• Crashing Asthmatic = worsening despite initial treatment to a point of respiratory failure or cardiac arrest.
• Consider anaphylaxis as the cause.
• Get help early – consult ICU and anesthesia early (or initiate transfer out),
• Failure of ventilation (causing hypoxemia) and hemodynamics (breath stacking > increased intrathoracic pressures > decreased venous return).
• Avoid intubation if possible.
• Use epinephrine (IV,SC, IM or IO) or Salbutamol IV.
• Consider anxiolytics – ketamine dissociative doses (0.1 mg/kg bolus – 0.1 mg/kg/hr infusion – sedation); or low dose fentanyl.
• Non-invasive ventilation can support tiring patient.
• Ventilator settings:
  • LOW
    • Resp Rate (RR) – start at 10/min
    • Tidal Volume – start at 7mls/kg
    • PEEP – start at 0-3 cm
  • HIGH
    • Peak Pressure Alarm – start at 60
    • Flow Rate – start at 80 liters/min
• Permissive hypercapnia – require heavy sedation +/- paralysis.

• Impending respiratory failure – RR slowing, patient somnolent; O2 sats decreasing.
• Other clues include:
  • PaCO₂ > 40 mmHg and worsening hypercapnia.
  • SpO₂ < 90% despite face mask O₂ supplementation.
  • Cyanosis.
  • Accessory muscle use for inspiration.
  • Sweating and agitation.
  • Brief speech.
  • Absent lung sounds upon auscultation.
  • Acidemia (pH < 7.10).
  • Hypotension, abnormal heart rhythm.
• Highest rates of mortality occur in young adults residing in inner-city environments.
• Risk Factors for respiratory failure:
  • Previous asthma exacerbations requiring ICU admissions.
  • Poor asthma control.
  • Substance use, mental illness, and inner-city population.
• An important trigger of life threatening exacerbations is anaphylaxis.

In patients in significant distress, measuring peak expiratory flow rate (PEFR) not usually possible.

• PEFR < 40% predicted or < 200 L/min in adults indicates severe obstruction.

Do not wait for arterial blood gas to manage patients.

Order PORTABLE chest x-ray if alternative diagnosis is suspected (e.g., pneumothorax, CHF, pneumonia) and bedside ultrasound (POCUS) not diagnostic.

Treatment goal is to maintain adequate ventilation and minimize barotrauma which may beat the expense of hypercarbia or acidosis – permissive hypercapnia.

Consult ICU and anesthesia early (or initiate transfer out), and closely monitor in the emergency department.

Provide aggressive bronchodilator therapy in the form of salbutamol (SABA) and ipratropium (SAMA).

• Continuous nebulization salbutamol, ipratropium.
• IV/IO methylprednisolone 125 mg.
• Magnesium 2 grams IV over 15 minutes.
• Administer epinephrine if 0.3-0.5 mg IM if suspected anaphylaxis or inability to use inhaled bronchodilators.
  • Repeat every 20 minutes for up to 3 doses.
• Alternate IV bronchodilatar: Salbutamol 5-10 Microrgram bolus and 5-10 microg/hour.

Consider anxiolysis – ketamine dissociative doses (0.1 mg/kg bolus – 0.1 mg/kg/hr infusion – sedation); or low dose fentanyl.

Provide supplemental oxygen.

• Aim for SpO₂ >92% in adults or >95% for pregnant patients.

Secure IV access.

• Administer IV bolus of normal saline as usually dehydrated.

Assess for comorbidities and alternate diagnoses such as COPD, CHF, pneumonia, obstruction of the upper airway, pulmonary embolism, aspiration.

Consider using:

• Helium-oxygen (no ideal dosing) – no good evidence and not readily available.
• Volatile anesthetic.
• Isoflurane (no ideal dosing) or Halothane (no ideal dosing) – call anesthesia.
• ECMO – ICU decision.

Intubation and mechanical ventilation is required if patient is showing signs of respiratory failure (listed above).

• intubate with a large bore endotracheal tube (≥8 mm).

Ventilator initial settings to minimize breath stacking and barotrauma.

• LOW:
  • RR – 10 breaths/minute
  • Tidal Volume – 7 mls/kg
  • PEEP – 0-3 cm H20
• HIGH:
  • Insp Flow Rate – 80 L/min
  • Set High Pressure alarm to 60

Tips:

• Permissive hypercapnia protects against breath stacking/barotrauma (trying to normalize is dangerous).
• Requires deep sedation:
  • Analgesic – Fentanyl – high dose.
  • Sedative hypnotic – Ketamine or propofol infusion.
• Paralysis.
• If arrests on ventilator:
  • Take of ventilator and push on chest to relieve breath stacking.
  • Check ETT for blockage (mucus plug).
  • Check for Tension pneumothorax (may decide to do bilateral finger thoracostomies).
  • Then start CPR/epinephrine (ASAP or in conjunction with above).

All need admission to ICU or transfer to higher level of care.

1. • https://emergencycarebc.ca/clinical_resource/asthma-exacerbation-in-adults-diagnosis/
   • https://emergencycarebc.ca/clinical_resource/asthma-exacerbation-in-adults-treatment/
   • https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1487869/
   • https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1230847/
   • https://pubmed.ncbi.nlm.nih.gov/11360044/
   • https://www.uptodate.com/contents/acute-asthma-exacerbations-in-children-younger-than-12-years-emergency-department-management?search=acute%20asthma%20exacerbation%20children&source=search_result&selectedTitle=2~150&usage_type=default&display_rank=2
   
   

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2. Godwin HT, Fix ML, Baker O, Madsen T, Walls RM, Brown CA. Emergency department airway management for status asthmaticus with respiratory failure. Respiratory Care. 2020; doi:10.4187/respcare.07723

   
   

3. Higgins JC. The “Crashing Asthmatic.” American Family Physician. 2003 Dec;67(5):997–1004. doi: https://www.aafp.org/pubs/afp/issues/2003/0301/p997.html

   
   

4. Hodder R, Lougheed MD, FitzGerald JM, Rowe BH, Kaplan AG, McIvor RA. Management of acute asthma in adults in the emergency department: Assisted Ventilation. Canadian Medical Association Journal. 2009;182(3):265–72. doi:10.1503/cmaj.080073

   
   

5. Thomson CC, Hasegawa K. Invasive mechanical ventilation in adults with acute exacerbations of asthma [Internet]. 2023 [cited 2024 Jan 8]. Available from: https://www.uptodate.com/contents/invasive-mechanical-ventilation-in-adults-with-acute-exacerbations-of-asthma