This could all be from a virus. My husband and I both had gastro symptoms over the weekend and Brian had both diarhea and vomiting.
Brian and your family are in my prayers.
The reference to gastro symptoms interested me. My niece's family of 4 and her parents (my sister & bro-in-law) all came down with some GI upset (mostly upper) 2-3 weeks ago. My niece got sick first & my sister took her to the fire station my nephew-in-law works at. He immediately took her to the emergency care clinic she's an RN for, and she was there for 11 hours while the doctors did IVs, X-rays, C-T, etc. Once they stabilized her, she went home. Within an hour, her husband was violently ill -- and then two hours later so were their 3YO dtr and 1YO son. My sister & brother-in-law had driven two hours to their lake house, and within an hour of getting there, they too were hit, worse than the dtr & son-in-law. A neighbor called, was apprised of the situation, told not to visit but did leave soup, beverages on their front porch.
They're not sure what hit all 6 of them. HOWEVER, when Jake went back to work at the fire station, they were getting calls from sick people with the same thing, who needed transport to hospitals to be stabilized.
I haven't seen any news stories of a similar illness, but who knows? It could be the same thing you & your family had, and with Brian's health compromised, something like this could affect him more and in different ways. Vomiting can cause dehydration, which can affect the heart and other organs.
At any rate, I'm praying that doctors find what is going on and find that magic bullet for Brian.
Will check for updates from you during the day.