By the description of the Stance keyword on the Rules Compendium, it ends in a very specific moment:
A stance lasts until the character assumes another stance or until the character falls unconscious or dies.
The system defines that when you reach 0 hit points, you are dying, and then says:
The creature is unconscious. (...) This condition ends immediately on the creature when it regains hit points.
The Ring of Invigoration has the following daily power:
Daily (Free Action) When you're reduced to 0 hit points, you can spend a healing surge.
So my question is: Does the ring's power actually kick in before the unconsciousness triggers, thus keeping up any stance, zones and other effects that require you to be alive and fighting, or does it kick in after that?