Well, I don't know if this makes your decision easier or harder, but all PDAs have the first four items on your list.

The last two, directions and IM, will presumably require Internet access. Is your emergency room a WiFi hotspot? Does WiFi cause potential problems with medical equipment?

If WiFi is an option, that's the best way to go. If not, the only other way to get on the Internet from a PDA wirelessly is to get a combination PDA/cell phone, which will be considerably more expensive and probably require a long-term contract. I don't know if cell phones can harm medical equipment either.

That just leaves Voice Memos - some PDAs have it and some don't, but there isn't exactly a pattern. Among the current Palm line, only the Zire 72 and LifeDrive currently have voice recording. I would recommend looking into voice recording after you have narrowed down the field by taking your Internet requirements into account.

Sometimes it seems like it's so hard to find a PDA that's "just right" and also has voice memo, or even just to get a PDA's voice memo working the way you want it at all, that for some users, it might be better just to get a separate digital voice recorder. I'm not saying Voice Memo never works, but it can be more complicated than a standalone, especially if you try to multitask while recording!