Ketamine 2017 – 1 of 2

Hey guys,

Let’s talk about Ketamine.
This is the first of two blogs to hopefully provoke some good discussions to get to know the drug a little better.
As usual, it’s important to put the theory into practice so Jumbo, Jo and Shane are setting up a practical scenario day for us on the 18th/July/17 (CHR Hub starting @ 1500hrs followed by BBQ).

These blogs are written based on the assumption that you have good understanding our CPG 2016-2018, and of course don’t forget to check out the Medsafe Ketamine Datasheet.

Beneficial characteristics include;

  • Anti-hyperalgesic and anti-inflammatory effects for acute and chronic pain management.
  • Recently, new insights have been gained on ketamine’s potential anti-depressive and anti-suicidal effects.
  • Fast onset, short half life.
  • Minimal effect on the central respiratory drive when given slowly, although rapid iv injection can cause transient apnea (10~15 sec).

Known ADRs (Adverse Drug Reactions)

  • Post-operative nausea and vomiting.
  • Increase the severity of nausea.
  • Increases salivary secretions, which may increase the incidence of laryngospasm*.

Note; Laryngospasm may be more common with IM administration (Melendez & Bachur, 2009).

Undesirable hallucination/agitation – emergence reaction/delirium (ED)

More common in;

  • patients >16 years of age.
  • females.
  • shorter operative procedures.
  • those receiving large doses, particularly when administered quickly.

Please note, our CPG do not use the term ED for the hallucinations associated with the administration of the drug. While we tend to refer ED as a general term for the hallucinations/agitations associated with the drug, ED is a reaction that emerges post anaesthesia as the name suggests, and it’s sometimes called post-anesthetic excitement.


‘Sub-therapeutic’ dose ?

This is the term used in our CPG explaining the ‘sub-therapeutic dose’ link to the undesirable hallucinations.
I was slightly confused with the term as I initially thought it meant giving low dose Ketamine is the cause of undesirable hallucination/agitation.
However, low-dose ketamine (slow infusion) is indicated not only for analgesia, but also indicated for depression and as an anti-suicidal.
The term ‘sub-therapeutic’ is not an absolute number or dose. Our CPG is advising that if the drug administration resulted in unwanted hallucinations/agitations, consider giving more ketamine to achieve desirable effects.

LIFL writes;

Emergence phenomena include recovery agitation, dreams, hallucinations and depersonalisation.They are less common in children than adults:

  • adults: 10-20% (as high as 30% in some studies), with 1-2% clinically significant.
  • children: 7.6%, with 1.4% clinically significant.

Benzodiazepines are useful for treating emergency reactions, but they do not decrease the likelihood of an emergence reaction occurring. Furthermore, co-administration of midazolam increases the risk of respiratory complications, although emesis is reduced.

In one study, involving adult patients in a non-emergency department setting, no emergence phenomena occurred if ketamine was administered in the following circumstances:

  • patients were interviewed in the preoperative area:
  • they were assured that the medication was safe and would provide complete analgesia during the procedure.
  • they were told that the anaesthetic medication would allow them to dream about a topic of their choice
  • they were instructed to concentrate on that pleasant thought/dream during induction of anaesthesia.
  • they were  encouraged to share their thoughts and feelings before undergoing ketamine sedation.
  • ambient operating room and recovery room stimuli were  minimized (e.g. noise and lighting).


Some key take home points to reduce the occurrence of hallucination and ED include;

  • Slow push

  • Calm environment

  • Making patient feeling safe with the drug

  • Gaining patient trust in us (perhaps most importantly)

Undesirable hallucinations/agitations can be disastrous if you are trying to manage spinal cord injury, TBI, etc, and can easily go against our foundation principle of ‘First, do no harm’.

Here is a great podcast from SMACC.



Some more on Ketamine next week…



Beaudoin, F. L., Lin, C., Guan, W., & Merchant, R. C. (2014). Low-dose ketamine improves pain relief in patients receiving intravenous opioids  for acute pain in the emergency department: results of a randomized, double-blind, clinical trial. Academic Emergency Medicine : Official Journal of the Society for Academic Emergency Medicine, 21(11), 1193–1202.

Gao, M., Rejaei, D., & Liu, H. (2016). Ketamine use in current clinical practice. Acta Pharmacologica Sinica, 37(7), 865–872.

Melendez, E., & Bachur, R. (2009). Serious Adverse Events During Procedural Sedation With Ketamine. Pediatric Emergency Care, 25(5). Retrieved from

Xu, Y., Hackett, M., Carter, G., Loo, C., Gálvez, V., Glozier, N., … Rodgers, A. (2016). Effects of Low-Dose and Very Low-Dose Ketamine among Patients with Major Depression: a Systematic Review and Meta-Analysis. International Journal of Neuropsychopharmacology, 19(4), pyv124-pyv124.



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