How often do you all hear one of us ask, “Well, at what Hg do you want to transfuse?”. It always becomes a game of “Guess What I am Thinking”. It often feels so arbitrary, that we could be playing the game of how many fingers I am holding up behind my back. What is the correct answer to this question? Is there a correct answer, or is it all ‘gut instinct’? Lets review some evidence.