What is the recommended dose of ketamine (intravenous anesthetic) for acute bronchial asthma exacerbations?

Ketamine Dosing for Acute Bronchial Asthma Exacerbations

Ketamine is not recommended as a first-line treatment for asthma exacerbations but may be considered in severe refractory cases at a loading dose of 0.2 mg/kg IV followed by a continuous infusion of 0.5 mg/kg per hour, particularly when intubation is being considered. 1

Treatment Algorithm for Asthma Exacerbations

First-Line Treatments (Must be optimized before considering ketamine)

1. Inhaled short-acting beta-agonists (SABA)

   • Albuterol 2.5-5 mg via nebulizer every 20 minutes for 3 doses
   • Then 2.5-10 mg every 1-4 hours as needed, or 10-15 mg/hour continuously 1

2. Systemic corticosteroids

   • Adults: Prednisolone 30-60 mg orally daily until control is established
   • Children: 1-2 mg/kg body weight for 1-5 days 2

3. Ipratropium bromide

   • 0.5 mg via nebulizer every 20 minutes for 3 doses, then as needed 1
   • Multiple high doses (0.5 mg nebulizer solution or 8 puffs by MDI in adults) 2

Second-Line Treatments

1. IV magnesium sulfate

   • 2 g administered over 20 minutes in adults 1

2. Epinephrine (for severe cases)

   • 0.3-0.5 mg subcutaneously every 20 minutes for 3 doses 1

Ketamine Use in Severe Refractory Asthma

Indications for Ketamine

• Severe asthma exacerbation unresponsive to standard therapy 2
• Impending respiratory failure despite maximal conventional treatment 1
• When intubation is being considered or planned 2

Recommended Dosing

• Loading dose: 0.2 mg/kg IV 1
• Maintenance infusion: 0.5 mg/kg per hour for 1-2 hours 1

Alternative Dosing Regimens (Based on Research)

• For more severe cases: 0.75 mg/kg IV bolus followed by 0.15 mg/kg/h continuous infusion 3
• Higher doses in intubated patients: Initial 1 mg/kg IV bolus followed by 1 mg/kg/h for 2 hours 4
• Low-dose option: 0.4-0.5 mg/kg IV followed by infusion of the same dose over 30 minutes 5

Monitoring Requirements

• Continuous cardiac monitoring
• Frequent vital sign assessment
• Oxygen saturation monitoring
• Mental status evaluation 1
• Peak airway pressure and blood gas measurements (in intubated patients) 4

Clinical Benefits of Ketamine in Asthma

• Bronchodilation effects 2
• Reduction in peak inspiratory pressures in mechanically ventilated patients 6
• Improved gas exchange and dynamic compliance 6
• May help avoid mechanical ventilation in severe cases 3

Important Considerations and Precautions

• Ketamine should only be used by clinicians experienced in airway management 1
• Benzodiazepines should be available to treat emergence reactions 1
• Consider anticholinergic premedication (e.g., glycopyrrolate) to reduce secretions, as ketamine can stimulate copious bronchial secretions 2
• Ketamine has sedative and analgesic properties that may be useful if intubation is planned 2

Contraindications

• Severe hypertension
• Severe coronary artery disease
• Increased intracranial pressure
• History of psychosis 1

Evidence Quality

The American Heart Association guidelines note that one case series suggested substantial efficacy for ketamine in asthma, but two randomized trials in children found no benefit compared with standard care 2. Most evidence for ketamine use in status asthmaticus comes from case reports and small studies rather than large randomized controlled trials 6.