D&D 5E Would you change a monster's hit points mid-fight?

[THEMNGMNT]

I operate pretty much the same way.

 

[Imaculata]

If an enemy is near death, and a player does an awesome action (maybe on a critical), I may rule in their favor and disregard the remaining HP. Just as long as they got a good fight out of it. There have been rare occasions where I misjudged the amount of damage the players can do, and had to bump the hitpoints of a boss a bit mid-fight.