Inotropes should be titrated to markers of perfusion, which (unless there is a Swann or non-invasive cardiac output monitor) is usually a thoughtful gestalt of the clinical exam, echo, labs, etc. While I recognize that nurses are capable of being thoughtful, it's a different matter from just responding to an isolated bedside variable like the blood pressure.
Titrating vasopressin is controversial. I don't usually do it, although I wouldn't argue if someone wanted to. In any case it's not exactly a model of fine-tuning; usually people just move between .04 and 0 in two or three clicks at most.
We predominantly use LA (left atrial), RA (right atrial), PA (far less common), peripheral art lines as well as calculating hemodynamics based on central venous and arterial gasses on our kids.