No one would ever actually do this, I’m sure – but the arrangement of this line is such that it would be interesting for Claudius to forget who he was talking to for a moment, slip and call Polonius “dear” – before correcting himself and saying, “my lord.”
It would add to the atmosphere of Claudius’ mental landscape – reflect the storm brewing in him, lead him to this speech that’s essentially a giant confession.
To see Claudius a little bit scattered, a little confused, could be very interesting for this scene, which feels as though it’s all business until the soliloquy.