Background: Ketamine is an effective medication used for chemical restraint in emergent settings. For managing patients with severe agitation, time is critical in order to prevent injury. Ketamine can be administered intramuscularly with a rapid onset and excellent sedation, allowingfor safe provision of care. The optimal dose for emergent chemical restraint has not been studied. Based on our experience, we hypothesize that a standard dose of 250 mg IM will reduce the need for intubation without increasing the need for additional sedation in orderto prevent injury. Methods: As a retrospective chart review, data was obtained by querying EMS patient care records for two EMS agencies. Included were adult patients who received intramuscular ketamine and transported to one of two affiliated hospitals. Excluded were those
who received ketamine for reasons other than chemical restraint. Hospital charts were then reviewed to determine dose administered, the need for a repeat dose, the need for additional sedation by EMS or within 30 minutes of hospital arrival, and whether the patient required intubation. Results: A total of 145 patients were included in final analysis; 11 patients received a single 500 mg dose of ketamine. The remainder received 150 to 300 mg (mean 265 mg). A total of 22 patients required a second dose (overall mean 300 mg). Of the 29 patients receiving > 300 mg, 7 required intubation, whereas 23 of 116 patients receiving 300 mg required intubation, for an overall intubation rate of 20.7% (similar research at higher doses resulted in a 30% intubation rate). Of the 134 patients who received 300 mg initially, 73 (54.5%) required additional sedation either by EMS providers or within 30 minutes of hospital arrival. When compared with prior similar research at higher doses, this demonstrated a statistically significant increase in the need for additional sedation (p < 0.0001). There were no significant injuries documented to responders or bystanders. There was one death noted due to methamphetamine toxicity. Conclusions: Although there was an increased need for additional sedation, a trend toward less frequent intubation suggests improved patient safety. With an educational focus on appropriate medication titration, we believe 250 mg is a reasonable initial dose for time-sensitive chemical restraint.