When a doctor tells a patient that the surgery could kill them and the patient goes ahead with it, then dies, could life insurance or medical examiner claim it was suicide?

NO

And no doctor will perform surgery on a patient if there is zero chance of survival, it just doesn't happen.

Ebees, no it is not suicide because the patient didn't preform their own surgery. As cdnreader mentioned above, all surgeons need to inform their patients of potential risks.

Dear Ebees,

I hear your concern but I believe all doctors warn their patients about potential risks even for the most common surgeries. Even if the patient passes during surgery or even after, it will not be considered a suicide. It should not affect any insurance claims.