Ketamine may be a safe and effective agent to sedate agitated and aggressive emergency department patients who have not responded to prior sedation attempts, according to a small study.

“Ketamine is a useful option for sedation in really difficult-to-sedate violent patients. It is a potentially safe and effective treatment when others have not been successful,” first author Dr. Geoffrey K. Isbister, from the University of Newcastle, New South Wales, Australia, told Reuters Health by email.

Dr. Isbister and colleagues conducted a subgroup analysis of 49 ED patients from two hospitals participating in the Droperidol or Midazolam (DORM II) study, an observational study of patients who had acute behavioral problems and required parenteral sedation and physical restraint.

ED staffs managed the patients with a standardized protocol, which started with a 10-mg intramuscular dose of droperidol, then another 10-mg dose of droperidol 15 minutes later if necessary. A clinical toxicologist reviewed all cases of patients not sedated after 30 minutes and decided what intramuscular dose of ketamine should be administered, based on a dose of 4 to 6 mg/kg used in other settings.

ED staff collected data on pulse rates, pulse oximetry, respiratory rate, and blood pressure every five minutes for the first 20 minutes and then every 30 minutes over the next two to four hours.

Of the 49 patients (median age, 37), 28 were men (57%). Police transported 20 patients to the hospital. ED staff administered droperidol alone before ketamine to 46 patients. Two patients received a combination of droperidol, diazepam, and midazolam, and one patient received midazolam alone. The median dose of ketamine used was 300 mg.

The median time to sedation post-ketamine for 44 of the 49 patients was 20 minutes and ranged from two minutes to 8.3 hours. Five patients required additional sedation within one hour, remained unsedated for two hours, or both. They received doses ranging from 100 mg to 400 mg.

“One of the five patients receiving 200 mg ketamine remained severely agitated for 12 hours (overnight) and was given no further sedation,” the researchers write.

Adverse events occurred in three patients after ketamine administration. Two patients vomited and the third experienced oxygen desaturation to 90% with no airway obstruction 40 minutes after administration.

Forty-three patients had a preadministration median systolic blood pressure of 130 mmHg. Fifteen minutes after administration median systolic blood pressure had risen by 5 mmHg. No patients experienced hypotension, but three patients’ systolic blood pressure topped 180 mmHg.

For 45 patients pre- and postadministration median pulse rates did not change.

Limitations of the study include its small sample size and the inability to determine whether ultimate sedation resulted from ketamine, delayed response to initial sedation, or both.

“Essentially larger studies across more hospitals are needed,” Dr. Isbister told Reuters Health. “You need large numbers to confirm that less-common adverse effects don’t occur.”

Nevertheless, the two hospitals are using ketamine. “Yes, it continues to be used in both hospitals, and it is now recommended on our state guidelines,” Dr. Isbister said.

Dr. Steven Green, of Loma Linda University Medical Center in California, and Dr. Gary Andolfatto, of Lions Gate Hospital, North Vancouver, British Columbia, Canada, wrote an accompanying editorial titled “Let’s ‘Take ‘Em Down’ With a Ketamine Blow Dart.”

“Ketamine intramuscularly is highly effective for the rapid control of agitated and violent patients and, although not devoid of risks, may represent the best option when there is truly an imminent threat to patient and caregiver safety,” they wrote. “In this circumstance, ketamine appears much more likely to get you out of trouble than to cause trouble. Bring on the blow darts!”

The National Health and Medical Research Research Council partially supported this research. The authors reported no disclosures.