You have to buy the
Expert First Aid - Under Wraps before you can advance past 150. It will allow you to skill up to 225. You can buy a copy for 1 gold from:
Alliance -Deneb Walker, Stromgarde Keep, Arathi Highlands
Horde -Balai Lok'Wein or Ghok'kah, Brackenwall Village, Dustwallow Marsh
They can also be found on the AH from time to time, but you'll likely pay more.
Happy...er...wound closings. =)
Edited for stupidity =(
Edited, Tue Dec 6 11:16:06 2005 by BrianTheFist