My advice is two, mainly:
1: search the entire city and all the ones you have passed through, as they are full of healing items. You may have skipped several.
2: As soon as you get a bit away from the enemies, they stop chasing you, so you can let them chase you for a bit to get them away from the area they're guarding and go through there later. In the hospital it is more difficult, but with a little patience, you can easily achieve it.