Well, my fathers' solution when things like this happen in his ward is to report it immediately and make sure they get treatment, at least the treatment he's allowed to provide and send them to whomever can help further. Seems like every day he tells me n mum about "well we had a patient with a ___ problem last night and I had to call the hospital to have them sent out. Hospital sent them back couldn't find anything blahblahblah but heart rate still low blahblahblah."
He's a psych nurse though, so they usually have to send patients with treatable physical issues to a proper hospital. They have a doctor on staff that apparently can't read the heart monitor right, and sometimes the hospital won't take the patient until they're in critical condition and get sent over in an ambulance. Or try to dump a patient with a physical problem that's creating an unusual mental state on the psych ward instead of treating them. Washington state has the best healthcare system. The anecdotes can be so bad they're laughable.
Apparently the nurse is to blame if the nurse doesn't report the problem immediately and it turns into a life threatening condition, but they can't pin it on you if you did everything you're expected to and things go wrong because people with more authority over treatment ignored you.