in Infants

Infants with anaphylaxis present unique challenges.

• Dosage: Use weight-based adrenaline dosing. A 150 microgram adrenaline autoinjector may be prescribed for infants weighing 7.5-10 kg and is generally preferred over ampoules and syringes in non-expert hands due to ease of use and reduced risk of dosing errors.
• Pallor: Infants may remain pale despite multiple adrenaline doses. This pallor may resolve without further intervention and should not automatically be interpreted as treatment failure.
• Over-treatment: Excessive adrenaline doses in infants can lead to hypertension and tachycardia, which can be misinterpreted as worsening anaphylaxis. Blood pressure monitoring can guide treatment and help avoid over-treatment.
• Positioning: Always hold infants flat during anaphylaxis management.

Positioning of Patients with Anaphylaxis: A Critical Intervention

Correct patient positioning is a crucial, often underemphasized, aspect of anaphylaxis management. Fatalities can occur if patients stand, walk, or sit upright too soon after anaphylaxis onset.

• Lay Flat: Patients must be laid flat immediately to improve venous return to the heart. Upright positions impair blood return, leading to hypotension and circulatory collapse.
• Avoid Standing and Walking: Patients should not stand or walk, even if they appear to be recovering. Use a wheelchair, stretcher, or trolley for transport.
• Recovery Position: If unconscious, vomiting, or pregnant, place the patient in the recovery position (left lateral for pregnancy).
• Sitting with Legs Outstretched: Patients with primarily respiratory symptoms may find it easier to breathe sitting with legs outstretched, but monitor closely and lay them flat if their condition deteriorates.
• Infants Flat: Hold infants and young children flat.
• Duration: Patients should remain lying flat until hemodynamically stable, typically at least 1 hour after one adrenaline dose and 4 hours after multiple doses.

Essential Equipment for Acute Anaphylaxis Management

Having readily available and well-organized equipment is vital for efficient anaphylaxis management. Emergency trolleys or anaphylaxis kits should include:

• Adrenaline (Epinephrine): 1:1,000 ampoules and ideally adrenaline autoinjectors for rapid administration.
• Syringes and Needles: 1mL syringes and appropriate gauge needles (22-25G, 25mm length recommended for IM injections for most ages). Shorter needles (16mm) for preterm infants and longer needles (up to 38mm) for very large adults may be needed.
• Oxygen and Airway Management: Oxygen source, rebreather oxygen masks, nebulizer masks, suction equipment, and airway adjuncts (e.g., oropharyngeal airways).
• Defibrillator: For cardiac monitoring and potential defibrillation if cardiac arrest occurs.
• Blood Pressure Monitoring: Manual blood pressure cuff.
• IV Access Equipment: IV cannulas (including large bore for rapid fluid resuscitation), IV administration sets.
• Intravenous Fluids: At least 3 liters of normal saline for fluid resuscitation.
• Hands-free Communication: A hands-free phone in the resuscitation area to facilitate remote consultation with specialists if needed.

Supportive and Additional Measures in Anaphylaxis Management

While adrenaline is the cornerstone of anaphylaxis treatment, supportive measures and additional therapies may be necessary, especially in severe or refractory cases.

Supportive Management (When Skills and Equipment are Available):

• Monitoring: Continuously monitor pulse, blood pressure, ECG, pulse oximetry, and level of consciousness.
• Oxygen Therapy: Administer high-flow oxygen and provide airway support as needed.
• Intravenous Access and Fluid Resuscitation: Obtain IV access, particularly in adults and children with tachycardia or hypotension. If hypotensive, administer rapid IV boluses of normal saline (20mL/kg) and consider additional IV access for ongoing fluid support.

Additional Measures for Refractory Anaphylaxis (In Clinical Settings):

• Intravenous Adrenaline Infusion: If there is inadequate response to 2-3 IM adrenaline doses or patient deterioration, initiate IV adrenaline infusion under specialist guidance. Use infusion pumps and dedicated lines for accurate and safe administration.
• Nebulized Adrenaline: For upper airway obstruction not responding to IM/IV adrenaline, nebulized adrenaline may be considered.
• Persistent Hypotension/Shock:
  • Aggressive fluid resuscitation with normal saline (up to 50mL/kg in the first 30 minutes).
  • Glucagon: In patients taking beta-blockers, glucagon may be considered to counteract beta-blockade and improve cardiovascular response.
  • Vasopressors: In adults with persistent hypotension despite adrenaline and fluids, selective vasoconstrictors (e.g., metaraminol, vasopressin) may be considered under specialist direction.
• Persistent Wheezing:
  • Bronchodilators: Salbutamol (albuterol) via metered-dose inhaler and spacer or nebulizer. Note: Bronchodilators are not first-line treatment for anaphylaxis and should be used adjunctively after adrenaline.
  • Corticosteroids: Oral prednisolone or intravenous hydrocortisone. Note: Corticosteroids are not first-line treatment and have a delayed onset of action; their benefit in acute anaphylaxis is uncertain.
• Antihistamines: Antihistamines are not effective for treating acute respiratory or cardiovascular symptoms of anaphylaxis and should not be used as primary or sole therapy. Sedating antihistamines should be avoided as they can mimic anaphylaxis symptoms. Injectable promethazine is contraindicated as it can worsen hypotension.

Actions After Adrenaline Administration and Discharge Planning

Following adrenaline administration, ongoing observation and comprehensive discharge planning are essential to ensure patient safety and prevent future episodes.

Post-Adrenaline Administration Actions:

• Observation: Monitor the patient for at least 4 hours after the last adrenaline dose due to the risk of biphasic reactions. Longer observation or overnight admission is recommended for patients with severe anaphylaxis, protracted reactions, comorbidities, or social factors that increase risk (e.g., living alone).
• Relapse and Biphasic Reactions: Be vigilant for signs of symptom recurrence. Biphasic reactions can occur in a significant percentage of anaphylaxis cases (3-20%).

Discharge Planning and Follow-up:

• Adrenaline Autoinjector Prescription and Training: Prescribe and, if possible, dispense an adrenaline autoinjector before discharge for patients at risk of re-exposure to allergens or with idiopathic anaphylaxis. Provide thorough training on autoinjector use using a trainer device.
• ASCIA Action Plan for Anaphylaxis: Provide the patient with a personalized ASCIA Action Plan for Anaphylaxis, accessible online, outlining steps for future anaphylaxis management.
• Clinical Immunology/Allergy Specialist Referral: Refer all patients who have experienced anaphylaxis to a clinical immunology/allergy specialist for:
  • Allergen identification and confirmation.
  • Education on allergen avoidance and prevention strategies.
  • Development of an ASCIA Action Plan.
  • Consideration of allergen immunotherapy (for venom allergy).
  • Management of co-existing conditions.
• Documentation: Encourage patients to document anaphylaxis episodes using an ASCIA allergic reactions event record to help identify triggers.
• Patient and Carer Support: Refer patients to allergy support organizations like Allergy & Anaphylaxis Australia or Allergy New Zealand for ongoing education and support.

By adhering to these anaphylaxis diagnosis criteria and management guidelines, healthcare professionals can significantly improve outcomes for patients experiencing this life-threatening condition. Prompt recognition, immediate adrenaline administration, and comprehensive follow-up are crucial in ensuring patient safety and well-being.