Paramedic use of ketamine for severe agitation and violence.

Objectives: Safety of prehospital ketamine use for the management of violent and agitated patients remains controversial. In 2018, Ontario introduced a prehospital medical directive for ketamine use in emergency sedation. Our aim was to report the indications and adverse events of prehospital ketamine use.

Methods: We completed a manual health records review of all electronic patient care records from three paramedic services (Peel, Simcoe and Halton) reporting ketamine administration from January 1, 2018 to May 31, 2022. Clinical indications, dosing, adverse events, and interventions to manage complications associated with ketamine administration were abstracted and analyzed using descriptive and bivariate statistics.

Results: Of 332 cases identified, 19 cases were excluded (final sample = 313). The most common indication for ketamine use was for endogenous causes (e.g., drug-induced psychosis, agitation from brain injury, delirium) (82.1%), followed by procedural sedation (9.6%) and analgesia (8.3%). When ketamine was administered as the first sedative, it was most often given intramuscularly (81.5%) with an average dose of 4.2 mg/kg. There were no vital signs documented prior to administration in 34% of cases. 30.3% (N = 82) of cases had adverse events after ketamine was given. Hypoxia (15.4%), airway compromise (14.8%), and secretions/emesis (7.0%) were most common. When ketamine was used as the first sedative, 19.6% of patients received oxygen, 11.8% had an airway adjunct (oro- or nasopharyngeal airway) and 5.5% required bag-mask-ventilation. Advanced airways were inserted in six patients. There were three cardiac arrests after ketamine use.

Conclusions: Prehospital ketamine is primarily used to sedate patients demonstrating severe violence or agitation related to various endogenous causes. Over 30% of patients develop adverse events after receiving ketamine. Although uncommon, we identified cases where patients required advanced airway placement and had cardiac arrest after ketamine administration. Paramedics should be prepared for the frequent number of adverse events after ketamine use.