Recent evidence suggests ketamine may attenuate harmful cellular cascades taking place after brain injury that result in permanent damage. The investigators are interested in researching the application of this in the setting of cardiac arrest. Following cardiac arrest, the brain is deprived oxygen for a period of time, leading to the imitation of these harmful cellular processes. The investigators hypothesize that patients who receive ketamine as part of their standard sedation procedures during cardiac arrest treatment have better neurological functioning compared to those who do not.

Inclusion Criteria:

• All out-of-hospital cardiac arrests (OHCA) with a "shockable rhythm" (ventricular fibrillation, pulseless ventricular tachycardia) that present to the Royal Columbian Hospital. The patient may be either in active cardiac arrest with shockable rhythm or may have achieved Return of Spontaneous Circulation (ROSC).
• Over 19 years of age
• Patients requiring sedation based on the assessment of the resuscitating physician.

Exclusion Criteria:

• Any other type of cardiac arrest
• Any history of previous, pre-existing neurological deficit
• Started on Extracorporeal Membrane Oxygenation (ECMO)
• Duration of cardiac arrest without ROSC is greater than 30 consecutive minutes
• Known contraindication or hypersensitivity to ketamine
• Awake patient or no standard sedation or no intubation required
• Inability to obtain deferred consent
• Currently enrolled in any other research study involving drugs or devices
• Patients who are pregnant
• Patients who are prisoners
• Patients residing in Long Term Care (LTC) facilities