Medical Futility - Like Ordering Osso Buco at a Vegan Restaurant

I used to analogize medical futility to ordering osso buco at a vegan restaurant (or to ordering "off" the menu more generally).  It simply is not simply something that the restaurant prepares or serves. Indeed, to serve such an item would run counter to the very mission and identity of the restaurant.  



Similarly, requesting life-sustaining treatment for a permanently unconscious patient with multi-organ failure is to request something that the ICU does not provide. It  runs counter to the very mission and identity of the ICU.



The analogy breaks down, of course, because ICUs provide that treatment all the time.  It is unclear that ICUs have a clear menu demarcating what they will and will not provide.