I'm going to assume none of this is protected or confidential information; because I don't know what apps would be appropriate for that.
If you really want to use Siri, the Notes app is about the only think that will give you full control
Activate Siri by long pressing the home button, then say Note, followed by whatever you want noted. You have to speak briskly, or Siri decides you're done and writes the note.
Each note is time and date stamped. You can see this in both the note list and at the top of an open note.
In addition to creating a Note, you can list notes with Siri with commands like
List all Notes,
List Todays Notes,
List Notes from June 25, or even
Find notes with Dr. Jacob.
Of course, all of this depends heavily on how well Siri understands what you say. If you use a lot of unusual medical terms you'll probably have to enter them manually.
If you do this, I would not depend on Notes for long term storage of your notes. For one, Notes doesn't offer a lot of organizing ability. Two, Notes has been known to lose notes on occasion. Not so much recently, but it happens.
For that I recommend Evernote.
The easiest thing would be to use Evernote straight up. You lose the ability to make new notes directly from Siri, but you can still use dictation. You can use dictation in any app that works with the native keyboard. So other note apps are also worth considering, especially if you have concerns about your notes (however encrypted) being stored in the cloud.
But if you want to use Notes, for it's Siri-ability, and Evernote for cleaned up and searchable notes, then another app called EverClip comes into play. This is an iPhone app, but it works fine on the iPad. What EverClip does is automatically gather anything you copy (from any app) into a list of stuff you can add to one or more Evernote notes. It's pretty cool. You start EverClip, go do you copying, then go back to EverClip to select and create notes.
Or you can email each note individually to the email address that comes with an Evernote account.
Anyway, whatever you do, I hope this gave you a few ideas.
Good luck.
P.S. For tips and tricks on how to use Dictation try this thread.
http://www.ipadforums.net/ipad-3-forum/81750-dictation-tips-tricks.html
Many of these commands will also work while creating a note using Siri.
