Records of 4252 patients aged 0-19 who received ketamine were reviewed for documented adverse events. Patients were all American Society of Anesthesiology Class I or II. 102 (2.4%) had an ‘adverse event’, defined as the occurrence of hypoxia by oxygen saturation lower than 93% on room air or clinical cyanosis, documentation of laryngospasm, airway obstruction, or apnea diagnosed clinically or by capnography, stridor, respiratory distress, or hypoventilation or hypercarbia as assessed by capnography. Cases with adverse events were compared with controls who had received ketamine without adverse events, but were not otherwise matched.

Of the adverse events, laryngospasm was documented to have occurred in 29/4252 cases (0.7%), hypoxia in 81/4252 (1.9%), and positive pressure ventilation was required in 33/4252 (0.8%). Intubation was required in one patient (0.023%). Compared with controls, patients with adverse events were more likely to have received IM, as opposed to IV, ketamine, although children who received IM ketamine were more likely to be younger than those who received IV ketamine (4.1 vs 7.9 years).
The retrospective design and other methodological limitations make it harder to draw conclusions other than what we know from existing literature, to which this large series adds: ketamine is given to a lot of kids with few adverse effects; larygnospasm is a real but infrequent occurrence that usually responds to simple manouevres; and intubation is extremely rarely required, but nevertheless may be necessary and therefore those physicians using ketamine should have advanced airway skills.
Serious Adverse Events During Procedural Sedation With Ketamine
Pediatr Emerg Care. 2009 May;25(5):325-8