What are the considerations for using continuous nebulisation with salbutamol (albuterol) or terbutaline for severe respiratory distress?

Continuous Nebulisation for Severe Respiratory Distress

Continuous nebulisation should be reserved for very severe asthma attacks in patients monitored in intensive care settings, as it remains under evaluation and is not superior to frequent intermittent nebulisation for most acute severe presentations. 1

Key Recommendations by Clinical Context

For Severe Acute Asthma

Frequent intermittent nebulisation is the standard approach:

• Administer nebulised β-agonist (salbutamol 5 mg or terbutaline 10 mg) initially, repeated every 20 minutes for the first hour if needed 1
• For poor response, add ipratropium bromide 500 μg to the β-agonist 1
• Continue 4-6 hourly intervals thereafter until peak expiratory flow >75% predicted and diurnal variability <25% 1

Continuous nebulisation dosing (when used):

• Terbutaline: 1-3 mg/hour 1
• Salbutamol: 0.3 mg/kg hourly (maximum 10 mg/hour) 1
• These doses have been used in trials, but more randomized controlled trials are needed to determine optimal dosing and duration 1

For COPD Exacerbations

Standard intermittent dosing is recommended:

• Nebulised salbutamol 2.5-5 mg or terbutaline 5-10 mg at 4-6 hourly intervals 1
• May be used more frequently if required 1
• For severe exacerbations with poor response, combine β-agonist with ipratropium bromide 0.25-0.5 mg 1

Critical safety consideration for COPD:

• Drive nebulisers with compressed air (not oxygen) if PaCO₂ is raised and/or respiratory acidosis is present 1
• Oxygen can be given simultaneously via nasal prongs at 1-2 L/min to prevent desaturation 1

Evidence Comparing Continuous vs Intermittent Nebulisation

Research shows no appreciable clinical difference:

• A randomized trial of 42 patients with acute severe asthma (mean PEF 24% predicted) found no significant difference in clinical scores, spirometric improvement, treatment failure rates (14% vs 9.5%), or hospitalization rates (38% vs 43%) between continuous and intermittent nebulisation 2
• Another randomized trial of 22 patients demonstrated that continuous nebulisation (7.5 mg/hour) was as safe and efficacious as intermittent dosing (2.5 mg every 20 minutes), with both groups doubling baseline spirometric values over 4 hours 3
• Both studies showed continued significant improvement beyond the initial 2 hours of high-dose therapy 2, 3

Practical Implementation Considerations

When continuous nebulisation might be considered:

• Very severe attacks requiring intensive care monitoring 1
• Patients not responding adequately to frequent intermittent dosing 1
• Early experience with this method is encouraging but still under evaluation 1

Logistical factors for decision-making:

• Continuous nebulisation requires specialized equipment (large volume nebulizers with 240 mL reservoirs) that can operate for up to 8 hours without refill 4
• Delivery efficiency to patient mask is approximately 90%, with about one-quarter of inhaled aerosol deposited in lungs 4
• The decision should be based primarily on logistical considerations and monitoring capabilities rather than superior efficacy 2

Common Pitfalls to Avoid

Do not use continuous nebulisation as first-line therapy:

• Standard frequent intermittent dosing is equally effective and better established 2, 3
• Metered dose inhaler with spacer may be as effective and cheaper than nebulisation for acute exacerbations, though not yet widely undertaken 1

Monitor for adverse effects with high-dose therapy:

• Both continuous and intermittent high-dose regimens are safe with no significant differences in vital signs or cardiac complications 2, 3
• Salbutamol can cause hypokalemia, cardiovascular effects, and may aggravate diabetes 5
• Continuous cardiac monitoring is appropriate for intensive care patients 3

Equipment maintenance is critical:

• Medication concentration increases by approximately 2-fold during 8 hours of continuous operation due to water evaporation 4
• This must be factored into dosing calculations for extended therapy 4