Hyperventilation Combined With Etomidate or Ketamine Anesthesia in ECT Treatment of Major Depression

Inclusion Criteria: * Adults patients aged 18 to 85 years * Diagnosed with Major Depressive Disorder, unipolar or bipolar depression * Undergoing ECT for treatment of their symptoms * Currently residing in Manitoba Exclusion Criteria: * Relative contraindications to ECT therapy (recent MI or CVA, increased intracranial pressure, intracranial mass lesion, intracranial aneurysm, epilepsy, known cardiac arrhythmia, pheochromocytoma, pregnancy) * Contraindications to etomidate (sepsis, primary or secondary adrenal insufficiency, porphyria) * DSM-V diagnosis of a lifetime history of psychotic spectrum disorder * Drug or alcohol dependence, or abuse within the past 3 months, soy-bean oil allergy