Ketamine for Acute Suicidal Ideation in the Emergency Department: Randomized Controlled Trial

Inclusion Criteria: * Patients age 18 to less than 75 who present to the SAMMC ED with either overt or incidental suicidal ideations with a SADPERSONS score 5 or greater that the treating provider feels warrant formal evaluation. Exclusion Criteria: * -Poor vital sign stability hypoxia: O2 \< 95%, hypotension: SBP\< 90 hypertension: SBP\>180 Heart rate: \< 50 or \>120 Respiratory Rate: \<10 or \>30 * Altered mental status or intoxication * Patient is unwilling to participate or provide informed consent * Any allergy to ketamine or diphenhydramine * Patient is female of child-bearing age and unwilling to provide urine or blood for HCG analysis * Pregnancy or breast feeding * Presence of chronic oxygen-dependent pulmonary disease, liver cirrhosis, or renal disease requiring dialysis * Presence of ischemic heart disease, heart failure, or a history of unstable dysrhythmias * Presence of intracranial mass or vascular lesion. * Presence of a history of psychosis or hallucinations (as assessed by electronic chart review) * Weight greater than 115 kg or less than 45kg * History of increased intracranial pressure/hypertensive hydrocephalus * Non-English speaking patients * Patient is acutely psychotic * Provider feels that patient currently or likely will require chemical and/or physical restraints * History of prolonged QT-interval