Agitated behaviors are frequently encountered in the prehospital setting and require emergent treatment to prevent harm to patients and prehospital personnel. Chemical sedation with ketamine works faster than traditional pharmacologic agents, though it has a higher incidence of adverse events, including intubation. Outcomes following varying initial doses of prehospital intramuscular (IM) ketamine use have been incompletely described.

To determine whether using a lower dose IM ketamine protocol for agitation is associated with more favorable outcomes.

This study was a pre-/post-intervention retrospective chart review of prehospital care reports (PCRs). Adult patients who received chemical sedation in the form of IM ketamine for agitated behaviors were included. Patients were divided into two cohorts based on the standard IM ketamine dose of 4mg/kg and the lower IM dose of 3mg/kg with the option for an additional 1mg/kg if required. Primary outcomes included intubation and hospital admission. Secondary outcomes included emergency department (ED) length of stay, additional chemical or physical restraints, assaults on prehospital or ED employees, and documented adverse events.

The standard dose cohort consisted of 211 patients. The lower dose cohort consisted of 81 patients, 17 of whom received supplemental ketamine administration. Demographics did not significantly differ between the cohorts (mean age 35.14 versus 35.65 years; P = .484; and 67.8% versus 65.4% male; P = .89). Lower dose subjects were administered a lower ketamine dose (mean 3.24mg/kg) compared to the standard dose cohort (mean 3.51mg/kg). There was no statistically significant difference between the cohorts in intubation rate (14.2% versus 18.5%; P = .455), ED length of stay (14.31 versus 14.88 hours; P = .118), need for additional restraint and sedation (P = .787), or admission rate (26.1% versus 25.9%; P = .677). In the lower dose cohort, 41.2% (7/17) of patients who received supplemental ketamine doses were intubated, a higher rate than the patients in this cohort who did not receive supplemental ketamine (8/64, 12.5%; P <.01).

Access to effective, fast-acting chemical sedation is paramount for prehospital providers. No significant outcomes differences existed when a lower dose IM ketamine protocol was implemented for prehospital chemical sedation. Patients who received a second dose of ketamine had a significant increase in intubation rate. A lower dose protocol may be considered for an agitation protocol to limit the amount of medication administered to a population of high-risk patients.