Board Thread:Questions and Answers/@comment-6296810-20140622193753/@comment-8986886-20140622210616

Most Shinigami would probably die before giving up their Zanpakuto, and as you mentioned we haven't seen anyone lose their sword permanently, so it's hard to say. Since each Asauchi houses its own spirit, I'm not sure substituting one Asauchi for another would work.

Kenpachi got his Asauchi from a dead Shinigami, so technically both of their Zanpakuto originated from the same spirit, which means that the Asauchi spirit is "reset" when the previous owner dies. What would happen if someone tried to use an Asauchi if its previous owner was still alive?

Since all Zanpakuto (save Ichigo's pre-reforging) are tied to Asauchi, it means that if you lose the Asauchi you can't release, or summon, your Zanpakuto (Byakuya's Bankai is an exception) In ep.322 @7min, Rangiku is forced to drop Haineko after it got a thousand times heavier from blocking Reigai-Izuru's attacks. She managed to retrieve her sword in the end though.