Why is nebulization with salbutamol (albuterol) contraindicated in laryngotracheobronchitis (croup)?

Salbutamol is NOT Contraindicated in Laryngotracheobronchitis (Croup)

Salbutamol is not contraindicated in croup; however, it is simply not the recommended treatment because it lacks efficacy for upper airway obstruction, which is the primary pathology in laryngotracheobronchitis. The appropriate nebulized treatment for croup is epinephrine (adrenaline), not beta-agonists like salbutamol 1.

Why Salbutamol is Not Used in Croup

Pathophysiology Mismatch

• Croup involves upper airway edema and inflammation at the level of the larynx, trachea, and bronchi, causing stridor and inspiratory obstruction 1.
• Salbutamol is a beta-2 agonist that works on lower airway smooth muscle to relieve bronchospasm, which is not the primary mechanism of obstruction in croup 1.
• The pathology in croup is subglottic edema, not bronchospasm, making bronchodilators mechanically ineffective for this condition 1.

Evidence-Based Treatment for Croup

• Nebulized epinephrine (0.5 mL/kg of 1:1000 solution, maximum 5 mL) is the recommended treatment to reduce upper airway edema and avoid intubation 1.
• The British Thoracic Society guidelines specifically recommend nebulized adrenaline for croup to stabilize children prior to transfer to intensive care and in stridor following intubation 1.
• The effect of nebulized epinephrine is short-lived (1-2 hours), and it should not be used in children who are shortly to be discharged or on an outpatient basis 1.

Additional Effective Treatments

• Nebulized steroids (e.g., 500 µg budesonide) or systemic corticosteroids (oral or intramuscular dexamethasone) are effective in reducing symptoms in croup within the first two hours 1, 2.
• All three steroid formulations (nebulized budesonide, oral dexamethasone, and intramuscular dexamethasone) have equivalent effectiveness for croup treatment 2.

Common Pitfall to Avoid

Do not confuse croup with bronchiolitis or asthma, where salbutamol may have a role:

• In bronchiolitis, salbutamol has shown variable effectiveness and is not routinely recommended, though a monitored trial may be considered 1, 3.
• In acute asthma, nebulized salbutamol is a cornerstone of treatment for lower airway bronchospasm 1.
• The key distinguishing feature is stridor (upper airway) versus wheezing (lower airway) 1.

Clinical Algorithm for Acute Upper Airway Obstruction

When a child presents with stridor and suspected croup:

1. Administer nebulized epinephrine (0.5 mL/kg of 1:1000 solution, max 5 mL) for immediate relief 1.
2. Give systemic corticosteroids (oral or IM dexamethasone, or nebulized budesonide 500 µg) for sustained effect 1, 2.
3. Monitor closely for 2-4 hours due to the short duration of epinephrine's effect 1.
4. Do not use salbutamol, as it will not address the upper airway edema 1.