I suspect that ships responding to medical emergencies, which are equipped with large holodecks, would have a programme they could run to make the space either into a triage facility or evacuation centre.
I wonder how far you could go with that. I've noticed that the Voyager's EMH has to pick up a medical tricorder to scan patients, his doesn't materialize with one at his waist. So while the holodeck could manifest beds and such, could it fill the emergency facility with all the "gadgets" that a future medical center would need to operate?
For example, the big scanner above the main examination bed in TNG's sick bay, in a holodeck would that still be a scanner, or just another part of the ceiling?