A prospective study of ketamine as primary therapy for prehospital profound agitation.

OBJECTIVE We investigated the effectiveness of ketamine as a primary therapy for prehospital profound agitation. METHODS This was a prospective observational study of patients receiving 5mg/kg of intramuscular ketamine for profound agitation, defined as a score of +4 on the Altered Mental Status Scale (AMSS), a validated ordinal scale of agitation from -4 (unresponsive) to +4 (most agitated). The primary outcome was time to adequate sedation (AMSS<+1). Secondary outcomes included need for additional sedatives, intubation frequency, complications associated with ketamine, and mortality. RESULTS Forty-nine patients were enrolled. Median age was 29years (range 18-66); 76% (37/49) were male. Median time to adequate sedation was 4.2min (95% CI: 2.5-5.9, range 1-25min) and 90% (44/49) had adequate sedation prehospital. Seven patients (14%) received a second sedative prehospital. Intubation occurred in 57% (28/49) of patients. Mechanical ventilation lasted <24h in 82% (23/28) of patients, and <48h in 96% (27/28) of patients. A single physician intubated 36% (10/28) of the patients. Complications related to ketamine included hypersalivation (n=9, 18%), vomiting (n=3, 6%), and emergence reaction (n=2, 4%). One patient died from complications of septic shock on hospital day 29, likely unrelated to ketamine. CONCLUSIONS In patients with prehospital profound agitation, ketamine provides rapid effective sedation when used as a primary therapy. Intubation was common but accompanied by a short duration of mechanical ventilation and appears to have been subject to individual physician practice variation.