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

Abstract

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.

Keywords: Agitation; EMS; Excited delirium syndrome; Intubation; Ketamine; Sedation.