Ketamine & Crisis Response Plan for Suicidal Ideation in the ED

Inclusion Criteria: * Adult men and women between the ages of 18 and 70 presenting to the Emergency Department with acute suicidal ideation. * Patient cleared for admission to the University Hospital inpatient psychiatric unit. * Decision to admit the patient to the inpatient unit or psychiatric stabilization unit made prior to consent to prevent study procedures from complicating or influencing the disposition and treatment as usual for suicidal patients reporting to the ED. * Individuals presenting to the ED for other complaints but found to have suicidal ideation necessitating admission will also be eligible. * Able to read and write English. Exclusion Criteria: * Serious mental illness with active and significant signs of psychosis, mania, hallucinations, paranoia, agitation, and drug-induced or other toxidromic symptoms. * Acute intoxication with clinically significant symptoms (as defined by the attending clinician's assessment of patients' clinical sobriety). * The patient is not capable of understanding the research procedures and providing informed consent for themselves. * Lack of reliable means to be available for follow-up assessments (e.g, working mobile phone). * Persistent resting blood pressure lower than 90/60 or higher than 180/110, or persistent resting heart rate lower than 45 beats/minute or higher than 120 beats/minute. * Injuries requiring procedural sedation. * Pregnancy or breast feeding. * Known hypersensitivity to ketamine. * Legal or illegal use of ketamine in the previous 90 days. * End-stage or severe cardiovascular (e.g., ACS or decompensated heart failure), liver, or kidney disease. * Patient is a prisoner. * Patient is physically restrained or actively under custody of law enforcement. Once a patient is no longer under custody of law enforcement or physically restrained, the patient may be considered eligible and may consent to voluntary enrollment in the study.