NEW YORK (Reuters Health) – Administering ketamine after morphine is more effective than continuing morphine only for reducing pain in adults who have experienced significant out-of-hospital trauma, an Australian team reports in the Annals of Emergency Medicine online January 16.

“Furthermore, adverse events were uncommon in this nonphysician EMS setting,” the authors point out.

Dr. Paul Andrew Jennings, with Monash University in Melbourne, Victoria, and colleagues note that while morphine is commonly used for acute traumatic pain, respiratory depression and nausea are drawbacks to its use.  Ketamine is appealing for use in the out-of-hospital setting, they explain, because of its analgesic and dissociative properties, and opioid-sparing effect. In addition, “it is purported to allow patients to maintain their pharyngeal reflexes and maintain their own airway, even when fully dissociated.”

To investigate further, the team conducted a randomized open-label trial involving 135 adults with significant out-of-hospital trauma pain and verbal pain scores greater than 5 after being given 5 mg IV morphine.  They were then assigned to receive either a 10-mg or 20-mg bolus of ketamine followed by 10 mg every 3 minutes, or 5 mg of morphine every 5 minutes, until pain free.

Median baseline pain scores were 7.5 in the ketamine group and 7.0 in the morphine group.  Scores were reduced by -5.6 and -3.2 points in the two groups, respectively, the authors report.  The difference of 2.4 points in favor of the ketamine protocol exceeded the specified 1.3 points for a minimum clinically important effect.

Furthermore, the ketamine group had a faster reduction in pain than the morphine group, the report indicates.

Adverse effects were minor, although the rate was higher with ketamine (39%) than morphine-only (14%).  No adverse event required withdrawal from the study, Dr. Jennings and colleagues note.

Summing up, they conclude, “Supplementing out-of-hospital opioids with low-dose ketamine is an effective strategy to mitigate trauma pain.”

They add, “Given the success of intravenous ketamine in the reduction of refractory acute pain, future research should focus on the effectiveness of alternative routes of administration, including intramuscular, intranasal, and topical applications. Furthermore, the utility of various dosing regimens such as continuous or patient-controlled infusion needs to be explored with respect to effectiveness and ease of out-of-hospital maintenance and administration.”

SOURCE:

Morphine and Ketamine Is Superior to Morphine Alone for Out-of-Hospital Trauma Analgesia: A Randomized Controlled Trial

Ann Emerg Med. 2011