A recent ACEP policy reviewed the safety and efficacy of ketamine for emergency analgesic use. The policy recommends dosing and monitoring protocols similar to other parenteral analgesics. Studies looking at low-dose ketamine (LDK) (also referred to as subdissociative-dose ketamine) support a trend toward improved analgesia compared to opiates with a similar or better side effect profile. Additionally, LDK augments the analgesia attained by patients who have already been given an opioid and reduces the need for re-dosing of opioid medications.
LDK has been shown to have a functionally equivalent efficacy to morphine for short-term analgesia in the emergency setting. Recommended dosing is 0.1–0.3 mg/kg as an IV infusion over 15 minutes. The predictability and dosing are less clear for the intramuscular (IM) route, though many physicians have reported IM delivery with similar efficacy.
At low doses, ketamine acts as an analgesic rather than anesthetic. Use of LDK should not require intensive monitoring and overall has less respiratory and hemodynamic effects when compared to opioids. According to the ACEP policy, LDK is safe for non-monitored use when dosed according to the aforementioned protocols. It may be selected as a first-line agent over opioid agents for some patients, particularly those with chronic opioid use, contraindications to opioids, or hypotension secondary to trauma or sepsis. Ketamine is contraindicated in infants younger than three months, but there has been no evidence to suggest that LDK should be avoided in or results in exacerbation of psychosis in patients with mental illness.
ACEP recommends disclosure of LDK side effects to patients prior to administration. Patients may experience nausea, dizziness, and dysphoria, which are often brief and typically mild. The frequency of these side effects was reduced when LDK was given as a short infusion rather than a bolus. Emergence reactions have not been associated with LDK when used in the typical dosing range.
So the next time the nurse asks you for an order for more morphine, consider LDK. There is a good chance your patient will thank you and will require less opioids during the emergency department stay.
Resources for Further Reading
- American College of Emergency Physicians. Optimizing the treatment of acute pain in the emergency department [policy statement]. Approved April 2017.
- Ahern TL, Herring AA, Miller S, et al. Low-dose ketamine infusion for emergency department patients with severe pain. Pain Med. 2015;16(7):1402-1409.
- Beaudoin FL, Lin C, Guan W, et al. 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. Acad Emerg Med. 2014;21(11):1193-1202.
- Bowers KJ, McAllister KB, Ray M, et al. Ketamine as an adjunct to opioids for acute pain in the emergency department: a randomized controlled trial. Acad Emerg Med. 2017;24(6):676-685.
- Miller JP, Schauer SG, Ganem VJ, et al. Low-dose ketamine vs morphine for acute pain in the ED: a randomized controlled trial. Am J Emerg Med. 2015;33(3):402-408.
- Motov S, Mai M, Pushkar I, et al. A prospective randomized, double-dummy trial comparing IV push dose of low dose ketamine to short infusion of low dose ketamine for treatment of pain in the ED. Am J Emerg Med. 2017;35(8):1095-1100.
- Richards JR, Rockford RE. Low-dose ketamine analgesia: patient and physician experience in the ED. Am J Emerg Med. 2013;31(2):390-394.
- Smith RK, Messman A, Wilburn J. Low-dose ketamine emerges as effective opioid alternative. ACEP Now. August 2017. Accessed Sept. 15, 2017.
Dr. Freess is assistant professor of emergency medicine at the University of Connecticut School of Medicine in Farmington.
Dr. Schiller is assistant professor of emergency medicine at the University of Connecticut School of Medicine and assistant professor of emergency medicine at the Frank H. Netter School of Medicine in North Haven, Connecticut.