In the DMG there is the optional rule on pg.266-267 for healing surges. Part of the text says
As an action, a character can use a healing surge and spend up to half his or her Hit Dice.
So what would you do as a DM for level 1 characters - because they only have 1 hit dice?
Seems to me this would be more needed at level 1 than any other level - but with the round down rules 1/2 == 0.