Never tried a hospital specifically but I've done a fair bit of EVP work in older buildings around Lancashire and the thing that always gets me is how hard it is to rule out contamination from background noise. Hospitals especially must be a nightmare for that - air conditioning units, distant PA systems, people talking in corridors. What are you actually picking up and at what frequency range? Are you using a spirit box or straight recorder?
The reason I ask is I've read a few accounts where people thought they had something genuinely anomalous and it turned out to be interference from medical equipment. Not saying thats whats happening with you, just curious how confident you are in the conditions when you recorded.
Also - what kind of weird results are we talking? Voices, tones, something else entirely? The detail really matters with EVP and I find people sometimes jump to conclusions without ruling out the mundane stuff first. Would love to hear more about the specifics before forming any opinion on it.