Hello, I am a psychiatrist.
I do not know of a specific psychiatrist in Louisiana or elsewhere who will prescribe Ketamine for treating depression, as it's use in this capacity is very experimental.
Ketamine is not a new medication; it was first studied in patients almost 50 years ago; it is an anesthetic (used for anesthesia), and it can cause hallucinations and dissociation. Because of its ability to foster dissociation, I would think it would be a very poor choice for use in someone who has PTSD and therefore maybe apt to dissociate anyway.
My suspicion is that a better option would be to find a very experienced psychiatrist who specializes in mood disorders - as not all of them do. Typically such psychiatrists may be found in university medical center settings, and they will direct specialized "mood disorder" clinics. If you tell me where you are in Louisiana (I'm not clear if you live in Alexandria or not), I will try to provide you with contact information for such a clinic.
Does this make sense?