Wow, I never heard of this. I had sedation dentistry to remove wisdom teeth and woke up just fine.
You are probably not almost 91.
The real question is why didn't the dentist check him out further due to his age? I know he looked and acted like a kid. He could out fish me and his daughter put together.
He was not the least bit overweight. He got up at 5 a.m. and ate an orange and a grapefruit. He looked 75 or less.