Eighty-seven studies were identified (n≥59,304, range one to 30,000) but the tables included only 86 studies: 26 comparative studies and 60 non-comparative studies. Most participants were included in the non-comparative studies. Fourteen of the comparative studies were randomised controlled trials (RCTs) and three of these were double-blind. In many studies all groups received the same ketamine regime; only 14 comparative studies (five RCTs) compared ketamine with other treatment regimes, different doses of ketamine, intravenous versus intramuscular ketamine or racemic ketamine.
Only one case of an adverse cardiorespiratory event was reported (a case report). Cardiostimulatory effects of ketamine were mitigated by sympatholytic agents in two comparative studies and a case report.
There were no reports of clinical indications of aspiration associated with ketamine; one small comparative study showed radiological evidence of contrast aspiration and also reported that ketamine patients maintained their pharyngeal reflexes, swallowing liquids if challenged. However, five non-comparative studies reported that ketamine patients required airway manoeuvres such as a chin-lift or jaw-thrust for positional obstruction. Laryngospasm was reported very rarely in adults and as either transient or responsive to bag-valve-mask ventilation (BVM) in two non-comparative studies and was considered not to be a risk in three other comparative studies of endoscopic (ear, nose and throat), dental and tonsillectomy procedures. Ketamine produced transient respiratory depression (sometimes included apnoea), usually within the first two to three minutes (five studies that included one small comparative study). Respiratory depression was more frequent when ketamine was used with concurrent agents known to depress respiration (four studies that included one comparative study where 40% and 60% patients required BMV and who received ketamine and midazolam at different doses versus none in the control group that received other drugs).
The rate of psychiatric adverse events associated with ketamine monotherapy ranged from 10% to 20% (seven studies that included six comparative studies and five RCTs). Sedating agents were effective in terminating and preventing ketamine emergence reactions (13 studies); environmental interventions also reduced such events (four studies). The incidence of vomiting associated with ketamine ranged from 5% to 15% (six studies that included an RCT). An evanescent patchy erythematous rash on the upper torso that required no treatment occurred with ketamine in 5% to 20% patients (four studies that included two comparative studies).
Other adverse events were reported.