AMAX4 Algorithm

What is anaphylaxis?

Anaphylaxis Definition (World Allergy Organisation 2020)

Most young people with anaphylaxis die from bronchospasm – especially food allergy which is the most common trigger presenting to emergency departments.  Bronchospasm also occurs in drug and venom allergy and causes death in young people.

Australia has the highest rates of documented food allergy and hospital anaphylaxis admissions in the developed world.

Severe anaphylaxis is an extremely challenging clinical scenario for even the most skilled clinicians and requires rapid escalation of potentially life-saving measures.

What is the AMAX4 algorithm?

AMAX4 is the initiative of emergency physician Dr Ben McKenzie and his wife Tamara McKenzie following the tragic death of their 15-year-old son Max McKenzie. Max sustained an hypoxic brain injury secondary to food anaphylaxis related bronchospasm/asthma.

The promotion of the AMAX4 algorithm aims to raise awareness and reform treatment through a didactic protocol to reduce deaths from anaphylaxis and asthma in young people to zero.

• Every emergency department should have programs where brief in situ practice of time critical team based procedures are practiced.
• Every ambulance service should have mechanisms in place to manage hypoxic asthma arrests and respond to potential rapid deterioration of acute asthma/ anaphylaxis.

The AMAX4 Algorithm

The AMAX4 algorithm applies to all clinicians who are capable of endotracheal intubation or are part of an intubating team.  Non intubating clinicians need to understand that it is unknown how long bag valve mask ventilation can oxygenate someone with critical asthma/anaphylaxis or severe airway obstruction before it fails.  The most senior person needs to devote every effort to deliver oxygen – a two person technique may help.

The 10 concepts informing AMAX4

Note: The 10 concepts are presented here in brief; they are expanded upon in the AMAX4 lecture on the AMAX4 website.

1. Time to hypoxic brain injury is 4 minutes. The time to hypoxic brain injury is extremely short and cannot be extended by CPR in hypoxic arrest.​
2. Airway pressures are HIGH (50-100 cmH₂0) – too high for any other device other than an endotracheal tube (ETT). BVM and LMA are unsuitable.
3. Immediately securing airway with ETT has multiple other benefits. Aspiration risk is high and consequences catastrophic.
4. The FIRST intubation attempt should be the BEST attempt. Muscle relaxant, video laryngoscopy, and best intubator in the room.
5. Inability to intubate on first attempt (Can’t Intubate, Can’t Oxygenate (CICO)) indicates immediate surgical airway.
6. Secure the airway! Prioritise oxygen delivery to prevent brain damage.
7. Intubation practice. Practice. Simulation. Practice
8. PneumothoraX. Pneumothorax rates are high when arrest or CPR is involved.
9. Xtreme Ventilation. Initially use a bag, not a ventilator.
10. Xtra medical therapy.

If unconscious needing assisted ventilation from asthma or anaphylaxis consider the following:

The AMAX4 website

Ben and Tamara have launched a website AMAX4 – Every Second Counts which includes full details of the AMAX4 algorithm.

AMAX4 lecture

The site includes a full one hour lecture presented by Dr. Ben McKenzie and has been divided into 6 easily digestible 10 minute sections.

1. Paediatric anaphylaxis, diagnostic criteria, severity grading system: Acute allergy is a continuum of disease from mild skin symptoms to cardiac arrest.
2. Anaphylaxis treatment from basics to critical care specialist management before arrest. Ben tells the tragic story of James Tsindos who died 8 weeks before Max suffering an almost identical series of problems in care.
3. Key anaphylaxis and asthma resuscitation concepts that are a “special circumstance
4. The “Maximum 4 minutes” until hypoxic ischaemic encephalopathy, the first of 10 concepts informing AMAX4. The impact of time critical care, and the concept of “Hard deck, Hard limits“.
5. Discussion of the remaining 9 of 10 concepts informing AMAX4
6. Ben talks about what happened to Max with a deeper understanding of the timeline of Max’s care with paramedics and the Emergency Department.

Max’s Story

Max McKenzie was an otherwise healthy teenager. He was talented, happy and loved. Max entered health care with normal oxygen levels alert and he was able to ask for help, but despite the emergency health care provided sustained an unsurvivable brain injury.

Simulation Training Video

Simulation Video applying the techniques in a real-time, simulation of treating hypoxic anaphylaxis and asthma.

Every emergency department should have programs where brief in situ practice of time critical team based procedures are practiced – especially if the case mix of high acuity patients is low in a particular department.

Understand the medical adjuncts, risk of obstructive hyperinflation, risk of pneumothorax and how to perform difficult ventilation in the face of high pressures and an obstructive pattern using a laerdal bag post intubation.

Drawing up push dose adrenaline (epinephrine)

How to PREPARE and LABEL adrenaline (epinephrine) for a bolus push dose of 1 mcg/kg in order to have solutions of 100mcg/mL or for smaller children 10mcg/mL

A single large 10mL vial of 1:10,000 contains 1 mg/10mL adrenaline.

• In a 10mL syringe: Each 1mL has 100 mcg of adrenaline (100 mcg/mL)

A single small 1mL vial of 1:1,000 contains 1 mg/1 mL adrenaline (1000 mcg/mL)

• This can be diluted with 9mL of normal saline or water for injection to make a solution of 1mg/10mL
• In a 10mL syringe: Each 1mL has 100 mcg of adrenaline 

For smaller children it is safer to make a solution of 10 mcg/mL

• To make this solution: Take 1 mL of a 1:10,000 solution and make it up to 10mL with 9mL of water for injection or normal saline.
• 10mL syringe: Each 1 mL contains 10 mcg of adrenaline (10mcg/mL)

Additional Resources

[cite]