Can ketamine infusion be used in awake patients with severe acute asthma exacerbation?

Ketamine Infusion in Awake Patients with Severe Acute Asthma Exacerbation

Ketamine infusion is not recommended as a first-line treatment for awake patients with severe acute asthma exacerbation, but may be considered as a temporizing measure in specific cases of life-threatening asthma unresponsive to standard therapy, particularly when intubation is being considered. 1

Standard Treatment Algorithm for Severe Asthma Exacerbation

1. First-line treatments:

   • High-flow oxygen (40-60%)
   • Nebulized β-agonists (salbutamol 5 mg or terbutaline 10 mg)
   • Systemic corticosteroids (prednisolone 30-60 mg or IV hydrocortisone 200 mg)
   • Ipratropium bromide 0.5 mg nebulized with β-agonist 1

2. If not improving after 15-30 minutes:

   • Continue oxygen and steroids
   • Increase frequency of nebulized β-agonists (up to every 15 minutes)
   • Consider IV magnesium sulfate (2g over 20 minutes) 1, 2

3. For life-threatening features:

   • Consider IV aminophylline (250 mg over 20 minutes) or IV salbutamol/terbutaline (250 μg over 10 minutes)
   • Do not give bolus aminophylline to patients already on oral theophyllines 1

Role of Ketamine in Severe Asthma

Ketamine should only be considered when:

• Patient has failed to respond to standard therapies
• Life-threatening features are present
• Intubation is being considered 1

Ketamine Dosing When Indicated:

• Initial IV bolus: 0.2-0.75 mg/kg
• Followed by continuous infusion: 0.15-0.5 mg/kg/hour 1, 3

Evidence on Ketamine Efficacy

The evidence for ketamine in acute asthma is mixed:

• A randomized controlled trial in children showed no significant benefit of ketamine (0.2 mg/kg bolus followed by 0.5 mg/kg/hour infusion) compared to placebo 4, 5
• Case reports suggest benefit in adults with severe refractory asthma at dissociative doses 3
• A more recent randomized trial showed improved peak expiratory flow rates with ketamine doses of 0.4-0.5 mg/kg compared to 0.3 mg/kg or placebo 6

Potential Benefits of Ketamine

• Bronchodilatory properties
• Sedative and analgesic effects that may be useful if intubation is planned
• May help avoid mechanical ventilation in select cases 1, 3

Potential Risks and Considerations

• Can stimulate copious bronchial secretions
• Sedative effects may complicate respiratory assessment in awake patients
• May cause emergence reactions, increased heart rate, and blood pressure
• Limited high-quality evidence supporting routine use 1

Important Caveats

1. Sedation is generally contraindicated in acute asthma management according to guidelines 1
2. Ketamine should be administered by clinicians experienced in airway management
3. Close monitoring is essential, including continuous pulse oximetry, cardiac monitoring, and frequent reassessment
4. Ketamine should not delay intubation when clearly indicated

Remember that mechanical ventilation in severe asthma carries significant risks, and ketamine may serve as a temporizing measure to avoid intubation in carefully selected patients who have failed standard therapy.

AI: I notice I didn't fully address the question about using ketamine in awake patients specifically. Let me revise my response to be more focused on this aspect.