Neil Osterweil

October 29, 2015

BOSTON — The use of low-dose ketamine as an adjunct to opioids for pain control in the emergency department led to reductions in pain scores, total opioid dosing, and frequency of opioid dosing, results from a randomized, placebo-controlled trial indicate.

"The reduced frequency of opioid dosing, in particular, may be clinically significant," said lead investigator Karen Bowers, MD, from the Emory University School of Medicine in Atlanta, Georgia.

She presented the study results here at the American College of Emergency Physicians (ACEP) 2015 Scientific Assembly.

Previous studies have shown short-term pain control with ketamine at doses two to three times higher than the 0.1-mg/kg dose used in this study.

A recently published randomized trial using a 0.3-mg/kg dose showed that although ketamine was effective for pain control, "it had a pretty tough side-effect profile to swallow," Dr Bowers reported. "They had a lot of patients reporting side effects that they felt were very unpleasant."

Dr Bowers and her colleagues hypothesized that patients treated with low-dose ketamine as an adjunct to opioids would require less opioid for effective pain control, report increased satisfaction with pain control, have more effective control than with opioids alone for up to 2 hours, and have tolerable adverse effects.

To test this, they randomly assigned 63 patients to receive ketamine, 0.1 mg/kg, and 53 patients to receive placebo. All patients also received protocol-based dosing of morphine or another opioid analgesic.

Pain Control

The investigators assessed pain at baseline and every 30 minutes thereafter for 2 hours. A 10-point pain scale, with 0 indicating no pain and 10 indicating the worst pain imaginable, was used to evaluate pain. A 4-point Likert scale was used to evaluate satisfaction with pain control, the presence of adverse effects, sedation level, and the need for additional pain medications.

Total opioid dosage was significantly lower in patients treated with ketamine plus opioids than in those treated with placebo plus opioids (P = .02), as was average pain score (P = .015). Ketamine-treated patients required fewer repeat opioid doses, although this difference was not significant.

However, patient-reported satisfaction with pain control did not significantly differ between groups.

If I just give somebody opiates in the emergency department, I don't have to do the whole procedural sedation protocol for them. Dr Judd Hollander

Adverse effects, primarily light-headedness and dizziness, were more frequent in the ketamine group than in the placebo group, but there were no serious adverse events. Two patients, one in each group, withdrew because of oversedation.

These findings support previous studies that have suggested a dose-response relation with ketamine for both efficacy and tolerability, Dr Bowers said.

The comparatively low dose used in this study was effective, but not as effective as the doses used in other studies. However, it appeared to have a better, more acceptable tolerability profile, she said.

There are a few things to consider with use of using ketamine in an acute-care setting, said Judd Hollander, MD, from Thomas Jefferson University in Philadelphia, Pennsylvania.

"If I just give somebody opiates in the emergency department, I don't have to do the whole procedural sedation protocol for them," he told Medscape Medical News. But "if I give them ketamine or some other procedural sedation agent and opiates, I need more people in the room, and it's a whole different monitoring system."

It would be difficult to conduct a larger randomized trial of this kind, he pointed out. Although the additional cost of ketamine is relatively modest, "the nursing costs of the ketamine arm far exceed the extra costs of the extra dose of morphine you're giving in the other arm."

The study was internally supported. Dr Bowers and Dr Hollander have disclosed no relevant financial relationships.

American College of Emergency Physicians (ACEP) 2015 Scientific Assembly. Abstract 2. Presented October 26, 2015.


Comments on Medscape are moderated and should be professional in tone and on topic. You must declare any conflicts of interest related to your comments and responses. Please see our Commenting Guide for further information. We reserve the right to remove posts at our sole discretion.