Can a coma patient survive several days unattended? In the movie _28 Days Later_ (and, to a lesser extent, the graphic novels/TV series _The Walking Dead_ ), there is a character who, because of some unfortunate circumstance, found himself in a coma. When he woke, he found that the world was quite different and had no knowledge of the events which happened in the preceding four weeks. To me, this implies that the hero was in the coma for at least three weeks. When he woke, he was clearly well enough to outrun some of the infected for at least a little while. Is that even possible? Can a coma patient survive several days unattended?

Survival of three weeks is definitely not possible. The longest time you can survive under ideal conditions without drinking (or being administered) any water is projected at 10 days.

Other than that (depending on whether the depth of the coma interferes with your breathing regulation), a few days should be survivable. But I doubt you'd be in a good enough condition to outrun a zombie afterwards. Hard to find references on that, though.