Ketamine is an anaesthetic agent with direct bronchodilatory properties at sub-anaesthetic doses. It may be given by infusion to treat patients with bronchospasm. Ketamine is rarely used for this off-label indication and evidence for clinical benefit is equivocal, however literature and clinical practice has shown a potential role.¹ It should therefore be reserved for those patients who have not responded to conventional therapy. A variety of infusion doses have been reported in the literature.^{1– 8} It will predominantly be used in intubated patients.

Ketamine has also been suggested as an induction agent choice for patients with life-threatening asthma who require intubation.⁹

• The patient should be dosed using ideal body weight

• A starting dose of between 0.5 to 1mg/kg/hr is suggested, increasing incrementally up to a maximum 2.5mg/kg/hr. An effect on bronchospasm should be seen within an hour. Ketamine’s adverse cardiovascular and dissociative effects will increase as the dose increases. The dose should therefore be maintained at the minimal rate that provides an adequate response.

• Patients with a cardiovascular history should commence at a dose no higher than 0.5mg/kg/hr.¹⁰

• Bolus dose of 1 to 2mg/kg. ^9,11

Ketamine commonly causes hallucinations, abnormal dreams, confusion, nystagmus, hypertension, tachycardia and nausea. Dissociative effects may also be seen when emerging from therapy; to alleviate these, a benzodiazepine such as midazolam may be given. Ketamine can increase respiratory tract secretions, potentially limiting its effectiveness as a bronchodilator.

Avoid if known allergy or acute porphyria. Caution in psychosis, uncontrolled hypertension, raised intracerebral or intraocular pressure and ischaemic heart disease.

Prepare a 500mg in 50ml infusion using glucose 5% or sodium chloride 0.9%. It is possible to use a more concentrated solution of ketamine, but this is not recommended. Advice should be sought from the ICU pharmacist for individual situations.

Ketamine is administered by intravenous infusion either centrally or peripherally. A ketamine monograph is available via the online injectable medicines guide (Medusa).

There is little information available on compatibilities with Ketamine. It is advisable to administer it alone when possible. Seek further advice on compatibility from the ICU pharmacist.

1) Goyal S & Agrawal A. Ketamine in Status asthmaticus: A review. Indian J Crit Care Med. 2013; 17(3): 154-161Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3777369/

2) Hemmingsen C, et al. Ketamine in the treatment of bronchospasm during mechanical ventilation Am J Emerg Med 1994; 12: 417 – 420.

3) Howton J, et al. Randomised double-blind placebo controlled trial of intravenous ketamine in acute asthma. Ann Emerg Med 1996; 27: 170 – 5.

4) Hemmings A, et al. Response to ketamine in status asthmaticus resistant to maximal medical treatment. Thorax 1994; 49: 90 – 91.Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC474120/

5) Levy BD, et al. Medical and ventilatory management of status asthmaticus. Intensive Care Med 1998; 24: 105 – 117.

6) Corbridge TC and Hall JB. The assessment and management of adults with status asthmaticus. Am J Resp Crit Care Med 1995; 151: 1296 – 1316.

7) Lau TT, Zed PJ Does Ketamine have a role in managing severe exacerbations of asthma in adults? Pharmacotherapy 2001; 21(9) 1100-1106

8) Garg D, Kaistha S, Sood D. Subanaesthetic dose of ketamine in intractable asthma. Journal of Indian Medical Association. 2011; 109 (6): 430,434.

9) Holley AD & Boots RJ Review article: Management of acute severe and near-fatal asthma. Emergency Medicine Australasia 2009 21 259-268 Available from: https://onlinelibrary.wiley.com/doi/10.1111/j.1742-6723.2009.01195.x

10) Strube PJ and Hallam PL. Ketamine by continuous infusion in status asthmaticus. Anaesthesia 1986; 41: 1017 – 9. Available from: https://associationofanaesthetists-publications.onlinelibrary.wiley.com/doi/abs/10.1111/j.1365-2044.1986.tb12744.x

11) Hameln Phama Ltd. Ketamine 50 mg/ml injection SmPC. 2020 [cited 2024 May 2] Available from: https://www.medicines.org.uk/emc/product/6935/smpc

12) UpToDate Lexidrug Editorial Advisory Panel. Ketamine: drug information. In: Post TW, editor. UpToDate [Internet]. Waltham, MA: UpToDate; 2024 [cited 2024 May 2]. Available from: http://www.uptodate.com

This guideline has been registered with the Trust. However, clinical guidelines are guidelines only. The interpretation and application of clinical guidelines will remain the responsibility of the individual clinician. If in doubt, contact a senior colleague or expert. Caution is advised when using guidelines after the review date.
This guideline is for use in Frimley Health NHS Foundation Trust hospitals only. Any use outside this location will not be supported by the Trust and will be at the risk of the individual using it.

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