Ep 187 Crashing Anaphylaxis – AMAX4 Algorithm and The Max McKenzie Case
Sep 26, 2023
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Dr. Ben McKenzie, EM physician and a PhD candidate, discusses the AMAX4 algorithm for anaphylaxis and asthma resuscitation. Topics include predicting severity, securing the airway, simulations, paralytics and bronchodilators, and taking action against anaphylaxis and severe asthma.
Prompt administration of intravenous (IV) epinephrine is crucial in severe anaphylaxis cases to prevent hypoxic brain injury within 4 minutes.
Urgent endotracheal intubation should be considered in respiratory distress or unconscious patients with severe asthma or anaphylaxis to prevent respiratory or cardiac arrest.
Deep dives
The Devastating Impact of Anaphylaxis and Asthma
Dr. Ben McKenzie, an emergency physician, shares the heartbreaking story of his 15-year-old son Max's tragic death from anaphylaxis. Despite prompt use of an EpiPen, Max suffered a respiratory arrest and eventually passed away from a severe hypoxic brain injury. Dr. McKenzie emphasizes the importance of understanding the physiological factors that contribute to the progression of anaphylaxis and asthma, particularly in young patients. He advocates for zero deaths from these conditions and highlights the need for healthcare professionals to anticipate and prevent worsening symptoms. By recognizing key clinical clues and promptly administering epinephrine, the primary medication for anaphylaxis, healthcare providers can potentially prevent severe complications and save lives.
The Dosage, Route, and Timing of Epinephrine
Epinephrine is the first-line treatment for anaphylaxis, but in severe cases, the standard intramuscular (IM) dose may not provide rapid relief. Dr. McKenzie emphasizes that for extremely sick patients, waiting for IM epinephrine to take effect (5-8 minutes) may not prevent hypoxic brain injury, which can occur within 4 minutes. In such cases, he advises administering intravenous (IV) epinephrine, as it has an instant effect. The recommended IV dose is 1 microgram per kilogram, although lower doses may be given if the patient is awake and talking. If a patient fails to respond after two IM doses, it is crucial to prepare for possible cardiac or respiratory arrest by having IV epinephrine and other resuscitative measures ready.
Airway Management in Severe Asthma and Anaphylaxis
Severe asthma and anaphylaxis cases may require urgent airway management to prevent respiratory arrest. While intubation was once seen as a last resort due to concerns about exacerbating bronchospasm, current management guidelines recommend timely intubation to avoid progressing to respiratory or cardiac arrest. Dr. McKenzie explains that patients experiencing respiratory distress, unconsciousness, or requiring bag-mask ventilation need prompt intervention. Endotracheal intubation provides the necessary airway control to deliver high-pressure ventilation, facilitate oxygenation, and resolve bronchospasm. In cases where intubation is challenging or unsuccessful, emergency front-of-neck access should be pursued without hesitation.
The Amax4 Algorithm: A Life-Saving Approach
Dr. McKenzie introduces the Amax4 algorithm, developed as a resuscitation guideline for asthma and anaphylaxis arrests. The A stands for adrenaline (epinephrine), emphasizing its role as the primary medication. The M highlights the importance of using a muscle relaxant to ensure the best conditions for successful intubation. The A also represents airway management, emphasizing the need for endotracheal intubation in critical cases. The X stands for extreme ventilation, emphasizing the use of additional bronchodilators and vasopressors to manage these severe conditions. Lastly, the number 4 signifies the critical timeframe of four minutes before hypoxic brain injury occurs, highlighting the need for rapid action and coordination among healthcare providers.
I had the enormous honour of interviewing Dr. Ben McKenzie, EM physician and a PhD candidate at the University of Melbourne studying the topic of resuscitation algorithms in anaphylaxis and asthma. The tragic death of his son Ben McKenzie at the age 15 from hypoxic respiratory arrest as a result of anaphylaxis and asthma in 2021 has led Dr. McKenzie on a mission to prevent deaths from anaphylaxis and asthma by educating emergency providers around the world using his AMAX4 algorithm as a framework...
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