This case is going to be on your mind for a while, sorry. The discussion about patho here has been good! The one idea I'll add is that it sounds to me like the ED provider may have been out of their depth. Elevated WBCs, hypotension, elevated lactic, febrile all sounds like sepsis. Poor EF, extensive medical hx, hypoglycemia all make it more complicated. I'm just not buying the lasix...Sat of 95% on 4L does not make me want to give lasix to a hypotensive patient (even with pressors fixing the numbers on the screen). If she had crackles that were audible without a stethoscope, lasix might have been appropriate to give in the ED, but otherwise this makes me think the provider didn't have a strong plan. What were her electrolytes pre-lasix?
In my hospital (which I'm not saying is perfect so I'd welcome any input!) this patient would have gotten an ICU consult and probably a cardiology consult while still in the ED. As you've unfortunately seen, this is not the kind of pt you want to keep in the ED...they need a primary team to start managing their case. As the nurse, you can push for this when you know your ED providers. Would it have changed the outcome? Maybe, maybe not; it sounds like she went south fast. Right now you're training your "eyes" on patients who make you nervous. These are the patients you want to be transferring out...get their labs, their stat ABC interventions and antibiotics, their tests, and get them admitted!