Early adolescence is the peak age for vomiting,

Emesis. Early adolescence is the peak age for vomiting, with
lesser risk in younger and older children.3 The literature
supports it as being more frequent with the IM route compared
with IV3,78 and supports no evidence of a dose relationship
within the usual range of clinically administered doses.3,75
When emesis occurs, it is typically late during the recovery
phase when the patient is alert and can clear the airway without
assistance.19,72 Vomiting does occur in some patients after
discharge, including some who do not vomit in the
ED.78,83,85,92,94 The incidence of vomiting in adults can be
expected to be 5% to 15%.26
Recovery reactions. The ability of ketamine to induce
hallucinatory reactions—both pleasant and unpleasant—during
recovery is legendary. Although these so-called emergence reactions
are rarely disturbing in children (1.4% incidence of reactions
judged clinically important in the large meta-analysis),3 their
incidence in adults varies widely (0% to 30%).4,12,16 The ED
experience thus far is that such recovery reactions are uncommon
and generally mild in adults24-28; however, clinicians should be
aware of the rare potential for pronounced reactions, including
nightmares, delirium, excitation, and physical
combativeness.4,12,16,36,38,43 Titrated benzodiazepines
appear to rapidly and consistently diminish such
reactions.4,12,16,19,20,36,71,83,84 Transient diplopia as a result of
rotary nystagmus is common during recovery, and transient
blindness has been reported.95
In the large meta-analysis in children, recovery agitation was
not related to age, dose, or other factors to any clinically
important degree, except a higher incidence in patients receiving
subdissociative (
3 mg/kg IM) dosing.3 In contrast to
traditional thinking, adolescents were not at substantially higher
risk.3,94

Recovery agitation without an apparent hallucinatory
component after dissociative sedation is not uncommon. Given
that it occurs at a frequency similar to that of midazolam
alone,92,96,97 such agitation appears to be a separate entity from
the ketamine-induced hallucinatory reactions.82 It has been
associated with the degree of preprocedural agitation but not the
degree of external stimulation during recovery.82 In one study,
emergency physicians graded the severity of ketamine recovery
agitation with a 100-mm visual analog scale, and the median

rating was 5 mm, ie, a magnitude of minimal clinical
importance.82
Delayed effects. Vomiting is common in the hours after ED
discharge.78,83,85,92,93 The evidence is insufficient to support
anecdotal reports of delayed psychopathological effects or
personality changes.4,82,98