Ketamine given to patients under anesthesia had no greater effect than placebo in reducing of depressive symptoms

"Heifets noted that the ketamine group did get better – much better. Their scores on the widely used MADRS depression scale halved on average – an improvement on par with that achieved in other ketamine studies with awake patients".

The problem was that patients receiving placebo got better at the same rate. Being under general anesthesia means large doses of GABAergic medications ie propofol, versed, which will would impact whatever circuits are purportedly impacted by Ketamine. Emergency Medicine doctor regularly use propofol or a benzo with the ketamine, because they know that propofol keeps patients from going into the K-hole. Ketamine in the 0.5 to 1mg/kg dose unpleasantly dissociates people, but if you give it with propofol they rarely have that reaction and are just generally sedated even with the more sedating effects of the propofol wear off.

Ketamine has well recognized short term effects in treatment of depressions - but also psychosis risks. Maybe just the conscious experience of ketamine trip is what works (for treatment of psychic diseases). Evidence suggests a full trip is whats of benefit due to the neural plastic window it creates. A better approach to this study would be to have patients hooked up to a saline IV drip where they would either administer ketamine or keep it on saline while the patient slept.