#EMConf: Ketamine vs Morphine for acute pain
Clinical Question: Is low dose ketamine (LDK) comparable to morphine in providing acute pain relief in adults in the emergency department?
The bottom line: Low dose ketamine may be as safe and as effective as morphine in providing analgesia for adults who present to the ED with acute pain.
Study #1: This study published by Motov et al. in the Annals of Emergency Medicine in 2015 is a single-center, prospective, double-blind randomized trial of adults aged 18 - 55 who presented to the ED with acute abdominal, flank, back, or MSK pain.
Methods: Convenience sample of N=90. Subjects underwent block randomization every 10 participants according to predetermined randomization list. An on-duty ED pharmacist prepared 0.3mg/kg of ketamine or 0.1mg/kg of morphine in 10mL normal saline. 45 patients received ketamine, and 45 patients received morphine. Pain scores, vital signs, adverse reactions were monitored every 15 minutes for 2 hours.
Primary Outcome: Reduction in pain numeric rating scores (NRS) at 30 minutes from administration of subdissociative ketamine or morphine as a single agent.
No significant difference in baseline NRS for LDK and morphine, 8.6 and 8.5, respectively
At 15 minutes, the mean difference in pain NRS between the two groups was -1.0 (95% CI -2.40 to 0.31), with LDK NRS 3.2 and morphine NRS 4.2.
At 30 minutes, the mean difference in pain NRS between the two groups was 0.2 (95% CI -1.19 to 1.46), with LDK NRS 4.1 and morphine NRS 3.9.
Secondary Outcomes: Need for rescue analgesia at 30 or 60 minutes, vital sign changes, and adverse reaction
No statistically significant difference was found between the two groups
Conclusions: Low dose ketamine appears comparable to morphine in relieving acute pain.
Limitations: Single center, small sample size, numerous exclusion criteria (difficult to generalize results)
Study #2: This study published by Miller et al. in the American Journal of Emergency Medicine in 2015 is a single-center, prospective, double-blind randomized trial of adults aged 18-59 who presented to the ED with acute abdominal flank, or extremity pain.
Methods: Convenience sample of N=45. Enrolled patients were given a random assignment number and envelope containing the study drug and dose (0.3mg/kg ketamine, 0.1mg/kg morphine). 21 patients received morphine, and 24 received ketamine. NRS, vital signs, adverse effects, RASS were measured every 20 minutes.
Primary Outcome: Maximum reduction of NRS from baseline in each group.
Baseline NRS was not statistically significant between the two groups.
LDK group: Max reduction in NRS pain of -4.9 (95% CI -5.8 to -4)
Morphine group: Max reduction in NRS of -5 (95% CI -6.6 to -3.5)
Secondary Outcomes: Levels of agitation or sedation measured by RASS scale, vital signs, adverse events, and need for repeat dosing.
No statistically significant differences were found, although LDK group was noted to require more repeat doses of analgesia.
Conclusions: Low dose ketamine and morphine provide similar reduction in acute pain without a significant difference in adverse effects or changes in vital signs. Ketamine works more quickly, but maximum analgesic does not appear to be sustained.
Limitations: single center, small sample size, numerous exclusion criteria (difficult to generalize results)
Motov S., Rockoff, B, Cohen, V, Pushkar, I,et al. (2015). Intravenous subdissociative-dose ketamine versus morphine for analgesia in the emergency department: a randomized controlled trial. Annals of emergency medicine, 66(3), 222-229.
Miller, JP, Schauer, S. G., Ganem, et al. (2015). Low-dose ketamine vs morphine for acute pain in the ED: a randomized controlled trial. The American journal of emergency medicine, 33(3), 402-408.