Our last game, someone got their "arm pinned to side".
I didn't have to say anything. The party understood that the arrow had to be removed and then they could use healing magics. A great first aid roll over 2-3 rounds and it was done. I think that specific crit helps in this case; not for every crit.
Now, they knew this from how we've played in the past, sure. But it seemed the right way for our group.
About the potions losing magical effect when broken..
Rune Paper would also be ruined if torn/burned/etc, (although it is tough stuff- another argument). This would cancel the stored spell.. So I agree with broken potion bottles with the caveat that you may have a small window of opportunity to get some effect.
In Of Channeling, 1. Create Holy Water was added to the Creations Cleric Base List (I don't think it's there in earlier copies of Spell Law.). "The water loses its effect if not placed in a clean receptacle". If you dump it on the ground, then it's no longer Holy.
In Channeling Companion, Holy Water is an 8th lvl spell in the Priest Base List Ceremonies but will "lose its potency quickly" if not stored in a container "as clean as possible".
For Channeling Potions, it could be that the Holy Water spell effects and restrictions are applicable.
If you smash the Holy Water bottle on a Vampire, it still has effect.
I grew up watching Sinbad and the Eye of the Tiger, where the witch, in bird form, breaks a potion of transformation and has to lick up the remaining spill for reduced effects; her foot is still that of a bird but the rest of her is human.
Watching this a few dozen times has likely biased my opinion. Stop Motion over CGI any day!
Every game is different. Have fun with yours.