There were challenges with recruitment in the ED due to ED staffing shortages and we were unable to meet the expected recruitment rate. The decision to stop study recruitment was solely due to operational and logistical limitations.

Suicide is a leading cause of death for children and adolescents. Since warning signs of suicide and links to precipitating events differ between age groups, suicide can be difficult to predict. As a result, children often seek care for suicidal ideation (SI) in the emergency department (ED) where a limited number of treatment options exist. Current psychotherapies and pharmacotherapies, such as antidepressants, provide benefit over weeks or months and thus limits their effective application in the ED. Consequently, when there is an imminent threat to the child's safety, the typical management solution is to admit the patient to a safe environment and hopefully de-escalate over time. To address a more rapid-onset treatment option for SI, a number of studies in adults have suggested that a single, sub-anesthetic dose of intravenous ketamine can rapidly reduce depression and SI severity. These results are promising, but large-scale trials are needed to determine if ketamine is a safe and effective treatment for acute suicidality in the pediatric population. This approach has the benefit of working rapidly, avoiding involuntary hospitalizations, and protecting patients from self-harm until they can be connected to longer term mental health resources. This study will compare the use of intravenous ketamine to both active and placebo controls in children 10 to 17 years of age presenting to the pediatric ED for SI. The primary objective of this pilot trial is to explore the adequacy and range of three instruments measuring suicidality and to determine the sample size required for a large definitive randomized control trial. This larger trial will be used to estimate the effectiveness of intravenous ketamine for reducing SI in children in the pediatric ED. The secondary objectives are to assess study feasibility and optimize study procedures. Given very few side effects reported in adult studies and the relatively benign nature of those reported, the investigators do not expect any major safety concerns in the study.

The study will enroll children and adolescents presenting with SI in the paediatric ED.

Inclusion Criteria:

1. 10 to 17 years of age
2. Respond "yes" to either question 1 (Passive Ideation) or 2 (Active Ideation) on the C-SSRS
3. Respond "yes" to either questions 3 (Method), 4 (Intent), or 5 (Plan) on the C-SSRS
4. Deemed acceptable and appropriate for admission to the on-site Child and Adolescent Psychiatry Emergency (CAPE) unit by a pediatric psychiatrist
5. Successful completion of Capacity to Assent.
6. Normal vital signs for age and a normal neurological exam (no focal deficits or abnormalities), as per attending clinician

Exclusion Criteria:

1. History of benzodiazepine or ketamine use in the past 3 months (ample wash out period)
2. Lifetime history of ketamine or benzodiazepine use disorder
3. Previous diagnosis of schizophrenia or active psychosis as per the treating physician
4. Lifetime history of schizoaffective disorder
5. Current hypomania, mania, mixed state
6. Clinically unstable, requires resuscitation or admission to a medical ward for stabilizing therapy (i.e., intensive care unit.)
7. History of cerebrovascular accident, uncontrolled seizure disorder, increased intracranial pressure
8. Uncontrolled hypertension, low or labile blood pressure, severe cardiac decompensation
9. Moderate to severe hepatic/renal impairment
10. Intoxicated or delirious
11. Suspected or confirmed pregnancy or women who are breastfeeding
12. Known allergy or sensitivity to ketamine and/or midazolam or any component in the formulation.
13. Neuro-cognitive impairment that precludes informed consent, assent, or ability to self-report pain and satisfaction
14. Inability to understand spoken and/or written English without the use of an interpreter
15. Previous enrollment in this study
16. No parent/guardian present.