The thing is that without proper load, pressing isn't going to do much anyways. The "leak" in the system will self-limit the net effect of the pressor at some point. Where we're going to have our first major problem however, is in that we are also diluting sodium and potassium with the massive amounts of fluid. (least we forget: hypokalemia / hyponatremia = eventual arrhythmia. its a matter of WHEN not IF) The problem becomes since total load can only be estimation at best (and most probably a crappy estimation.) We really have no way of calculating the when. It will then become that our real solution in trauma cases is blood products or electrolytes or electrolytes plus blood products depending upon the given state. If we've infused more than a pre-defined amount of fluids then we need to be dealing with electrolytes in some way or another. (and with particularly large amounts of fluids we might be dealing with this problem sooner than later.) Really either way we go, until we plug the hole, we're going to have trade-offs involved that we're just going to have to learn to deal with in turn. Hence, we need to be thinking in more of a holistic approach to this as opposed to limiting ourselves to any one technique.I suppose if you frame it as though giving a pressor is "less bad" then diluting clotting factors and platelets with large volumes of fluid and PRBC's, then there definitely might be something to the idea.
I just don't see raising the pressure in a container when the container has a leak being beneficial, if your goal is to minimize volume loss from the container. Pressure doesn't necessarily equate to flow, and I don't know if reducing flow through the cerebral and hepatic and renal vessels by constriction is any better than reducing flow as a result of volume loss, especially when you consider that higher pressure is going to mean more volume being driven to areas of less resistance - the leaks in the vessels.