• Ketamine is a phencyclidine (PCP) derivative, and its therapeutic effects rely on N-methyl-D-aspartate receptor inhibition.
• It can be used as an analgesic, for procedural sedation and anesthesia induction.
• It is also increasingly used in prehospital settings.
• BCEHS guidelines recommend bolus dosing as follows:
  • Analgesia dose range – 0.1 to 0.3 mg/kg IV, 0.75 mg/kg Intranasal, 0.5 mg/kg IM.
  • Procedural sedation dose range – 0.1 to 0.5 mg/kg
  • Anesthesia induction dose range – 1.0 to 2.0 mg/kg
• Also attractive option for patients presenting to the ED with acute pain, especially when contra-indications to opioids or opioid tolerance.
• Studied more in the context of post-operative pain, but also shown to be effective in treating acute pain in the ED.
• Still much more research needed to establish contra-indications and the significance of adverse event rates at subanesthetic doses.
• Relative contraindications include severe cardiovascular disease, Elevated intracranial pressure or intraocular pressure, cirrhosis, psychosis, pregnancy – extrapolated from higher dose ketamine contraindications.
• Nausea, vomiting, and psychomimetic effects (eg. vivid dreams, hallucinations, dissociation) are possible side effects – less significant at low doses.
• Adverse effects of ketamine generally treated with benzodiazepines/clonidine.

For management of acute pain these are some guideline dose ranges, however starting at the lower end and titrating as needed is recommended based on analgesia & side effects:

• Intermittent bolus doses: 0.1 – 0.35mg/kg (eg. q4hrs or followed by infusion).
• Continuous infusion: 0.1-0.5 mg/kg/hour (max 1mg/kg/hour infusion).

There is limited evidence for use in chronic pain, and ideally a pain specialist should be consulted before initiating treatment.

• Low quality evidence to support short term improvement in pain for spinal cord injury (eg. 0.4 mg/kg/hour for 5 hours daily for 7 consecutive days), and complex regional pain syndrome (eg. 0.35 mg/kg/hour for 4 hours daily for 10 days).
• Lack of evidence for longer term pain relief, and limited evidence for use in other causes of chronic pain.

Ketamine treatment for analgesia is recommended to be done under medical supervision, often in a hospital setting.

If larger doses required consider cardiac monitoring and frequent vital signs.

Respiratory depression uncommon side-effect, but possible with larger doses administered quickly. Have resuscitative equipment available.

Advise patients to avoid driving and heavy equipment use for 24 hours if otherwise well enough to discharge.

1. BC EHS handbook:

   https://handbook.bcehs.ca/drug-monographs/ketamine/

   
   

1. Balzer N, McLeod SL, Walsh C, et al. Low-dose ketamine for acute pain control in the emergency department: a systematic review and meta-analysis. Acad Emerg Med. 2021;28:444-54.

   
   

2. Cohen SP, Bhatia A, Buvanendran A, et al. Consensus Guidelines on the Use of Intravenous Ketamine Infusions for Chronic Pain From the American Society of Regional Anesthesia and Pain Medicine, the American Academy of Pain Medicine, and the American Society of Anesthesiologists. Reg Anesth Pain Med. 2018;43(5):521-546.

   
   

3. Schwenk ES, Viscusi ER, Buvanendran A, et al. Consensus guidelines on the use of intravenous ketamine infusions for acute pain management from the American Society of Regional Anesthesia and Pain Medicine, the American Academy of Pain Medicine, and the American Society of Anesthesiologists. Reg Anesth Pain Med. 2018;43:456-66.

   
   

4. Silverstein W, Juurlink D, Zipursky J. Ketamine for the treatment of acute pain. CMAJ. 2021 November 1;193:E1663.

   
   

5. Tran K, McCormack S. Ketamine for Chronic Non-Cancer Pain: A Review of Clinical Effectiveness, Cost-Effectiveness, and Guidelines [Internet]. Ottawa (ON): Canadian Agency for Drugs and Technologies in Health. 2020 May 28.