Does Medically Induced Coma Require Patient S Consent?

In regard to medically induced coma - if patient is conscious beforehand, their consent is obtained right? The procedure effects though, would this be similar to say, being given a sedative or anesthesia before surgery or even an individual being lethally injected - minus the lethal, basically they go to sleep and that s it until the meds are reduced? So if issue which required the induced coma does not resolve and life support is removed - that person s last conscious thought likely would be off similar to being carted off to surgery or the like?