I remember when working for EMS and at one point, the fad for killing yourself at the time was drinking rubbing alcohol.
This girl did it and dropped her heart rate to something like in the teens. EMS came to the 911 call and found her "dead", cold and clammy with no pulse. So pronounced her dead and the medical examiner came hours later, when the morgue truck came and they found out she was alive. Was a big thing in the news at the time.
I had a call once after that where similar happened but we luckily saw the bottle near them, but the heart rate was so weak and faint, barely would think the person was alive, but brought them back.