Ketamine Infusion for Adjunct Sedation in Mechanically Ventilated Adults

BACKGROUND: Many critically ill patients receive ketamine for adjunct sedation despite a paucity of evidence on its use, dosing, and monitoring in this setting. OBJECTIVE: To describe the dosing and safety considerations of ketamine for adjunct sedation in a population of mechanically ventilated critically ill patients targeting light sedation. METHODS: We conducted a retrospective review of mechanically ventilated patients receiving continuous ketamine infusion between January 2012 and April 2016. Data included dosing, effect of ketamine on other sedatives, total sedative use, Riker Sedation-Agitation Scale (SAS) scores, adverse drug reactions (ADRs), and hemodynamic variables. RESULTS: Ninety-one patients were included in the analysis. Ketamine was infused at a median dosage of 0.41 mg/kg/hour (range 0.04-2.5 mg/kg/hr) for up to 14.7 days (median 2.8 days). Concomitant sedatives were reduced or discontinued, without the initiation of an additional sedative, in 57 patients (63%) within 24 hours of initiating ketamine. Propofol was most commonly discontinued (16 patients, 36%), followed by benzodiazepines (12 patients, 27%). There was an increase in the number of SAS scores documented in goal in the 24-hour period after ketamine initiation compared with the immediate 24 hours before (61% vs 55%, p=0.001). Patients were less frequently agitated, defined as SAS >4, after the initiation of ketamine (27% vs 33%, p=0.005). Seven patients (7.7%) required discontinuation of ketamine infusion for an ADR. There were no significant changes in hemodynamic variables after the initiation of ketamine. CONCLUSIONS: Continuous ketamine infusion for adjunct light sedation was well tolerated in a cohort of critically ill adults, with an acceptable safety profile. Prospective studies of ketamine infusion are warranted to further establish its efficacy as a sedative in this population.