Not much you can do once they have your loved one in ICU. The doctors will do what they will do and it usually isn't very beneficial, especially for the elderly.
UTIs are easily managed usually with D-mannose. It's a kind of sugar, so you just have to sweeten a drink with it two or three times a day. Very often, it does the trick in one day.
If the individual is able to drink and it was MY loved one, I'd be in there with a nice cup of herbal tea sweetened with D-mannose to give them two or three times a day. It can't hurt and it can save.
But, that's likely not possible since the person is in septic shock. Very dangerous. As noted by others, IV vitamin C is what I would be demanding and then, when there is sufficient recovery to sit up and drink, D-mannose to drink.
But this should never have gone this far or gotten this bad. The person should have said something sooner and been started on the D-mannose. Or someone who loves that person should have been paying attention and asking questions and taking action sooner.
But, hindsight is 20/20, as they say. Let's hope this lesson is survivable.