she said, but I'll tell you you don't know anything. Then we started. On the way
The grandmother finishes her thought from the previous stanza, telling the young folks that they don't know nearly as much as they think they do.
We think this line gives her a kind of dignity. Her body might be failing her, but she's got a wealth of knowledge from her long life. She knows things that only a person who's lived as long as she has can know.
The last two lines of the stanza are short and to the point. They're now in the ambulance and headed to the hospital.
Something about the almost bland nature of the words makes them even more moving. The speaker doesn't play into the melodrama of the situation.
He reports the facts. And the facts are scary.
We're left hanging as another enjambment ends this stanza and leads us into the next.