Andrew Gorlin, M.D.
Consultant, Department of Anesthesiology
Assistant Professor of Anesthesiology
Program Director, Anesthesiology Residency
Mayo Clinic Arizona
Ketamine
Ketamine is an NMDA antagonist which, when administered intravenously at sub-anesthetic doses (≤0.3mg/kg bolus or ≤0.3mg/kg/hr infusion), provides analgesia and has a significant opioid sparing effect in the perioperative setting. There is also evidence that ketamine is useful in treating acute pain in patients who are opioid tolerant. Sub-anesthetic infusions of ketamine can be safely administered on standard medical-surgical units.
Perioperative indications for ketamine infusion:
- Very painful procedures
- Intractable opioid-resistant pain
- Highly opioid tolerant patients
- Clinical need to minimize opioids
- High risk for persistent post-surgical pain (eg amputation, thoracotomy, etc)
Ketamine Pros:
- Non-opioid analgesic which reduces perioperative opioid consumption
- At sub-anesthetic doses has minimal hemodynamic effects
- At sub-anesthetic doses has no effect on respiratory drive or airway patency
Ketamine Cons:
- Low-moderate incidence (7-16%) of psychomimetic effects such as hallucinations and dysphoria
- Low incidence of diplopia (4-9%)
- Especially when administered in combination with other CNS depressants may contribute to sedation
Ketamine contraindications
- History of psychosis
- Unstable cardiovascular disease
- Liver or renal failure
How to administer ketamine:
- Anesthesia team can give single bolus with induction and/or serial boluses (every 30-60 minutes) in the operating room
- Post-operative infusion requires coordination with the OR, PACU, med-surg unit
- Ketamine is a controlled substance and should be prepared in a secure storage system (such as a PCA cartridge) by pharmacy and administered by an infusion pump
- Dose should be ≤0.3mg/kg/hr based on Ideal Body Weight; a good starting point for most patients is 10mg/hr
- A separate IV is preferable though it can be safely “piggy-backed” onto another line as long as it is on a distal port (ie, close to the patient)
- Side effects can be managed on a case by case basis but typically hallucinations and other complains will stop within an hour of stopping the infusion
- Use of benzodiazepines to reduce psychomimetic effects is controversial and may cause more problems with sedation and delirium
How to get ketamine “approved” for med-surg units: PENDING