Asthma; Severe, Life Threatening

This section is ONLY an Adult protocol; however, the practitioner may find this protocol's information useful for pediatric patients and consider use of similar treatment with weight appropriate equivalent doses at their discretion.

Asthma consists of 3 components

• Bronchoconstriction/Bronchospasm
• Airway inflammation
• Mucous impaction

Pharmacotherapy can impact bronchoconstriction and airway inflammation.

It is important to note the following

• Wheezing is often absent in severe asthma as air movement is too poor to even generate wheezing
• Oxygen saturation is not a reliable measure of how severely ill the patient is
• Successful treatment with bronchodilators commonly results in decreased oxygen saturation
• Work of breathing and CO₂ retention are often more critical factors
• Peak flow, when possible, is a reliable, readily available measure of severity of asthma

Treatment

• Oxygen, even in cases of normal oxygen saturation
• Beta-2 Agonist, either Albuterol, Salbutamol, or Levalbuterol. Albuterol should be administered 2.5-5 mg nebulized every 15-20 minutes or 10-15 mg/hr continuously.
• Steroids should be administered early; methylprednisolone (Solumedrol®) 125 mg IV is typical. This will impact airway inflammation, but will take hours before effect.
• Ipratropium (Atrovent®) 0.5 mg nebulized × 1 dose may be beneficial
• Magnesium sulfate 1.2-2 grams IV (mixed in 100 mL of NS) and infused over 20 minutes has reasonable evidence of benefit in severe asthma exacerbation
• Adrenergic injectables (use one agent)
1. Epinephrine 1:1,000, 0.3 mg subcutaneously q20 minutes × 3 doses
2. Terbutaline 0.25 mg subcutaneously; can be repeated in 30-60 minutes

Ventilation

• BiPAP applied early may be utilized in the alert patient
• Intubation may be necessary when respiratory failure occurs despite all other measures (low PO₂ on high flow O₂, high PCO₂, respiratory muscle fatigue). RSI should be utilized and the largest possible ETT should be used. Ventilator settings should allow for maximal time for the lungs to empty air as "auto-PEEP" may occur and hyper-inflation, hypotension &/or pneumothorax may occur.

If intubated

• Ventilator settings
  • 100% Oxygen
  • Rate of 6-10 BPM
  • Small tidal volumes (6-8 mL/kg)
  • Short inspiratory time with Inspiratory:Expiratory ratios of 1:4 or 1:5
• Continue with inhaled albuterol and other pharmacologic agents
• Permissive hypercapnea is common and reduces barotrauma (ventilate to level to maintain O₂ sat, not to normalize PCO₂)
• Deterioration when intubated occurs due to:
  Tube displacement, obstruction of the tube or lungs from mucous plugs or other causes, pneumothorax, other equipment failure (make sure oxygen is plugged to wall and ventilator is working).
• In severe cases, settings may even need to go to as low of a rate as 2 BPM with tidal volume of 3-5 mL/kg.

Source: Circulation 2005;112. 2005 AHA Guidelines for CPR and ECC.